Stab Electric Trim Motor

[N14ND]

Finally getting to run wire through the airframe and instrument panel. Checking my switches when I noticed that the trim motor does not have a cutoff at either end of travel. My motor just keeps running. The jackscrew stops at the required travel movement, but the motor keeps on spinning if the switch is depressed. There's no binding or anything. I am used to jackscrew actuator motors stopping at each end of travel. Is this the way that the stab jackscrew is designed? (Model: Pittman 9234C120-R3, 73633 Rev E)

Thanks.
Andy

[akarmy]

Yep that's the way they work. It's the same motor unit that's used in all the RV flap systems. It runs to the end of travel then just spins. Now many people have built all sorts of interesting electronic systems along with limit switches and other innovations to shut down the motor at the end of the run, but it's really not needed as far as I can tell and just add's more complexity and additional failure points.

[kitfox812]

Does anyone know of any servicing needed on the jackscrew.

During the annual, I cleaned the outside but does it need removal for
cleaning or anything?

[akarmy]

Not that I know of. Again on the RV's we used them for thousands of hours with no maint. Some people have had problems with oil dripping down from the grease pack on the screw. The oli fouls the brushes on the motor. You will know when the motor stops moving for good. You can open it up and clean out the oil to get it working again.

I think for annual I would run it from stop to stop and make sure it's tight with no excess play or other problems and call it good.

[kitfox812]

thanks andy, doing my first legal annual since our class

[akarmy]

Cool. I'm doing my first also, while I install the electric trim system and clean up a few other details. Been in the paint booth for 4 weeks now and it's getting kind of old! But soon it will be done.