Geschrieben von Capt. Paul Wilson
Die Auswertungen zum Absturz der AF447 haben so manchen Piloten nachdenklich werden lassen: Können die heutigen Piloten noch per Hand Flugzeuge durch die Stratosphäre steuern? Oder sollten die Bordcomputer besser programmiert werden?
50 years ago when jet airliners began flying in the stratosphere pilots did occasionally hand fly the machines at cruise altitude. One of these occasions was when the aircraft entered thunderstorm activity. This activity often produced violent turbulence with a simultaneous updraft on one side of the aircraft and a downdraft on the other side producing conflicting instrument readings across the cockpit and large changes in pitch attitude and climb and descent indications. The procedure in this situation was to disengage all automatics, autopilot and autothrottle, to handfly the aircraft simply to maintain the constant attitude with a thrust setting that was known to produce a speed at the present altitude about the middle of the “buffet boundaries”. Because they knew how to handfly at altitude these pilots were familiar with the appropriate attitude and thrust settings for the condition.
It has been said that even test pilots have been caught out by conflicting instruments resulting from lost pitot/static information and crashed, but the above procedure was taught to all airline pilots. Since then the designers have been persuaded to let computers take over what pilots are better at, flying the aircraft, and left pilots to do what computers are better at, monitor conditions for any deviation. It is my understanding that very few airline pilots today ever handfly the aircraft at cruising altitude so are unlikely to know, to the accuracy needed, the pitch attitude and thrust settings for cruise conditions. If that is the case then we have to find a way to program the computers to do the job!
I suggest that all the information is available in the aircraft’s computer’s memories and a program could be constructed comparatively easily to take effective action in this situation. A switch or button could be provided that the pilots would operate when the “jet upset” conditions were identified. The computer program would then take over the flying of the aircraft to new parameters, holding the pitch attitude and maintaining heading and thrust to give a speed between the buffet boundaries until the pilots can resume normal control. The required information for these settings is already in the computer memories and the weight is known so the only variable in doubt is altitude. This program could use the mean altitude taken over the last ten minutes as a datum to make the calculations and if that is not available in the FMS it could be accessed from the FDR. It might be a little inaccurate but it would serve the purpose for the safety case.
I have “been there” on two separate occasions in the past and lived to tell the tale but if the pilots are not in practice then the computer solution might just save the day.
Captain Paul Wilson flog in der Royal Air Force (RAF) die V-Bomber, später bei British Airways B707, leitete das britische Berichtssystem CHIRP und war anschließend als Berater für EUCARE tätig.
