Mar 6, 2007

Aftermath of an engine failure...

The problem began when an engine exploded sending a piece of shrapnel into the fuel tank. The captain performed a rejected takeoff drill and unaware that a fire had erupted in the wing, continued to taxi the aircraft clear of the runway. Meanwhile, passengers were caught between the obvious need to get out, and announcements from the flight attendants to remain seated.

The subsequent investigation (html version) (pdf version) revealed shortcomings in communication procedures between the pilots, flight attendants and passengers. As often happens in the industry, this accident triggered improvements in emergency procedures at other airlines, including my own.

Here is an excerpt from the report:

Survival Aspects

Passengers who were on the left side of the aircraft near the
wing were almost immediately aware of the existence of fire. As
the aircraft slowed, several passengers left their seats, and, as they
more became aware of the fire, a general level of agitation
developed. The number two flight attendant seated in the rear of
the aircraft heard a passenger yell "fire" within ten seconds of
the occurrence; the purser and number three flight attendant
both seated at the front of the aircraft, were aware of the fire
within twenty-five seconds of its occurrence.

In accordance with published procedures for a rejected take-off,
the three flight attendants remained in their seats awaiting
instruction from the captain. Al l assumed that, because the
aircraft continued to taxi, the captain was aware of the
situation and that it was under control. As the fire continued
to increase in size, the flight attendants attempted to contact
the flight crew. The number two flight attendant, seated in the
rear of the aircraft, attempted to notify the flight deck of the
fire by using the aircraft interphone system. Although the
signal tone was heard on the flight deck, it went unanswered
because the first officer mistook the tone for that associated
with the passenger flight attendant call button.

The number two flight attendant continued
in his attempts to contact the flight
deck and also began to call the front cabin flight attendant
station. The purser attempted to enter the flight deck but was
unable to do so because the door was locked in accordance with
standard company procedures. The door was unlocked in response
to her knocks, and, about 45 seconds after the take-off was
rejected, she entered the flight deck and, after first asking if
they had blown a tire, informed the captain of a fire at the
back. In the meantime, the number three flight attendant made a
brief public address (PA) announcement for the passengers to
remain seated and calm. After having been informed by the
captain to prepare for an evacuation, the purser then returned to
the cabin. Upon returning, she answered the interphone and was
informed by the number two flight attendant that there was a fire
at the back and that the aircraft should be stopped. Throughout
this period, the aircraft continued to taxi slowly up C-4.

The purser then returned to the flight deck, advised the captain
of the deteriorating situation, and was again directed to prepare
for evacuation. The purser then left the flight deck and
directed the two flight attendants to prepare for evacuation.
When the aircraft stopped, the three flight attendants initiated
an evacuation by opening their doors and inflating the escape
slides.

There was no general announcement of the evacuation made by
either the captain or the flight attendants. Evacuation commands
were given to passengers as they exited the aircraft. The
passengers' decisions to leave their seats and evacuate were
based on their perceptions of the emergency situation and their
observations of the flight attendants opening the exits.
Passengers were at the doors awaiting the inflation of the escape
slides.

Four exits were used during the evacuation; these were as
follows: main entrance door (left front); galley service door
(right front); right over-wing exit; and right rear service door.
The main entrance door was opened by the number three flight
attendant and the galley service door by the purser. The right
over-wing exit was opened by the passenger seated next to it at
the urging of several passengers seated nearby. The first few
passengers out this exit reported that the escape slide at the
galley service door had not yet deployed when they exited the
aircraft. The right rear service door was opened by the number
two flight attendant.

Shortly after the evacuation commenced, fire melted windows along
the left side of the aircraft. When the windows melted through,
heat and smoke entered the aircraft, and the cabin environment
quickly deteriorated. Substantial quantities of smoke also
entered through the right over-wing exit and right rear service
door.

Conditions within the aircraft cabin were significantly worse in
the aft section. Heat was felt as the windows melted through.
Those passengers who had been seated beside the windows nearest
the fire experienced some singeing of hair and clothing. Smoke
obscured visibility almost totally during the latter stages of
the evacuation.

Passenger perceptions in the forward part of the cabin differed
markedly from those in the aft. It took much longer for them to
be aware of the existence of fire, and, even then, some did not
perceive the seriousness of the situation.

Most passengers chose the closest exit for evacuation. Many
stopped to retrieve handbaggage before they left. Those
passengers who exited through the main entrance door and galley
service door were seated primarily in rows one through seven.
Most initially chose to use the main entrance door until the
number three flight attendant began directing alternate
passengers to the galley service door. The passengers who exited
through the right over-wing exit were almost all seated in rows 8
through 16. With only a few exceptions, the rear exit was used
by all passengers seated aft of row 16.

The evacuation was without panic; however, a sense of urgency
prevailed. There was some pushing, and several people went over
seat backs to get to the exit ahead of others already in the
aisle. There was no noticeable yelling or screaming.
As the evacuation progressed, smoke began to thicken and obscure
vision. Smoke conditions were worse in the aft section of the
cabin. Passengers who exited via the rear exit reported that
they were unable to see the exit and were required to follow the
person ahead to locate it. By the time most had reached this
exit, the smoke had lowered to about knee height. The bottom
portion of the door and the slide were all that was visible. The
passenger who was the last one to exit via the over-wing exit
reported he had to drop to his knees to breathe fresh air before
he was able to reach the exit. Only when he neared the exit, did
it become visible through the smoke.

AI1 passengers who exited via the over-wing exit jumped off the
leading edge of the wing. The vertical drop from the wing to the
ground is in excess of six feet, and this distance increases as
one moves outward from the wing root. Smoke and flames near the
trailing edge influenced the passengers to go forward after they
bad left the aircraft. Most jumped down from the wing inboard of
the engine, although several proceeded out the wing before
dropping to the ground.

The rear slide was observed to deflate, because of fire damage,
immediately after the number two flight attendant exited the
aircraft .

A precise determination of the time taken to evacuate the
aircraft could not be made; however, it is estimated that the
evacuation took between two and three minutes .

Four passengers sustained serious injuries during the evacuation.
All four exited the aircraft via the right over-wing exit. Three
of these passengers sustained bone fractures of varying severity
when they jumped to the ground from the leading edge of the wing.
The fourth passenger, who was apparently the last person to exit
the aircraft, sustained pelvis and rib fractures when he fell to
the ground, after slipping on foam on the wing.

Mumerous other passengers sustained minor bruises, cuts,
abrasions, and sprains during the evacuation. Some singeing of
hair and mild blushing of the skin from heat were also reported.
Blood samples were taken from the 29 passengers who reported to
hospital. Carbon monoxide levels were minimal when measured, and
there were no reports of other toxic substances.

Following the evacuation, the passengers and crew gathered in
groups a short distance from the aircraft and observed the
fire- fighting activities.
...

5 comments:

Aviatrix said...

That could have been much worse. It sounds like another 45 seconds delay and there would have been people who didn't get off that airplane.

Are there procedures to prevent that from happening again?

I've never flown an airplane where I couldn't just turn around to see how the passengers were doing at the back.

Aluwings said...

Communication between flight attendants and pilots is even more of a problem now that everyone has locked flight deck doors (I notice that this was part of this company's policy even in 1984).

I was planning to make another post relating specifically to some of the ways our procedures were adapted since this accident.

As they say: "Please standby for new ATIS message" ha ha...

Garrett said...

I guess on large transport aircraft not only do you not really know what is going on in the cabin, you also can't tell nearly as easily as someone seated in 16A that there is a punctured fuel tank on fire. Seems like over the years there have been many incidents and accidents where the inability to easily see portions of the airplane made things much worse.

Not that there is really anything you could do about this. Would a bunch of CCD cameras pointing at the hard to see bits make any difference, i.e. would you stop immediately and evacuate the first time you heard of trouble from the back if you had a picture of it?

Another thought, it should actually be relatively (in the realm of aerospace budgets) easy to build cameras that look at the aircraft for fires outside of the places traditionally monitored. Perhaps a solution to a practically nonexistent problem though.

Ron said...

The pilots seem to have been caught up in the fact that although the FA was reporting a fire, there was no sign of it on the instrument panel. Not that they fixated on this, but it ate up some time.

Were I in their shoes, with the info they had available, I would probably have done the same thing.

I don't fly airliners, but as I understand it, after an RTO, you're monitoring brake temps, talking to ATC, and trying to figure out which checklist to run.

One thing they could do (and may have done since then) is change the FA call tone so that it's significantly different from the passenger call sound. The first officer got the two confused.

Aluwings said...

Ron, I suspect that the PWA crew in this incident had the same training we used to get, namely if the RTO is 'just' due to an engine failure or other straight-forward item, then you might as well roll clear of the active runway.

RTO training now emphasizes that for any serious rejected take-off we must bring the aircraft to a complete stop on the runway and set the parking brake before assessing our true status.

This at least ensures easy access to the aircraft for the emergency vehicles.

I hope to post a more complete look at RTOs before too long... They are one of the things we practice most in the simulator and for good reason.