Trim problem on Saratoga

Dtaglila

Looking for anyone that has expert with Piper electric trim on a Saratoga. Working on PA32-301 with an electric trim problem, works great in the trim down motion, but when reversing to trim up the clutch chatters and hardly moves the cable. We have checked the cable tensions and they are set correctly. Any help would be greatly appreciated.

Scott Sherer

Hi and thanks for writing. You're going to need to check the entire cable pathway. The pulleys, the rear end, the trim knob and spiral gear pointer, too. My trim jammed in flight just last month and it was found to be the spiral gear pointer on the trim knob. Good luck. And don't forget the AD on the cables. They may need to be replaced.

empannin

Do you have a dual button trim switch on the yoke where both must be actuated to adjust the trim? If so, this might be the issue. The left (smaller button) engages the clutch and the right (larger button) drives the motor. If it "clunks" moving only the small button up or down that is correct. If you move the large button only nothing should happen.
This is a safety feature to prevent runaway trim.
It is possible there is a wiring issue in the up circuit and I would start with the switch to make sure the micro switches inside are working correctly and then trace back to the roll trim motor.
I have not found a wiring diagram for this in my piper Seneca IPC or maint. manual.
Does the Saratoga also have a manual trim wheel? if this moves freely in both directions then it is likely the clutch motor.
If you do not have a manual wheel for trim then this is a big safety issue in the current state as the forces on the yoke to overcome down trim would be significant.

empannin

Manual:
https://www.comancheflyers.com/publication/view/piper-pitch-trim/

griff390

Dtaglila;

Scott and Eric's troubleshooting tips are spot on. Check everything Scott mentioned in detail.

If that doesn't work, follow the electrical troubleshooting tips in Eric's post. Eric's 2nd to last paragraph contains a VERY important key. If the manual trim wheel is difficult to move, you probably have a cable or pulley problem. If the manual wheel moves freely in both directions, you probably have a clutch or servo motor problem.

Here are a few other items to check:
This next paragraph is a synopsis from another Piper forum where a similar problem was reported. An often overlooked item for electric trim on Pipers is the main servo plate on the electric trim servo. "Over time the cable wears a deep groove into this pulley and the cable starts to bind making it harder to move and rendering the electric trim almost useless. ... This is the most overlooked issue on PA28 trim systems." I know your plane is a PA32, but many of the systems are similar.

You mentioned the tension was checked, but also ensure the cable is the proper part number and length. Had a friend who's Cherokee 180 had trim issues. Turns out that prior to him owning it, someone had installed the wrong trim cable (it was tensioned properly, but was the wrong part). Once the correct cable was installed, the trim worked properly.

Have your A&P/IA confirm that the cables are routed correctly around the servo motor pulleys. Improper routing can cause the electric trim to work correctly one way but not the other.

Check the servo motor for worn gears, bearings, and especially the clutch. Finally, ensure that all pulleys turn freely, and that the jack screw on the stabilator is clean and properly lubed.

Let us know how it turns out.

Dtaglila

Thanks to the folks that have commented. Here is what we found, all the pulleys were free and working as intended, we did notice that on full down trim travel the motor worked fine, at the full travel mark we noted the trim turnbuckle was making contact with the upper pulley. We also found the switch to be extremely worn out from years of use. Pulling the switch out enough to check it with a meter proved our suspicions that the contacts were toast. The switch price is a tad bit pricey at $1225.00.

Dtaglila

Update, after the switch R&R we still having the same problem. Though the switch wasn’t the full problem, testing of the switch found intermittent contact. The testing of the servo proved a problem with the clutch on the pitch servo. The servo has been removed and sent in for bench test and repair.

Scott Sherer

OK, thanks for the update.

empannin

I found another tip somewhere on the KFC225 systems (which is a different trim manual)
1) the autopilot disconnect switch King used was undersized and it can sometimes be a source on intermittent failures in the AP and trim.
2) Watch out for the butt connectors used between the yoke harness and the rest of the plane. The motion of the yoke over time can break the connection under the heat shrink.

jagcapt1

Does anyone know who repais electric trim servos/clutches? I have a PA32. The pitch trim servo runs but the clutch dos not engage on the cable.

empannin

Does the clutch actuate? It is possible the clutch side of the switch is not working. I think on the king systems one side of the split trim switch is the clutch and the other is the trim motor.