This is not for me personally. I am trying to help someone out who helps me out a lot.
A colleague of mine is one of several people who installed the autopilot on a customer aircraft. There is also an avionics wiring guy involved. The aircraft owner is the “prime contractor”. No avionics shop is involved. The whole job was done under the FAA STC.
The Aspen is displaying a NOT COMMUNICATING WITH AUTOPILOT message. This message remains present continuously.
Despite the above message, the autopilot is reported as working in all lateral modes in flight, but there is no pitch control. If you select any pitch related mode i.e. VS, ALT, the aircraft pitches down.
The EFD1000 IM is 200+ pages… I reckon there could be some config issue in the Aspen, and/or possibly in the STEC.
The wiring harness came with the STC, amazingly.
Can anyone think of anything obvious?
Many thanks 
I dont know if this is of any help … probably not but try it anyway
My autopilot (STEC 55X) played up a few weeks ago, everytime I connected the autopilot it piched up or down sharply.
Engineer was ready to send it back for overhaul when someboby said to me … " you do drain the static drains before every flight ? "
Did that, now works perfectly
Peter wrote:
Despite the above message, the autopilot is reported as working in all lateral modes in flight, but there is no pitch control. If you select any pitch related mode i.e. VS, ALT, the aircraft pitches down.
I am no Avionic guy but what I do know is that there is NO input in terms of pitch that the AP gets from the Aspen. Altitude hold and VS are steered by an independent altitude sensor in the STEC setup. The fact that the AP pitches down whatever would tell me that there is something wrong already there. Possibly a misbehaving main computer or a problem with the altitude sensor and its connection to the static line.
Interesting; many thanks. But then how does it e.g. fly an ILS or LPV? The L and V guidance for an ILS comes from a VHF nav radio, and for LPV it comes from a WAAS GPS.
So what could that Aspen error message mean? I can only be based on RS232 or ARINC429 comms. With analog connections there is (generally, in avionics) no feedback.
My suspicion is that some comms ports on the Aspen need configuring, and this has not been done. Or perhaps the Aspen has some comms port(s) which are faulty. It is not that uncommon in avionics installations to find that say 1 our of 3 comms ports is duff, so you move the connection to one of the others (and not necessarily document it 
).
What serial comms connections are there between an EFD1000 and a 55X? I don’t have the wiring diagram for this STC, but could get it.
If the installation includes an ACU2, it should support Altitude preselect and vertical speed with the Stec 55X. I would get the appropriate install manuals and they should provide guidance.
