Posts about: "Auto-throttle" [Posts: 22 Page: 2 of 2]¶

Hi all, amazing thread! I hope I can add a couple of autopilot questions:

1. Did anyone ever use the IAS Hold button in the vertical mode, i.e. control speed with pitch instead of autothrottle? I always thought it might be used during climbout to maintain 250 knots under 10000 feet at full throttle.

2. How did the autopilot work in 'Go Around' mode and was it ever used, or were go arounds always done manually?

Thanks in advance,

Jim

Bellerephon:

Interesting!
About eighteen months ago a MD11 piloting friend and I had a close look at that machine to see if we could identify any features that might explain its poor hard landing record. We came up with a tentative explanation that the shortish tail arm combined with high pitch inertia led to a slight, but significant, increase in the delay between elevator application and flight path response (negative elevator lift effect) and that this could make attempts to make flight path corrections from very near the ground hit or miss affairs (no pun intended!). The response was crisper at higher airspeeds and (with admittedly limited experimentation) he concluded that leaving the autothrottle engaged down to a lower height above the runway improved matters. Avoiding late corrections and just taking the medicine could also be a good idea.

One of the boffins at RAE Bedford raised this elevator negative lift effect as a possible Concorde concern about the time of first flight, but experience then and for some time after suggested this was not a big problem.

Now I am wondering whether the sequence :- increased wind/greater turbulence/more chance of needing last minute (second?) corrections/negative elevator lift effect/more hard landings might be a reasonable explanation of the question posed in the OP.

Did Mike Riley offer anything along these lines? or if not what did he come up with?