Dec. 30, 2014: With the apparent discovery of the main wreckage of AirAsia Flt 8501 in about 100 ft of water, recovery of the airplane and its black boxes should be a relatively straight-forward operation.
Our previous posts have outlined general areas of inquiry. With this post, we drill down into some of the flight and airplane questions that will be part of the inquiry. We talked with an Airbus A320 captain for a major US airline in forming these issues. This captain has been flying for US carriers for 30 years and is rated on Boeing 737s, the McDonnell Douglas DC-10 and the A320.
- Pitot tubes: There has been plenty of speculation in the media about whether the pitot tubes on #8501 might have frozen over in a manner similar to Air France 447 in 2009, leading to a series of events that resulted in the crash of 447 and perhaps 8501. There has been only one reported incidence of pitot tube issues on the A320 that we know of and this pilot has never experienced such a circumstance.
- Airspeed: It’s been reported, but as yet not verified, that based on one of the Internet flight tracker sites, 8501 at one point reached an altitude of 36,300 ft, an indicated ground speed of 343 kts and a true airspeed of about 184 kts. Bearing in mind that this is unconfirmed information, the A320 captain’s reaction was, “That’s not good.” At that altitude, the airspeed should be at least 400 kts.
- Altitude: The flight had been at 32,000 ft and requested a higher altitude due to weather. This request was denied due to conflicting traffic above. If the flight tracker information is correct, how did the flight reach 36,300 ft? The A320 pilot said it would not be at all uncommon for huge updrafts to put the airplane at the higher altitude in a very short period. Huge downdrafts could also push the airplane down. Only read-outs of the flight data recorder (FDR) and cockpit voice recorder (CVR) will clarify this.
- Did the pilot know what he was flying into? Although the pilot requested a course deviation and different altitude due to thunderstorms, did he have a full appreciation for what he was flying into? Only the CVR will likely clarify this. If he did, why didn’t he make a declaration of the seriousness of the situation to ATC? Again, perhaps only the CVR will answer this question. If he didn’t have a full understanding, why not? Was the cockpit weather radar display accurately or inaccurately “painting” the picture for the pilot?
- Was there a failure of one or both engines? If the storm “drowned” one or both engines, or if hail damaged the engines, shutting them down, the airplane was doomed. The FDR and CVR will answer these questions, along with forensic analysis of the engines.
- Was there a high altitude upset? Did extreme turbulence cause the flight to “upset” from its flight attitude, and if so, by the time the pilot recovered, was it too late and the plane impacted the water? The answer will lie with the FDR and CVR.
- Did any structure separate from the airplane prior to impact? If there was an upset, did flight controls or the vertical or horizontal tail separate from the aircraft during a descent, dooming the airplane? Structural analysis and FDR/CVR will answer these questions.
- Did the airplane go into a deep stall? Extreme turbulence could have caused a deep stall, which could cause the A320 to go from Normal Law to Alternate Law–that is shifting control from the computerized flight envelope protection to direct control by the pilot. In this event, our A320 captain said, the pilot essentially winds up flying by the seat of his pants, feeling G forces, and using basic flight horizon and attitude instruments to try and fly his way out of the problem. CVR and FDR data will answer this question.
There are hundreds of more questions to be answered–but these will be some of the key ones.