Squawk Box

May 2015 Issue




Switched

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

Beechcraft Model F33A Bonanza
Nav Light Switch Internal Short

The navigation light circuit breaker switch trips and will not reset. Fault in circuit breaker switch (p/n 35-380132-101). These switches are the new and improved versions installed under AD 2008-13-17, but are continuing to fail internally.

Part total time: 7.0 hours


Beechcraft Model 58 Baron
Failed Landing Light Switch

Landing light switch was hot and emitting smoke. Switch was installed per AD 2008-13-17. The new switches add an insulator preventing a failed “open” switch from conducting current through the hold-open spring. Apparently, this failed switch had a defect allowing current to flow through this spring. This switch is rated for 10,000 cycles, but the failures seem to be at no more than 4000 cycles.

Part total time: 1486.0 hours

Cessna Model R172E
Inop Landing/Taxi Light Switch

Landing/taxi light inoperative due to switch (p/n 0713035) failure. Troubleshooting found switch overheated, burned and power wire showed evidence of overheating. Cessna service bulletin SB09-6 requires inspection and replacement of landing light switches but does not identify the R172E (T-41C), which has a different p/n. The landing light circuit and switches were not designed for continuous use of the landing and/or taxi lights in flight.

Part total time: Unknown

Cessna Model 208B Grand Caravan
Overheated Landing Light Switch

During approach, pilot noticed burnt electrical smell and small amount of smoke in cockpit. Pilot donned oxygen mask and reduced electrical load per emergency checklist. Aircraft landed without incident. Inspection revealed overheated right landing light switch and possible overheated pitot heat switch. Switches (p/n MS25306-222) replaced with new.

Part total time: 10,768.0 hours

Piper PA-31T Cheyenne
Failed Landing Gear Downlock Switch

After gear extension, right main gear indication remained red (in-transit). Crew elected to return to base and determined by visual inspection from the cabin that the gear was down and locked while en route. Flight landed without problem. Inspection revealed the right downlock switch (p/n 4793603) was unserviceable.

Part total time: 22,708.0 hours

Piper PA-46-350P Malibu Mirage
Intermittent Flap Operation

Pilot reported flaps would not extend from 10 to 20 degrees unless selector handle was manipulated. Condition was intermittent. Found flap switches on selector cam to be out of adjustment. Slight pressure on the selector handle rod would actuate flaps normally. Adjusted flap switches IAW maintenance manual.

Part total time: 510.0 hours