Air France 447
The final report on the Airbus A330 Rio to Paris Air France 447 accident is not out yet but preliminary information provides a lot of food for thought. It is a safe bet that many thousands of words will be written about this. They will come from all points of view and represent a multitude of opinions. Here is mine.
The accident sequence started when the airspeed sensing system on the airplane went haywire, likely because of pitot system icing. When the autopilot was fed erroneous data, it disconnected. The captain had just gone on a rest break in the cabin so one of the two first officers in the cockpit took manual control of the airplane. To control what was an apparent increase in indicated airspeed, caused by the pitot anomaly, the nose was pitched up by the pilot. The airplane climbed from Flight Level 350 to 38,000 feet where it stalled. The airspeed was low not high. Everything was backwards.
The captain was called to the cockpit but apparently did not retake control of the aircraft.
The crew flying never recovered from the stall and the airplane descended to the surface of the ocean. It had gone from 38,000 feet to the water in under four minutes. All during the descent the angle of attack was deeply into the area of aerodynamic stall, reaching as much as 45-degrees.
The nose of the airplane was held or trimmed up for most of the descent. The wings rocked back and forth but lateral control was never fully lost. Despite the high angle of attack, the engines were apparently running and responsive up to the moment of impact. It is the opinion of most that the stall could have been broken and the airplane recovered. This, though, would have taken a lot of altitude. It might have also taken an almost instantaneous burst of brilliance in the first couple of minutes after the stall, when a recovery could have been possible without crashing into the water.
When the airplane reached the ocean surface, it was descending at a rate of 10,912 feet per minute. The pitch attitude was 16.2 degrees nose-up and the airplane was in a 5.3 degree left bank. The groundspeed was 107 knots. Airspeed indications varied widely during the descent, as reflected by the flight recorder.
Flight 447 was flying in or near the Intertropical Convergence Zone where there are usually numerous thunderstorms. The crew made a small heading adjustment right before the event started, presumably for weather. The airplane was flying in some turbulence and they had reduced airspeed from .82 to .80. No significant turbulence was reported or recorded and it is unlikely the Captain would have gone to the cabin on a rest break had the path ahead appeared menacing.
The A330 is a highly automated airplane as are all modern airliners and new-production general aviation airplanes. Operation of these airplanes requires specialized training and the mental dexterity to operate complex systems and to compensate when they malfunction. This is not the first time an automated airplane has crashed because of a problem with one or more of the systems and it won’t be the last.
The lesson is that, in a heartbeat, the automation can crap out and hand the pilot an airplane that has to actually be hand flown using basic knowledge and good piloting skills. The information supplied by the systems can be flawed, too, as it was in this case.
Nobody will ever know much if anything about the thought processes of the pilots as this event unfolded. I have no idea what the sounds and feelings would be in an A330 in such a completely developed stall but it could not have felt normal. One observer noted that the word “stall” was not used by the crew. Surely, though, they knew that something was badly wrong even though, almost as surely, they didn’t know what was wrong. If they had known, they would have tried to do something about it.
When confusion is induced by erroneous instrument readings, the basics of flying remain the same but the basics of pilot thinking do not. Quite obviously there was an indication of increasing airspeed which is what prompted the pilot to pull the nose of the airplane up which resulted in the stall. At this point the pilots might have become completely confused because of conflicting information.
There was a similar accident years ago, in a Boeing 727. The airplane was climbing, the pitot heat was not turned on, and when it passed through the freezing level, in clouds, the pitot iced over. As the airplane climbed, this resulted in an erroneous and continuing increase in indicated airspeed. The pilot flying pulled the nose up to try to control the airspeed and stalled the airplane. As with the A330, the stall warning activated which was apparently thought to be in error because the pilots were trying to deal with increasing airspeed, not a stall. The 727 descended from 24,000 feet to the ground (elevation 1,090) in 83 seconds.
I can relate to such confusion because, to use that hackneyed old saying, I have been there and done that.
It was on May 28, 1975. I was flying a brand-new Cessna T210, en route from Cessna Field in Wichita to a fuel stop in Colorado Springs.
There was a front to traverse and it got wet and bumpy. The rain was so hard that the airspeed was jumping around a bit. To help with the bumpy part I asked for a higher altitude. To help with the fluctuating airspeed I selected the alternate static source.
As I pitched the nose up and started to climb, the airspeed started increasing. To that point in the flight there had been no indication of convection but I wondered if I had suddenly flown into an updraft.
Then I thought I should take stock. The pitch attitude was normal, the engine power was set for climb, and there was no increase in air noise as would be found with increasing airspeed. My plan was to maintain the correct pitch attitude and think for a minute.
As is always a good practice I thought back to anything I had changed. The static source was the culprit. The alternate static system had been incorrectly hooked up when the airplane was assembled and when I selected it, it completely closed the static system instead of letting it vent to the cockpit as it was supposed to do.
By going back to the primary static source, I calmed things back to normal.
I’m going to digress for a moment for another lesson on how brand-new airplanes need to be flown with caution and suspicion.
We were taking two new T210s to Monument Valley for some air-to-air photography. After stopping at Colorado Springs we both vaulted up into the Flight Levels in honor of the Rocky Mountains. The other T210, flown by Chuck Hinson of Cessna, was ahead and 2,000 feet above us at FL220.
Chuck called the controller and told him he had a power failure and was declaring an emergency. I called the controller and told him I was responding to the emergency by circling where I was because I knew the other airplane would be descending through my altitude and we were flying in clouds.
As Chuck descended, he realized he still had some power. The turbo hose on the airplane had been incorrectly installed when the airplane was assembled and it had come loose, making it a normally aspirated airplane at 22,000 feet, or, one with not much power. So, two brand-new airplanes with manufacturing screw-ups, all in one day.
Pilots do have to always be ready for glitches. Anything can and will eventually happen. In an automated airliner you would think the flight control system would have an autopilot reversionary mode that would set cruise power, maintain a level- flight pitch attitude and keep the wings level without regard to other inputs. From reading the preliminary findings on the A330 crash it is certainly obvious that they need to go back to the drawing board and evaluate all the warning and flight control system things that happened and overwhelmed the crew, all because of a relatively simple loss of accurate airspeed indication.
In the meanwhile, pilots can always handle what automation doesn’t comprehend when something goes wrong. By hand, we can set cruise power, maintain a level-flight pitch attitude and keep the wings level. The next step would be to troubleshoot whatever is going on. That might be called basic airmanship, something that needs to be stressed while preparing pilots to operate automated airplanes. Bells and whistles are fine when they work correctly but in the end the system that leads to a successful outcome is called “pilot-in-command.”