Early last Thursday morning, May 19,
EgyptAir Flight 804, an Airbus A320 carrying 56 passengers and 10 crew members,
went down in the Mediterranean on its way from France's Charles De Gaulle
International Airport to Cairo.
The plane apparently broke up in the air and there are no
survivors. Search parties have
begun to recover pieces of the wreckage, and data transmitted from the plane suggests
that a bomb might have caused the crash.
But a definitive conclusion about the cause will have to await the
recovery of the flight data recorders, if they can be found.
Generally speaking, commercial aviation
safety has been a spectacular success story. If you drive to the airport, the risky part of your journey
is over once you park the car. But
determined terrorists can evade security measures to bring a plane down, and no
amount of design improvements can make a modern airliner 100% secure against
attacks. In the case of Flight
804, we are fortunate to have information transmitted by the Aircraft
Communications Addressing and Reporting System (ACARS) that has provided
material for early speculation about the cause of the crash.
Within a day, a number of sources
provided news media with ACARS data transmitted for a period of about two
minutes around the time of the crash.
Two indicators associated with windows on the right side of the cockpit
and several smoke alarms went off.
An aviation expert cited in The
Telegraph (UK) speculated that a bomb in or near the right side of the
cockpit could have blown out a window, and the resulting cabin depressurization
at cruising altitude would have caused condensation fog that can set off smoke
alarms. As the plane broke up, the
ACARS system could have kept working, which explains the length of time between
the initial transmission and when communication was lost.
ACARS has been helpful in investigating
other crashes, such as the Malaysian Air Flight 370 that went down over the
Indian Ocean on Mar. 8, 2014.
Although numerous pieces of that plane have been recovered in widely
separated locations, the underwater search for the main body of the aircraft
continues to this day.
The part of the Mediterranean over which
EgyptAir Flight 804 went down includes some of its deepest waters, over 3000
meters (more than a mile) deep. So
it will be a challenge to find the flight data recorders, especially if the
search takes longer than 30 days, which is about as long as the recorder underwater
locator beacons operate.
The continuing mystery of the Malaysian
Air Flight 370 crash led to calls for live streaming of flight-recorder data in
addition to hard-copy logging on the plane, and in the ACARS data that was
recovered for the EgyptAir flight, we see that even in the absence of
regulations requiring such streaming, airlines have begun to take advantage of
digital communications channels to transmit data that can be helpful both for
maintenance and in case of a crash.
Other improvements that could be made to flight-recorder technology
include automatic ejection and flotation, as is already done for recorders on
military aircraft. Instead of
sinking with the plane, military flight recorders are ejected during the crash
and automatically deploy flotation devices which makes them much easier to
locate on the water's surface.
Since national governments usually bear the burden of paying for
underwater searches, you would think that they would see the logic in offering
to reimburse airlines for the additional expense of military-style flight
recorders. But logic isn't the
only consideration in international politics.
If the flight recorders and cockpit
voice recorders are recovered, the question of whether the crash was deliberate
will probably resolve itself pretty quickly. If it was indeed a deliberate act, the question then becomes
one of criminal investigation, and the security at De Gaulle International
Airport will come under scrutiny.
As long as airliners are flown by human beings, the trustworthiness of
the pilots is an essential link in the security chain. Assuming the pilots were not themselves
part of a conspiracy, that leaves the possibility that someone planted a bomb somewhere
in the cockpit. While cockpits are
now typically sealed off from the rest of the plane during flight, it's
possible that maintenance workers or others can get into them while a plane is
on the ground. The Telegraph reported that the short
stopover in France may not have allowed security personnel enough time to give
the plane a thorough going-over before it took off for Cairo.
Whatever the cause of the crash turns
out to be, we will learn something from it. If it was mechanical failure, which seems unlikely but is
still possible, it may affect all A320 Airbuses out there, but if there is such
a problem it hasn't shown up more than once, apparently. If, as seems more likely, there was a
deliberate act of sabotage, the technique used by the saboteurs will have to be
guarded against in the future.
Either way, sixty-six lives have been
lost in what was in all probability an avoidable tragedy. Most of the time, the vastly complex
systems of design engineering, maintenance, operations, and security for air
travel work essentially perfectly, and when we get on a plane we don't usually
give much thought to the question of whether we'll be getting off under our own power or not. But the price of such liberty is
eternal vigilance, and I hope the lessons eventually learned from this tragedy
make future ones even less likely.
Sources: I referred to reports from CNN.com at http://www.cnn.com/2016/05/21/middleeast/egyptair-flight-804-main/
and The Telegraph (UK) at http://www.telegraph.co.uk/news/2016/05/21/egyptair-crash---smoke-detected-inside-the-aircraft-cabin-as-sea/,
as well as the Wikipedia articles on Aircraft Communications and Addressing
System, flight recorders, and Malaysia Airlines Flight 370.
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