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TECHNICIAN'S BENCH
Frequently Asked Troubleshooting Questions

Rodney Sinclair
Tech. Rep.

Providing dealers with answers to installation and maintenance questions on S-TEC autopilots is one of our most important Technical Support activities. Here are some of the most frequently asked questions our technical support personnel receive.

Q: Where do you install the Flap Compensator Pot?
A: If a Flap Compensator Pot is to be installed, the location will be specified on the Flap Compensator Installation drawing. There will also be a section in the table of contents of the applicable installation manual.

Q: How do I hookup the GPSS converter if I'm installing a Sandel and it uses an ARINC 429 signal?
A: Parallel the connection. An ARINC 429 is capable of handling at least five devices on the same output.

Q: I installed a GPSS converter. The heading works fine, but what do I do when the GPSS mode flashes?
A: A flashing GPSS mode on the converter can mean two things. One, your ARINC 429 signal may be invalid. Is the GPSS set-up to output ARINC 429 low speed? Two, your ground speed may not be sufficient. The GPSS converter must have a minimum ground speed of 45 knots. How fast can you taxi? Can you put the GPSS into demo mode?

Q: Where do I start when the aircraft either climbs or dives when the mike button is pressed to transmit?
A: Over the years it has become customary to place the autopilot at the bottom of the radio stack. Check the standing wave ratio on the comm. radios, a high S.W.R will affect the altitude transducer. Make sure the coax cables are routed away from autopilot wiring, and check for proper antenna bonding.

Q: In a new install, what causes the aircraft to climb or dive while altitude is engaged?
A: The pitch servo may be wired backwards. Check the installation instructions to find out if the servo installation requires clockwise or counterclockwise installation. All servos are setup for counterclockwise installation. If it is reversed, switch pins 3 & 4 on the 9-pin connector at the servo. After this is completed, also switch pins 6 & 8. These corrections will place the trim indications into the proper orientation.

Q: Why do I keep getting an error code of 4 on my Fifty FiveX display?
A: On the Fifty Five X, after the self-test is complete, a software version number is annunciated. Number 4 is our current software version, not an error code.

Q: I installed a new autopilot and modified it for my heading system. Everything works, but why do I have an 8º offset in heading mode?
A: Make sure the jumper in the autopilot is changed from AC to DC if the heading system is DC.