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Islip Avionics, Inc.
In-Flight Avionics Troubleshooting Guide

KEEP THIS GUIDE IN THE AIRCRAFT. This will help troubleshoot a problem in-flight and help Islip Avionics diagnose a problem after all these common problems have been considered.

Download PDF for printing: Pilot's Trouble Shooting Guide.


General Troubleshooting
  • Check the aircraft circuit breaker or fuses.
  • Is there an aircraft voltage problem?
  • Could water have leaked on to the avionics?
  • Could a connector be loose or wires broken from recent maintenance?
  • Is the unit seated correctly in its mount?
  • Do you hear alternator or magneto noise?
  • Are any antennas corroded, dirty, broken, oil coated, or delaminated?
  • Is it intermittent?
  • Is heat, cold, altitude or time a factor?
COM Radio / Audio Panel / Intercom
  • Are the audio switches set correctly?
  • Is the auto mode being used?
  • Is the volume set correctly?
  • Is ICS in pilot isolation mode?
  • Is a mic key stuck?
  • Do you hear both the phone and speaker?
  • Does it both receive and transmit?
  • Do you hear sidetone?
  • Do you transmit carrier without voice?
  • Does it make noise with squelch disabled?
  • Try a different headset or microphone.
  • Try an emergency or isolation mode.
  • Are the plugs or jacks corroded?
  • Do all positions have the same problem?
  • Does the second COM act the same way?
VOR / ILS
  • Do you receive the ident tone?
  • Do the needles or flags move at all?
  • Can you select a reciprocal OBS course?
  • Does the TO/FROM flag work?
  • How many degrees off is the VOR?
  • Does the VOR test (self or VOT)?
  • Does the VOR have 20 degrees deflection?
  • Does the Localizer work but not the VOR?
  • Are you close or far from the station?
  • Could tail antenna shadowing be a factor?
  • Is the indicator switched to the correct NAV?
  • Is there a NOTAM of any outages?
Transponder
  • Does both Mode-A and Mode-C work?
  • Is Mode-A inop or just wrong codes?
  • Is Mode-C inop or just wrong altitude?
  • Does the reply lamp illuminate?
  • Is the dimmer turned down?
  • Is it in the correct mode?
  • Does it recycle (power off then on)?
  • Does it test?
  • Does DME interfere?
GPS
  • Verify the correct waypoint.
  • Check present position or nearest airport.
  • Are at least three satellites being tracked?
  • Is the satellite geometry poor?
  • Are the satellite signal levels adequate?
  • Has a current almanac been downloaded?
  • Is the hold mode selected?
  • Is the NAV selected to an ILS frequency?
  • Is there a NOTAM for outages?
  • Are there any warning messages?
Autopilot
  • Does the autopilot engage?
  • Can you overpower the autopilot?
  • Do the controls lock when engaged?
  • Could the control cables be too loose?
  • Is the aircraft out of trim?
  • Is the gyro vacuum within limits?
  • Does the autopilot hold wings level?
  • Does the autopilot hold heading?
  • Do the wings rock?
  • Does the autopilot respond to basic pitch hold?
  • Is the autopilot following a precessing gyro?
  • Does the autopilot hold altitude?
  • Does the autopilot lose altitude in a turn?
  • Does the autopilot porpoise?
  • Does the autopilot respond to NAV?
  • Does the autopilot respond to an ILS?
  • Does the manual electric trim work?
  • Does the autotrim work?
Marker Beacon
  • Does the lamp illuminate?
  • Do lamps test or are they dimmed?
  • Is high or low sensitivity selected?
  • Is the audio turned down or not selected?
  • Are the lights seen, but tones not heard?
Radar
  • Does it paint clouds and ground clutter?
  • Is the gain turned down?
  • Does the radar test?
  • Does the display spoke?
  • Does the tilt work?
  • Is stabilization on or off?
  • Are the images smeared?
  • Does it lose targets at high ranges?
  • Is the radome damaged or delaminating?
DME
  • Does the DME receive an ident tone?
  • Is remote channeling selected?
  • Is the display dimmed?
  • Do the GS and TTS function?
  • Does the DME work on different channels?
  • Does the DME test?
  • Does the transponder interfere?
ADF
  • Is the unit in ADF mode?
  • Does the ADF point to the station?
  • Does the needle move in test?
  • Does the unit receive in ANT mode?
  • Does the unit receive in ADF mode?
  • Do all three frequency bands (200-399, 400-799 & 800-1699) work?
  • Do you hear alternator or magneto noise?
  • Is the reception better with the engine off?
  • Are other radios interfering with the ADF?
  • Is the aircraft structure shadowing the antenna?
  • Is there a NOTAM of any outages?
General Avionics Longevity Tips
  • Install a cooling fan. Outside forced air is not recommended.
  • Cover the instrument panel when the aircraft is parked.
  • Exercise autopilot clutches and motors at least once a month.
  • Instruct your mechanic to keep control cables tight for best autopilot responce.
  • Know where your autopilot and trim circuit breakers are by feel.
  • Turn the avionics on after the alternators are on-line and off before shutdown.