AF 447 Thread No. 10

[gums]

A/P laws versus FCS laws

I had not seen Sully's opinion of the accident. Thanks for reminding us.

So I hear the narrator describing the onset of the accident - loss of the speed inputs and A/P disconnects. Then Sully talks about the constant back stick. As with Sully, most here will never understand the thinking of the PF. He may have still thought " I can't stall this jet".

So I posit we maybe should look at the A/P reversion modes as much as the FCS reversion laws.

In short, why not simply go to an "attitude hold" mode if only speed inputs are FUBAR? My archaic VooDoo had such a mode called "control stick steering", and was limited by AoA and gee. If you relaxed on the stick the sucker maintained an attitude, and not an AoA or gee. The AoA limiter would come into play long before the gee limiter.

For those flying the 'bus, just put in a tiny back stick that is commanding 1.1 gee versus 1.0 gee. And with all respect for Doze, the system commands a gee, not an attitude or AoA. The THS will trim to reduce the reuirement to hold that tiny back stick, right? But if I continue to hold it, the THS will move more and my pitch attitude will continue to rise. No need to hold full back stick. Just a timy amount will provide the same thing we saw with AF447's pitch.

So my idea is to look at the A/P reversion as much as the flight control law reversion. If the gyros/accelerometers are still working, then the crew has some time to figure out what's going on. No need to go "full manual" in a back-up control law.

What do the 'bus drivers here think?