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Landing Gear Relay C/B (Update)#3

GeeBee

By GeeBee
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GeeBee Grand Master

GeeBee

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A little help please. M20R Ovation 2 GX.I have an annoying problem with the Landing Gear C/B. popping every once in a great while. It has happened two times in the past 100 hours. I put her on jacks, cycled the gear 10 times, nothing unusual. Has any body experienced this problem and what was your fix? I am leaning towards chattering relays or intermittent up and down switches. I really don't want to shotgun this with replacing relays and switches if there is a definitive path to isolate the problem.

 

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Airways Rising Star

Airways

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I had the same problem (M20K). Of course the mechanic was unable to reproduce the problem on the ground, but they found some light chafed wiring (which they relocated) and they lubricated the gear. It never happened again. 

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Scottknoll Collaborator

Scottknoll

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Here’s a log entry from the previous owner of my Ovation when they had a similar issue. Hopefully it helps, ended up being chafed wire as well. Wire was from annunciator panel to CB.

TROUBLESHOOTED LANDING GEAR 1 AMP CIRCUIT BREAKER POPPING, JACKED AIRCRAFT, REMOVED INSTRUMENT PANEL AVIONICS, INSPECTED FOR CAUSE OF CIRCUIT BREAKER PROBLEM, REMOVED BELLY PANEL, TESTED SOLENOIDS AND ALL WIRES, COULD NOT FIND PROBLEM, PERFORMED SEVERAL GEAR RETRACTION TEST WITH THE AIRCRAFT SIMILATION OF FLIGHT, ALL SYSTEMS WORKED NORMAL ON JACKS, TEST FLEW AIRCRAFT ALL SYSTEMS OFF, CIRCUIT BREAKER POPS IN FLIGHT, REJACKED AIRCRAFT AND TROUBLESHOOTED ALL SYSTEMS, FOUND WIRE CHAFFED FROM ANNUNCIATOR PANEL TO CIRCUIT BREAKER, REMOVED AND REPLACED WIRE WITH NEW, TESTED ON JACKS OPS GOOD, TEST FLEW AIRCRAFT, OPS GOOD, CIRCUIT BREAKER WORKS SATISFACTORY, NO OTHER MAINTENANCE PERFORMED AT THIS TIME


Sent from my iPhone using Tapatalk

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M20S Driver Experienced

M20S Driver

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On 6/3/2020 at 6:03 PM, GeeBee said:

A little help please. M20R Ovation 2 GX.I have an annoying problem with the Landing Gear C/B. popping every once in a great while. It has happened two times in the past 100 hours. I put her on jacks, cycled the gear 10 times, nothing unusual. Has any body experienced this problem and what was your fix? I am leaning towards chattering relays or intermittent up and down switches. I really don't want to shotgun this with replacing relays and switches if there is a definitive path to isolate the problem.

 

I have three Gear CBs on my Eagle.  Gear Actuator, Gear Relay, and Gear warning.  Which one is the one popping?   

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M20S Driver Experienced

M20S Driver

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Just now, GeeBee said:

Gear Relay. Sorry, I should have made that clear. Previously in the logbook it had a similar problem and it was the override switch shorting. Going to swing the gear tomorrow to see what we can see.

 

 

 

One more question.  Does it pop during actuation or randomly in cruise with gear up or down?

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larryb Mentor

larryb

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I had this happen in my Encore. The problem was a piece of the gear hardware gets super close to the up limit switch screw terminals, and can short out. Only visible with gear up on jacks.

My shop had replaced the Up limit switch at annual, and 20 hours later this happened to me. Unfortunately for me, this manifested 2500 miles away from home and my shop. I was able to work around it by leaving the CB popped until ready to put gear down. I would move the LG switch to Down and then reset the CB and all was fine. The shop was not able to replicate on the ground, but the mechanic noticed a tiny burn spot on one of the screw terminals. It was an un-used screw, no wire connected. So he simply removed the screw and I never had the problem again.

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GeeBee Grand Master

GeeBee

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Put the airplane on jacks today. Was able to duplicate the problem. Bad over ride switch. 

Called Lasar, they had to call Mooney because the switch showed "out of production". Thanks to some nice work by Corrine at Lasar with the factory, she had the factory alternative switch on its way to me. Since this is the second time in 3 years the switch has failed, I purchased two extra. They are cheap. 16 bucks each.

 

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larryb Mentor

larryb

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So here is how you fix that.

 

Typical LED forward current is 20ma or 0.02 Amp. Resistor needed (28-2.5) / 0.02 = 1275 ohm. Round that to 1300 if you like. Power dissipation is (28 - 2.5) * 0.02 = .510 watts. Round that to 1W.  So a 1 watt 1300 ohm resistor should do it. If you have the part number for the switch and can find the datasheet for the switch you could refine the numbers, but these should get you in the ballpark. Pay attention to the polarity when you install it.

 

10 cents each

https://www.mouser.com/ProductDetail/KOA-Speer/MOS1CT528R132J?qs=sGAEpiMZZMtlubZbdhIBIAkLiGKeVnd8QhClgcYo4E0%3D

 

Larry

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GeeBee Grand Master

GeeBee

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Thank you! I thought a dropping resistor might be the answer. When I ordered the switch the factory came back with the new switch part number and said to install it without guidance that a dropping resistor would be needed. Since there are 28volt LEDs one would have to surmise this switch had one. Once the first one blew out, I entered the part number in google and it came up as made by E Switch and discovered the nature of the LED from the E Switch website. Your numbers are spot on by they way. Good job!

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GeeBee Grand Master

GeeBee

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Got it all installed and it works great, just have to put in that dropping resistor for the indicator light. Thank you larryb for calculation and the link! They worked great and there is no more problem. For those of you wondering the new switch from Mooney is made by E-switch part # RP8100B2M1CEBLKRED. That is the E-Switch part # and the Mooney part #. The Cutler-Hammer and NKK Switches listed in the parts manual are no longer available from any source as near as I can tell.

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