View Single Post
Old 24th Aug 2012, 18:49
  #92 (permalink)  
TTex600
 
Join Date: Jul 2009
Location: DFW
Age: 57
Posts: 246
Originally Posted by HazelNuts39
The BEA comment is correct, of course. But in the circumstances of AF447 it is mostly theory. It applies if you approach the stall slowly, in still air at low altitude gently manipulating the stick so that you can feel the stickforce increasing the closer you get to the stall. The subtle change in stickforce characteristics hardly matters to a stressed pilot who jerks the stick backwards to increase pitch from 6 to 12 degrees in a couple of seconds. I quantified the difference in terms of stick angle and force.
I'm probably in over my head here, maybe you guys are talking about some deeper issue, but....

I never tried to stall a transport category jet above 17500ft, so I must speculate, but I think you over rate the "subtleness" of stick force characteristics. I'll leave it up to the more research minded among us to find the regulatory standard, but if memory serves there is a minimum value of stick force per knot of deviation from trimmed speed. For the simple minded pilots out there, including me, that means that it takes an ever increasing amount of stick force to fly further and further away from trimmed speed. If the aircraft is trimmed for M80/260KIAS, and the pilot slows down, he must exert an not insignificant amount of force on the stick in order to maintain his new speed. Assuming of course that the aircraft does NOT trim automatically.

I think the BEA wording that you quoted is correct, and it is correct all of the time. It matters not whether you enter the stall from low and steady, or from high and unstable (flight path), either scenario in a "classic aeroplane" (BEA words) requires increased stick force to move and hold the airplane in the slower, approaching stall, situation.

The Bus, offering ZERO control feedback, denies its pilot, completely denies its pilot, this time tested tactile clue to airspeed.

The point I want to make is simple, in our scenario but in a "classic aeroplane" the pull necessary to stall the airplane would not have been "insignificant". In our scenario in the accident airplane, the pull force necessary to induce a stall was apparently "insignificant".
TTex600 is offline