Ask Captain Lim ~ All about Aviation

Dear Captain Lim,

I read from a Chinese Aviation magazine (April 2008) about this subject. It was reported that the crash was probably due to the existence of water (a natural phenomenon) in the fuel. The water was frozen solid when the giant plane was enroute from Beijing to London via the Artic Ocean. The frozen water or existence of mould blocked the fuel supply to the engines. As a result, the engines ignored the instruction of the flight computer to a small increase in power during its final approach. Was this a reasonable guess as to the cause of the crash?

Also, have all 777 pilots been trained to handle a complete engine failure during the final approach? I'm going to fly on a Boeing 777 on the same route in June 2008. Shall I consider choosing other airlines using other kind of aircraft?

Best Regards,

Janus Poon

Hi Janus,

Your questions give me an opportunity to update all on the BA Boeing 777 crash at London on 17 January 2008.

The AAIB report stated that, "Whilst the aircraft was stabilized on an ILS approach with the autopilot engaged, the auto thrust system commanded an increase in thrust from both the engines.  The engines both initially responded but after about 3 seconds the thrust of the right engine reduced.  Some eight seconds later, the thrust reduced on the left engine to a similar level.  The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust."

So it is confirmed that the engines did not fail but was still on low power. However, the engines failed to respond to further demands for increased thrust from the auto throttles and subsequent movement of the thrust levers fully forward by the flight crew.

At that point of time, the total fuel on board was indicating 10,500 kg (more than enough) which was distributed almost equally between the left and right main fuel tanks with a minor imbalance of about 300 kg.

At approximately 175 ft in the final glide at idle power, the autopilot disconnected and the aircraft descended rapidly. Its landing gear made contact with the ground some 1,000 ft short of the paved runway surface just inside the airfield boundary fence. During the impact and short ground roll, the nose gear collapsed, the right main landing gear separated from the aircraft and the left main landing gear was pushed up through the wing.

With the latest news update and report from the investigators, fuel exhaustion becomes the most likely cause. What caused the fuel exhaustion is still not very clear yet.

The Chinese magazine suggested that the problem may be due to the existence of freezing water in the fuel.

In fact, it was reported by the pilots that the plane had indeed encountered extremely cold temperatures (ambient temperatures as low as -65ºC to -76ºC) over the Chinese/Mongolian border and also after crossing the Ural Mountains. If it were due to fuel freezing as suggested by the magazine, the engines would have been affected there and then (but the fuel is heated on the Boeing 777). Perhaps, during the final approach with the tank level falling and swilling with turning movement of the aircraft or with thawing taking place in the tanks, water was introduced to the engines causing them to fail to produce the thrust when demanded.

Another interesting theory of the crash may be due the effect of some kind of electromagnetic interference on the EEC (electronic engine control - the mastermind of the electronic fuel metering system) of the Boeing 777 - possibly caused by the British Prime Minister's motorcade passing nearby. The argument seems to suggest that when an aircraft approaches and enters an electromagnetic field or if the motorcade was subjected to electronic attacks, the motorcade defense systems would take the aircraft to be an incoming threat.

Well, on the balance of probabilities it seems the fuel contamination scenario is a far more likely cause.  

Boeing 777 pilots are all trained to handle whatever emergencies that may arise.  Handling single engine failures is a mandatory check done every 6 months. Complete engine failures are extremely rare (the BA Boeing 777 did not have complete engine failures) but even that, pilots are competent to react to this kind of scenario - just like what the First Officer did without any loss of lives.

Are the Boeing 777s safe to fly? Well, since they are still flying, perhaps we can assume it is already known that they are safe. So, despite this unusual accident, I still believe the Boeing 777 is one of the safest plane around.

See two videos below...