Squawk Box

September 2017 Issue

Ignition Switches

The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.

Beechcraft Model 58 Baron
Burned Contact Points

The right engine failed to turn over upon application of starter. Pilot noted smoke and burning smell from under the instrument panel. Upon inspection, it was found that the ignition switch cups were severely worn, and the contact points were burned. The switch was replaced and the aircraft was returned to service. Submitter suggests disassembly and inspection of these switches for worn components and proper lubrication on a 500-hour basis to prevent recurrence.

Part total time: 8263.0 hours

Cessna Model 172N Skyhawk
Shorted Starter Switch

Aircraft was shut down IAW checklist. On restarting, the master switch was turned on and the engine began to turn over without the ignition key in the start position. When the master switch was turned off, the starter disengaged. Internal parts of the start switch shorted out and caused starter to be live once master was turned on—key was in the “off” position. No injuries resulted. A new switch was installed and the aircraft returned to service.

Part total time: 411.0 hours

Magneto Starter Switch

Cessna Model 172S Skyhawk SP
Damaged Magneto Switch

Ignition key can be pulled out of the ignition switch regardless of switch position.

Part total time: 3204.0 hours

Cessna Model 182T Skylane
Faulty Magneto Switch

Ignition switch could be rotated counterclockwise past the “off” position and engage the starter. Switch replaced and aircraft returned to service.

Part total time: 687.0 hours

Cessna Model TR182 Turbo Skylane RG
Defective Start Switch

Aircraft lost electrical power on approach. Pilot hand-pumped the gear down and landed without any further problems. Troubleshooting revealed the starter and starter contactor were inoperative. Once both items were replaced, the ignition switch was found to stick in the start position. Removed ignition switch and determined it had caused the starter to become engaged and was the ultimate problem.

Part total time: Unknown

Diamond DA20C1
Worn Starter Switch

The pilot reported the starter would engage when the switch was turned to the start position, prior to pushing in on the switch to engage the starter. Maintenance confirmed the starter was engaging with light pressure on the switch. If the ignition switch was turned to the both position, very little pressure on the switch would make the engine turn over. The replacement switch required being pushed at least halfway in before the starter would engage.

Part total time: 357.0 hours