Stabilator Bearing and S-TEC 55X

[Greg Banfield]

Troubleshooting a porpoise issue and have looked at all the usual suspects (transducer, computer, servo, voltage, static system, cables, pulleys). S-TEC thinks there is binding in the stabilator system. It seems fine to me, but that is very subjective. AP and I are considering replacing the stabilator bearings as I think they are originals and might be causing just enough friction to make the S-TEC porpoise slightly.
Question: Is there a documented pull force spec that can be measured to give me an idea how good or bad my twinkie is in regards to force need to move yoke out /in?

[N3322G]

Hmmm. I run a C2000 and it gets its sensing from the attitude indicator and when it porpoises, it generally means the attitude indicator needs O/H. Where does the STEC gets its sensing?; IIRC it gets it from somewhere else? That would be my first guess - and it is a guess.

[Greg Banfield]

Pat-

S-TEC uses pressure transducer and accelerometer. I do not have target altitude capture in my installation so no inputs for that. I was more interested in the elevator. My elevator will stay in the position I place it in full up, down, center and not move. Was wondering it that is not correct and the elevator should drop from full up to at least level on it own. This may be an indication of friction in the system, but since I don’t fly other aircrafts, hard for me to know.

[N3322G]

The stabilator on my Twin moves freely when I raise it on pre-flight and I allow it to gently return to the starting position from which I moved it.

If I were you I'd take it to a knowledgeable Comanche guy like Jim Hiatt in Ft Lauderdale so you don't pay someone for the leaning curve and possible errors.

[Clarence Beintema]

Greg,

Have your maintenance people disconnect the pitch control cable accessed through the panel on the right side of the fuselage. Once free of the cable you will be able to move the stabilator to determine the cause of the friction. Like a good many Comanches the bearings have not been greased since they were manufactured and there is no provision to do so in service.

A new set of beatings may be in your future, along with that you should be doing sb 1160 & 1189, setting the travel stops and checking the balance.

Clarence