National Transportation Safety Board Safety Recommendation May 8, 2001

航空

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航空

7350
National Transportation Safety Board
Washington, D.C. 20594
Safety Recommendation
Date: May 8, 2001
In reply refer to: A-01-16 through -22
Honorable Jane F. Garvey
Administrator
Federal Aviation Administration
Washington, D.C. 20591
On November 20, 2000, about 1222 eastern standard time, a flight attendant/purser was
killed during an emergency evacuation of American Airlines flight 1291, an Airbus
Industrie A300B4-605R, N14056, at Miami International Airport (MIA), Miami, Florida. The
airplane was pressurized until the flight attendant/purser opened the left front door (1L); he was
then forcibly ejected from the airplane. Visual meteorological conditions prevailed, and an
instrument flight plan was filed. The flight was operating as a 14 Code of Federal Regulations
Part 121 scheduled international passenger flight. There were 133 persons on board. During the
emergency evacuation, in addition to the 1 flight attendant/purser who was killed, 3 passengers
sustained serious injuries; 18 passengers and 1 flight service director1 sustained minor injuries; and
the 2 pilots, 6 flight attendants, 1 off-duty flight attendant, 1 flight service director, and the
remaining 100 passengers reported no injuries. The airplane sustained minor damage.
The flight departed MIA for Port Au Prince International Airport, Haiti, and had been
airborne for about 8 minutes when the flight crew encountered a problem with the automatic
pressurization system. The captain stated to National Transportation Safety Board investigators
that the automatic cabin pressurization controllers would not control cabin pressure when the
airplane was climbing through 16,000 feet and that the electronic centralized airplane monitor
1 Flight service directors are language translators who receive emergency procedures training for land and
over-water evacuations for the aircraft to which they are assigned.
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(ECAM) display2 showed the forward outflow valve3 opened fully.4 The cabin altitude was
climbing at a rate of 2,000 feet per minute, and the cabin altitude indicator showed 7,000 feet.
The captain decided to operate the pressurization system in the manual mode (and closed the
outflow valves) and, about 11 minutes after departure, indicated to air traffic control (ATC) that
the flight would return to MIA. At that point, the pilots began performing the American Airlines
A3005 Cabin Pressurization Manual Control Checklist,6 which is contained in the American
Airlines A300 operating manual.
The captain stated to Safety Board investigators that during the return to MIA, the flight
attendant call chimes sounded erratically and the lavatory smoke detectors sounded continually.
Passengers and cabin crewmembers complained about pressure in their ears. About 3 minutes
before landing, the captain declared an emergency to ATC and requested that aircraft rescue and
firefighting (ARFF) personnel stand by for the landing. After the airplane landed at MIA, ARFF
personnel checked the exterior of the airplane and reported no signs of fire. The cockpit voice
recorder indicates that a flight attendant reported smelling smoke to the flight crew. The captain
indicated to Board investigators that he observed the illumination of a cargo loop light7 on the
cockpit overhead panel. The captain then ordered an emergency evacuation of the airplane, and
the American Airlines A300 Ground Evacuation Checklist8 was performed. The flight attendants
heard the sounding of the evacuation signaling system and attempted to open the emergency exits
to begin the emergency evacuation but were having difficulty doing so. A flight attendant
reported to the flight crew that the doors would not open. While the flight attendant/purser was
struggling to open the 1L door of the airplane, the door suddenly burst open, and he was forcibly
ejected onto the ramp and was killed. Preliminary findings from the investigation revealed that
excess air pressure inside the cabin caused the door to burst open.
Although this accident investigation is ongoing,9 the Safety Board identified several safety
issues that require the Federal Aviation Administration’s (FAA) attention.
2 The ECAM display is a cathode ray tube screen located in the cockpit. The system is automatic and displays
messages and system diagrams to pilots. It provides operational assistance for both normal and abnormal airplane
system situations.
3 The two outflow valves open and close during flight and on the ground to maintain control of cabin
pressurization.
4 Postaccident examination of the accident airplane by the Safety Board’s Systems Group revealed that
insulation blankets partially blocked the forward outflow valve and almost fully blocked the aft outflow valve.
5 All A300 airplanes that American Airlines operates are A300-600 airplanes.
6 The American Airlines A300 Cabin Pressurization Manual Control Checklist is similar to that of Airbus.
The entire checklist cannot be performed at one time; rather, pilots must initiate the checklist and then complete it
later in flight. According to the accident captain, he did not perform all of the items in the Cabin Pressurization
Manual Control Checklist because of his other priorities at the time, including addressing the smoke indications
and landing the airplane.
7 Illumination of a cargo loop light may indicate a fire in the cargo compartment. No evidence of fire was
found in the Safety Board’s postaccident examination of the airplane.
8 The American Airlines A300 Ground Evacuation Checklist, which is contained in the American Airlines
A300 operating manual, is similar to the Airbus A300-600 On Ground/Emergency Evacuation Checklist.
9 The description for this accident, MIA01FA029, can be found on the Safety Board’s Web site at
<http://www.ntsb.gov>.
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Pressurization System
Airplane pressurization systems can be operated in automatic and manual modes. The
manual mode of operation, which is considered by both the Airbus A300-600 and American
Airlines A300 operating manuals10 to be an abnormal procedure, is used on the A300-600 airplane
when the automatic mode becomes inoperative and allows the flight crew to manually operate the
electric motors that control the outflow valves. The Airbus A300-600 and American Airlines
A300 Cabin Pressurization Manual Control Checklists, which are contained in the companies’
respective operating manuals, both address the manual mode of the pressurization system. With
the pressurization system in the automatic mode, the airplane is pressurized upon landing, but the
outflow valves automatically open slowly (and depressurize the airplane) within 45 seconds of
landing, assisting in passenger comfort. However, with the pressurization system in the manual
mode, the airplane does not automatically depressurize after landing because the automatic
operation of the electric motors that open and close the outflow valves is inhibited. Therefore,
when operating the airplane’s pressurization system in the manual mode, the flight crew must fully
open the outflow valves as indicated in the Cabin Pressurization Manual Control Checklist by
selecting the Cabin Vertical Speed Control switch to the UP position before landing to ensure that
the airplane is depressurized.
As indicated earlier, the accident captain began performing the items in the Cabin
Pressurization Manual Control Checklist but did not complete the checklist, including the item
that instructs pilots to select the Cabin Vertical Speed Control switch to the UP position to open
the outflow valves and depressurize the airplane before landing. The captain indicated that he did
not complete the checklist because of his other priorities at the time. During postaccident
interviews with Safety Board investigators, the pilots of the accident airplane stated that they
were not aware that the airplane would not automatically depressurize after landing because this
issue was not mentioned in the operating manuals or during training.
The investigation confirmed that the pressurization system description section in the
Airbus Industrie A300-600 operating manual does not state that the airplane will not
automatically depressurize after landing if the pressurization system is being operated in the
manual mode. The investigation also confirmed that the American Airlines A300 operating
manual does not contain this information. Further, because the American Airlines training
program for the A300-600 airplane only covers the information in the American Airlines A300
operating manual, the training program also fails to address this issue.
The Safety Board is concerned that because of the lack of information in the Airbus
Industrie A300-600 operating manual and the American Airlines A300 operating manual and
training program about this issue, flight crews of Airbus Industrie A300-600 airplanes might be
unaware that the airplane does not automatically depressurize upon landing when the
pressurization system is in the manual mode. Although proper completion of the Cabin
Pressurization Manual Control Checklist should result in the airplane being depressurized upon
10 The manufacturer’s operating manual provides flight crewmembers with information on the technical,
procedural, and performance characteristics of the aircraft. This manual is suitable for training and may be used as
a crew manual or to aid operators in developing operating manuals and procedures.
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landing, the Board’s experience has shown that pilots sometimes do not properly complete
checklists, as occurred in this case. This investigation found that pilots may not be aware that one
of the repercussions of failing to complete the checklist is the airplane remaining pressurized upon
landing. The Board notes that regardless of a flight crew’s reasons for failing to complete the
checklist, if the pilots had known that the airplane was still pressurized, they would likely have
depressurized the airplane before permitting the door to be opened.11 Therefore, the Safety Board
believes that the FAA should require that the Airbus Industrie A300-600 operating manual clearly
state that automatic depressurization of the airplane upon landing will not occur when the
pressurization system is being operated in the manual mode. Further, the Safety Board believes
that the FAA should review all Airbus Industrie A300-600 operators’ operating manuals and
training programs and require revisions, if necessary, to ensure that they clearly indicate that
automatic depressurization of the airplane upon landing will not occur when the pressurization
system is being operated in the manual mode.
Checklists for Emergency Ground Evacuation
The Airbus Industrie A300-600 On Ground/Emergency Evacuation Checklist and the
American Airlines A300 Ground Evacuation Checklist, which are contained in the companies’
respective operating manuals, direct the flight crew to select the Ram Air switch to the
ON position during a ground evacuation. This switch allows fresh outside air to flow into the
airplane when it is airborne and depressurizes the airplane by opening both outflow valves when
the airplane is in flight or on the ground and the pressurization system is being operated in the
automatic mode. When the pressurization system is being operated in the automatic mode, the
Ram Air switch is used as a backup method of ensuring that the outflow valves are open and is
also used to open the outflow valves if the evacuation occurs less than 45 seconds after landing.
However, the Ram Air switch does not control the outflow valves if the pressurization system is
being operated in the manual mode. Therefore, when the flight crew of the accident airplane
selected the Ram Air switch to the ON position while performing the checklist for ground
evacuation,12 the outflow valves did not open and depressurize the airplane because the
pressurization system was being operated in the manual mode.
The pilots of the accident airplane stated to Safety Board investigators that they were
unaware that the Ram Air switch did not control the outflow valves when the pressurization
system was being operated in the manual mode and that this information was not included in their
ground or simulator training or documented in the operating manuals. The investigation
confirmed that the Airbus Industrie A300-600 operating manual does not state that the Ram Air
switch will not control the outflow valves if the pressurization system is being operated in the
manual mode. The investigation also confirmed that the American Airlines A300 operating
11 As indicated earlier, postaccident examination of the accident airplane by the Safety Board’s Systems Group
revealed that insulation blankets partially blocked the forward outflow valve and almost fully blocked the aft
outflow valve. Although the manual opening of the outflow valves would likely have allowed the airplane to
depressurize, the depressurization would have occurred at a rate that is substantially slower than normal because of
the partial blockage of the valves.
12 The Airbus and American Airlines checklists for emergency ground evacuation do not include information
about the operation of the pressurization system in manual mode.
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manual does not contain this information. Further, because the American Airlines training
program for the A300-600 airplane only covers the information in the American Airlines A300
operating manual, the training program also fails to address this issue.
The Safety Board is concerned that because of the lack of information in the Airbus
Industrie A300-600 operating manual and the American Airlines A300 operating manual and
training program about this issue, flight crews of A300-600 airplanes might be unaware that the
Ram Air switch will not control the outflow valves if the pressurization system is being operated
in the manual mode. The Board notes that if the pilots of the accident airplane had known that
the Ram Air switch would not control the outflow valves when the pressurization system was
being operated in the manual mode, they would likely have depressurized the airplane before
permitting the door to be opened. Therefore, the Safety Board believes that the FAA should
require that the Airbus Industrie A300-600 operating manual clearly state that the Ram Air switch
will not control the outflow valves and depressurize the airplane when the pressurization system is
being operated in the manual mode. Further, the Safety Board believes that the FAA should
review all Airbus Industrie A300-600 operators’ operating manuals and training programs and
require revisions, if necessary, to ensure that they clearly indicate that the Ram Air switch will not
control the outflow valves and depressurize the airplane when the pressurization system is being
operated in the manual mode.
The Airbus Industrie A300-600 operating manual states that maximum differential
pressure13 at landing should not exceed 1 pound per square inch (psi) and that the Ram Air switch
should not be selected ON when the differential pressure exceeds 1 psi. These design limitations
ensure that the airplane is not rapidly depressurized, which could cause passenger discomfort.
Further, according to the Airbus Industrie A300-600 operating manual, the cabin doors should
not be opened unless the cabin differential pressure is 0 psi because any pressure in the airplane
would make operation of the doors difficult and could result in an opening similar to the one that
occurred during this accident.
The Airbus Industrie A300-600 On Ground/Emergency Evacuation Checklist and the
American Airlines A300 Ground Evacuation Checklist do not require the flight crew to ensure
that the cabin differential pressure is 0 psi before signaling the flight attendants to begin the
emergency evacuation (and, therefore, open the doors). Further, because the American Airlines
training program for the A300-600 airplane only covers the information in the American
Airlines A300 operating manual, the training program also fails to address this issue. The Safety
Board notes that an additional item in the ground evacuation checklist directing the flight crew to
check the differential pressure before signaling the flight attendants to begin the emergency
evacuation would have alerted the accident flight crew that a pressurization problem existed.
Therefore, the Safety Board believes that the FAA should require that the Airbus Industrie A300-
600 On Ground/Emergency Evacuation Checklist direct flight crews to ensure that the cabin
differential pressure is 0 psi before signaling flight attendants to begin an emergency evacuation.
Further, the Safety Board believes that the FAA should review all Airbus Industrie A300-600
13 Differential pressure, indicated by a cabin differential pressure gauge on the pressurization panel in the
cockpit, is the difference between the pressure inside the airplane and that outside the airplane.
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operators’ checklists and training programs for emergency ground evacuation and require
revisions, if necessary, to ensure that they direct flight crews to verify that the cabin differential
pressure is 0 psi before signaling flight attendants to begin an emergency evacuation.
Parking Checklist
The accident airplane was not parked at a gate; therefore, the pilots did not perform a
parking checklist. However, the Safety Board notes that during its investigation of this accident,
a safety issue related to parking checklists was identified that requires the FAA’s attention.
The Parking Checklist in the Airbus Industrie A300-600 operating manual contains an
item requiring the flight crew to ensure that the cabin differential pressure is 0 psi before
permitting the flight attendants or gate agents to open the cabin doors upon arrival at the gate.
However, the Parking Checklist in the American Airlines A300 operating manual does not contain
this item. Further, because the American Airlines training program for the A300-600 airplane
only covers the information in the American Airlines A300 operating manual, the training program
also fails to address this issue. The Safety Board is concerned that a similar accident could occur
anytime the cabin doors are opened and the cabin differential pressure has not been verified at 0
psi. Therefore, the Safety Board believes that the FAA should review all Airbus Industrie A300-
600 operators’ checklists and training programs for parking and require revisions, if necessary, to
ensure that they direct flight crews to verify that the cabin differential pressure is 0 psi before
permitting flight attendants or gate agents to open the cabin doors upon arrival at the gate.
Therefore, the National Transportation Safety Board recommends that the Federal
Aviation Administration:
Require that the Airbus Industrie A300-600 operating manual clearly state that
(1) automatic depressurization of the airplane upon landing will not occur when
the pressurization system is being operated in the manual mode; (A-01-16) and
(2) the Ram Air switch will not control the outflow valves and depressurize the
airplane when the pressurization system is being operated in the manual mode.
(A-01-17)
Review all Airbus Industrie A300-600 operators’ operating manuals and training
programs and require revisions, if necessary, to ensure that they clearly indicate
that
(1) automatic depressurization of the airplane upon landing will not occur when
the pressurization system is being operated in the manual mode; (A-01-18) and
(2) the Ram Air switch will not control the outflow valves and depressurize the
airplane when the pressurization system is being operated in the manual mode.
(A-01-19)
Require that the Airbus Industrie A300-600 On Ground/Emergency Evacuation
Checklist direct flight crews to ensure that the cabin differential pressure is
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0 pounds per square inch before signaling flight attendants to begin an
emergency evacuation. (A-01-20)
Review all Airbus Industrie A300-600 operators’ checklists and training programs
for emergency ground evacuation and require revisions, if necessary, to ensure that
they direct flight crews to verify that the cabin differential pressure is 0 pounds per
square inch before signaling flight attendants to begin an emergency evacuation.
(A-01-21)
Review all Airbus Industrie A300-600 operators’ checklists and training programs
for parking and require revisions, if necessary, to ensure that they direct flight
crews to verify that the cabin differential pressure is 0 pounds per square inch
before permitting flight attendants or gate agents to open the cabin doors upon
arrival at the gate. (A-01-22)
Acting Chairman CARMODY and Members HAMMERSCHMIDT, BLACK, and
GOGLIA concurred in these recommendations.
By: Carol J. Carmody
Acting Chairman