Switch Hunts

The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.


Beech Model 65 Queen Air
Failed Gear Limit Switch

Landing gear limit switch (p/n MS250261) failed to stop motor during retraction, causing landing gear circuit breaker to pop. Aircraft landed without incident. Re-rigged the switch IAW maintenance manual. Retraction test and ops check okay.

Part total time: Unknown

Beech Model 65-A90-1/U-21A King Air
Failed Gear Limit Switch

The 50 amp circuit breaker tripped when cycling landing gear. Found gear limit switch in floor had failed completely. Both switches replaced and adjusted IAW service manual. Gear cycle okay; no further problems found.

Part total time: Unknown


Beech Model A100 King Air
Frozen Flap Limit Switch

When approach flaps were selected, the flaps did not move. The crew conducted a flaps-up landing without incident. Examination revealed the up-limit switch was full of frozen water. Investigation revealed the aircraft had been washed just prior to dispatch. The switches were cleaned and dried out and checked serviceable.

Part total time: Unknown

Beech Model B300 King Air
Faulty Flap Up-Limit Switch

On approach with flaps selected to approach position, the indicator showed no movement and after a visual check, the flaps were still in the up position. Followed the no flap/unknown position checklist. Landing was uneventful. Maintenance replaced a faulty flap up-limit switch.

Part total time: 806.0 hours

Cessna 172N Skyhawk
Faulty Flap Limit Switch

Flaps would not extend during preflight inspection. Maintenance personnel discovered faulty limit switch. Replaced switch (p/n S1906-1) with new. Function tested as serviceable and aircraft returned to service.

Part total time: Unknown

Piper PA-28R-201 Arrow III/V
MLG Limit Switch

On takeoff, gear warning light illuminated with full power, flaps up. Right main landing gear position light inoperative. Inspection of right MLG failed to note any defects. Adjusted right MLG down-limit switch. Gear retraction, extension and free-fall tests were satisfactory.

Part total time: 55.0 hours

Piper PA-44-180 Seminole
Damaged NLG Limit Switch

Inspection revealed that the nose gear down-limit switch tab was bent. When the hydraulic cylinder locked the nose gear down, the tab would spring out of position and sit on top of the strike block. During free fall, it would stay in its place and function properly. Upon replacement of the switch (p/n 86409002) and tab with a new unit, it was noted that the old switch required more travel to activate. Once the new switch was installed and adjusted, system no longer failed.

Part total time: Unknown


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