Originally Posted by
Smilin_Ed
Autotrim is useful in ensuring that the aircraft remains trimmed when in autopilot so that when the autopilot is disconnected, either by the flight control system or by the pilot, he is not dumped into an out-of-trim situation. However, as I have said several times before, when I am hand-flying, I don’t want the system changing the trim. I want to do that myself.
Fair enough, that's your opinion - but have you ever actually flown a FBW Airbus? Plenty that have state that the autotrim is completely unobtrusive when hand-flying and that the aircraft as a whole handles rather well.
You have stated that there are good and sufficient reasons for the design of the software in the hand-flying mode, but
AFAIK you have not offered any reasons why that design is preferable to my reasons for disconnecting autotrim when hand-flying.
In fact I did, but it's several threads back - one of the reasons was the ability to have hands on throttle and stick in a pilot incapacitation scenario.
That’s your opinion as a non-pilot. It seems to be the consensus on this forum that the pilots of AF447 were not taught properly. It is my opinion, as a pilot, that because the autotrim continued to follow the inexplicable nose-up inputs by the PF, stall recovery would have been made more difficult, had they ever attempted stall recovery.
And it is my opinion that had the pilots been taught how to use the manual trim wheel then they would have had an option for correcting the position it ended up in due to the overcontrolling that occurred just after FMC disconnect. Of course, more fundamentally than that had they been taught how to handle the aircraft properly manually at cruise flight even that knowledge would have been a mere "nice to have".
And for the record, while I am a non-pilot and have never flown solo, I have been at the controls of gliders and trainers in my youth. I'm not just some techie trying to dictate the way you should fly, I'm just saying that there are valid reasons why the design is the way it is.
Sometime back, someone here offered that the pilots of AF447 only needed to let go of the controls and the aircraft would have returned to normal flight on its own. While that is true with conventional flight control systems and a properly trimmed aircraft (for cruise), it was not true with AF447 because the autotrim had changed the pitch trim from a stable, level-flight setting.
And had they let go of the controls then the elevator demands would have ceased and the trim would have returned to neutral. In addition, the trim wheel is available to move the THS back to a neutral position far quicker than the autotrim would have. There were plenty of ways to recover, but the overriding problem is that the crew failed to recognise the situation they were in and the reason they were in that situation (overcontrolling at altitude). The reason they overcontrolled was because their training was lacking, which is the fault of the airline and the industry.
Originally Posted by
deSitter
Well said, Smilin_Ed! Being a know-all is so endemic in the computer world that it's refreshing to hear the other side put the foot down.
Not helpful -the only one showing a dismissive and arrogant attitude is you.