TECHNICAL REPORT Incident of aircraft Airbus A-340

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TECHNICAL
REPORT
IN-062/2002
Incident of aircraft
Airbus A-340
registration EC-IDF,
at Madrid-Barajas
Airport (Madrid) on
7 September 2002
Technical report
IN-062/2002
Incident of aircraft Airbus A-340 registration
EC-IDF, at Madrid-Barajas Airport (Madrid)
on 7 September 2002
MINISTERIO
DE FOMENTO
SUBSECRETARÍA
COMISIÓN DE INVESTIGACIÓN
DE ACCIDENTES E INCIDENTES
DE AVIACIÓN CIVIL
Edita: Centro de Publicaciones
Secretaría General Técnica
Ministerio de Fomento ©
NIPO: 161-03-011-0
Depósito legal: M. 23.129-2003
Imprime: Centro de Publicaciones
Diseño cubierta: Carmen G. Ayala
COMISIÓN DE INVESTIGACIÓN DE ACCIDENTES E INCIDENTES DE AVIACIÓN CIVIL
Tel.: +34 91 597 89 60 E-mail: ciaiac@mfom.es C/ Fruela, 6
Fax: +34 91 463 55 35 http://www.mfom.es/ciaiac 28011 Madrid (España)
Foreword
This report is a technical document that reflects the point of view of the Civil
Aviation Accident and Incident Investigation Commission (CIAIAC) regarding
the circumstances in which happened the event being investigated, with its
causes and its consequences.
In accordance with the provisions of Law 21/2003 and Annex 13 to the Convention
on International Civil Aviation, the investigation has exclusively a
technical nature, without having been targeted at the declaration or assignment
of blame or liability. The investigation has been carried out without
having necessarily used legal evidence procedures and with no other basic
aim than preventing future accidents.
Consequently, any use of this report for purposes other than that of preventing
future accidents may lead to erroneous conclusions or interpretations.
This report has originally been issued in Spanish language. This English translation
is provided for information purposes only.
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Technical report IN-062/2002
T a b l e o f c o n t e n t s
Abbreviations ............................................................................................................................... vii
Synopsis ........................................................................................................................................ ix
1. Factual information ............................................................................................................... 1
1.1. History of the flight ........................................................................................................ 1
1.1.1. Flight Madrid-Tenerife Norte ............................................................................. 1
1.1.2. Stop in Tenerife Norte ....................................................................................... 3
1.1.3. Flight Tenerife Norte-Madrid ............................................................................. 4
1.1.4. Actions taken after landing and evacuation of the passengers ......................... 5
1.2. Injuries to persons .......................................................................................................... 7
1.3. Damage to aircraft ......................................................................................................... 7
1.4. Other damage ................................................................................................................ 7
1.5. Personnel information .................................................................................................... 8
1.5.1. Pilot in command .............................................................................................. 8
1.5.2. Copilot .............................................................................................................. 8
1.5.3. Type rating training ........................................................................................... 9
1.6. Aircraft information ........................................................................................................ 9
1.6.1. Airframe ............................................................................................................ 9
1.6.2. Description of the brake system of the A-340-313 ........................................... 10
1.6.3. Abnormal and emergency procedures related to the brake system .................. 18
1.6.4. Previous maintenance on the aircraft ................................................................ 20
1.6.5. Previous incidences in the brake system of aircraft EC-IDF ............................... 20
1.7. Meteorological information ............................................................................................ 24
1.8. Aids to navigation .......................................................................................................... 24
1.9. Communications ............................................................................................................ 25
1.10. Aerodrome information .................................................................................................. 25
1.10.1. Airport of Tenerife Norte ................................................................................ 25
1.10.2. Airport of Madrid-Barajas ................................................................................ 25
1.11. Flight recorders .............................................................................................................. 25
1.11.1. Cockpit voice recorder .................................................................................... 25
1.11.2. Flight data recorder ......................................................................................... 26
1.12. Wreckage and impact information ................................................................................. 26
1.13. Medical and pathological information ............................................................................ 28
1.14. Fire ................................................................................................................................ 29
1.15. Survival ........................................................................................................................... 29
1.16. Tests and research ......................................................................................................... 29
1.16.1. Ground test to locate the problem ................................................................. 29
1.16.2. Release to service of the aircraft ..................................................................... 30
1.16.3. Inspection of the master cylinder S/N H2121 .................................................. 31
1.16.4. Inspection of the dual valve (BDDV) S/N H2718 ............................................. 33
1.16.5. Additional testing of the master cylinder S/N H2121 ...................................... 33
1.16.6. Inspection of the pedal cover .......................................................................... 33
1.17. Organizational and management information ................................................................ 34
Technical report IN-062/2002
vi
1.17.1. Technical flight records of the aircraft ............................................................ 34
1.18. Additional information ................................................................................................... 35
1.18.1. Telex to the operators issued by Airbus Industrie ............................................ 35
1.18.2. History of similar cases .................................................................................... 36
1.18.3. Other safety actions carried out by the manufacturer of the aircraft .............. 37
1.19. Useful or effective investigation techniques ................................................................... 37
2. Analysis ................................................................................................................................. 39
2.1. Operation during the Madrid-Tenerife flight .................................................................. 39
2.2. Maintenance actions in Tenerife Norte .......................................................................... 40
2.3. Operation during the flight Tenerife Norte-Madrid-Barajas ............................................ 41
2.4. Actions after the aircraft came to a stop ....................................................................... 45
2.5. Origin of the residual pressure ....................................................................................... 45
2.6. Previous history of residual pressure .............................................................................. 46
2.7. Suitability of the operational procedures ........................................................................ 50
3. Conclusions ............................................................................................................................ 53
3.1. Findings .......................................................................................................................... 53
3.2. Causes ........................................................................................................................... 54
4. Safety recommendations ...................................................................................................... 55
Appendices ................................................................................................................................... 57
Appendix A. Diagram of tracks on runway 33 of Madrid-Barajas Airport ............................... 59
Appendix B. Details of the trouble shooting procedure applied after the incident ................. 63
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Technical report IN-062/2002
Abbreviations
00 °C Degrees Celsius
00° 00’ 00’ Degrees, minutes and seconds
AENA «Aeropuertos Españoles y Navegación Aérea», provider of ATC and airport services
AGL Above Ground Level
AMM Aircraft Maintenance Manual
ATC Air Traffic Control
bar Bar, unit of pressure
BDDV Brake Distribution Dual Valve
BITE Built-in test
BSCU Brake & Steering Control Unit
CMM Component Maintenance Manual (i.e. of a master cylinder, valve, etc.)
CMS Central Maintenance System
CVR Cockpit Voice Recorder
DFDR Digital Flight Data Recorder
DH Decision Height
DME Distance Measuring Equipment
E East
ECAM Engine and Crew Alerting Monitoring
FCOM Flight Crew Operating Manual
FOT Flight Operations Telex, communication of Airbus to the operators to inform on operational
issues
ft Feet
g Gravity acceleration
GPWS Ground Proximity Warning System
h: min: sec Hours, minutes, seconds
hPa Hectopascal
IAS Indicated airspeed
IFR Instrument Flight Rules
KCAS Knots of calibrated airspeed
kt Knots
Ibs Pounds
LRU Line Replaceable Unit
m Meter
mb Milibar
METAR Meteorological report
MHz Megahertzs
MLG Main landing gear (there are three legs in the MLG of the A-340: left, centre and right)
N/A Not affected
NLG Nose landing gear
NM Nautical Mile
OIT Operators Information Telex
P/N Part Number
S/N Serial Number
SOP Standard Operating Procedures, prepared by the manufacturer of the aircraft
SSCVR Solid State Cockpit Voice Recorder
TFU Technical Follow-up (communication on in-service difficulties issued by Airbus)
TSM Trouble Shooting Manual
TWR ATC Control Tower
UTC Universal Time Coordinated
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Technical report IN-062/2002
Synopsis
On 7 September 2002, at 13:03:27 h, the left and right legs of the main landing gear
of the aircraft Airbus A-340 registration EC-IDF touched down onto runway 33 of
Madrid-Barajas Airport. At that moment, there was a residual pressure of 800 psi on
the alternate hydraulic system of the brakes of the left main landing gear leg. The crew,
that had already detected the presence of that residual pressure at 12:58:02 h when
the WHEEL page of the ECAM was deployed before lowering the landing gear, had
decided to land with the antiskid system disconnected, and had voluntarily moved the
«antiskid & nose wheel steering» switch to the OFF position.
At the beginning of the landing roll, the pilot in command applied reverse, did not press
the brake pedals and used right rudder with the intend of keeping the aircraft aligned
with the runway axis. At a point between 240 m and 900 m beyond the threshold of
runway 33, the four wheels of the left main landing gear leg burst, and the aircraft
deviated initially to the right of the runway axis and then to the left until both crew
members applied full right brake, and the pressure reached 2500 psi on the brakes of
the four right wheels that locked and burst.
Finally, the aircraft came to a stop with the left main landing gear leg at 5m from the
left end of the asphalt area of runway 33, and at 146 m before the axis of the taxiway
J-1, with the fuselage rotated around 10° to the left of the axis of runway 33. The rims
of wheels 1, 2, 4, 5 and 6 suffered heavy damage, as well as the brakes 1, 5 and 6,
due to the drag with the runway surface. There was a fire that affected all the wheels
of the right and left legs of the landing gear, and it was quickly controlled by the fire
fighters of the airport.
Runway 33 remained closed during approximately 6 h and 15 min and there were no
personal damages.
The investigation determined that the cause of the residual pressure in flight was the
left master cylinder P/N C24592020 S/N H2121, which had a length and a dead band
longer than specified.
It is considered that the cause of this incident was the fact that, as a consequence of
the appearance of residual pressure in flight in the left brakes, due to the fact that the
left master cylinder P/N C 24592020, S/N H2121 was defective, and due to the lack of
a procedure to be applied in that case, the crew voluntarily disconnected the antiskid
system when the residual pressure was still present, which produced the burst of the
left tires at touchdown.
The following factors could have prevented the incident:
— The existence in the Operations Manual of instructions to be followed in the case of
residual pressure being observed in flight.
— The knowledge by the affected flight crew of similar cases that had been reported
as complaints during June 2002.
— A more comprehensive analysis of the previous squawks of residual pressure.
— A more detailed training on the brake system during the type rating courses.
Technical report IN-062/2002
x
1. FACTUAL INFORMATION
1.1. History of the flight
1.1.1. Flight Madrid-Tenerife Norte
The aircraft took off from Madrid-Barajas Airport on 7 September 2002, at 06:56 h
UTC1, with 263 people on board (12 crew members and 251 passengers). The destination
was the Airport of Tenerife-Norte. The takeoff weight was 201033 kg and the landing
weight in Tenerife was 184333 kg. The maximum landing weight is 190000 kg.
It was the first flight of the aircraft since 28-7-2002, because it had been repaired after
a bird strike on the nose area that happened on that date.
The flight was normal and, during the approach to runway 12 in Tenerife-Norte, when
the landing gear was lowered at 9:19:24 h, the copilot noticed that in the wheel page
of the ECAM there were indications of residual pressure in the brakes of the left MLG.
The 24 bars that represent the brakes of the 4 wheels of that landing gear were lit in
amber colour.
The crew considered that this indication, which is not associated to any caution message,
could be spurious, and for that reason they decided to land without additional
measures.
The aircraft continued the approach with the antiskid system connected and with the
autobrake systems disconnected. After switching off the autopilot, the copilot was
the PF during the approach and landing in manual mode with the autothrust connected.
After touching down, according to his statement, the copilot noted that the aircraft started
deviating to the left of the runway, and therefore applied progressively right rudder
until reaching full deflexion. Then he applied brakes, initially right toe brake and then
both brakes, always steeping more the right pedal, until the aircraft, which initially had
approached at around 8 m from the left side of the runway 12, deviated towards the
right and finally came to a stop with its centre of gravity separated around 5 m to the
right of the runway axis.
The DFDR data show that at the moment of the landing there was a pressure of 900
psi in the left alternate brake system. After the left and right legs touched the ground
at 9:21:43 h and the spoilers started to deploy, the brake pedals were not pressed, and
therefore the alternate system remained active and the 900 psi of pressure were trans-
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Technical report IN-062/2002
* All the times used in this report are UTC, except where specifically noted. It is necessary to add two hours to have
the local time in Madrid-Barajas Airport, and one hour to have the local time in Tenerife-Norte Airport.
mitted to the wheels. The copilot used more and more right rudder to counteract the
increasing tendency to veer to the left as the airspeed was decaying. Within 9:21:50 h
and 9:22:03 there were small movements of the right brake pedal, of around 8° (the
following angle values correspond to the pedal potentiometer; the maximum deflexion
of the pedal corresponds to a pedal potentiometer position of 68.80°; the maximum
physical pedal deflexion is 14°11’) that were not enough to send pressure to the normal
brake system until 9:22:03 h, at which moment both pedals were pressed (52° the
right pedal and 26° the left pedal), the normal system was pressurized and the residual
pressure of the alternate system was released. From that moment on, the aircraft behaviour
regarding braking was normal.
The tower said to the crew at 9:27:10 h that they could vacate the runway at their discretion
and the crew of EC-IDF answered that they had a brake problem and they would
call back when ready to leave the runway.
The tower advised another traffic that was in short final to be ready to go around
because the runway was occupied.
The crew of EC-IDF switched off and then on the BSCU. The residual pressure had
disappeared. At 9:27:43 h, they told the tower controller that they were going to
leave the runway «through the first on the left» and started a taxi by their own
means until they confirmed «runway vacated» at 9:29:25 h and asked for the possibility
to stay at that point of the taxiway for a few minutes. The tower requested
them to move a little more forward because they still protruded a little bit over the
runway.
The aircraft moved as requested and at 9:29:52 h they said that they were proceeding
to the parking apron. The tower asked whether they needed towing or were able to
move by their own means, and also whether they needed further help.
The crew answered that they would taxi by their own means. At those moments, they
were noting that the temperature of the four brakes of the left MLG was increasing a
lot, and called their ground operations department to advise that maybe a maintenance
action was going to be needed. Operations asked whether fire fighting services were
going to be needed and the pilot in command answered in the positive and requested
that nobody approached the aircraft.
At 9:33:35 h, the flight that had landed after EC-IDF called tower to advise that they
were seeing smoke coming out from the «left rear wheel» of that aircraft.
The crew of EC-IDF acknowledged the information and thanked for it. The temperature
of the wheels of the left MLG had continued increasing until an ECAM caution was
triggered. The aircraft contacted ground movement frequency at 9:35:36 h and the controller
asked whether they needed that the fire fighters applied water or preferred the
Technical report IN-062/2002
2
wheels to be cooled alone. The crew answered they were going to check with the maintenance
personnel and finally rejected the offer to apply water.
1.1.2. Stop in Tenerife Norte
CWhen the aircraft reached the parking, chocks were put in the wheels and the brakes
were cooled using two fans provided by the line maintenance of the operator and another
provided by the fire fighters that were around the aircraft. The passengers disembarked
the aircraft in a normal way.
According to his statement, the pilot in command informed the ground maintenance
personnel about the incidence during the landing and it was commented that the problem
would be consulted with the operator’s main base in Madrid.
According to their statement, the maintenance personnel entered the cockpit and saw
the high brake temperature caution and observed in the post-flight report that there
had been a caution of «Brakes residual braking». They tried to test the BSCU 1 and 2
but they were unable to do that.
The information gathered shows that while the maintenance personnel were trying to
locate technical advice in the Madrid base, the passenger boarding of next flight Tenerife-
Madrid started, with the same flight crew that had flown the previous leg.
Some information was interchanged with the pilot in command, who understood that
the maintenance personnel had no inconvenience for the starting of the flight back to
Madrid. However, these personnel were still considering the possibility of lifting the left
MLG to check the free movement of the wheels, although in the end this action was
not carried out because during the previous taxi to the apron the wheels seemed to
have behaved correctly.
Once the boarding ended, a person from maintenance Madrid called the line maintenance
Tenerife and was informed about the situation. Since in the ECAM screen there
was no caution, and the brake temperature had fallen within normal limits, this conversation
did not produce further maintenance actions and therefore the doors were
closed and the aircraft started the taxi for takeoff.
The maintenance personnel advised the pilot in command to watch the temperature
during the taxi just in case a new cooling was needed. The aircraft taxied normally, and
the pilot in command informed that after the takeoff he would leave the landing gear
down for some minutes to further cool it.
In the aircraft logbook the crew did not write any squawk after the landing in Tenerife.
The maintenance personnel wrote that the normal «transit» line check was comple-
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Technical report IN-062/2002
ted, but they did not report any of the actions carried out on the brake system. Neither
in that flight nor in next flight (Tenerife-Madrid where the incident happened) was the
aircraft acceptance form signed by the pilot in command.
1.1.3. Flight Tenerife Norte-Madrid
The aircraft, with the flight identifier IB-0959, took off around 10:55 h from Tenerife,
after a taxi of 5 min since the moment of chocks off during which the general behaviour
of the aircraft was checked and it was confirmed that no new cautions appeared.
The takeoff was normal, with a weight of 173404 kg, compared with the maximum
takeoff weight of 275000 kg. There were 247 passengers and 12 crew members on
board.
The brake temperatures were still slightly high, and therefore the crew left the landing
gear down for several minutes after lift-off.
The flight progressed normally. The crew did not show excessive concern with respect
to the reappearance of the failure in Madrid.
At 12:58:02 h, with the landing gear still up, the copilot called the WHEEL page of the
ECAM and they saw again the there was residual pressure in the brakes of the left MLG,
because the bars that represented the brakes appeared again in amber colour. The crew
disconnected and then connected the BSCU but the amber bars did not disappear.
At 12:58:38 h landing gear down was selected, the system started its normal self-checks
and the residual pressure disappeared momentarily but almost immediately appeared
again. The crew again disconnected during 24 s and then connected the BSCU,
although this action, not permitted by the operational procedures when the landing
gear is extended, did not succeed in eliminating the residual pressure indication.
Since the moment they noticed there was residual pressure in the left leg, both pilots
were commenting the possible actions to be taken. It was discussed the possibility of
discontinuing the approach, and it was commented that the only solution would be to
disconnect the antiskid because in that case the system was not going to brake by itself,
and, therefore, to lock the wheels.
Finally, the copilot disconnected the antiskid system and nose wheel steering switch
after asking the pilot in command for conformity.
The aircraft continued its approach to runway 33 of Madrid-Barajas Airport with the
pilot in command acting as PF. The aircraft configuration was flaps down and landing
Technical report IN-062/2002
4
gear down, without autopilot but with autothrust connected, and with the antiskid and
the autobrake off. The spoilers had not been armed during the approach.
The pilot in command, taking into account the low weight and the length of the runway
in Barajas, had decided to touchdown as soon as possible onto the runway and to
apply thrust reverse, without touching the brakes as long as it was not indispensable.
There was no communication to the passengers or cabin crew, and the ATC was not
informed that there could be some problem with the aircraft.
The approach continued and the pilot in command recalled after the incident that the
aircraft touched the ground over the numbers of runway 33. The left and right MLG
touched down around 13:03:27 h and the reversers were selected three seconds afterwards.
The central MLG and the NLG touched down at around 13:03:32 h. At the
moment the main legs touched down, the spoilers did not deploy, because they were
not armed.
When the reversers were deployed, the spoilers deployed in accordance with the
system design, which always deploys them even when they were not armed during
the approach.
At the first moment they touched down the wheels of the left leg were braked with
around 800 psi of residual pressure. The pilot in command, without pressing the brake
pedals, applied progressively more and more right rudder to try to keep the aircraft aligned
with the runway axis.
At 13:03:45 h the right brake pedal was pressed up to the limit, which made the pressure
to increase up to around 2500 PSI and the wheels of the right MLG burst in that
area.
Finally the aircraft came to a stop at 13:04:01 h in such a manner that the left leg
remained at around 146 m before the axis of the taxiway J-1 (the first exit after the
intersection of runways 33 and 36L) and at around 5 m from the end of the paved runway
shoulder, that is, it has crossed the line of the lateral runway edge lights. The longitudinal
axis of the aircraft had turned around 10 degrees to the left with respect to
the axis of runway 33 and, therefore, the nose MLG leg also remained at approximately
5 m away from the lateral end of the paved runway shoulder.
1.1.4. Actions taken after landing and evacuation of the passengers
After the aircraft came to a stop, the crew informed the tower that they had a problem
with the brakes and that they were going to remain on the runway. The ATC commanded
the next aircraft that was approaching to runway 33 to go around and called
the fire fighters.
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Technical report IN-062/2002
At around 13:04:32 h, that is, approximately 30 s after the aircraft came to a stop, the
aircraft that was going around informed by radio that the EC-IDF had fire on the wheels.
The air traffic controller answered that with so much smoke she could not really see
what had happened. Then she commanded another aircraft to go around.
When they heard the information about fire on their wheels, the crew of EC-IDF decided
to shut down the engines. For several minutes, they were evaluating the possibility
of ordering an emergency evacuation of the airplane. After 3 min and 8 s since the aircraft
stopped, the flight crew addressed the passengers to advise them to remain seated
without using the mobile telephones.
At 13:06:22 h the crew called by radio their Operations Department to request assistance
to transport the passengers and to tow the aircraft. They called then tower to ask
for confirmation that only smoke was present in the wheels and on their side informed
the air traffic controller that the fire fighters were already around the aircraft. The tower
answered saying that it was confirmed that the fire was extinguished and asked for the
possibility of the aircraft to taxi to leave the runway.
When she received a negative answer from the flight crew, that suspected that they
had all the wheels burst, the air traffic controller commanded other aircraft to go
around while in the airport several services started to coordinate and communications
were held with approach control services after the local alarm was activated. The surface
of runway 36R was inspected and was open for arrival traffic around 13:16 h, while
runway 36L was still active for takeoffs.
In the meanwhile, inside the aircraft, the crew said to the passengers that there had
been a problem with the brakes and that coaches would arrive soon to take them from
the aircraft to the terminal. This address took place after a request of the pilot in command
4 min and 8 s (13:08:09 h) after the aircraft stopped.
Technical report IN-062/2002
6
At 13:24 h the passengers started coming out the aircraft using door 1R and a stairway
provided by the ground handling personnel. When all the passengers had left the aircraft,
the crew also evacuated it. The passengers were taken to the terminal by shuttle
coaches.
The maintenance personnel of the operator replaced all the wheels of the left and right
MLG and around 18:25 h the aircraft was towed towards the maintenance hangars.
The area was cleaned and runway 33 and its lighting system were inspected. At 19:21
h runway 33 was again open for arrival traffic.
1.2. Injuries to persons
Injuries Fatal Serious Minor/none
Crew 12
Passengers 251
Others
1.3. Damage to aircraft
The eight wheels of the left and right MLG burst during the landing roll, and the wheel
rims dragged over the runway surface. The lower part of the four left brake assemblies
was totally disintegrated as a consequence of the contact with the ground. The
eight wheels and their brake assemblies were replaced.
After the incident, following a troubleshooting procedure prepared by Airbus (see 1.16)
and before any further flight, the left brake master cylinder P/N C24592020, S/N H2121,
was also replaced.
The left leg assembly of the MLG had eventually to be completely replaced, because of
the loads suffered during the landing roll once the wheels had burst. There was fire on
all the wheels of the left and right MLG, but no other part of the aircraft was affected
by that fire.
1.4. Other damage
After a visual inspection, it was determined that there was no appreciable damage to
the paved surface of runway 33 of Barajas airport. Therefore, there was no other
damage in addition to those to the aircraft.
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Technical report IN-062/2002
1.5. Personnel information
1.5.1. Pilot in command
Age: 59 years old
Nationality: Spanish
Title: Airline Transport Pilot
Licence: Valid since 21-1-2002 until 21-1-2007
Type rating: Pilot in command A-340. He had also flown DC-9, B-
727 and A-300
Total flight time: 10439 h
Hours in the type A-340: 3250 h
Hours in the last 90 day: 175 h
Latest simulator check: 8-4-2002
He attended the A-340 pilot in command type rating course in Iberia within 12-5-1997
and 13-7-1997, with a flight instructor that got his rating in Airbus/Miami. Afterwards,
he attended the following two-day recurrent training courses also in Iberia:
January 1998; July 1998; March 1999; November 1999; June 2000; November
2000; January 2001; July 2001.
On 8 April 2002 he renewed the type rating after some sick leave.
The pilot in command had flown last time on 29 August before initiating a new activity
period on 7 September at approximately 5:50 h.
1.5.2. Copilot
Age: 33 years old
Nationality: Spanish
Title: Airline Transport Pilot
Licence: Valid until 29-10-2006
Type rating: Copilot A-340. He had also flown MD-87
Total flight time: 2310 h
Hours in the type A-340: 1420 h
Technical report IN-062/2002
8
Hours last 90 days: 210 h
Latest simulator check: 27-10-2001
He attended the A-340 type rating course in Iberia within 23-6-2000 and 17-8-2000,
with a flight instructor that got his rating in Airbus/Miami. Afterwards, he attended the
following two-day recurrent training courses also in Iberia:
July 2001; October 2001; May 2002.
The copilot had flown last time on 6 September, and had had 16 h and 30 min of rest
before initiating a new activity period on 7 September approximately at 5:50 h.
1.5.3. Type rating training
The Training Manual of the operator was reviewed and it was found that the initial
type rating course included 6 h of ground instruction devoted specifically to electrical,
hydraulic, landing gear and APU systems. Later on, the second session in flight simulator,
which had an estimated time of completion of four hours, was devoted to
ECAM, actions after failures, and hydraulic and electrical systems with generated failures
and the corresponding ECAM actions. The operator stated that they used as a
base the Airbus recommended training syllabus and procedures as included in the Airbus
«A340 Flight Crew Training Manual», from which they provided the investigation
with the relevant pages of the «Standard Course». Additionally, they stated that their
refreshment courses covered all the systems of the aircraft every two years, i.e. one
year below the JAA requirement of three years to complete the review of all the
systems.
After the incident, the manufacturer reviewed their syllabus for A-340 type rating in the
part relative to brakes and they concluded that their recommended syllabus was adequate
and no change was needed. No information was gathered regarding the details
of the residual braking training recommended or provided.
1.6. Aircraft information
1.6.1. Airframe
Make: Airbus
Model: A-340-313
Serial number: MSN 474
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Technical report IN-062/2002
Registration: EC-IDF
Year of manufacture: 2002
M.T.O.W.: 275000 kg
Operator: Iberia L.A.E.
Total flight time: 960 FH
Total flight cycles: 133 FC
1.6.2. Description of the brake system of the A-340-313
According to the description of the Operations Manual prepared by the operator of the
aircraft, the A-340 has brakes in the wheels of the right and left MLG (the central leg
of the MLG does not have brakes) that may be applied by any of the two independent
brake systems (normal system, or green system, and alternate system, or blue system).
There are also autobrake and antiskid.
The brake commands may come from the pilot, when the brake pedals are pressed, or
from the autobrake, with a deceleration rate previously selected by the crew. When in
normal mode, all those commands are controlled by the Brake System Control Unit
(BSCU) that has two channels. The alternate (blue) system is hydromechanical.
This BSCU also checks the residual pressure and the temperature of the brakes and provides
information on the speed of the wheels to other systems of the aircraft.
In flight, only the alternate system is pressurized and available. During landing, the brakes
revert to the normal system at the moment the brake pedals are pressed or at the
moment of touchdown if the autobrake system is armed.
When the normal system pressurizes and is active, the feed of pressure to the alternate
system is automatically cancelled. The brakes also momentarily revert to the normal
system in flight when the landing gear is lowered, while several auto tests are being
performed in the brake system.
1.6.2.1. Antiskid system
The antiskid system provides a maximum braking efficiency maintaining the speed of
the wheels at the limit of slipping. The antiskid function is automatically disconnected
on ground when the speed is below 10 kt. There is a switch (A/SKID & N/W
STRG) in the cockpit with to positions (ON/OFF) that allows the manual connection
and disconnection of the antiskid and the nose wheel steering functions at the
same time.
Technical report IN-062/2002
10
The antiskid system never increases the pressure by itself, but simply releases or maintains
the pressure applied by other parts of the system (the pedals or the autobrake).
1.6.2.2. Autobrake system
This system reduces the delay in the braking action in the event of an acceleration-stop
to improve the performances and establishes and maintains a deceleration rate during
landing to improve the comfort and reduce the workload of the flight crew.
The system may be armed before the landing pushing the switches LO, MED or MAX
(braking rate low, medium or maximum) under certain conditions, including that the
antiskid system must be electrically energized.
During the landing roll the autobrake action starts with the command to extend the
spoilers.
The normal procedures of the operator (Operations Manual A340, 2.01.63, 4-12-2000)
indicate that in final the autobrake may be selected at LO or ME («if required») and
then add: «In the event of crosswind, contaminated or short runway, or under low visibility
conditions, select LO or MED. In a dry runway of normal length, normally the use
of autobrake is not necessary».
However, the procedures recommended by the manufacturer of the aircraft indicate:
«Use of the autobrake is recommended.
Use of MAX mode is not recommended at landing.
On short or contaminated runways, use MED mode.
On long and dry runways, LO mode is recommended.
Note: If, on very long runways, the pilot anticipates that braking will not be needed,
use of the autobrake is unnecessary.
Press the appropriate pushbutton, according to runway length and condition, and
check that the related ON light comes on.«
1.6.2.3. Brake modes
There are four modes of operation of the brakes:
A) Normal braking: when there is hydraulic pressure of the first system, called green
hydraulic pressure and the switch A/SKID & N/W STRG is in ON, among other conditions.
The control is electrical through the BSCU, and the braking command is
provided with the pedals or automatically by the autobrake (on ground) or when
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Technical report IN-062/2002
the landing gear lever is moved to «UP» (in flight). There is no indication to the
crew of the hydraulic pressure applied to the brakes.
B) Alternate braking with antiskid: when the normal or green hydraulic pressure is not
enough, and the switch A/SKID & N/W STRG is in the ON position, there is an automatic
selection of the blue or second hydraulic system, and the alternate braking
system is available. In this case, the control is achieved through the pedals through
an auxiliary low pressure circuit that actions the DUAL valve. The BSCU continues
controlling the antiskid system. The pressure sent to the left and right brakes, and
the pressure of the accumulator, appear in a triple indicator located in the centre
of the instrument panel (see Figure 1).
It is important to note that the pressure transducer to the triple indicator and to
the ECAM indication is the same. For this reason, spurious indication of residual
pressure may occur in the ECAM and in the triple indicator at the same time, and
those transducers were mentioned in the TFU (see 1.6.3) as a common cause of
the false residual pressure indication.
C) Alternate braking without antiskid: If the switch A/SKID & N/W STRG is manually
moved to the OFF position, or there is a failure in the electrical supply or failure
of the BSCU, or when there is a low hydraulic pressure in both the green and
blue systems, the antiskid system is disconnected. The control is achieved through
the pedals, that actuate the DUAL valve, while the servo valves of the alternate
system are fully open and all the pressure commanded by the pedals reach
Figure 1. View of the triple indicator of pressure. The landing gear is down, but the antiskid
switch is in OFF. Therefore, the vertical bars that represent the brakes of every wheel do not
appear in the WHEEL page of the ECAM screen
Technical report IN-062/2002
12
directly the brakes, and therefore the pilot has to regulate the pressure with the
pedals with reference to the triple indicator to avoid the lock and burst of the
wheels.
D) Parking brake: In this mode the brake receives the hydraulic pressure of the blue
system or of the accumulator through the DUAL valve. This brake may be used in
emergency.
1.6.2.4. Indications, warnings and cautions
In addition to the triple indicator mentioned above, the WHEEL page of the ECAM
(«Engine indication and alert monitoring») presents a schematic indication of the eight
wheels of the MLG that have brakes (four on the left leg and four on the right leg)
together with additional information on the brake system, including the status of the
antiskid system, of the autobrake system (AUTO BRK), rate of autobrake selected (MED),
and brake temperature (F in the attached Figure 2) of every wheel (numbered as shown
in item D in the attached figure).
Figure 2. Wheel page of the ECAM
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Technical report IN-062/2002
On the other hand, in both sides of each wheel three vertical bars appear (item E in the
Figure 2) that represent the brakes of that side of the wheel. They appear in green
colour in flight, when the landing gear is down and the antiskid is operative, and on
ground when the brakes are released and the antiskid is active. They appear in amber
colour in the event that there is residual pressure or if there is a failure in the release
of the brakes.
The indication R («release») always appears in white colour.
There is residual pressure whenever, with the brakes released, some pressure is trapped
anywhere in the normal or alternate systems. On ground, when the pressure of at least
one wheel is above 15 bar with the pedals released, there is a «Master Caution» with
audible sound and visual indications in the page WHEEL of the ECAM. This caution is
inhibited in the ground when the speed is higher than 80 kt and during takeoff, climb,
cruise, descent and landing until the speed is below 80 kt.
The page WHEEL is automatically shown in the ECAM every time «landing gear down»
is selected, even when there is no caution or warning in the system.
1.6.2.5. Schematics of the alternate brake system
A brief and schematic description of the physical layout of the brake system of the A-
340 is presented here below, together with its situation when the alternate system is
working. For that purpose, the attached Figure 3, copied from a familiarization training
course of the manufacturer.
As it can be seen in the figure, the automatic selector allows the pressure of the alternate
or «blue» system is feeding the brake circuit. The brake distribution dual valve
(BDDV) or «dual valve» is a very important component of the system, and each of its
sides is activated by an auxiliary low pressure circuit that comes from the pedal of that
side. When the pedal is pressed, that low pressure activates the corresponding side of
the BDDV (as represented in the figure), in such a way that the blue pressure reaches the
«alternate servo valve». This servo valve opens or closes as controlled by the BSCU that
in turn receives information from the antiskid when it is active, as it happens in the condition
represented in the figure. In such a case, the pressure is regulated to keep an optimum
rate of braking with a certain amount of slip of the wheels determined by the
design of the system and the wheel do not lock even when the pedals are fully pressed.
However, if the switch A/SKID & N/W STRG that can be seen in the figure is moved to
the OFF position, the BSCU is disconnected and the servo valve is fully open, and therefore
any hydraulic pressure of the blue system called upon by the BDDV is transmitted all
along to the brakes. Under those conditions, the pilot must carefully watch the triple
indicator (also represented in the figure) to keep the pressure on each side or leg of the
MLG at 1000 psi as a maximum, because otherwise there is a risk to lock the wheels and
almost certainly burst them.
Technical report IN-062/2002
14
Figure 3. Schematics of the brake system. The alternate system is operating with the antiskid
system ON in the represented condition
When the alternate brake system is active, each pedal applies pressure to the auxiliary
low pressure system through a master cylinder that can be seen in figures 1.6.2.5.2 and,
in greater detail, 1.6.2.5.3. When there is no force F applied, the chambers C1 and C2
are communicated and full of hydraulic fluid because the valve is kept outside its seating
by the spring R2. When the pedal is pressed (force F) the sliding assembly is compressed
downwards against spring R2 and there is initially a dead travel. The hydraulic
fluid goes from chamber C1 to chamber C2 and comes out through port B. If the pedal
deflexion continues, when the dead travel ends, and the preformed packing moves with
the sliding assembly up to it is pressed against the valve, in such a way that the flow
between chambers C1 and C2 is cut, and pressure in chamber C1 starts raising. The sliding
assembly moves the valve and presses springs R1 y R2 and produces the reduction
of the volume of chamber C1 and the fluid flows out through port A towards the dual
valve (BDDV). The pressure in chamber C1 is proportional to the resistance opposed by
the hydraulic fluid in the external system connected to port A.
If the brake system is in normal mode (with green hydraulic pressure), the movement
of the pedals is electronically sent to the BSCU that processes the intention of the pilot
and the information of the antiskid system to command directly the normal servo valve
and to apply the corresponding pressure to the wheels. The dual valve does not work
in that condition.
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Technical report IN-062/2002
Figure 4. Drawing of the master cylinder. When the pedal is pressed, a force F is applied in the
upper part of the cylinder
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16
Figure 5. Detailed cutaway of the master cylinder
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Technical report IN-062/2002
According to the Component Maintenance Manual (CMM) «Master Cylinder C24592020»,
dated 31 July 1992, the total length of the cylinder must be between 170.050 mm and
170.100 mm, and the dead band must be between 0.4 mm and 0.5 mm (there was a
typo in the CMM, page 703, in which it is mentioned «dead travel 0,4 to 05»).
1.6.3. Abnormal and emergency procedures related to the
brake system
1.6.3.1. Abnormal procedures
The Operations Manual prepared by the operator in Spanish language, Paragraph 3-
02.32, dated 20-3-2001, mentions two abnormal procedures related to the circumstances
of the event:
«BRAKES A/SKID FAULT» AND «BRAKES A/SKID NWS OFF»: (English translation) The first
warning appears in the event of antiskid failure and the second when the switch A/SKID
& N/W STRG is in OFF. In both cases, the maximum brake pressure must be 1000 PSI, and
the brake pressure must be watched in the triple indicator. The effect of brake application
is much higher than in normal mode and therefore the pedals must be pressed smoothly
without exceeding the mentioned pressure. The landing distance increases by 1.4.
«BRAKES RESIDUAL BRAKING» (dated 30-4-2002): (English translation) If the warning
appears on ground, immediately after engine start or during taxi, make a reset of the
BSCU selecting the switch A/SKID & N/W STRG to OFF. If the warning does not disappear
a maintenance action is required. NOTE: to make the reset of the BSCU it is needed
that the aircraft is still and the parking brake applied. The indication «ON BRAKE 1
(2, 3, 4, 5, 6, 7, 8») appears for the information of the crew when there is brakes residual
pressure affecting one or two wheels.
In this latter case that brakes residual pressure appears in any of the wheels (amber bar
on those wheels) there is no instructions about what the crew must do. There is no clear
indication in the abnormal procedure whether the warning appears in flight, on
ground or in both cases (see 1.6.4.4. above with the description of this indication copied
from the Operations Manual, Chapter «Systems»).
For the understanding of the circumstances of the incident described in this report, it is
very important to distinguish between the CAUTION of «brakes residual pressure» and
the INDICATION of «residual pressure in wheel(s) number X, Y...».
— The caution consists of an audible gong, MASTER CAUTION light, and the text
«RESIDUAL BRAKING», and may only appear on ground. In flight the caution is inhibited,
even though there is actual residual pressure. When it appears on ground, the
Operations Manual of the operator requests that a reset of the BSCU be made and,
if the caution continues, to call Maintenance.
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18
— The INDICATION (vertical bars in amber colour in one or more wheels) may appear
on ground or in flight when the page WHEEL of the ECAM is displayed, which
always happens automatically when landing gear is selected down. When this indication
appears, the Operations Manual does not provide any procedure to be followed.
The Flight Crew Operating Manual (FCOM) prepared by the manufacturer of the aircraft
differs from that prepared by the operator about the actions to be taken in the event
a «RESIDUAL BRAKING» caution is displayed (always on the ground), because there is
no mention to make a reset of the BSCU, but simply to call Maintenance.
However, the SOP of Airbus does require making a reset of the BSCU in Chapter «Supplementary
Techniques» (3.04.32 P1) where they say: «In case of braking/steering difficulty,
the crew may perform a BSCU reset to recover correct functioning of the system.
In particular, this applies to the following ECAM Warnings: ... Brakes residual warning».
Also the «Technical Follow-up» issued to cover the appearance of residual pressure in
flight and the «Flight Operations Telex» on the same subject (see paragraph 1.6.3) mentioned
the possibility of making a reset of the BSCU.
The SOP of the manufacturer do not allow making a reset of the BSCU in flight with
the landing gear down.
The FCOM de Airbus did not provide, in the date of the incident, instructions about
what to do if INDICATION (amber bars) of residual pressure was noticed in some wheel
during flight.
1.6.3.2. Emergency procedures
The only emergency procedure related to the brake system included in the Operations
Manual of the operator (3.01.32, 1-10-2000) is the following:
«ÉRDIDA DE FRENADA»: (English translation) if brakes are not available, maximum
thrust reverse, release the brake pedals, disconnect the switch A/SKID & N/W STRG,
carefully press the brake pedals, limit the brake pressure to 1000 PSI, check the
BRAKES PRESS indicator, and maintain directional control with differential braking
as the nose wheel steering is not available. If still brakes are not available, the parking
brake must be used making short and continuous applications of the parking
brake to stop the aircraft. At the beginning of each parking brake application some
asymmetric braking could appear. When ever possible, the application of the parking
brake must be delayed until the speed has decreased, to reduce the risk of tire
burst and difficulties in directional control.
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Technical report IN-062/2002
1.6.3.3. Checklist in final
The Operations Manual prepared by the operator, Chapter 2.01.63, 15-10-2001, says that
«(English translation) The checklist of FINAL is read by the PNF, at request of the CM-1,
and is answered by the CM-1 and the CM-2 as applicable. Its completion guarantees
that the aircraft is safe for landing. The checklist of FINAL appears in the E/W D of the
ECAM below 1500 ft with the landing gear extended.»
«A/THR CHECKED SPEED OR OFF
LDG SIGNS ON
LDG GEAR DN
FLAPS LDG
SPLRS ARMED
Checklist of FINAL completed.»
1.6.4. Previous maintenance on the aircraft
The aircraft suffered a bird impact in the nose area on 28-7-2002, when it was approximately
at 7000 ft of altitude, and as a consequence repair maintenance was carried
out in which a technical team of the manufacturer provided on site support, and during
which the brake pedals were disassembled and then assembled again as a whole
assembly, in other words, the subcomponents of the pedal assemblies were not dismounted.
After the repair, the team of the manufacturer conducted a complete operational
test of the alternate brake system, according to AMM Task 32-43-00-710-801.
The results were OK.
At that time, a scheduled inspection A-2 was carried out when the aircraft had 957 h
of flight.
The day of the incident the aircraft made its first flight after those maintenance tasks.
1.6.5. Previous incidences in the brake system of aircraft EC-IDF
The following abnormalities related to the event were reported in June 2002:
Date Abnormality Corrective action taken
07-06-02 When the LG is lowered residual pressure
appears in left wheels 1, 2, 5 and 6 with
subsequent heating.
08-06-02 In descent with clean configuration the brakes
residual braking lights on brake 1, 2, 5
and 6, at parking 500 °C+ of temperature
reached.
Carried out System Test BSCU channels 1 and
2 Test OK. Carried out System Test BSCU
«Norm BRK» in channels 1 and 2 Test OK.
Test of BSCU channel 1 and 2 results correct.
Technical report IN-062/2002
20
According to the information gathered, those abnormalities were not reported to the
manufacturer. However, similar squawks were reported to Airbus in year 2001 due to
the residual pressure that appeared in aircraft EC-GUP.
Late in the investigation process, the operator stated that AMM Task 32-43-00-710-801
«Operational test alternate brake system» was carried out on 11 June 2002 (the day of
the last squawk). They said that, although the task was not specifically recorded on the
logbook, the technician recorded other actions like checking the free rotation of the
wheels that are a part of the task. This is the last action to be carried out after the application
of TSM task 32-40-00-810-927 (see below). Regarding this task, they also stated
that the «fault confirmation» (look at the triple indicator to see if there is pressure) was
also carried out on 11 June 2002 (see table above).
The manufacturer was indeed aware of other indications of residual pressure, and they
had issued the «Technical Follow-up» (TFU) 32.42.21.002 «Brakes residual braking
ECAM warning» in September 2000 in which it was mentioned that the warning used
to be due to a spurious indication, caused by the pressure transducers or by the monitoring
of the BSCU, although it was also stated that the residual pressure could also be
real. The TFU mentioned the possibility of resetting the BSCU using the switch of the
antiskid. The TFU also called for two troubleshooting procedures, which would detect
whether the pressure indication was real or spurious. Both tasks (32-40-00-810-839 and
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Technical report IN-062/2002
Date Abnormality Corrective action taken
09-06-02 In the landing the message residual Braking
appears in wheels of left leg (N° 1-2-5-6), it
disappears after a reset in the parking.
10-06-02 In approach residual pressure in left leg
brakes. Solved after several resets of Nose
Wheel Stering switch (there was indication
of pressure in the brake indicator) and pressing
the brakes at the same time. See previous
reports.
11-06-02 At landing appears in the ECAM «Residual
Brakes» in the left leg.
The servovalve connectors are cleaned and
the pressure transducer of wheels associated
(9GG1, 10GG1, 11GG1, 12GG1 and 5-
6-7-8GG1). It is inspected the status and
condition of dual valve (5403GG), Master
Cylinder (5422GG) and filter LP-B RSVR
(5011JM2) and no abnormalities found.
System Test and Normal BRK Test of both
BSCU OK.
Test of BSCU and reset of the brake system
carried out, results OK.
the residual pressures in left leg are checked,
OK. It is verified the accumulators Sys Blue
OK. Cleaned transmitters 3GK1 and 3GK2.
Sys Test to BSCU from MCDU carried out.
The message in ECAM disappears.
885) started with a built-in test of the BSCU, which was the corrective action taken by
the maintenance personnel in most of the reported cases, with results OK. According
to the tasks, the BITE test would act as a confirmation of the real nature of the residual
pressure.
This TFU was closed in August 2003, once the Service Bulletins A340-32-4187 and A-
340-32-4193 were issued by Airbus to solve the problem of spurious indication.
The manufacturer also issued the FOT 999.0030/002 «BSCU Reset subsequent to a
brakes residual braking» dated 19-04-2002 in which the spurious messages of residual
pressure were described and the need to make a reset of the BSCU was mentioned.
The different documents issued by Airbus before the incident were due to a history of
residual braking indications, that, as previously mentioned and among other aircraft,
affected to A-340 EC-GUP also operated by IBERIA. Within 1-11-2001 and 23-11-2001
there were several reports on that aircraft involving residual pressure indications, both
on ground and in flight. Those reports were reported to Airbus, which worked closely
with Iberia to try to solve the issue. A lot of communications took place at and after
those dates between Iberia and Airbus. Several troubleshooting procedures were proposed
and several components were replaced on EC-GUP until the problem finally disappeared.
The manufacturer stated that Iberia had never formally informed them of the results of
the recommended troubleshooting actions of EC-GUP.
Furthermore, the manufacturer added that TSM task 32-40-00-810-927, which is named
«Brakes alternate system has residual pressure in the left MLG», should have been
applied at since the beginning after the five reports in June 2002. They said that TSM
task requests the replacement of the master cylinder if the fault cannot be reproduced
on ground.
The entry points for this TSM task were analysed by the manufacturer after the incident
and they provided evidence that several of the clues present during the squawks in June,
like the «BRAKES RESIDUAL BRAKING» caution, the displayed amber bars, or the CMS
fault message «MASTER CYL L(5422GG)/DUAL VALVE (5403GG)» would have led to the
mentioned task 32-40-00-810-927.
This task consists of the following actions as applicable to the present incident:
« .../... (other text)
3. Fault confirmation.
Technical report IN-062/2002
22
A. Test.
(1) On the panel 117VU, put the parking brake to OFF.
(2) If the lower left indicator of the triple pressure indicator (2GK) shows a pressure,
depressurize:
— The Blue Hydraulic system
— The reservoir of the Blue Hydraulic system
— The Park Brake accumulators
4. Fault isolation
A. Procedure
(1) If the lower left indicator of the triple pressure indicator (2GK) shows a pressure:
replace the PRESS XDCR-BRAKE, BLUE L.../...(otro texto)
B. Procedure
(1) If the lower left indicator of the triple pressure indicator (2GK) does not show
a pressure: replace the MASTER CYLINDER-ALTN BRK L, CKPT (5422GG)
(2) If the fault continues: replace the DUAL VALVE-ALTN BRK.../...(other text).
(3) If the fault continues: replace the FILTER-LP, B RSVR.../...(other text)
C. Test
(1) Do an operational test of the alternate brake system (Ref. AMM Task 32-43-
00-710-801)»
The TSM introduction explained on pages 8 and 10 the meaning of «Fault confirmation
» in case of «ermanent fault» and «Intermittent fault».
In the first case, the «fault is confirmed on ground by performing the test required in
the fault confirmation paragraph. Consequently, the procedure must be applied to troubleshoot
the aircraft».
In the case of an «intermittent fault», specific instructions are provided as follows:
«The fault is not confirmed on ground by performing the test required in the fault
confirmation paragraph. Faults are sometimes generated by electrical transients or
similar events without the aircraft system being faulty. If the confirmation test result
is “TEST OK” or equivalent, no further action is required (unless specified in the fault
isolation procedure). The aircraft may be dispatched. It is recalled that the TSM has
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Technical report IN-062/2002
been designed to isolate/troubleshoot hard faults. However depending on the airlines
organization, the following can be applied “to trap” intermittent faults:
— if test OK (fault not confirmed) dispatch the aircraft, then perform a monitoring
of the reported symptom on the following flights by checking:
– the previous leg reports
– the PFR/Previous PFRs (if available)
– the log book of the previous flights
after 3 occurrences of the same phenomenon (even through the test still OK),
the other steps of the TSM procedure shall be followed and the LRU involved
be removed. (other text).
— if test NOT OK (fault confirmed), apply the trouble shooting procedure.»
The manufacturer was consulted regarding the practical way of carrying out the task
-927 in this case, and they answered that, because of that «intermittent failure concept
», the -927 procedure should have been applied completely, including the replacement
of the master cylinder on the 9th of June 2002 (after the third squawk). The maintenance
personnel of the operator had a different interpretation because they seemed
not to be applying the intermittent failure part of the TSM, and they said that if there
is no pressure in the triple indicator at the beginning, there is no «Fault confirmation»
and therefore the task ends. They added, late in the investigation process (see above),
that even though this fault confirmation failed because they checked the pressure in left
leg on 11 June 2002, they still applied the operational test 32-43-00-710-801 to be sure
that the system was OK.
1.7. Meteorological information
The METAR at Madrid-Barajas Airport on 7-9-2002 at 13:00 UTC was:
LEMD 071300Z 23011 KT 180V250 9999 FEW080 SCT150 27/07 Q1016 NOSIG
The information gathered shows that the temperature of the atmosphere in the province
of Madrid at 13000 ft of altitude approximately matched that of the International
Standard Atmosphere (ISA).
1.8. Aids to navigation
They do not affect the circumstances of this incident.
Technical report IN-062/2002
24
1.9. Communications
The communications worked normally all the time during the incident. The relevant
communications of the conversations with the control towers of Tenerife Norte and
Madrid-Barajas has been reproduced in other parts of this report.
1.10. Aerodrome information
1.10.1. Airport of Tenerife Norte
This airport has an asphalt runway, 12-30 of 3400 × 45 m. The runway stripe has
3520 × 300 m.
The aerodrome category for rescue and fire fighting is 8 (aircraft of less than 61 m of
total length and 7 m of maximum fuselage width).
1.10.2. Airport of Madrid-Barajas
The airport has three asphalt runways: 33-15 (4100 × 60 m), 36R-18L (3700 × 45 m)
and 36L-18R (4350 × 60 m). The runway stripe has a width of 300 m in all of them.
The aerodrome category for rescue and fire fighting is 9 (aircraft of less than 76 m of
total length and 7 m of maximum fuselage width).
The day of the incident runway 33 was being used for landings and runway 36L for
takeoffs. As a consequence of the incident, when runway 33 remained out of service,
runway 36R was open for landings.
1.11. Flight recorders
1.11.1. Cockpit voice recorder
The aircraft had a solid state cockpit voice recorder (SSCVR) Honeywell P/N 980-6022-
001; S/N 6393705700, that is able to record the latest 120 minutes of the voices and
sounds in the cockpit in four channels. Channel 1 records the sound of the headphones
and boom microphone in the pilot in command position; channel 2 records the
sound of the headphones and boom microphone of the copilot position; channel 3 the
sound of the headphones and boom microphone of the flight observer position; and
channel 4 the cockpit environment sounds through the area microphone.
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Technical report IN-062/2002
The recorder starts recording since the moment the first engine is started, and keeps
continuously recording the sound of the four channels until five minutes after the last
engine has been shut down. It can also operate in manual mode on ground.
The files corresponding to the 4 channels were downloaded and the sound could be
reproduced with a good quality and made it possible to identify the text of almost all
the conversations between the pilots and communications with the ATC.
Each channel had 2 h, 1 minute and 10 s of sound. Part of the flight from Tenerife Norte
to Madrid had been recorded, exactly 1:21:29 (81 minutes and 29 seconds) elapsed
before the aircraft stopped on runway 33 of Barajas, and then continued recording for
11 minutes and 54 seconds until the recording stopped because the engines were shut
down. Then, a new recording period started with duration of 28 min and 5 s in which
it could be heard the voices of maintenance personnel working inside the cockpit after
the incident.
Therefore, the moments previous and later the incident itself were recorded and the
pertinent information provided by the conversations and other sounds has been used in
several parts of this report.
1.11.2. Flight data recorder
The aircraft was equipped by a digital flight data recorder (DFDR) able to record the
latest 25 h of a total of 663 parameters of the aircraft. The reading of this DFDR was
carried out without problems in a laboratory with capacity for it and the relevant information
provided by the different parameters has been reproduced in several parts of
this report.
The DFDR also showed the following actions of the flight crew:
— During the cruise flight to Madrid the pages of ECAM were not deployed to check
the status of the different systems.
— The spoilers were not armed during the landing in Madrid.
1.12. Wreckage and impact information
The aircraft came to a stop besides the left side of runway 33, with its longitudinal axis
rotated around 10° with respect to the runway axis and with all its wheels on the
asphalt area.
Technical report IN-062/2002
26
The left MLG leg was beyond the runway edge lighting line, and remained approximately
at 5 m from the runway shoulder end, that is, at 40 m from the axis of runway 33,
that has 60 m of total width (distance between the white lines of runway edges), and
at 146 m from the axis of the taxiway J-1. The nose landing gear also remained at
approximately 5 m from the runway shoulder end and at approximately 120 m from
the axis of taxiway J-1.
Therefore, that left MLG leg remained at 313 from the intersection of the axes of runways
33-15 and 36R-18L.
When the runway could be inspected, it was noticed that starting in the point the aircraft
had stopped and coming back in the sense towards the threshold of runway 33
(i.e. going in the sense contrary to the movement of the aircraft during the landing roll),
tracks of the wheels of the left and right MLG legs could be clearly noted. The tracks
consisted of eight dark lines that corresponded to the sides of the tires showing that all
the wheels had burst. At 60 m form the point where it was stopped, the track of the
left leg crossed the runway edge lighting line (at 2 m from the next runway edge light),
and 60 m backwards it crossed the white line of the runway side stripe. During the previous
60 m it could be seen that the wheel rims number 1 and 5 (both outboard wheels
of the left leg) had dragged along the runway, although no appreciable grooves or
other damage to the runway surface was noticed.
At 240 m from the point it finally stopped (i.e., at 73 m from the intersection of runway
36R), the tracks of the right MLG leg disappeared at a point located 8.2 m to the
left of the runway axis.
The tracks of the left leg continued being visible going backwards, they crossed the
intersection of runway 36R and started softening and blurring being confused with the
tracks of other aircraft 630 m aft of the point where the aircraft stopped (i.e. at 900 m
from the threshold of runway 33).
The damage to the aircraft consisted of the burst of the eight wheels of the left and
right legs and damage to the brake assemblies number 1, 5 and 6 with the following
description:
Wheels 1, 2, 5 and 6 showed heavy rubbing with loss of material of the rim and tire
burst, due to friction with the runway.
Wheel 3 had friction in the rim and tire burst due to contact with the runway.
Wheel 4 had friction in the rim with loss of material and tire burst due to friction with
the runway.
Wheels 7 and 8 showed tire burst due to friction with the runway but the rims did not
have noticeable damage.
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Technical report IN-062/2002
Figure 6. Wheels 3, 4, 7 y 8 (right leg; seen from the rear right angle) after the aircraft stopped
on the runway. The white line is the runway side stripe marking of 33. Note the two narrow
tracks of every wheel after they burst
The brake assemblies 1, 5 y 6 showed heavy rubbing with loss of material in the fitting
and in the brake disks, due to friction with the runway.
When the aircraft was inspected in a hangar, there were no signs of fire having affected
the landing gear. The lower part of the wing and the inboard flaps did not show
any traces of smoke.
The maintenance personnel of the operator replaced the wheels of the aircraft on the
runway and then the aircraft was towed to a hangar.
1.13. Medical and pathological information
There were no personal damages during the event.
Technical report IN-062/2002
28
1.14. Fire
At Tenerife Norte Airport there was no fire, although there was smoke coming out the
wheels due to the high temperature reached by the brakes.
At Madrid-Barajas Airport, a lot of smoke was seen from the tower immediately after
the incident. Another aircraft said on the radio that EC-IDF had fire on the wheels. The
fire fighters were advised by the tower around 13:06 h, and at 13:09:45 h the crew
confirmed to the tower that they were around the aircraft. At 13:09:55 h, the tower
had already received confirmation from the fire fighting crew that the fire was extinguished.
According to their report, the fire fighters, which had been warned by the tower, reached
the area of the incident and found all the wheels in fire, and they positioned
around the aircraft and quickly extinguished the fire and then continued cooling the
gears. They used a total of 250 kg of chemical powder and 1750 l of foam, although
this later figure was higher than the amount normally needed due to the malfunction
of one of the extinguishing vehicles.
According to some information gathered later on, the flames were clearly visible from
the area of the south tower of the airport. However, when the aircraft was inspected
in a hangar, there were no rests of combustion in any part in the wheel area.
1.15. Survival
There were no accelerations of such a high magnitude as to produce impacts in the passenger
cabin. An emergency evacuation was not commanded, and the passengers left
the aircraft in a normal way using air stairs provided to the aircraft and were taken to
the airport with shuttle coaches.
1.16. Tests and research
1.16.1. Ground test to locate the problem
After the incident, the specialists of the manufacturer proposed to carry out a functional
check of the brake system of the aircraft following a test plan outlined in the «Technical
Disposition» of Airbus Ref. TD/B/2002/0341 (Issue 2), that basically consisted of
trying to reproduce the residual pressure in the alternate system through the use of the
pedals and the parking brake. If the residual pressure was not reproduced, then the flow
rate during the bleeding of the left and right low pressure lines (between the BDDV and
the master cylinders) should be measured to look for restriction points in the circuit. The
details of the contents of the Technical Disposition are included in Appendix B. This pro-
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Technical report IN-062/2002
cedure was not a part of the previous maintenance documentation of the aircraft. It
was specifically prepared for the occasion after several weeks of work of the specialists
of the manufacturer.
The test was carried out and it was found that the failure produced during the incident
could not be reproduced, but the flow rate measurement showed that there was no
flow in the left low pressure circuit while the flow in the right circuit was 50 cl in 20 s.
This meant that there was no way for the return flow from chamber C1 to chamber C2
through the left master cylinder (see Figure 4), that is, that there was no “dead band”
and the pressure was trapped inside chamber C1 even when the pedal was not pressed
at all.
This could be due to one of the two following factors:
a) The master cylinder was defective, with a length longer than the 170 mm specified,
in such a way that is should be compressed when assembled in the aircraft, producing
the closure of the valve.
b) The rigging of the left pedal was defective, in such a way that the cylinder, even
having the correct length, had still to be compressed during assembly, again producing
the already mentioned closure of the valve.
The master cylinder P/N C 24592020 (Functional Item Number 5422GG), S/N H2121 was
replaced by other master cylinder off the shelf and the flow rate test was done again,
and this time a flow of 50 cl in 25 s was obtained. With this result, the specialists of
the manufacturer confirmed that the master cylinder was defective and was the component
producing the residual pressure. Pedal rigging pins were installed to confirm
correct rigging of the pedals.
The master cylinder was sent to its vendor-manufacturer, Messier-Bugatti, for a detailed
inspection and teardown.
1.16.2. Release to service of the aircraft
After the replacement of the master cylinder mentioned in the previous paragraph, the
specialists of the aircraft manufacturer issued the Trouble Shooting Report N°
3048/SEE32/TSR/1002 that confirmed that «the original master cylinder was faulty and
was the sole cause of the residual braking behaviour. Also, it is confirmed that the pedal
rigging is satisfactory». Although not specifically required by the manufacturer specialists,
the operator carried out a flight test and it was noticed that after some time most
of the pressure of the alternate brake system was lost, while the normal system functioned
correctly.
Technical report IN-062/2002
30
Then the BDDV P/N 5403GG S/N H2718 was replaced and the brake system carefully
purged. A new flight test showed that both brake systems functioned correctly and the
aircraft was returned to service.
The replaced dual valve was also sent to Messier-Bugatti for additional inspection.
1.16.3. Inspection of the master cylinder S/N H2121
The master cylinder disassembled from aircraft EC-IDF after the incident was subject to
several tests at the facilities of its manufacturer in Molsheim (France). The cylinder had
been sent in a sealed package and it was intended to retain as much hydraulic fluid inside
as possible.
The tests carried out were the following:
— Dimensional measurement: The length was 170.31 mm (the nominal value is between
170.050 and 170.100 mm). The «dead travel» was 0.58 mm (the nominal
value was between 0.4 y 0.5 mm). The total travel was 21.68 mm (the specified
value is 20.5 to 22.3 mm).
— Hydraulic fluid: the master cylinder was empty. It was not possible to recover hydraulic
fluid for its analysis.
— Operational test: The graph load vs. travel was prepared according to the Component
Maintenance Manual (CMM). It was observed that the results were outside
tolerances in a series of points both in load (compression) and extension of the cylinder.
For instance: with 10 mm of travel in load the force should be between 139
Nw and 153 Nw; the measured value was 162 Nw (7% above the specified limit).
— It was made a flow rate test under pressure. For that purpose, with the port B open,
a pressure of 2.4 bar was applied to port A and the flow vs. travel of the cylinder
was measured. In compression there was a flow of 2.17 l/min when there was no
travel and the value of the flow was being lower. With 0.33 mm the flow was 0.01
l/min and with 0.34 mm there was no flow anymore. In unload of the cylinder there
was no flow with 2 mm of travel, and the travel was reduced up to the moment
that with 0.36 mm the flow started being 0.01 l/min.
— The cylinder was disassembled and no noticeable defects were found. The different
subcomponents were dimensionally checked and all of them were found inside tolerances
except the «small» spring or spring valve (spring R1) that reached the nominal
length with a load of 4 Nw instead of the 5 Nw of the specification. The specialists
in the system considered this difference was not significant. The preformed
packing of the valve was deformed because of the contact with the valve, and had
no longer the squared section with which it was manufactured.
The cylinder was assembled again and it was adjusted in such a way that the length
and the dead travel were the same as previously, and the operational and flow rate tests
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Technical report IN-062/2002
were carried out again. The master cylinder was now inside specified limits during compression,
but it was still slightly outside tolerances during the extension. A possible
explanation for this behaviour was that some minute particles that were producing a lot
of friction inside the cylinder could have been eliminated during the disassembly and reassembly.
After this test the length was measured again and it had increased up to
170.35 mm. The dead travel had decreased from the previous 0.58 mm to 0.48 mm,
and no clear explanation was obtained for this fact. The flow rate test provided the
same results as previously.
Messier-Bugatti informed that those cylinders are manufactured by a subcontractor. The
S/N H2121 passed its quality control after manufacture on 13-6-2000, and it was then
recorded a dead travel of 0.44 mm (inside limits) and a total travel of 21.90 mm (inside
limits), with the diagram load-travel inside tolerances. However, the length of the
cylinder was not recorded during quality control acceptance tests at that time. Messier-
Bugatti informed that «The unit is adjusted during assembly».
The acceptance test did not include a flow rate test under pressure.
Information gathered from technicians of the manufacturer indicated that they had
never seen a cylinder with a length above specifications.
The master cylinder was reserved for further investigation at the facilities of Airbus in
Filton (United Kingdom). See paragraph 1.16.5.
It was requested to Messier-Bugatti to provide an analysis of all the information
retrieved during the tests in order to establish a hypothesis of the circumstances or
the subcomponent of the master cylinder that made its length to be outside tolerances
and that ultimately produced residual pressure in the alternate system of the
A-340 EC-IDF.
Messier-Bugatti never provided a detailed analysis, but answered through an E-mail on
12-9-2003 that no subcomponent of the cylinder had been identified as defective, and
that in December 2002 they had modified their procedures to include a systematic measurement
of the length of every cylinder after manufacture. They also added that
«remains a doubt as to the possible implication of other parts such as brake pedal
assembly».
1.16.4. Inspection of the dual valve (BDDV) S/N H2718
The dual valve was disassembled from EC-IDF following a flight test carried out after
the incident. It was subject to several tests at the facilities of its manufacturer Messier-
Bugatti in Molsheim (France). The valve had been sent in a sealed package and it was
Technical report IN-062/2002
32
intended to keep inside as much hydraulic fluid as possible. However, the package was
opened at Messier-Bugatti and only 1 ml of liquid could be collected.
The recovered fluid was observed in the microscope by specialists of the manufacturer
of the component, who indicated that it contained some metal particles between 15
and 80 microns. There was not enough liquid to carry out a more complete analysis.
A functional test was performed in accordance with CMM 32-43-16, which includes a
«roces Velbal d’Essai» (test plan). All the results of this analysis were found inside tolerances.
Messier-Bugatti stated that the valve was in normal operating conditions and
was released as far as the investigation was concerned.
1.16.5. Additional testing of the master cylinder S/N H2121
The cylinder was sent to the facilities of Airbus in Filton (United Kingdom) to be put into
a test bed to simulate the actual conditions of a flight of aircraft EC-IDF. The temperature
changes that appear in climb, cruise and descent were considered as a main factor
leading to the build-up of residual pressure in the alternate brake system.
Airbus carried out additional testing, but, even though the test conditions were more
stringent, it was no longer possible to reproduce the residual pressure. However, because
the cylinder had already been disassembled (see 1.16.3), the feasibility of those results
was doubtful and had anyway to be analysed. It was concluded that, after disassembly,
the master cylinder was no longer «the same» as during the incident. Therefore, no conclusion
could be drawn from the additional testing.
1.16.6. Inspection of the pedal cover
Time after the investigations on the master cylinder took place, the pedal cover that was
installed on EC-IDF upon delivery was pointed out as a possible cause of residual pressure.
Therefore, an inspection for scratches and marks was carried out on that cover
several months after the incident. The main function of that cover was to avoid that
some foreign objects as pocked calculators or pens could fall to the brake assemblies.
The results of the inspection were:
1. There was no chaffing or scratching present on the MSN474 pedal assemblies covers.
2. All clearances between the pedal assemblies and their covers were sufficient to
allow normal operation.
3. The operation of the pedal assemblies during braking inputs was normal.
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Technical report IN-062/2002
4. The marks seen on the master cylinders of EC-IDF did not indicate any abnormality.
1.17. Organizational and management information
1.17.1. Technical flight records of the aircraft
On board the aircraft there should always be a block of forms of the aircraft flight logbook.
Each form triplicates in 3 pages, from which the last (page 3/3, yellow colour)
must always remain attached to the block. In the right upper area of the form there is
a square titled «Capt. Acceptance» with a space for the signature of the pilot in command
of the aircraft. There is a column called «Complaints» («Anormalidades») to be
filled up by the crew, other called «Maintenance Actions» («Correcciones») to be filled
by the maintenance personnel and other column of signatures of the maintenance personnel
that have handled the complaints reported by the crew. The result of that handling
may be «Fixed», «Under observation» or «Deferred».
The Basic Operations Manual prepared by the operator (revised on 26-5-2002), in
paragraph 8.1.11, gives instructions to the flight crews to fill in the flight logbook
forms, that basically are «All the required data in the form must be carefully completed
». It is also stated that: «In the spaces reserved for the signature it is necessary no
only sign, but to provide the identification number. The captain will sign the square of
aircraft acceptance of the form corresponding to the flight that is going to be carried
out. In this way, he will record the acknowledgment of the corresponding inspections,
as reflected on page 3/3 of the previous flight logbook, and of the abnormalities and
maintenance actions that are also written in this page 3/3 of the previous flight. This
signature of the captain will also serve as confirmation of the complaints and data
recorded during his flight. In the event there are no complaints, the word “NIL” will
be written».
The «Manual de Procedimientos de Mantenimiento en red» («Maintenance Procedures
Manual») of the operator (Section 2, Revision 7 of 18-6-02) also provides guidance for
the handling and completion of the flight logbook pages. It is mentioned that the maintenance
action after the reported complaints must always be done in accordance with
the established documentation and, in the event that maintenance action or repair is
not included in the documentation, the corresponding instructions will be consulted to
the corresponding Engineering Support Department, and this circumstance will be reported
in the flight logbook.
The MOE-145 («Maintenance Organization Exposition») and the “Manual de Procedimientos
de Mantenimiento en red” (Section 2, Revision 7) contain instructions for the
treatment of the flight logbooks by the line maintenance personnel and the transit inspections
of the aircraft. It is stated that in the event the ground personnel find an
Technical report IN-062/2002
34
abnormality during their line inspection, even though it was not reported by the crew,
they must record it in the column of «Maintenance Actions» of the logbook. In the description
of the maintenance action reference to the corresponding part of the Maintenance
Manual must be done.
In summary, the crew must review the logbook of the previous flight and the captain
must sing the aircraft’s acceptance in the logbook page of the actual flight
been prepared, and this will show that he is aware of the disposition of the previous
complaints. The signature will also validate the new complaints noted during
his flight, whose maintenance actions will be accepted by the captain of the next
flight, and so on.
1.18. Additional information
1.18.1. Telex to the operators issued by Airbus Industrie
On 31-10-2002 Airbus issued an «Operators Information Telex» in which the operators
were informed of aircraft A319, A320, A321, A300, A300-600, A310, A330 and A340
of the circumstances of the event happened on 7-9-2002, and of the actions to be
carried out by the crews in the event they noticed residual pressure in flight. The Telex
said that in this case:
«AS USUAL, THE NORMAL BRAKING AND ANTISKID SYSTEMS HAVE TO BE USED,
AND THIS EXPLAINS WHY THERE IS NO ECAM/FCOM PROCEDURE EXCEPT [for
A300-600 and A-310]. IN ADDITION, USING THE AUTOBRAKE (AS RECOMMENDED
IN THE SOP) PREVENTS ASYMMETRICAL BRAKING DUE TO RESIDUAL BRAKING
PRESSURE IN THE ALTERNATE BRAKING SYSTEM, SINCE ALTERNATE PRESSURE IS
NOT SUPPLIED TO THE BRAKES WHEN NORMAL BRAKING IS ACTIVE.
HOWEVER, IN THE LIGHT OF THE REPORTED EVENT, AIRBUS WILL PUBLISH SOME
RECOMMENDATIONS FOR ALL AIRCRAFT, IN THE FCOM STANDARD OPERATING
PROCEDURES’ “APPROACH PHASE”, TO AVOID SWITCHING OFF THE ANTISKID
AND NOSEWHEEL STEERING FUNCTION, AND POSSIBLY TO ELIMINATE ALTERNATE
RESIDUAL BRAKING PRESSURE.
A330/A340 RECOMMENDATIONS DIFFER SLIGHTLY FROM THOSE OF THE OTHER
AIRCRAFT TYPES, SINCE RESIDUAL BRAKING (FROM THE NORMAL OR ALTERNATE
BRAKING SYSTEM) IS DISPLAYED ON THEIR ECAM WHEEL PAGE. ON OTHER AIRCRAFT
TYPES, ONLY RESIDUAL BRAKING ON THE ALTERNATE SYSTEM IS VISIBLE,
AND IS DISPLAYED ON THE TRIPLE INDICATOR.
FOR A330/A340 AIRCRAFT (NOT APPLICABLE TO A340-500/600):
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Technical report IN-062/2002
WHEN THE LANDING GEAR IS DOWN:
– ECAM WHEEL PAGE CHECK
– THE ECAM WHEEL PAGE APPEARS BELOW 800 FEET, OR AT LANDING GEAR
EXTENSION.
– CHECK FOR THREE (A330), OR FOUR (A340) LANDING GEAR GREEN INDICATIONS.
– IF RESIDUAL PRESSURE IS INDICATED, PRESS THE BRAKE PEDALS SEVERAL TIMES.
SELECT “AUTO BRK MED”. IF RESIDUAL PRESSURE REMAINS:
– BEWARE OF POSSIBLE BRAKING ASYMMETRY AFTER TOUCHDOWN, WHICH
CAN BE CONTROLLED USING PEDALS.
– DO NOT SWITCH OFF THE A/SKID & NWS: THE ANTISKID FUNCTION LIMITS
THE EFFECT OF RESIDUAL BRAKING, AND PREVENTS TIREBURST.»
Additionally, Airbus modified the «Standard Operating Procedures», paragraph 3.03.19
of the «Flight Crew Operating Manual» (FCOM) to include the relevant information of
the telex.
Before the incident, those recommendations were not included in any Airbus document.
1.18.2. History of similar cases
The manufacturer of the aircraft informed that they were aware of several cases of brake
residual pressure in flight, and that it was known that most of those indications were
spurious (see paragraph 1.6.3 with mention to the TFU issued to cover the matter). No
failure of the brake system detected in flight had produced an incident that ended in
tire burst during landing.
The operator informed (see 1.6.3) that in year 2001 there was a long period during
which aircraft EC-GUP was affected by residual pressure, and they worked with Airbus
to solve the problem.
1.18.3. Other safety actions carried out by the manufacture of the aircraft
In addition to the telex mentioned in 1.18.1, the manufacturer started a revision of their
procedures of testing the brake system at the end of the assembly line and modified
parts of the maintenance manual associated to the master cylinder.
Technical report IN-062/2002
36
They also started the study of a modification to the design of the master cylinder to
avoid that environmental factors could produce the appearance of residual pressure in
the brake system.
1.19. Useful or effective investigation techniques
None.
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Technical report IN-062/2002
2. ANALYSIS
2.1. Operation during the Madrid-Tenerife flight
When the landing gear was lowered during the descent to Tenerife the crew observed
in the WHEEL page of the ECAM that the 24 bars that represent the brakes of the wheels
of the left MLG were lit in amber colour, indicating that there was pressure trapped.
Under those conditions, they did not check the triple indicator located in the central
panel of the cockpit, which would have allow them to note that the pressure was in
the left alternate system, not in the normal system.
Anyway, although the information recovered suggest that the crew did not recognize
the origin and possible effects of the problem and they thought there was a «spurious
indication», they made the right decision of landing with the antiskid connected, which
was correct, and without autobrake, as they were used to do in occasions at the discretion
of the captain.
However, they decided to retard the application of brakes to prevent possible braking
problems in the event there really was a malfunction of the systems, instead of an indication
failure as they suspected. The result of this decision was that during the time the
brake pedals were not pressed, the alternate system was still active and, therefore, the
900 PSI of residual pressure that were present were transmitted to the left wheels, and
the aircraft started deviating towards that side. At the moment of touchdown there
were several pressure releases in the left brakes commanded by the antiskid system
intermittently, and the wheels did not burst.
The copilot, that was the PF during the landing, applied right rudder as coherent with
his intention to delay the brake application, until the deviation was very important, and
the aircraft approached up to 8 m to the left edge of runway 12 and a decrease in the
effectiveness of the rudder was noted as the speed was reducing. At those moments,
he applied heavily right brake and also left pedal, until the aircraft deviated to the right
of the runway axis and came to a stop. The right pedal application started when the
aircraft had between 60 kt and 70 kt of ground speed, and reached its maximum value
when the speed was 50 kt.
At the moment of pedal application, the green or normal system was activated and the
residual pressure of the alternate system fell to 0 psi. However, when the speed was
below 80 kt the pedals had not yet been pressed and there was still a pressure of 900
psi and, when the inhibition of the caution of «brakes residual braking» ended, this caution
was displayed in the ECAM (see paragraph 1.6.4.4).
The result of those circumstances was that the crew was surprised by the behaviour of
the aircraft, and they thought there had been a malfunction in the brake system that
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Technical report IN-062/2002
remained during the landing roll, and that the brakes heated until the corresponding
ECAM warning was displayed. However, the presence of the antiskid allowed an effective
braking action and avoided the burst of the tires.
Once they had vacated the runway, the crew reset the BSCU. If at those moments they
had checked the triple indicator or the ECAM wheel page, they would have noted that
the residual pressure had disappeared, and therefore that action, required by the Operations
Manual of the operator if the caution appears on ground, was not needed. The
procedures of the manufacturer indicate in one chapter that maintenance action is
required if the caution is noticed at engine start or during taxi, and in other chapter
(«Supplementary techniques» 3.04.32 P1) that the crew may reset the BSCU. That
applies when the aircraft is on ground.
2.2. Maintenance actions in Tenerife Norte
When the aircraft was parked in the apron, the crew commented with the maintenance
personnel the circumstances they had faced during the landing. At those moments,
the immediate problem they had was a high brake temperature, which was cooled with
fans.
From the information gathered it could be concluded that the ground maintenance personnel
was fully aware of the problem of residual pressure that had to be handled
during the previous descent and landing. They actually saw the «ost-Flight Report» provided
by the aircraft that had recorded that the caution «Brakes Residual Braking» had
appeared at 9:12 h in the phase «Cruise 06». This caution was not displayed to the
crew at those moments, because it is inhibited. During the landing roll, below 80 kt,
the warning was displayed at around 9:22 h when the inhibition ended.
However, the flight crew had not recorded any complaint or squawk in the flight logbook,
neither the residual pressure appearance, nor the deviation during the landing
roll, nor the high brake temperature.
The ground personnel took action to determine the origin of residual pressure, but did
not write anything in the logbook. The maintenance procedures indicate that if the
ground personnel detect any malfunction, they must write it down even when not previously
reported by the flight crew.
Afterwards, the data gathered suggest that while the line maintenance personnel was
trying to contact another department of the operator to seek support information to
treat the problem of residual pressure, the boarding of the passengers started for the
flight back to Madrid. This fact probably produced additional stress regarding the
need to dispatch the aircraft as soon as possible. Anyway, given the facts that the
residual pressure had disappeared and that the support personnel in Barajas could not
Technical report IN-062/2002
40
be contacted, the «transit check performed» box of the logbook was completed and,
since there was not any complaint recorded in the logbook, theoretically there was
also nothing to correct, and the doors were closed and the pilot in command decided
to initiate the flight, with the understanding, according to his statement, that the aircraft
was released to service. After the boarding, contact with maintenance people in
Madrid was finally achieved, and the situation was commented but no further maintenance
action was carried out. The maintenance personnel gave additional instructions
to the crew, which in turn had decided that if during taxi any malfunction of the
brake systems was noted, they would return to the parking area for additional maintenance
action.
The captain did not complete the box «Captain Acceptance» («aircraft acceptance by
the captain») of the next page of the logbook that pertained to the flight of the incident.
It is considered that it is possible that some doubts or misunderstandings existed regarding
who had ultimate responsibility over the aircraft at every moment, but it would
have been necessary to make additional efforts to understand with detail the causes and
possible effects of the residual pressure in the brake system. The BSCU test was initiated
but not completed. Therefore, the intended maintenance actions were not finished.
In this case, the facts that the aircraft veered to the left and very high temperatures
were achieved, including smoke coming out from the wheels, should have been sufficient
to remove any doubt about the spurious nature of the fault. It should have been
clear that the residual pressure had been real during the landing and therefore more
troubleshooting was needed.
When the aircraft started taxiing again, the «RESIDUAL BRAKING» caution had disappeared
and the crew did not report problems with the controllability of the aircraft
during the taxi towards the runway and takeoff.
2.3. Operation during the flight Tenerife Norte-Madrid-Barajas
After the doors were closed and the taxi started, the crew came to the conclusion that
the brake system was functioning normally, and proceeded with the takeoff. The landing
gear was left down for some time to cool the brakes that still had a slightly high
temperature. During the return flight to Madrid, the crew had at least two hours to
study the actions to be taken in the event the residual pressure reproduced during the
descent.
The DFDR data show that the pages of the ECAM were not displayed to check the status
of several systems, as required by the Operations Manual (2.01.52, 15-09-200,
«Watch the evolution of the parameters of the engine and aircraft systems though the
ECAM, regularly calling the different pages...»).
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Technical report IN-062/2002
During the descent to Madrid, the residual pressure in the left side of the alternate
system had started to increase progressively when the aircraft was at 13000 ft.
At 12:58:02 h, the page WHEEL of the ECAM was deployed and the crew detected that
pressure, because they saw in amber colour the 24 bars representing the left brakes.
The reaction of the crew was to reset the BSCU, moving to OFF and then to ON the
switch ANTI SKD & N/W STRG, but the amber bars did not disappear.
Faced with this situation, the crew expressed their concern, because the preceding landing
in Tenerife, where the deviation had been considered to be caused by the malfunction
of some component of the brake system during the landing roll.
The residual pressure continued increasing and 500 psi were reached at the moment in
which the landing gear was lowered, at 12:58:38 h when the aircraft was approximately
at 4000 ft. At that moment, the page WHEEL of the ECAM was automatically
deployed and the aircraft carried out several auto checks of the hydraulic system, and
the normal brake system was momentarily connected and the residual pressure of the
left side released until the checks finished and returned to its previous value.
They carried out another reset «cycle» of the BSCU, for 24 s. This action, carried out
once the landing gear was down, was contrary to the operational procedures of the aircraft,
and was unable to make disappear the amber bars, although they probably disappeared
momentarily while the BSCU switched off and then on.
Should the crew checked and interpreted correctly the triple indicator, they would have
noticed that the residual pressure was in the alternate brake system, which is not controlled
by the BSCU. This could have help conclude that the resets of the BSCU would
not be effective in the build up of residual pressure.
Under those conditions, there was a conversation in the cockpit in which it was said that
one possibility would be to disconnect the antiskid, with the intention, according to the
later statements of the crew, of avoiding that electronic systems not controlled by the pilots
applied or released braking pressure in the uncertain conditions in which the whole system
seemed to be. Finally they disconnected again the switch A/SKID & N/W STRG that was
maintained in that condition for the remainder of the approach and landing. Thus, the possibility
of activating the normal brake system (that had no residual pressure and that would
have been activated at the moment of pressing the brake pedals) was precluded.
The autobrake system was not armed, and anyway it would not have functioned because
the antiskid was disconnected.
The aircraft continued its approach and the crew commented the possible behaviour of
the system during the landing. The conversations indicated that there were certain
Technical report IN-062/2002
42
doubts about the functioning of the brakes in the status they were. The copilot read
the corresponding part of the Operations Manual, reminding clearly that the pressure
should be checked in the brake indicator and that it should not be above 1000 psi any
time, because otherwise the wheels would burst.
Almost simultaneously to the moment the tower authorized the landing in runway 33,
with wind 210° and 10 kt, the crew decided to land close to the threshold of the runway
and use reverse without touching the brakes. At those moments, the «Glide slope
» warning of the GPWS sounded, with the aircraft at 600 ft of radio-altitude. The
PF said that this warning should be disregarded because, according to a later statement,
he wanted to carry out a somewhat low approach to touchdown as soon as
possible.
On the other hand, with the time employed in the revision of the brake system in the
manuals and deciding what to do regarding the residual pressure, it is very probable
that the checklist of final was not read and completed (paragraph 2.01.63 of the Operations
Manual of the operator). One of the consequences of this fact was that the spoilers
were not armed during landing.
There were no special instructions given to the passengers and the tower was not advised
that some abnormality with the brake system could appear, to allow the fire fighters
to take positions with time in advance. As it happened in Tenerife-Norte, at least a
high brake temperature could be expected that even produced smoke at that airport.
Those facts must be regarded as being a part of a situation with high workload and
some uncertainty inside the cockpit. The workload would have been produced by the
mental evaluation of the different malfunction scenarios of the brakes and the corresponding
corrective actions, and the use of the manual, which eventually absorbed most
of the attention of the crew at those final moments of the approach. Even though there
was available time during the cruise flight, the crew was exposed to face the problem,
look up for information and make decisions in the moments previous to the landing,
after having lowered the landing gear.
The aircraft floated for 3 s in the flare until the right and left MLG legs touched down
about 240 m after the threshold of runway 33, at 13:03:27 h. Since the antiskid was
inactive, there was no momentarily release of pressure as it happened during touchdown
in Tenerife. Therefore, when they contacted the runway, the left wheels where
locked and it is probable that they burst soon afterwards.
Approximately 7 s later, the copilot asked whether the aircraft had a tendency to deviate.
The captain and PF answered: «For the moment no», and added two seconds later:
«Yes, it deviates, yes» and then «It departs a little bit». Seven seconds later the captain
told the copilot to apply pedal and then to brake with the right brake. The copilot answered
he was already braking.
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Technical report IN-062/2002
At 13:03:45 h the right pedal was fully pressed, making the pressure of the alternate
system of that side to increase up to 2500 psi, and the pressure of the left side to
decrease down to 600 psi from the initial 800 psi of trapped pressure built-up during
the flight.
The left pedal was not pressed any time and the aircraft finally came to a stop with all
the wheels burst.
According to some braking marks noted in runway 33 after the incident, the first point
where tracks of the bust left wheels are clearly noticed is 630 m rearwards the point of
final stop of the aircraft (i.e. approximately 900 m away from the threshold of runway
33). This would indicate that initially the aircraft touched down (at 240 m from the
threshold) and the residual pressure of 800 psi that was amassed in flight started actuating
in the left side. To avoid the deviation the PF applied more and more right rudder,
in a scenario similar to that faced in Tenerife, although now the pressure was 800 psi
instead of 900 psi in Tenerife. At a given moment, the left wheels burst because they
had touched down already locked, and from that point in which the aircraft had approximately
100 kt of speed, the directional control was much lesser because of the combination
of decrease of effectiveness of the rudder with the burst of the tires, that
initially decreased the braking force on that side.
The aircraft deviated in that area to the right of the runway axis to move then clearly
to the left starting approximately at 100 m before the intersection with runway 36R.
This fact could be due to the continuous decrease of the effect of the rudder and the
loss of part of the left tires and dragging of the rims and brakes assembly along the
runway surface.
The PF decided to apply right brake and 40 m after crossing runway 36R the right
pedal started to be pressed until it reached its stop when the aircraft was 73 m
beyond the intersection of both runways. In this point, tracks of the right wheels were
first noticed in the runway. These tracks showed a heavy braking action until the right
tires burst because a high pressure up to 2500 psi was applied. That braking action in
the right side prevented the nose of the aircraft moving further to the left of the runway
axis and from that point on the aircraft had a straight trajectory towards the runway
left edge.
The left wheels crossed the runway side stripe marking in a point located 120 m before
the final position of the aircraft, while the right wheel came to a stop just above that
marking (see the white line of Figure 6).
Finally, the braking action (although reduced because of the burst of all the wheels) and
that of the thrust reverses that were deployed after touchdown, allowed the aircraft to
be stopped inside the asphalted zone, although with the left wheels beyond the runway
edge lighting line.
Technical report IN-062/2002
44
2.4. Actions after the aircraft came to a stop
The information gathered indicate that although the fire fighters were not previously
warned, at 13:09:55 h, that is, after 3 min and 55 s the tower activated the alarm, they
had extinguished the fire of the wheels and had the situation under control. It took
some time to the flight crew to receive information from outside the cockpit regarding
the status of the aircraft.
The aircraft stopped at 13:05 h and at 13:05:41 h another aircraft informed by radio
that the wheels were on fire.
Initially, the flight crew were evaluating the need to shut down the engines, advise the
cabin crew to be prepared or to order an evacuation. In the mean time, they called their
company to request assistance. They were seeing fire fighters around the aircraft, but
did not have clues of fire or smoke. At 13:08:24 h they addressed the passengers and
the cabin crew members to advise them to remain seated without using the mobile telephones.
Therefore, there was a period of 3 min and 24 s since the aircraft was stopped until the
passengers were addressed. During that period, the crew had some workload to communicate
with the tower, to check the status of the systems of the aircraft, to evaluate
the available information that was incomplete at the first moments, and to think of
the options to be followed before informing the passengers.
The data retrieved in the investigation show that the air traffic control and airport services
worked correctly in a coordinated manner all the time. The local air traffic controller
(tower) that was controlling the traffic in runway 33 for landings kept the situation
under control all the time. Runway 36R was immediately inspected and was open
for traffic at 13:16 h (approximately 11 min after the aircraft came to a stop after the
incident).
2.5. Origin of the residual pressure
The tests carried out on the aircraft and at the facilities of Messier-Bugatti led to the
conclusion that the origin of the residual pressure in the left alternate brake system of
the aircraft EC-IDF was the master cylinder P/N C24592020, S/N H2121 that, once disassembled
from the aircraft, had a length of 170.31 mm (the nominal value was between
170.050 mm and 170.100 mm) and a dead travel of 0.58 mm (the nominal value
was between 0.40 mm and 0.50 mm).
With those dimensions, the cylinder had to be compressed at the moment of assembly
on the aircraft, in a way that made the dead travel to be 0.37 mm, which is 0.03 mm
below the lowest tolerance of the specified value.
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Technical report IN-062/2002
In those conditions, the alternate system could work in a normal way during a lot of
flights or during a lot of phases of those flights, with the only difference that the aircraft
would start braking with an angle of pedal deflexion slightly below the nominal
value. However, due to the thermal expansion of the hydraulic fluid during the descent
from cruise, under certain conditions, it is probable that the dead travel was plugged,
thus preventing the return of hydraulic fluid from chamber C1 to chamber C2 of the
cylinder, and eventually building up the residual pressure.
The master cylinder had passed its quality control after manufacture on 13-6-2000, and
the dead travel was then measured to be 0.44 mm and the total travel 21.90 mm, with
the load-travel diagram inside tolerances. The total length of the cylinder was not required
to be recorded during the acceptance tests at that time. Therefore, it could not be
documented whether the cylinder was already outside specifications after manufacture
or whether the length of the part was unsettled later on, although it seems more probable
the first possibility.
The defective internal subcomponent of the cylinder that was producing the difference
in actual length with respect to the nominal length, or the part of the cylinder that was
ultimately responsible for the build-up of residual pressure could not be determined. No
detailed analysis of the behaviour of the component was received from Messier-Bugatti.
On the other hand, although Airbus carries out flight test after manufacture of their aircraft
with duration of about three and a half hours, from which there are two hours at
cruise altitude, and also the operator carries out acceptance flight tests, those flights did
not detect any residual pressure. Since the flights did not include long periods of cruise
at high altitude, it is probable that they did not produce thermal changes important
enough during descent. However, the flight Tenerife-Madrid had a profile somewhat
comparable to that of the flight tests (regarding time at cruise altitude) and there was
indeed residual pressure.
2.6. Previous history of residual pressure
The aircraft was delivered by the manufacturer to the operator in May 2002. Until the
date of the incident it had completed 131 flight cycles.
Since 7 to 11 of June 2002 there were five abnormalities reported regarding presence
of residual pressure in flight in the wheels of the left leg. In the two first cases, there
was an important increase of temperature of the brakes during the landing roll.
One of the squawks indicated «In descent with clean configuration the brakes residual
braking lights on brake 1, 2, 5 and 6, at parking 500 °C + of temperature reached».
Another report said: «In approach residual pressure in left leg brakes. Solved after seve-
Technical report IN-062/2002
46
ral resets of nose wheel steering switch (there was indication of pressure in the brake
indicator) and pressing the brakes at the same time. See previous reports».
Additionally, in year 2001 there was a long history of residual pressure that affected A-
340 EC-GUP of Iberia. The problem was reported to Airbus that worked with the operator
to solve the problem. The TFU 32.42.21.002 stated that «Operator’s reports have
shown that the ´Brakes residual braking ECAM warnings are often spurious», although
it was also mentioned that they could be real and troubleshooting was needed to confirm
the fault. Airbus stated that they were never formally informed of the results of the
recommended trouble shooting actions of EC-GUP.
Therefore, the maintenance personnel and several pilots of the operator were already
familiar with the problem, and at least in one of the cases they had used several resets
of the antiskid system to make disappear the pressure, although with the fundamental
change of «pressing the (pedals) brakes at the same time». The deflexion of the pedal
was recommended by Airbus after the incident as the way to release the residual pressure
if noticed in flight (see paragraph 1.18.1). Previously, the manufacturer was not
familiar with this problem, because, according to the information gathered, they had
never received reports of actual residual pressure in flight from Iberia or from any other
operator, and attributed any clue of pressure to spurious indications, and therefore
recommended to reset the BSCU under some circumstances.
Those 5 reports of abnormalities could have contributed to prevent the incident on 7-
9-02 if, from an operational point of view, the information on abnormalities had been
provided to the crews of A-340, it is possible that the pilots of the flight of the incident
would have been familiar with the situation and with the actions taken is similar cases.
Also, if from a maintenance point of view, they would have been more thoroughly
investigated by the personnel of the operator, contacting with the manufacturer as
needed, maybe the origin of the residual pressure would have been detected at that
point. The manufacturer stated that high brake temperatures (that appeared in the
first two squawks) were clear clues to indicate that the residual pressure was not
spurious. Additionally, the analysis of the TSM carried out by the manufacturer showed
that, with the available clues and indications, the task 32-40-00-810-927 should
have been applied, at least after the third squawk according to the TSM introduction
(see 1.6.5).
However, it remains doubtful that the application of this task in an isolated way by the
personnel of the operator would have detected the faulty component and led to the
replacement of the master cylinder. The task (see 1.6.5) requests a fault confirmation
by means of setting the parking brake to OFF and then looking for pressure in the triple
indicator. Since the residual pressure had an intermittent nature and was no longer
present after the landings in June, maybe their interpretation would have been that this
«fault confirmation» action had failed and therefore the rest of the TSM task would not
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Technical report IN-062/2002
have been completed. Apparently they were not aware of the intermittent fault concept
mentioned in the introduction of the TSM.
Since the TSM has been designed to isolate/troubleshoot hard faults, it is considered
that the possibility of dispatching the aircraft until having 3 intermittent occurrences of
the same phenomenon should be further analysed by the manufacturer, and some additional
guidance should be provided in the TSM introduction. To avoid any confusion, it
should be highlighted in pertinent parts of the TSM that all available clues must be carefully
considered before dispatching again an aircraft after the first and second occurrences.
The operator also stated that they considered the instructions of the TFU should be
applied in first place, and those instructions were not consistent with those contained
in the Trouble Shooting Manual in this matter (i.e. the TFU did not refer to the proper
TSM procedure). Therefore, they applied that TFU alone on the first two days of
squawk.
On the third day (there was no high temperature reported that day) they also checked
transducers, status and condition of dual valve, master cylinder, and filter, and they performed
a system test and BSCU test. The transducer, dual valve, cylinder, and filter are
mentioned in the task -927 (see 1.6.5), although no task was specifically recorded on
the logbook and no component was replaced.
On the fourth day (with no high temperature reported) only the BSCU test and reset
were carried out, which would correspond to the TFU instructions.
The fifth and last day (with no high temperature reported), it seems a mixture of tasks
was performed, including checking of pressure in the left leg, cleaning of transmitters,
test of BSCU, and checking of wheels free to rotate. Then the squawks ceased.
The operator stated, late in the investigation process, that an operational test of the
brake system was carried out that day (11 June 2002), to be sure that the brake system
was free of any trouble. That test is the last action of TSM task -927.
The manufacturer stated that the appropriate manual to be applied is the TSM, regardless
of other ad-hoc maintenance information that may have been issued. The TFU was
never re-issued to match the tasks of the TSM. This TFU was closed in August 2003,
once the Service Bulletins A340-32-4187 and A-340-32-4193 were issued by Airbus to
solve the problem of spurious indication. It is considered convenient to issue a safety
recommendation regarding the need of consistency between the different maintenance
documentation.
Additionally, it seemed that different interpretations existed of what to do after the
«Fault confirmation» of the task 32-40-00-810-927, because the maintenance people
Technical report IN-062/2002
48
seemed to be unaware of the intermittent failure concept of the TSM, and therefore
two safety recommendations on the matter are issued.
In summary, it seems that the intermittent nature of the residual pressure, together with
differences of interpretation of the maintenance documentation or lack of knowledge
regarding the meaning of «fault confirmation» for «hard faults» and «intermittent
faults», masked the solution of the problem.
The operator also stated that they used to communicate with the manufacturer in many
other instances of malfunctions reported by the flight crews.
The main factor that caused that the squawks in June 2002 were not communicated to
Airbus was the awareness of the maintenance personnel, and even of most flight crews,
of a long history of spurious cautions and indications associated to the BSCU, both in
A-340 (including EC-GUP in year 2001) and in A-320, reflected in TFU and FOT of the
manufacturer. Most of the corrections of the reported abnormalities included tests of
the channels of the BSCU. In several instances, the correct result of those tests led to
the conclusion that the caution or indication was due to a possible temporary malfunction
of that component.
It seems clear that this factor influenced both the line maintenance actions in Tenerife
and the decisions made by the flight crew. Additionally to the history of spurious indications,
there was the fact that it was a new aircraft recently delivered, and their experience
indicated that in the event of an unexplained indication, the probability of that
indication being spurious was greater in that period.
In any case, apart from any previous history of spurious indications and from the interpretation
of the available maintenance documentation, there were clues in some of the
events (like high temperature after landing) to indicate that the pressure could have
been real, although with an intermittent nature, and that more maintenance actions
were needed.
Taking into account the maintenance carried out before the incident, it was considered
necessary to issue two safety recommendations regarding enhanced analysis of reported
intermittent malfunctions and enhanced training to the maintenance personnel
focused to analysis of reported intermittent malfunctions.
After 11-6-2002, there were no further reports of residual pressure in flight until the
aircraft had a bird impact on 28-7-2002 and was removed from service for repairs.
Then, after the first flight since that repair, the incident happened on 7-9-2002.
In summary, since 21 May (start of operation of the aircraft) until 6 June there was no
report of residual pressure. Since 7 to 11 of June there were 5 reports during 5 continuous
flights, and then the pressure disappeared, or at least was no longer reported,
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Technical report IN-062/2002
until it appeared again in the first two flights after the bird impact (Madrid-Tenerife and
Tenerife-Madrid).
No evidence has been found to explain this behaviour. One hypothesis was that the
maintenance tasks carried out during the fixing of the 5 complaints, together with the
braking during those landings, eventually «corrected» in some way the behaviour of the
left master cylinder. Then, in the repairs after the bird impact, the brake pedals were
disassembled and re-assembled as a whole assembly to the fuselage, and no part or
subcomponent of the assembly were removed in those operations. In paragraph 1.16 it
is explained that the rigging of the pedals was considered correct in the tests carried
out by Airbus after the incident.
In any case, it can be concluded that the tolerances and rigging of the master cylinder
are so tight that, under certain conditions there may be susceptibility to environmental
conditions simply by means of small deviations of those tolerances.
It seems clear that it would be positive that the design of the master cylinder was modified
to make it more resistant to the influence of the mentioned factors. Airbus has already
initiated this and other safety actions (see 1.18.3). It is considered convenient to
issue a safety recommendation related to this fact.
2.7. Suitability of the operational procedures
The Operations Manual of the operator did not have any procedure to be applied in the
event that residual pressure was detected in flight. Neither did have the Standard Operational
Procedures (SOP) of the manufacturer.
When faced with this situation, a flight crew had the following options:
— To take no action, with the understanding that if the Operations Manual does not
say anything, there is no need to do anything, and to land in a normal way, with
antiskid connected and without delaying the application of brakes. If this had been
the course of action taken in the landing in Barajas, the result would have been that
at touch down (should the autobrake have been connected) or at application of left
brake, the residual pressure would have been released and the braking action would
have been normal.
— To seek technical support on the effects of the indication of residual pressure and the
actions to be taken. This support could have been sought after landing in Tenerife
but in flight, during the approach to Barajas and after having lowered the landing
gear, it was much more complicated, because a go around would have been to be
carried out to try then to communicate with the ground personnel of the operator.
— To make on board the decision to initiate some action to mitigate the possible
effects of that indication based in previous experience. This was the option taken by
Technical report IN-062/2002
50
the crew in this case, using the negative experience they had in the landing in Tenerife
in the same conditions of residual pressure, and therefore they decided to disconnect
the antiskid and to delay the application of brakes as much as possible
during the landing.
After the incident, the manufacturer issued a telex to the operators (see paragraph 1.18)
and modified their SOP to clarify the actions to be taken by the crew under that situation.
Among those actions is to leave the antiskid connected during the landing and to
press the pedals in flight to release the residual pressure.
It is considered those actions are convenient to prevent similar events, because the previous
SOP did not adequately cover that contingency, since an indication was described
(amber bars in the page WHEEL of the ECAM) without clarifying whether it was displayed
in flight, on ground or in both cases, and without providing instructions to be
followed in that event.
In this case, a crew faced with that situation in flight, with no information on previous
similar cases and without having seen it during training, as it was this case according
to the information gathered, could be unsure whether the lack of procedure was due
to an omission of the manual more than to the intend of the designers that no action
was needed. A more comprehensive knowledge of the brake system would have helped
the crew to make the right decision. Even though the reaction of other crews of
the same operator that faced residual pressure indications in flight was not the same
and those flights ended with no consequences, it is considered that a more detailed
study of the brake system of the A-340 during training for initial type rating would be
recommendable. The manufacturer stated that their recommended syllabus was enough
for the crews to understand the brake system of the A-340. The operator devoted 6 h
on the ground to study the electrical, hydraulic, landing gear and APU systems. Additionally,
there was a four-hour session of flight simulator to cover ECAM and failures
associated to electrical and hydraulic systems.
On the other hand, several discrepancies have been observed between the Operations
Manual of the operator and the SOP of the manufacturer:
— The manufacturer specifically recommends using the autobrake except on very long
runways where it is expected that braking will not be necessary, whereas the operator
says that in a dry runway of normal length, normally the use of autobrake is
not necessary.
— The operator requires to make a reset of the BSCU if the message «Brakes residual
braking» appears on ground, while the manufacturer requires that Maintenance is
advised in that case with no further action taken by the crew in the corresponding
procedure of the SOP, although they allow the reset in the Chapter «Supplementary
techniques». The text of the FOT of Airbus on the matter also mentions the possibility
that the crew make a reset.
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Technical report IN-062/2002
Information retrieved from several sources indicates that there was a culture among
operators that the use of the autobrake appreciably increased the worn of the brakes
and also the heating (sometimes with a negative influence in the dispatch of the aircraft).
Therefore, in certain occasions it was intended to limit the use of this system by
crews in runways with enough length.
After the incident, the operator required the use of autobrake in the procedure of the
Operations Manual (2.01.63) in the event residual pressure was detected after lowering
the landing gear.
Although there is no requirement for the Operations Manual of an operator is completely
identical to the procedures recommended by the manufacturer, in this case, given
the fact that both aspects could have influenced the outcome of the incident, it is
recommended that the manufacturer clarifies whether or not a reset of the BSCU should
be performed on ground when the caution is displayed. The operator should then adapt
their Operations Manual to the conditions established by the manufacturer in this matter
and also regarding the use of autobrake.
Technical report IN-062/2002
52
3. CONCLUSIONS
3.1. Findings
1. The pilots had valid licenses and were adequately qualified for the flight.
2. During the descent to Madrid-Barajas Airport the residual pressure of the left brakes
alternate system started increasing when the aircraft was at approximately
13000 ft of altitude and it reached 800 psi when the aircraft was at approximately
500 ft of radio-altitude, at 13:02:45 h.
3. During the approach to Madrid-Barajas Airport, before lowering the landing gear,
the crew observed in the corresponding page of the ECAM that there was residual
pressure on the brakes of the left leg and, in absence of a procedure to be
applied, switched off and then on the BSCU. Afterwards, they selected landing
gear down and, with the gear down and locked, switched off the BSCU for 24 s
and then switched it back on. They observed that there was still residual pressure
on the brakes of the left leg, and disconnected again the BSCU moving the
switch A/SKID & N/W STRG to the «OFF» position.
4. During the landing on runway 33 of Madrid-Barajas Airport the spoilers were not
armed.
5. The aircraft touched down with the left and right legs of the MLG at approximately
240 m past the threshold of runway 33, at 13:03:27 h. After three seconds,
thrust reversers were selected, they worked normally, and the spoilers started
deploying.
6. The PF applied right rudder, without pressing the brake pedals, during the first 18
s of the landing roll.
7. Between 240 m and 900 m past the threshold of runway 33 the wheels of the
left MLG burst because they were already locked when the aircraft touched down.
8. At 13:03:45 h, the right brake pedal was fully deflected (68°) and the pressure of
the brakes alternate system increased up to 2500 psi, when the aircraft was
approximately 70 m past the intersection of runway 33 with runway 36R.
9. At 73 m past that intersection there were track markings on the runway indicating
that the wheels of the right leg bust in this area because they were blocked
by the pressure of 2500 psi applied with the right pedal.
10. The eight wheels of the left and right legs of the MLG burst because of friction
with the runway surface. The tire rims 1, 2, 4, 5, and 6 showed signs of rubbing
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Technical report IN-062/2002
with loss of material by friction with the runway surface. The brake assemblies 1,
5 and 6 showed heavy rubbing with loss of material of the casing and the disks
by friction with the runway surface.
11. There had been 5 complaints that referred to appearance of residual pressure in
flight within 7-6-2002 and 11-6-2002 that were not notified to the manufacturer.
There had also been several reports of residual pressure in other A-340 registered
EC-GUP in November 2001, which had been notified to the manufacturer.
12. The aircraft made on 7 September 2002 its first flight since 28 July 2002, when
it had suffered a bird impact and was subject to the corresponding repair.
13. The master cylinder, P/N C 24592020, S/N H2121, was the component that produced
the residual pressure in flight. This cylinder had a length of 170.31 mm,
which was 0.21 mm longer than specified. The dead travel of the cylinder (before
being installed on the aircraft) was 0.08 mm longer than the value specified.
The ultimate subcomponent inside the master cylinder that was causing the residual
pressure could not be determined.
14. The Operations Manual of the operator, and the Standard Operational Procedures
(SOP) of the manufacturer, did not contain procedures to be followed in the
event residual pressure was observed in flight. Both manuals specified that if the
antiskid system was inoperative, the braking is carried out with the alternate
system, and the pressure applied to the brakes must not exceed 1000 psi.
3.2. Causes
It is considered that the cause of this incident was the fact that, as a consequence of
the appearance of residual pressure in flight in the left brakes, due to the fact that the
left master cylinder P/N C 24592020, S/N H2121 was defective, and due to the lack of
a procedure to be applied in that case, the crew voluntarily disconnected the antiskid
system when the residual pressure was still present, which produced the burst of the
left tires at touchdown.
The following factors could have prevented the incident:
— The existence in the Operations Manual of instructions to be followed in the case of
residual pressure being observed in flight.
— The knowledge by the affected flight crew of similar cases that had been reported
as complaints during June 2002.
— A more comprehensive analysis of the previous squawks of residual pressure.
— A more detailed training on the brake system during the type rating courses.
Technical report IN-062/2002
54
4. SAFETY RECOMMENDATIONS
Airbus issued a telex to the operators in October 2002, and later on modified the
FCOM to include instructions to the crew in the event of appearance of residual pressure
in flight, and started a review of their procedures of checking the brake system
in the assembly line of the aircraft. They also started the study of a possible modification
of the design of the master cylinder to avoid the build-up of residual pressure
in flight.
Messier-Bugatti modified in December 2002 their procedures of quality control after
manufacture of master cylinders to include the checking and recording of the total
length of every cylinder. However, it could not be determined which subcomponent of
the cylinder, and the environmental conditions of operation, that ultimately produced
the residual pressure in flight. Therefore, it is possible that such a pressure can appear
again in aircraft A-340 equipped with this type of master cylinder, and it is considered
necessary to issue a safety recommendation regarding this fact.
Iberia stated that they had established the «Centro de Control de Mantenimiento»
(C.C.M.) with a view, among others, to improve the communication with remote maintenance
units.
REC 09/04. It is recommended to the DGAC of France that, in collaboration with Airbus
and Messier-Bugatti, conducts a deep evaluation of the characteristics
of design, manufacture and maintenance of the master cylinders of
the brake system of the A-340. This evaluation should have the goal of
preventing that cylinders accepted by the different quality controls of the
manufacturers at component manufacturer, final assembly, and flight testing,
might produce residual pressure on the brake system under certain
conditions of operation.
REC 10/04. It is recommended to the DGAC of Spain to encourage Iberia to take
action to improve the communication channels between their different
departments in a way that allows that flight crews and maintenance personnel
may, at any time and from any airport, seek quick and effective
engineering and operational support regarding situations not adequately
covered by the manuals available to them.
REC 11/04. It is recommended to the DGAC of Spain to encourage Iberia to improve
their methods of analysis of reports of abnormalities by the flight crews,
consulting with the manufacturer when needed, in such a way that it is
prevented the intermittent appearance of the same complaint, and that
the useful information resulting from that analysis is provided to flight
crews and maintenance personnel.
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Technical report IN-062/2002
REC 12/04. It is recommended to the DGAC of Spain that the training methods provided
to the applicable maintenance personnel of Iberia are monitored in
order to assure that in the correction of the reports of intermittent malfunctions
provided by flight crews, all the available maintenance documentation,
as well as all the available clues, are used to analyse the causes
of the malfunctions.
REC 13/04. It is recommended to Airbus that they should revise the content of the
pertinent parts of the TSM in order to provide additional guidance regarding
the maintenance procedures to be applied in the event of intermittent
faults, taking into account the kind of fault and the available clues
before dispatching again the aircraft. All operators should be informed on
the results of that revision.
REC 14/04. It is recommended to Airbus that in the training they provide to maintenance
personnel there is enough information to deal with intermittent failures.
REC 15/04. It is recommended to Airbus that it should be assured that the TSM and
other specific or temporary maintenance documentation, like a «Technical
Follow-up», is consistent and equally updated in regard to their technical
content.
REC 16/04. It is recommended to the DGAC-France that the training syllabus recommended
by Airbus to the airlines for type rating of A-340 is reviewed in
order to assure that it leads to an adequate understanding of the details
of the brake system of the aircraft.
REC 17/04. It is recommended to the DGAC-Spain that the training syllabus used by
Iberia for initial type rating of flight crews in Airbus A-340 is reviewed to
assure that enough time is devoted to reach an adequate understanding
of the details of the aircraft brake system. This review should take into
account any possible change in the Airbus recommended syllabus.
REC 18/04. It is recommended to Airbus that the content of the Abnormal Procedures
and Supplementary Techniques of the A-340 FCOM are revised to
unify the criteria of actions to be taken when the caution «Brakes residual
braking» is displayed on ground.
REC 19/04. It is recommended to Iberia that their Operations Manual of the A-340 is
updated with the guidelines provided by Airbus regarding the use of
autobrake during landing and the actions to be taken when the caution
«Brakes residual braking» is displayed on ground.
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APPENDICES
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APPENDIX A
Diagram of tracks on runway 33
of Madrid-Barajas Airport
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APPENDIX B
Details of the trouble shooting procedure
applied after the incident
(1 TO 4 ARE ITEMS TO PREPARE THE AIRCRAFT FOR THE PROCEDURE)
...
5. Check for pressure (LH & RH ALT brake) using the cockpit triple gauge.
If pressure remains, Go to (6)
If no pressure remains, Go to (8).
6. If RH ALT pressure, unscrew caps K on the BDDV (5403GG)
If LH ALT pressure, unscrew cap I on the BDDV (5403GG)
If the pressure remains on the triple gauge, replace the BDDV (5403GG)
If the pressure clears on the triple gauge, replace LH (5422GG) or RH (5423GG) master
cylinders.
7. Repeat tests (5) & (6).
If the pressure remains, the Dual Shuttle Valve (5404GG) should be replaced.
If the pressure clears, a dimension check of brake pedal rigging is required.
A quick test is to measure the distance between centre lines of master cylinder mounting
holes. They should be the same as each other and be within the range of
170+0.1/+0.05mm.
Note that no compression of the Master Cylinder should be required to mount it in position.
(Further checks see AMM 32-43-12-000-801, Removal of the Cockpit Alternate
Brake Master Cylinders).
8. Fully depress and then release LH & RH brake pedals.
If pressure remains on pedal release, Go to (6).
If pressure clears on pedal release, Go to (9).
9. Apply and release park brake.
If the pressure remains, the Dual Shuttle Valve (5404GG) should be replaced and test
repeated. (AMM 32-43-14-400-801 Dual Shuttle Valve – Removal/Installation).
If the pressure clears on parking brake release, go to (10).
10. If residual braking cannot be reintroduced, the following modified low-pressure
circuit bleeding procedure (AMM 32-43-00-870-801, replenishment of the Alternate
Braking Control Reservoir) should be used to check for restrictions in the low-pressure
circuit.
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With all AIC systems depressurised, attach a bleed hose to the bleed valve of the alternate
brake control reservoir (5424GG). Put the other end in a container to catch the
fluid. Drain until no fluid flows.
Unscrew cap a port ‘J’ of the BDDV and attach a bleed adapter (as identified in the bleeding
procedure). Measure the flow to the bleed container from port ‘J’ of the BDDV
(5403GG) when supplying fluid at a pressure of up to 4 Bars.
NOTE: Once the bleed valve opening is set for the first the test on side J (WH side) it
should remain in the same position for side K (RM side).
The supply flow and pressure set for the first the test on side J (L/H side) should remain
in the same position for side K (RIH side).
Repeat the above, this time connecting the port K of BDDV (5403GG).
Compare the flow rate from the pipe into the container. If the flow rates from the two
sides are different or are restricted, a blockage is suspected.
11. Detach the master cylinder with restricted flow from the pedal assembly. Carry out
a flow rate check as in (10).
If flow rate does not increase to rate of the ‘good’ side, then the master cylinder should
be replaced.
If flow rate increases to rate of the ‘good’ side, then the pedal assembly should be
removed and re-rigged.
END OF THE PROCEDURE
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