From: Melchior FRANZ <[EMAIL PROTECTED]> > Get into an aircraft with autopilot (preferably one with 2D panel, e.g. > the c182), climb to some safe altitude, then switch the autopilot to > altitude lock. Now pitch up or down manually and watch the elevator > trim go to the opposite direction. While it is off, unlock the altitude. > The elevator trim is left at its last position, which may be quite > extreme and can make the aircraft somewhat difficult to handle, until > it is (slowly?) trimmed back to a sane state by the pilot.
Actually, there are two kinds of vnav autopilots; one runs the trim and the other applies elevator forces directly. Both are popularly in use. For the former, the unpatched behavior is correct and generally preferred. Its advantages (see other messages in the thread) outweigh disadvantages for use in real aircraft. It is important to remember to turn off the autopilot before trying to do hands-on flying. Some aircraft detect stick forces and sound a warning while forcing an automatic disconnect. It would be useful to implement this feature (as a type-specific option) into the FGFS codebase because its benefit is similar to your intent. For the latter, where elevator forces are applied directly, the problem of fighting the trim does not occur. Instead you have the danger that the autopilot may be operating with considerable elevator forces so that a sudden disconnect can be extremely surprising and difficult to recover from. Again, since many light aircraft use elevator autopilots, we need to support this mode (with its dangerous risk) as well. Hope that helps ... _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
