Tony Peden writes:
>
> On Sun, 2003-06-08 at 11:36, Norman Vine wrote:
> > David Megginson writes:
> > >
> > > The only problem comes when the AP is trying to handle turbulence --
> > > it might be trimmed all the way up or down handling a temporary spike
> > > when it disengages.  Apparently newer AP's are better at detecting and
> > > handling that as a special case, but the old ones made for some pretty
> > > interesting moments, so a lot of pilots insist(ed) on hand-flying
> > > through rough air.
> >
> > Try flying with the HUD not the Panel and engage the AP when
> > at cruising altitude then use the arrow keys to increase the desired
> > altitude under AP control by 1000 ft or so and note the elevator_trim
> > and elevator control positions on the HUD
> >
> > This should highlite the what the initial 'complaint' was about
>
> It doesn't really matter ... you are still going to run into the same
> problems when the autopilot disconnects.

Well Yes and No :-))

The ETC is a 'low rate' device that takes a *long* time to reset
whereas the EC is 1 to 1 with the amount of virtual force applied
so in FGFS if you fly with the AP in elevation lock and you are in
the process of changing elevation and you disengage the elevation
lock you are left in the situation of the trim, a low rate device, at
probably close to maximum deflection and this requires an equal
but opposite reaction with the manual elevator control to get back
to level flight which is OK and probably quite realistic but it is a
real juggling act to get the ECT back into a 'sane' position as it
requires a simultaneous equal but opposite adjustment to the EC
until equilibrium < both neutral > is achieved.

I am sure that 'some' real AP's are that minimally designed but ....
I sure hope they all aren't :-)

I guess it would help if we had a something other then a single
step <pulsed > interface to the ECT too.

I also think this is compounded by some of the FGFS internal
AP logic as to how the ETC and the EC interoperate and some
of the 'kludges' made to try to accommodate many different
models with basically the same system

Cheers

Norman


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