Takata,
Quote:
Originally Posted by
Machinbird
The problem with the trim is that it moved to a high aircraft nose up setting without crew awareness.
Takata
Any pilot flying an aircraft with autotrim should know that his trim will follow his stick imputs, shouldn't he?
Yes, assuming he knows he made the stick inputs.
Quote:
Originally Posted by
Machinbird
It appears that a FBW aircraft requires the pilot to know exactly what mode the aircraft is operating in or else the question arises, "What's it doing now?"
Takata
Isn't it one of the basic skill needed for one wanting to be rated for a specific type? What makes you think that many FBW pilots don't know exactly in what mode their aircraft is operating?
Takata, suppose we sat a pilot down and hit him with a fire hose stream. Do you think he can remember his birthday while this is going on?
Perhaps a couple of recent accidents make me think that way.
Quote:
Originally Posted by
Machinbird
In the case of the AF447 crew, they had no attention to spare to consider what the trim might be doing
Well, considering that the trim was doing what a type rated PF asked, and what it is always supposed to do in such a case, what would be the point to consider that it would take more "attention" than usually?
Takata, have you ever been in a
really stressful situation while flying? From your comments, it appears that you have not. That is fortunate for you, if so, but it gives you a blind spot with respect to the effects of in flight stress. You seem to be assuming that the initial pitch up to FL375 was deliberate.
Quote:
Originally Posted by
Machinbird
thus the nose up demands caused the trim to run silently to a high setting
Hence, as usual when imputs ask for a lot of nose up, what is wrong with that?
Nothing down low when setting up for a landing, a whole lot is wrong when it happens at cruising altitudes. The problem is the silent motion of the trim. They needed to know it was moving so that they could monitor it.
Quote:
Originally Posted by
Machinbird
without the knowledge or anticipation of the crew.
What make you believe that a type rated crew would not anticipate it or lacked the knowledge that it will do exactly that? Do you think that it wasn't what they wanted, nose up?
Yes, I think that they didn't want all that nose up initially. Later, after the stall, who knows?
Quote:
Originally Posted by
Machinbird
Once at a high setting, the trim acted to stabilize the aircraft in the deep stall that they eventually achieved.
Right, the PF achieved a full stall with the help of the side stick, thrust and THS trim. Hence, what's wrong with the side stick, the thrust lever and the THS trim?
Just an opinion at this point, but the addition of TOGA thrust coinciding with the second stall warning is too reminiscent of an airline approach to stall procedure as recently taught, except pitch control was improper/clueless as it had been since PF said"I have the controls."
Once in the stall, it was imperative that stall recognition occur, but it seems, it didn't. Without AOA indicatiors, without stall warning, without comprehending that the decreasing altitude was real, there was one final item that could have explained the situation and that was the THS trim position.
Quote:
Originally Posted by
Machinbird
When the Captain arrived on the flight deck, he had to puzzle out what he was seeing. From the jump seat, the indications were essentially hidden by the wheels themselves.
Beside hindsight, what makes you believe that the Captain would have immediately recovered the situation with all the trim settings displayed under his nose? He wasn't there from the begining of the crisis and still possibly far behind the other pilots. He also might have seen the Flight Control page, where the THS trim setting is displayed, right in front of him...
There is no surety that the Captain would have been able to puzzle out the situation in time if he had seen the THS trim, but if he had noted its very abnormal position, there is a logical thought process that should follow that would lead to stall recognition. For him to check the THS position, he would almost certainly have to form the thought to check it and then lean over for a peek.
Quote:
Originally Posted by
Machinbird
The THS autotrim system has virtually eliminated the problem of trim-runaway, but it has replaced that problem with a new set of problems.
I still can see the problem with the THS trim. If they had acknowlegded their stalled situation in time, they would have immediately applied full and sustained nose down imputs, hence, THS trim would very likely follow that. If, for whatever reason, THS trim would not follow those imputs, not enough elvators authority should have attracted PF attention about considering that trimming nose down could help him... at least, theoretically if his training level wasn't the issue.
We seem to agree that they likely never tumbled to the fact they were in a stall. The recent Perpignan trim related accident combined with the AF447 accident seem to indicate that there are issues in trim position awareness in Airbus land.
My apologies for a rather cursory reply, unfortunately I have limited time during the week.