An airliner some years ago crashed into the Everglades in Florida because the autopilot
was unknowingly disengaged by accidental knee pressure on the Yoke as the pilot
was getting out of his seat.  Specs showed that the minimum 45 pounds pressure required was faulty.
The aircraft had been in a holding pattern pending confirmation that the gear was down, since the
indicator lamp was burned out and the spare broke upon attempted removal from its recessed
location.  Unknowingly the aircraft was slowly descending and the last thing on the voice
recorder ws the co-pilot "Hey, there's something wrong with the instruments" when he
noticed the altimeter showed just above ground level.
If I understand the FG issue correctly, then I would think that a sudden movement of
the Yoke could be used to disengage the autopilot.
Tom Markowitz
----- Original Message -----
From: Ampere K. Hardraade
To: FlightGear developers discussions
Sent: Saturday, June 30, 2007 12:12 AM
Subject: Re: [Flightgear-devel] [off list] patch for control lockingbyautopilot

On June 28, 2007 09:44:54 am Roy Vegard Ovesen wrote:
> On Wednesday 27 June 2007 23:05, woodyst wrote:
> > > >> The diffs are at
> > > >> and
> > > >>
> AFAIK real life autopilots can be overpowered by the pilot. Wheter this is
> done by brute force or if the servos can sense that they are being
> overpowered and then let go, I don't know. Since we don't have any force
> feedback support in Flightgear, we'll have to make the autopilot sense that
> it is being overpowered.
> The hard part will be how to decide that the pilot is trying to overpower
> the autopilot. One possibility is to press a button to tell that you are
> overpowering.

My guess is that it probably monitors the integrated term in a PID controller,
and disengages when the value reaches a certain threshold.


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