Cloudmirth Posted July 25, 2021 Report Share Posted July 25, 2021 OK folks, here's a poser for you. Yesterday I was flying my '69 C and when I went to lower the gear just after it locked down the 70 amp alternator breaker tripped off and the entire electrical system went dead. I reset the breaker and all was well again. Upon leaving the airfield I raised the gear and flew home without issue but upon lowering the gear once again the Alt. breaker tripped and the electrical system went dead. Reset the breaker and again, all is well. Note, the gear breaker never tripped and there was never any odor of overheated wires or other obvious electrical system issues. It seems to me that if the gear motor was pulling too many amps, (as an aside the gear motor and transmission were overhauled by Lasar about 2 months ago) the gear breaker should trip, not the alternator breaker and, if the alternator breaker were to trip I don't believe that should take out the entire electrical system. So, I've got some thinking to do here and I'm open to thoughts on this subject. Quote Link to comment Share on other sites More sharing options...
markgrue Posted July 25, 2021 Report Share Posted July 25, 2021 A few things to check. With the engine not running, turn on the master. What works? Turn on everything. Note what works and what does not. I suspect that the battery is not powering part of the system. If that is the case then when flying the alternator is powering everything and when you throw in intermittent loads like the gear motor it does not have the capacity to run it all. Normally the battery would make up the shortage and the alternator would recharge the battery when the load drops. Mark Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 26, 2021 Report Share Posted July 26, 2021 Something may be aging, needs lube, or is out of rig… Adding to the load… Most CBs in our ships are temperature sensitive, mechanical, and prone to wear… The going over center step in the gear motion… increases the load on the motor… The CB is getting a lot of additional work under these conditions… What was the OAT during the flight? Lets invite @M20Doc if he has seen a main breaker trip before the gear CB trips… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted July 26, 2021 Report Share Posted July 26, 2021 If your up limit switch wasn’t working, the gear motor will run until it bends something or blows A breaker. It is weird that it blows the alternator breaker before it blows the gear breaker. Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 26, 2021 Report Share Posted July 26, 2021 Something's not right with the alternator or the breaker. The alternator cannot put out 70 amps so it cannot trip the breaker. The purpose of the breaker is to protect against a short in the alternator itself or the wire from the alternator to the bus. You might try putting it on jacks and cycling the gear on the battery to eliminate any issues with the gear itself. Skip Quote Link to comment Share on other sites More sharing options...
FastTex Posted July 26, 2021 Report Share Posted July 26, 2021 A very similar thing happened to me a few years ago when I got my Mooney. My A&P and I were puzzled. We even replaced the breaker and overhauled the electric motor and the gear box! I felt it was happening with cold weather or after a flight with not so hot hair, anyhow long story short: - it was a bracket set in the wrong place (by like 1/2") on one of the levers/pipes that move the landing gear. My mechanic noticed and old mark with the original position and put it back. No more problems since then. What we thing it was happening is the system was being stressed in excess and this was causing a higher current being drawn by the motor tripping the breaker. I tried to find the picture with no luck. I will keep trying. Hope this helps. Quote Link to comment Share on other sites More sharing options...
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