What Caused Egypt Air Disaster?

June 2016 | Dios Kurniawan

Almost a month after the Egypt Air Flight 804 disappearance on May 19, the tragedy remains a confounding mystery for the aviation world. The answer as to what has caused this accident might be best provided by the cockpit voice and flight data recorders, which are now still lying on the seabed of the Mediterranean Sea. However because of the depth of the sea, the underway recovery of these black boxes can take weeks even months, and the answers might not be forthcoming any time soon.

So what has caused Flight 804 to plunge into the sea? Modern planes don’t just fall out of the sky. Flight 804 was flying at cruise altitude, the safest phase of a flight with the computers flying the aircraft, and the pilots should not have very much to do. The aircraft was an Airbus A320, a technologically advanced jetliner and also the most popular in the world, second only to Boeing 737, with great safety record. The weather was reported fine at that night. Also, the Airbus was not flying over conflict area, therefore surface-to-air missile attack (as in the case of Malaysia Airlines MH17) was a remote possibility. The pilots did not transmit distress call, hence something very sudden must have come about.

There have been at least three well-known occurrence of fatal accidents involving trouble at cruise stage; the Adam Air Flight 574 in 2007, Air France AF774 in 2009 and just recently Air Asia QZ8501 in 2014. All involved a combination of technical and human errors, with the latter to blame most (GermanWings crash last year is not discussed here because it involves the possibility of a suicidal pilot).

At the time of writing this article, there is no solid source of information available for investigation. What we have is very limited data, the most compelling one is the ACARS (Aircraft Communications Addressing and Reporting System) messages received from the doomed flight. They are publicly available in the mass media as shown below.

ACARS messages (source: CNN)

We can think ACARS like SMS (short text messages) in our mobile phones. ACARS is designed to send automated messages to the ground, for instance to give the airline maintenance personnel a heads up to possible equipment issues to be addressed upon landing at the destination. In the final moments of Flight 804, the avionics systems sent out a series of ACARS messages which reported faults and malfunctions. They provided valuable information on estimating what happened during the last few minutes of the flight.

Let’s take a look at those ACARS messages as shown in the picture above, and I will try to decode and to estimate the situation happened in the aircraft from each of the messages.

There have been seven messages sent within four seconds, indicating something of a significant scale occurred in a very short period of time. The first three were sent almost at the same time:

  • 00:26 ANTI ICE R WINDOW – this shows the anti-ice heater in the right cockpit window was damaged. Most probably because the window itself has been destroyed (see next message).
  • 00:26 R SLIDING WINDOW SENSOR – this shows the right cockpit window (the co-pilot/first officer position) was not closed properly. Very likely it had been blown away  by an explosive decompression. The co-pilot might have been incapacitated or unconscious at this point.
  • 00:26 SMOKE : LAVATORY SMOKE – this indicates smoke was detected in the lavatory/toilet. Smoke may also be a result of rapid decompression as the cabin was losing air pressure.

One second later, ACARS sent another message :

  • 00:27 AVIONICS SMOKE – there are two avionics bay in Airbus A320; one is just beneath the cockpit, the other is at the tail of the aircraft. Considering the first three messages, it is very likely that the smoke warning came from the avionics bay underneath the cockpit. It also could suggest that the avionics bay was affected by the explosive decompression, and the aircraft skin started to peel off.
  • 00:28 R FIXED WINDOW SENSOR – this suggests that the right fixed window, located next to the sliding window which was blown away two seconds earlier, was also dislocated from its position. With two windows missing at 37,000 feet, the situation inside the cockpit must have been very chaotic. Both pilots, if they were still conscious at that time, could not do any effective corrective action with the wind and noise.

The final two messages indicated that the two important flight computers were damaged:

  • 00:29 AUTO FLT FCU 2 FAULT – one of the two Flight Control Unit (FCU) stopped working. The FCU is the pilot’s interface to the autopilot, which allows the aircraft to fly straight and level, following a preprogrammed route. FCU is located in the cockpit. Most likely the FCU no.2 was damaged as a result of the explosive decompression seconds earlier.
  • 00:29 F/CTL SEC 3 FAULT – Almost at the same time as the destruction of the FCU, one of seven flight control computers that controls the wing’s spoilers and elevators was also damaged. This is the last ACARS message received from the aircraft.

Airbus A320 Computers (Diagram: Dios K)

To give you some understanding on flight computers, as depicted in the diagram above, there are three types of flight computers onboard Airbus A320 : FAC, SEC and ELAC. Each of which manages physical control surfaces on the wings and tail. They allow pilot’s input from the sticks and pedals to be translated into aircraft’s change of attitude and direction (turning, climbing, descending, reducing speed, etc.).  Losing one computer should not bring down the plane as the computers are designed to take over each other’s tasks when necessary.

The ACARS messages from Flight 804 only told us that one of the three SEC was unavailable. Essentially, if one SEC is faulty, the plane can still fly with the other computers. But if all three computers are damaged, pilots ability to control the aircraft would be virtually lost. In the case of Flight 804, apparently the ACARS did not report fault on the other computers because the ACARS transmitter itself might have been damaged and was unable to send more reports. Probably more than one computer were malfunctioning at the final minutes of Flight 804.

Three minutes after the last ACARS message was sent, the plane disappeared from radar. No emergency call was made.

Something catastrophic happened so suddenly that the pilots did not even have time to radio a distress call. The pilots were most likely swamped with multiple warning that popped up in their cockpit’s screens, and at the same time, they might be busy trying to cope with the rapid degradation of control along with the loss of critical flight computers. The blown windows just made the situation worse for them.

In my opinion, judging from the ACARS messages above, the evidence strongly indicates an explosion inside the aircraft. The explosion might be small, not the kind that would destroy the whole plane instantly, however the resulting decompression was enough to rupture the avionics bay, eventually devastating vital computer systems of the aircraft. Pilots were unable to control the plane and it plunged into the sea.

Probable area of explosion (diagram taken from FlightGlobal.com)

One possible scenario: some sort of incendiary or chemical sparked the fire or small explosion somewhere inside the cabin or in the underfloor cargo hold. The fire spread quickly to the avionics bay, puncturing a hole on the fuselage resulting in the explosive decompression. This could be an indication of, but not necessarily, a terrorist attack.

Yes, this is only a speculation based on small amount of data available at this point. Until a more definitive data is acquired from the flight recorders, this could arguably be the most probable explanation of the accident.