The disappearance of a 777 and 239 people has been described as an 'unprecedented' event. (RAeS NAL Archives)

During the three weeks since the disappearance of flight MH370, there have been many theories put forward as to what might have happened aboard the aircraft. At a recent high level RAeS Flight Operations Group conference, BILL READ polled a selection of the experts there with some of the most vital technical and operational questions still outstanding.   

On 8 March, a Malaysian Boeing 777-200 on an overnight flight from Kuala Lumpur to Beijing lost contact with air traffic controllers less than an hour after take-off. No distress call was made. The aircraft was initially thought to have crashed into the Indian Ocean but evidence subsequently emerged that suggested the aircraft’s transponder and ACARS system had both been deliberately switched off while the aircraft changed direction but continued flying. Investigators now believe that the aircraft eventually crashed into the Southern Indian Ocean when satellite images of wreckage have been seen. At present, attempts to locate and recover wreckage are being hampered by bad weather.

A gathering of experts

During the three weeks since the disappearance of flight MH370, there have been many theories put forward as to what might have happened aboard the aircraft. This week, the RAeS Flight Operations Group (FOG) held a two-day conference at 4 Hamilton Place on the subject of the role of the Aircraft Commander in the 21st Century which included speakers representing pilots, airlines, manufacturers and regulators. We took the opportunity to ask a selection of these highly experienced and extremely knowledgeable speakers some questions as to what might have happened aboard the missing 777. A summary of their amalgamated answers appears below:

What are your views on these alternative theories?

1. The aircraft depressurised but continued to fly
It’s possible. This would explain the initial change in altitude and heading, as well as subsequent lack of communication but not why the ACARS and transponder were turned off.

2. The aircraft was overcome by toxic fumes
Unlikely. The pilots should have been able to send out a distress call and, again, it does not explain why the ACARS and transponder were turned off.

3. There was an onboard fire which damaged the communications systems
Again unlikely. This would explain the lack of communication but it is unlikely that the aircraft would have then continued to fly as long as it did if the fire continued to burn.

4. The aircraft was hijacked
A possible theory but the aircraft was not flown to another destination nor was it used as a weapon for a suicide terrorist attack. If it was an individual hijacker, then no one person or motive has been established and, if it was a group, no organisation has claimed responsibility.

5. The aircraft was deliberately diverted by the pilot/co-pilot
Possible again but no reason for this has not been identified. If it was a suicide attempt then why did the aircraft continue to fly for so long?

Technical questions:

1. How easy is it to turn off ACARS and transponder?
Turning off the transponder can be done from the cockpit and is done routinely whenever aircraft have landed. Turning off ACARS is more complicated and would need someone with systems knowledge having to go into the aircraft’s avionics bay.

2. Could the aircraft’s communication systems have been disabled by any other means – such as fire/birdstrike/power failure/sabotage by third party from avionics bay?
Birdstrike is unlikely to have caused such damage but the other explanations are all possible. It is possible to disconnect communication systems from avionics bay but this should have been prevented if security was adequate.

3. The IFE moving map would have shown that the aircraft was going off course. So why were there no mobile phone calls sent from passengers or cabin crew aboard flight?
The IFE map may have been turned off. Most of the passengers may have been asleep and not realised anything was wrong until it was too late to do anything. If they tried to phone later in the flight, the aircraft would have been in a remote area over the ocean where there was no signal. Alternatively, the passengers and cabin crew may have been incapacitated in some way, such as by hypoxia due to cabin depressurisation.

4. How long could the aircraft be flown if depressurised?
The aircraft could continue to fly automatically untiI the fuel ran out. The effect on the people on board would vary depending on the altitude of the aircraft. If the aircraft was above 35,000ft, it would take about one minute before everyone was incapacitated. However, if the aircraft had depressurised, oxygen masks for the passengers should have descended automatically which would work for around 15 minutes. The flight crew could have lasted longer using oxygen masks depending on whether they used pure oxygen or an oxygen mix.

4. Could either the data or the homing beacon on the ‘black boxes’ be tampered with during flight?
No. The cockpit voice recorder (CVR) and flight data recorder (FDR) cannot be tampered with.

5. Could data from aircraft still be sent to satellite if aircraft had landed/crashed in sea?

6. The RAeS Flight Operations Group has written a report about dangers of lithium-ion batteries as cargo. Could they be responsible for a fire?
Possible but unlikely. It has been reported that lithium batteries were being carried in the rear hold of the aircraft but the aircraft is unlikely to have continued flying for so long if a fire had broken out. It also does not explain why the communication systems were turned off.

7. What happens when an aircraft flying on autopilot comes to the end of a FMS waypoint? Carry straight on, circle etc?
There are options for the aircraft to either continue on its current heading and to begin circling.

8. Is live (or triggered) streaming of black-box data feasible?

Yes it can be done but it would be very expensive for an airline to fit such systems to every aircraft in its fleet.

9.   What do you think will be the implications of this incident for the aviation industry?
-    A change in ATC procedures as to when an aircraft must make contact.
-    Improved communications between different international civil and military organisations
-    All airlines need to have 'crisis cell' which is activated for aircraft accidents
-    Aircraft positions and status could be transmitted regularly to airline and manufacturers – but systems would be expensive to install.

Simultaneous failures?

 The hunt continues for the wreckage and the vital CVR and FDR. (RAAF).

One technical expert highlighted the fact that, for every plausible scenario suggested so far as to what might have happened to MH370, there was at least one contradictory statement. “If it was hypoxia, then who turned the aircraft?” he asked. “If it was a fire, then how did it continue flying?” “If it was the flight crew, then why did the cabin crew not intervene?” He suggested that, perhaps, more than one scenario occurred simultaneously – such as a wiring fire and depressurisation.

But, until more evidence is found, nothing can be proved.

Bill Read
27 March 2014