ETOPS - Extended Range 180 minutes

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2011-4-9 1
Extended-range twin-engine operations (ETOPS) have become common practice in
commercial aviation over the last 15 years. Maintenance and operational programs
for the twinjets used in these operations have received special emphasis, and
reliability improvements have been made in certain airplane systems. Many
operators are now considering the merits of the ETOPS maintenance program for
use with non-ETOPS airplanes.
In 1953, the United States developed regulations that prohibited two-engine
airplanes from routes more than 60 min (single-engine flying time) from an
adequate airport. These regulations were later formalized in U.S. Federal Aviation
Administration (FAA) Federal Aviation Regulation 121.161. The ETOPS program,
as outlined in FAA Advisory Circular (AC) 120-42A, allows operators to deviate from
this rule under certain conditions. By incorporating specific hardware improvements
and establishing specific maintenance and operational procedures, operators can
fly extended distances up to 180 min from the alternate airport. These hardware
improvements were designed into Boeing 737-600/-700/ -800/-900 and 777
airplanes.
ETOPS - Extended Range 180 minutes
2011-4-9 2
1. ENGINE HEALTH MONITORING
ETOPS maintenance procedures were created to ensure the safety and reliability of
flights operating at extended distances from alternate airports and to prevent or
reduce the probability of a diversion or turn back with one engine out. These
maintenance procedures are equally effective for any commercial airplane with any
number of engines. Most traditional maintenance programs are based on regularly
scheduled preventive maintenance and on the ability to predict or anticipate
maintenance problems by studying failure rates, removal rates, and other reliability
data. However, the ETOPS philosophy is a real-time approach to maintenance and
includes continual monitoring of conditions to identify problems before they threaten
airplane operation or safety.
2011-4-9 3
Two items in the ETOPS maintenance program that best illustrate this real-time
approach are oil consumption monitoring and engine condition monitoring.
Oil consumption monitoring.
A typical maintenance program requires checking engine oil before every flight (but only
once each day on the 737, as approved by the FAA) and the auxiliary power unit (APU)
oil less frequently (such as every 100 hr). The quantity of oil added and flight hours for
each leg should be noted in the maintenance logbook.
The oil consumption rate, the amount of oil used per hour of operation on the previous
flight leg, should be calculated for both engines and the APU during ETOPS before
dispatch. The resulting number provides a better indication of oil usage or loss than the
quantity of oil added. If the rate is acceptable, the flight can be released; if not, the cause
of the increased usage must be addressed before dispatching the airplane on an
ETOPS flight. This increase can frequently be caused by an oil leak, which is easy to
detect and repair.
The consumption rate data is also logged to track long-term variations in consumption
rates (fig. 1). This allows the operator to determine if problems are developing so they
can identify and implement solutions before serious engine or APU degradation occurs.
2011-4-9 4
Engine condition monitoring (ECM).
For many years, ECM computer programs have been available for all engines used on
Boeing airplanes. The engine manufacturer supplies ECMs to help operators assess the
general health of their engines. The programs allow for monitoring of such parameters
as N1, N2, exhaust gas temperature, fuel and oil pressures, and vibration (fig. 2). Most
operators use an ECM program regardless of whether they fly ETOPS routes. ETOPS
operators are required to use ECMs to monitor adverse trends in engine performance
and execute maintenance to avoid serious failures. These failures could cause in-flight
shutdowns, diversions, or turn backs. In some cases, oil consumption data and ECM
data can be correlated to define certain problems.
2011-4-9 5
2. PREDEPARTURE SERVICE CHECK
FAA AC 120-42A requires certain ETOPS systems to be checked before each flight.
Boeing determined that the transit check in the maintenance planning data document
was sufficient to meet the AC requirement. This is because certain systems relating to
ETOPS were redesigned for greater reliability and dispatch requirements were altered
for ETOPS (e.g., minimum equipment list requirements). However, because of the oil
consumption monitoring requirements for ETOPS, the APU check interval on the 737,
757, and 767 was changed to the transit check for ETOPS airplanes. The engine oil
servicing interval changed only on the 737. These two changes and the calculation of
consumption rate are the only changes necessary to the standard transit check to form
the ETOPS predeparture service check.
2011-4-9 6
3. BASIC AND MULTIPLE-SYSTEM MAINTENANCE PRACTICES
Two programs -- resolution of discrepancies and avoidance of multiple similar system
maintenance -- are outlined in AC 120-42A.
Resolution of discrepancies.
This program requires items that are repaired or replaced to be checked for proper
installation and operation before the work is signed off on the maintenance log. This
ensures that the item is actually fixed and that no new problems were introduced during
maintenance. This maintenance practice is applicable to all airplanes. Avoidance of
multiple similar systems maintenance.
Maintenance practices for the multiple similar systems requirement were designed to
eliminate the possibility of introducing problems into both systems of a dual installation
(e.g., engines and fuel systems) that could ultimately result in failure of both systems.
The basic philosophy is that two similar systems should not be maintained or repaired
during the same maintenance visit. Some operators may find this difficult to implement
because all maintenance must be done at their home base.
However, methods exist for avoiding the problems that may be introduced by working on
two similar systems simultaneously. For example, different personnel can perform the
required work on the similar systems, or they can ask each other to review the work
done on each system. If the systems are checked after performing maintenance
according to the resolution of discrepancies program, any problems introduced during
maintenance should be identified and corrected before releasing the airplane for flight.
2011-4-9 7
4. EVENT-ORIENTED RELIABILITY PROGRAM
An event-oriented reliability program associated with ETOPS differs from conventional
reliability programs, which rely on historical data or alert levels to determine when an
item should be investigated for possible corrective action.
In an event-oriented reliability program, each event on an ETOPS-significant system is
investigated to determine if a problem could be reduced or eliminated by changing the
maintenance program. Examples of events include a failure, removal, or pilot report.
Events can also be monitored to detect long-term trends or repeat items. Not all events
warrant such detailed investigations; continual monitoring and awareness of problem
areas reflects the ETOPS real-time maintenance philosophy.
SUMMARY
Although three- and four-engine Boeing airplanes (as well as some earlier 737s) are not
specifically designed or improved for ETOPS, the ETOPS maintenance approach can be
applied to those airplanes and offer operators significant improvements in reliability,
performance, and dispatch rates. The approach can be applied at minimal cost, which
can later be offset by reduced maintenance costs and other costs associated with
diversions or turn backs..
2011-4-9 8
Questions from CTEC class to Boeing dealing with bleed air systems.
1. When the 220 psi over pressure switch is activated due to an over pressurization
problem and the PSROV is stuck in the open position, where does the air bleed to?
The multiple failure situation stated would be most unfortunate! However, should there
be an overpressure fault, and the PRSOV remain open (note duct pressure indication)
after the BLEED TRIP OFF light illuminates, the excess pressure would go straight to
the pneumatic system. There are no pressure relief valves in the pneumatic system
except for the APU bleed valve and high stage valve pressure relief valve. Note: For the
APU bleed valve to relieve pressure on the pneumatic system, with the APU not running,
would also require the additional failure of the APU bleed check valve. The pneumatic
system ducts are designed to contain an air pressure of 250 psi. The remaining pressure
relief is the relief valve for the high stage valve. This valve opens at 160 psi and its
primary purpose is to protect the inner high stage valve mechanism. Due to the volume
of air present in the interstage duct, it is not designed to relieve all the excess pressure
in the interstage duct.
2011-4-9 9
2. How can we regulate engine pressure if this occurs at the Top Of Descent?
To answer the question, the only way for a pilot to regulate the engine bleed pressure
should both the high stage valve and the PRSOV fail open is to reduce power on the
affected engine. Unregulated pressure of the 9th stage of the HPC at idle, at sea level, is
approximately 18 psi. Unregulated 9th stage pressure at takeoff power is approximately
350 psi. Unregulated pressure of the 5th stage of the HPC at idle, at sea level, is
approximately 7 psi. Unregulated 5th stage pressure at takeoff power is approximately
160 psi. For an ETOPS flight, if this condition occurs before reaching equal distance
point (EDP) the pilots would air turnback. If the condition occurred after EDP, the pilots
would have to continue on with one engine power reduced to near idle speed.
Boeing 737 Operations Manual, Checklist Introduction, Chapter C1, Non-Normal
Checklists, Section 2: “Non-Normal checklist Operation: …While every attempt is made
to establish necessary non-normal checklists, it is not possible to develop checklists for
all conceivable situations, especially those involving multiple failures. In certain
unrelated multiple failure situations, the flight crew may have to combine elements of
more than one checklist and/or exercise judgment to determine the safest course of
action. The captain must assess the situation and use sound judgment to determine the
safest course of action.”
2011-4-9 10
3. What components can cause an overpressure on the ground while on T/O roll?
Example: moving the throttle from idle to T/O power.
•A fast engine acceleration where a slower reacting high stage valve could cause high
9th stage pressure to activate the over pressure switch before the high stage valve fully
closes. Note: There is always a slight lag between pressure changes at the 9th stage of
the HPC, relative to N2 speed changes, and reaction by the high stage valve. This lag
can increase with an older, more warn out valve.
•Mx inadvertently installs a 180-psi overpressure switch on the bleed air regulator
instead of the 220-psi overpressure switch preferred for AQs –7B26 engines. Note:
Using a 180 psi overpressure switch on –7B26 and –7B27 engines can possibly cause
nuisance bleed trip conditions.
•A failure (crack or break) of the high stage valve downstream sense line. Note: This line
provides interstage duct pressure reference to the high stage valve for pressure
regulation.
•A failure to the full-open position of the high stage valve.
•Failure of the overpressure switch on the bleed air regulator.
•Failure of the K8 relay in the air conditioning accessory unit (ACAU).
2011-4-9 11
4. When the lower display unit is showing the systems page (display of FLT CTRL Pos,
Hyd Qty), when an engine alert comes up (Lo oil Qty), will the message come up
automatically on the displays or do you have to return to the engine primary page to see
the message alert?
If the lower DU is in MFD and is currently showing Systems, any abnormal secondary
engine indication alert will automatically activate the upper center display to show a
compacted secondary engine display. The alert will now be visible on the upper center
DU while the lower center DU will continue to show Systems information.
2011-4-9 12
5. Do you have any Maintenance Tips on bleed trip problems
and duct split problems or any other helpful information?
•Check for proper function of the two duct pressure transmitters.
•Check for proper function of the duct pressure indicator.
•Check for proper function of the precooler control valve sensor.
•Check for proper function of the 450F thermostat for the PRSOV.
•Check to ensure the sense line from the 450F thermostat to the PRSOV is intact, not
leaking, no loose connections.
•Check to ensure the PRSOV downstream sense line is intact, not leaking, no loose
connections.
•Check for proper and smooth operation of the PRSOV.
•Check to ensure there are no internal leaks in the PRSOV.
•Check for proper operation of the 490F overtemp switch.
•Check for proper operation of the 180/220 psi overpressure switch, whichever one is
installed.
•Check to make sure the high stage valve closes completely.
•Check for proper operation of the precooler control valve.
•Check the precooler for obstructions, debris, clogging, damage.
•Check to ensure the seal between the precooler control valve and precooler is intact, not
damaged, and in the correct position.
•Check the inlet to the precooler control valve, on the left side of the 12:00 fan support strut
is not obstructed by dirt or debris, is not damaged.
Note: The last four items are particularly important after the flight crew reports of bird
ingestion by an engine.
2011-4-9 13
Is it mandatory for the pilots to use the fault reporting manual on the 737-700?
It is not mandatory for pilots to use the fault reporting manual (FRM), just as it is
not mandatory for Mx to use the fault isolation manual (FIM). Using the FRM
would be one of these reasons:
 Flight crew preference
 Flight Ops departmental required procedure
 Foreign regulatory requirement (if one exists)
2011-4-9 14
 Background
– Previous engine oil consumption limitations were common for all 737
minor models.
• Commercial 737NG oil consumption limited to 0.25 gallons per hour.
• 737 Boeing Business Jets limited to 0.22 gallons per hour
• Limitation contained in AMM section 71-00-00
– The FAA has changed position on engine oil consumption limitations.
• Required limitation in Section 9 of the Maintenance Planning
Document during certification of new minor models.
– 737-900
– 737-800 w/ winglets
Engine Oil Consumption
Limitations
2011-4-9 15
No 9 0.22
737-900 No 0 0.34
Yes 0 0.31
737-800 No 0 0.33
Yes 9 0.22
737-700BBJ
737-700,-700C No 0 0.30
737-600 No 0 0.29
Oil
Endurance
(gal/hours)
Number of
Auxiliary
Tanks
Winglet
Equipped
737 Minor
Model
Revised Oil Consumptions Limitations
– FAA has approved revised oil consumption limitations for the 737
• Minor model unique oil consumption limitations provide increased
consumption limits for non-BBJ airplanes.
2011-4-9 16
 Boeing Publication Changes
Airplane Maintenance Manual Revision.
• Revised minor-model specific oil consumption limitations will be
published in AMM section 71-00-00
• Scheduled for October 2002 revision
Maintenance Planning Document Revision
• Revised MPD Section 9 text will allow use of minor-model specific
limits for 737-900 model & 737-800 model with winglets
• SUBTASK 12-13-11-970-002
• Before each flight, the indicated engine oil level in the flight
compartment with the engine not in operation must be 60% full or
12.00 U.S. quarts (11.40 liters) or more.
• There must be 7 quarts (6.65 liters) or more of oil remaining in the tank by the
end of the scheduled flights for possible takeoff and go-around (TOGA)
operation.
• Calculate the oil usage from the flight(s) duration and the specific engine oil
consumption.

kinran

bocome

ETOPS - Extended Range 180 minutes

linairm

楼主辛苦了，好东西

koutsoupan

Thank you!