172 RG Gear Breaker Random Failures

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supertrooper2002

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supertrooper2002
I often fly an early 80's 172RG that recently started having issues with the landing gear after a 2 month maintenance grounding (prop seal fix). The first time was the first flight out of maintenance - the red light (Unsafe Condition) over the green, gear down light came on after lifting the gear following take-off and stayed on for the full flight. When I dropped the gear lever on down wind the circuit breaker popped and no gear dropped. I pushed the circuit breaker in and the gear came down and the gear light turned green. I took it to the A&P (5 weeks later - turns out gear jacks need maintenance too) and they put it on the jacks and had the breaker pop when they lifted the gear but never again after 5-6 cycles up & down. I've flown it 3-4 times since then with only one issue (breaker popped while lifting gear after takeoff and rear gear came up but not the nose gear - pressed breaker in and nose gear came up normally). A&P thinks it might be a worn pump / motor or old circuit breaker. Any other ideas?
 
Could be an old circuit breaker with oxidized contacts. That causes excessive heating in the breaker and trips it early.

Could be that the terminals on the circuit breaker are loose or corroded. More heating that finds its way into the breaker and trips it. Look for discolored wiring in the crimp terminals, and of the insulator sleeve on the terminal. Check the screw that connects the breaker to the bus.

Could be the brushes in the powerpack motor are shot, offering resistance to the current and slowing the motor, which then actually results in higher current flow due to less inductive reactance in the motor. Brush checks are a 500-hour item and aren't that hard to do.

Could be worn bearings in the powerpack motor, allowing the armature to drag on the field shoes.
 
supertrooper2002 said:
I often fly an early 80's 172RG that recently started having issues with the landing gear after a 2 month maintenance grounding (prop seal fix). The first time was the first flight out of maintenance - the red light (Unsafe Condition) over the green, gear down light came on after lifting the gear following take-off and stayed on for the full flight. When I dropped the gear lever on down wind the circuit breaker popped and no gear dropped. I pushed the circuit breaker in and the gear came down and the gear light turned green. I took it to the A&P (5 weeks later - turns out gear jacks need maintenance too) and they put it on the jacks and had the breaker pop when they lifted the gear but never again after 5-6 cycles up & down. I've flown it 3-4 times since then with only one issue (breaker popped while lifting gear after takeoff and rear gear came up but not the nose gear - pressed breaker in and nose gear came up normally). A&P thinks it might be a worn pump / motor or old circuit breaker. Any other ideas?
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When a breaker is popping in the Cessna landing gear system the most likely cause is bad motor. Get out the logbooks and determine if/when it was replaced.
 
Magman said:
Couldn’t the “ bad motor” be the brushes as Dan said?

Diagnose before buying works for me.
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By the time the breakers are tripping the armature has been damaged in my experience.
 
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