Aviation Attorney Arthur Wolk says a recent emergency airworthiness directive may explain what could have caused crash of AirAsia Flight QZ8501.

The latest word from the Government of Indonesia is that the cause of the crash was entry into a thunderstorm that resulted in so much ice accumulations that one or more engines failed and the airplane stalled.

Any ice accumulation sufficient to shut down one of these engines would literally have to be so large that it covered the entire engine inlet. The aircraft is equipped with inlet heat to prevent just such an accumulation which has never happened even without inlet heat. The inlet is about 6 feet around.

Large ice accumulations if the heat was off could cause foreign object damage to an engine but it would take far more than one engine being damaged to cause the loss of this airplane.

Loss of an engine simply means the crew must descend to a lower altitude but this crew ascended so power was available and thus the engine didn’t fail.

An aerodynamic stall that apparently is misunderstood by the Government official is also virtually impossible due to a single engine failure.

The remaining engine  has more than enough power to maintain flight albeit at a lower altitude.

The Emergency Airworthiness Directive issued December 10th says that ice can prevent angle of attack sensors from operating, pitch the airplane nose down and prevent the sidestick controllers from allowing the crew to pull out of a dive. That scenario is far more likely as is a breakup due to turbulence.

If the pitot tubes used to provide airspeed data to the computers iced up, the aircraft can stall due to misinformation provided to the flight control system.

The current theory appears to be generated from industry representatives attempting to establish pilot error as the cause rather than airplane defect. That undue influence on investigators happens all the time.

If they don’t figure out or disclose or fix how the airplane’s computer architecture contributes to these accidents, they will continue to occur.

The weather was bad, and perhaps the crew should have refused to take the flight but Airbus needs to be transparent about how pilots need to have the last word how the airplane operates not the computers that interface with them.

Arthur Alan Wolk

January 4, 2015


Pilatus PC-12 Crash Stinks: Answers are needed!

Fourteen people killed in an aircraft that can only carry ten has the stench of carelessness all over it. Most PC-12s can safely hold only six to nine passengers and one or two pilots. Why were there so many aboard the Pilatus PC-12 and where were they seated? Where was the baggage and where was it stowed? How much did it weigh? Why did the aircraft divert? What were the qualifications and experience of the pilot? Was there a second pilot aboard?

These preliminary answers are needed to explain why the Pilatus PC-12 fell out of the sky, nose down, before several eyewitnesses. Did it aerodynamically stall because it got too slow on final approach? Did it accumulate ice when flying at altitude and suffer a tail stall when the final flaps were selected? The weather at the accident site looked good but there was an area of significant icing en route. Did the engine quit as it has a number of other times in PC-12s, dooming the aircraft to a crash short of the airport?

My calculations show that to stay within the gross weight limits, the pilot could only have put about 160 gallons of fuel aboard, less than what is required for a two and one-half hour flight plus reserves. The payload of a Pilatus PC-12 is about 3,900 pounds. Seven adults weigh a minimum of 1,300 pounds. Seven children weigh about 500 pounds minimum. These passengers were going skiing, so baggage is figured at about 1,000 pounds total which includes skis, boots, poles, clothes, etc. Together, that comes to 2,800 pounds, leaving about 1,100 pounds available for fuel or about 160 gallons.

The flight plan was for two and one-half hours en route which, together with required reserves, would have left very little useable fuel at the time of arrival and would have explained the diversion to a closer airport. Essentially the National Transportation Safety Board needs to look at whether the fuel was managed properly, or whether the engine quit on a short final approach with the fire coming from unusable fuel that misted or perhaps there was more unusable fuel than certified.

Other questions must also be answered. Some of the equipment on board may have had a non-volatile memory chip that could be helpful but the fire and impact may have destroyed that forever.

The Pilatus PC-12 like so many other turboprops has deicing boots that inflate to remove accumulated ice. These boots have proved inadequate in many other turboprops and if runback ice accumulated on the tail, or on the wings at altitude, and could not be shed, the extension of flaps might have shifted the center of lift aft and caused a tail stall which would have pitched the nose down sharply as described by witnesses.

Coming on the heels of Continental Flight 3407 at Buffalo for similar reasons, it is long overdue that turboprops be prohibited from flying in icing conditions until they all are retrofitted with anti-ice instead of deicing equipment. That way ice is not permitted to accumulate at all on aircraft that have proved time and time again their inability to fly in icing conditions safely.

This crash, like most, will be found to have been preventable and unnecessary. How horrible for these parents and their families!

– Arthur Alan Wolk