STEC Servo

[Richard Lanning]

Anyone know where the STEC servo would be located in a PA24-250 besides the obvious - in the wing?

Chasing phantoms in my plane again. STEC 60 would not hold heading. Avionics shop sent out the main computer and found nothing wrong with it. Next step is to look at the servo. Maintenance shop was asking me where the servo is located and I don't know which wing it is in.

Thanks

[Kristin Winter]

The only location I have seen for a roll servo is under the back seat. I have never seen one in the wings, but there is a first for everything.

[Richard Lanning]

So much for the obvious.

Thanks. I just don't want the avionics guy spending hours trying to find the thing.

[Charles Schefer]

I'm sure Kristin is correct. The stock servos for the Altimatic III are in the floor under the rear left seat (roll) and under the pilot' rudder pedals (pitch). I would think that any newer installed autopilot would put the servos in the same places.

- Charles

[Matt Bogard]

I had some problems with my STEC 60-2 not holding altitude last summer. I sent the computer in and it got a clean bill. The plane then went to Arnold Hill at Des Moines Flight Services who did some great old-school troubleshooting. There were several pins in the rack that were loose, a couple connectors, and a ground screw. Much better approach than replacing parts until everything worked. I recommend them in a heartbeat!

This is the log entry:

Removed S-Tec 0111 altitude module for testing. Put unit on bench and supplied plus 10 VDC and tested module for stable and proper output. Verified module appears to work correctly. After reinstalling Altitude Module, installed S-Tec Break-Out box in aircraft for testing of a/p system. Found + 10 volts DC output from pitch computer to altitude module is good, tested voltage at module, found altitude variable input to Pitch Flight Guidance Computer good at computer, Tested for proper 14 Volts DC power at Both Pitch and Roll computers, tested for proper grounds at both pitch and roll computers found ground connections were loose , tested for proper Regulated 10 volts DC from both pitch and roll computers to Mode controller, tested good. Tested Pin tensions in Pitch Flight Guidance Computer rack Found several loose pins and replaced. Tested pin tensions at mode controller found several weak and replaced. Tested all interconnect wiring between A/P mode Controller and Pitch Flight Guidance computer. Tested Start voltage on Pitch Servo, found servo starts at 1.5 VDC, burnt motor in and re-tested motor now starts at 1.1 volts DC.

Ramp tested in accordance with S-Tec 60.2 Pilots Operating Handbook Part Number 8783, 2nd Edition Dated 1 November 2001 Section 4 Pre-Flight tests system passed.

[Steve Marcozzi]

You probably have it fixed by now, but I have a Stec 30 that was all over place on heading. Solution was to tension the aileron cables as well as the bridle cable on the roll servo. In light to moderate turb, it made me about half sick. If memory serves me, the service manual lists aileron cable tension as 25lbs plus or minus 20% and 15lbs on the roll servo bridle cable. Check the manual to be sure. 25lbs was too heavy on mine, so we ended up at 20lbs. Pitch servo motor is behind the baggage compartment bulkhead in the bottom area of the tailcone.

To access the roll servo, you take out the baggage compartment floor and the servo is under the seat. Access to the servo and aileron cables is good.

Hope you got it fixed already!

Steve