Posted for "colyncase on earthlink" <colyncase@earthlink.net>:

 JHK,
    I don't know.   that's part of what I am trying to find out.
    probably you hook up a signal input to the auto-pilot to the switched side
of the trim switch.
  ----- Original Message -----
  From: James H. Keyworth
  To: Lancair Mailing List
  Sent: Thursday, November 16, 2006 9:54 AM
  Subject: [LML] Re: trim vs. a/p
 
 
  Colyn:
 
        "...wired so that pilot operation of the trim kicks the auto pilot
off.."
 
  How would you wire it that way?
 
  JHK

[One way would be to use a dpdt relay to control the  A/P circuit and two 3pdt relays to control the pitch trim.  Assume that the hot side of all 3 coils are each fed by their respective breakers (one for the A/P system, one each for the pitch/roll/and yaw trim relays (allowing you to disconnect any individual trim suffering a runaway or other fault.) This way you will simply be sending grounds to actuate the relays (common prectice).

Starting with the up/down trim switch (typically a momentary contact SPDT center off) with a ground hooked to its (center) common you would connect the up-switched side to the negative side of the up-trim relay coil.  On the up-trim relay use the #1(+) & #2(-) common and NO contacts to switch power to the trim motor.  Same thing for the down-switched side of the trim switch to the down relay coil, except the the wiring to the trim motor from the down relay would have terms 1 & 2 reversed from how they're wired on the up relay (ie, 1=-, 2=+), causing the motor to run in the opposite direction.  This gets the trims working.

Connect ground to the one side of the A/P engage pushbutton (momentary contact SPST NO) and send its other (switched) side in series through the #3 common/NC contacts of both trim relays, then out of them to the negative side of the A/P coil.  (If "series" doesn't do it for you, here's the path.... ground to 1 side of A/P pushbutton... wire from other (switched) side of A/P pushbutton to up-trim relay #3 common contact... wire from up-trim relay #3 NC contact to down-trim relay #3 common contact... wire from down-trim relay #3 NC contact to negative side of A/P relay coil... phew.) This way if either trim relay is actuated the ground path to the A/P coil from the A/P engage button is broken by the opening of the trim relay's #3 NC contact, disallowing the actuation of the A/P relay while either trim circuit is operating.  Put a ground to A/P relay #2 common terminal and send the #2 NO contact back to the same place you sent the switched ground from the A/P engage pushbutton (the first connection to the trim relays' #3 contacts, (up-trim relay #3 common contact in the above explanation))... this terminal on the A/P relay acts as a latch for the A/P relay coil but is first routed through the series connections of the #3 NC contacts of the trim relays, once again releasing the A/P with any actuation of the pitch trim switch.  I'll try to do a schematic for you... pictures always make these things easier to understand.   <Marv>     ]