King 150 electric trim failure

[smccray]

Place your bets.... I took off this morning anticipating a normal flight.  My autopilot and electric trim worked fine at the end of my last flight.  This morning.. no worky

Autopilot tested normal on startup.  I did not test the electric trim (probably should have).  Trim was set for takeoff at the end of my last flight via the trim switches on the yoke.  When I took off, I tried to give the plane electric nose down trim on climb out but it didn't work.  I switched to manual trimming and the take off was otherwise uneventful.  In the air I ran a couple tests- the autopilot computer would not pass the self test in the air.  I tried pulling the breaker a couple times and rebooting, as well as flipping the trim switch above the yoke on/off and I didn't get any response.  The autopilot wouldn't pass the self test and the trim wheel didn't move.  Autopilot test did not subsequently work on the ground.

Thoughts? Avionics shop is going to take a look in the morning.  Plane is hangared, no one has flown the plane since the last flight, no maintenance.

[Parker_Woodruff]

and the electric trim switch on the panel was on?

[smccray]

and the electric trim switch on the panel was on?

Yes.  I flipped it off when the electric trim stopped working on me when I was close to the ground, but I turned it back on when testing in the air and on the ground.

[carqwik]

Mine would fail intermittently yet the autopilot self-test would pass on the ground...so I took off the trim switch from the yoke, sprayed some electrical contact cleaner...and now it works just fine.  Have no idea if this might help you but it's worth a shot.

 

[Fetus]

The couple of times I've had my KAP-150 fail in flight (divergent pitch oscillation/porpoising while trying to maintain altitude) was due to either the cooling hose had fallen off the backside inlet or my avionics cooling fan had bitten the dust.  The KAP-150 front edges were uber hot to the touch and would not pass a self-test airborne.  Of course, it magically fixed itself after troubleshooting later in the hangar and it had cooled off.  Fixing the cooling issue solved those issues.  But I don't recall the electric trim being inop when my AP went wonky, so maybe an unrelated failure mode from mine.

[smccray]

Thanks for your thoughts guys.  We'll see what the shop says.

[CAVU Aviation]

I have a Mooney M20R (Ovation) and I just had the same failure in my King 150 AP this morning.  After my run-up, I went through the AP test and it failed.  My trim rocker switch was on, but the electric trim wouldn't do anything.  Reset the circuit breaker and same result.  Did you find out what caused your failure?

 

[flysamo]

went you change auto pilots say from king to Garmin, is the electric trim motor change out during change over or is the system separate. know king has 2 clutch units with motor used to adjust trip. Garmin uses digital control, 

[PT20J]

The GFC 500 has it’s own trim servo - all the B-K stuff comes out except most people reuse the yoke mounted B-K switches.

Skip

[StevenL757]

On 4/17/2021 at 9:28 AM, Richard Griessmeyer said:

I have a Mooney M20R (Ovation) and I just had the same failure in my King 150 AP this morning.  After my run-up, I went through the AP test and it failed.  My trim rocker switch was on, but the electric trim wouldn't do anything.  Reset the circuit breaker and same result.  Did you find out what caused your failure?

Similar problem with mine just prior to the decision to replace the autopilot.  Turned out the panel-mounted electric trim switch was fine, as was the split switches on the control column.  Turned out I had a bad pitch trim servo.  Given the other servos probably weren't far behind, and the repair cost on the older KS177/178/179 servos was in excess of $3000, it made better sense to upgrade.

[Jhj123]

I had this problem.  The KFC 150 would sometime pass the test on ground and sometimes fail.  The yoke switch would work, intermittently.  The A/P would not trim. Took the bird to Executive Autopilots at KSAC.  Dave found two issues, one was a bad solder on the switch post.  He re-tested and could could hear the clutch engage and hear the motor drive but it wouldn't move the controls.  On bench testing the servo he found the clutch wasn't fully engaging, he cleaned and re-aligned the engage assembly and voila! problem solved.

 

Highly recommend Executive Autopilots, class acts from start to finish

 

 

[carusoam]

Great Pirep Jhj!

Best regards,

-a-