Originally Posted by aa73
Thanks for the correction regarding roll rate.
But why does Airbus "auto-trim"? As a pilot I **WANT** to trim out the forces myself - so that I am in concert with what I want the airplane to do. When I put my 757 in a bank, I trim slightly nose up and it's exactly how I've flown for 20+ years.
I don't **WANT** autotrim, as it removes me from control that much more. I want to know where my trim is at all times. Is there any way to disconnect the autotrim and keep 100% "hands on" operation?
edit: in response to TTex: understood about the FBW not failing in AF447. But - and this is a big but - do you Airbus folks believe that the lack of "cues" (sticks not moving together, throttles not moving) contributed to the lack of the pilots' SA?
aa, This site has a large number of engineers/programmers/techies who can tell you why it autotrims. I only know that it does. I agree, I want an airplane to stay on trim speed when I put it there, I hate having to chase airspeed when hand flying.
You can not disconnect auto trim, and contrary to the flight manual, you can't trim like a normal aircraft. Even if you attempt to manually trim, the system will fight you and remove your input as soon as you release the trim wheel. This is because the trim trims for "g" and for flightpath, unless you train your brain to trim for flightpath or "g", you will never get it in trim.
The AF447 discussion has about a million responses on at least seven threads, so I'll let you dig through them regarding the FBW failing. FWIW, my
opinion on AF447 is this: everything contributed to the accident. In no particular order, I think poor training and procedures (based upon some utopian claim that the airbus flys like any other airplane), combined with auto trim that trimmed nose up well past the stall angle of attack, combined with the FP's limited experience (outside of the AB world and in manual flight), combined with the PM's lack of CRM, combined with bad pitot tubes, combined with flat glass/tape style displays, combined with non-linked SS's, all caused the accident. Oh yeah, had the crew been trained in cruise level Unreliable Air Speed drills, or how to properly take the controls, they would likely be drinking wine on the beach at Rio today.
For your future line flying, many of us have developed our own personal procedure for indication anomalies at cruise. It goes something like this.....ANY possible discrepancy of A/S, etc, leads to A/P off, Auto Thrust off, Flight Directors OFF, set 80% N1 and hold 2.5 degrees nose up and ignore all else until you are absolutely certain that you have it under complete control. You have to trust something, attitude and power are the most reliable instruments so we go with them.