gear blows breaker

[Scot Findlay]

has anyone had a problem with the gear breaker blowing just before the gear is completly up. the handle is less than 1/2 " from complete up. reset and goes down fine.. anything that reoccures along thease lines

thanks

[Zach Grant L1011jock]

Yes, lots have. First, you need to re-rig the gear. Next, check your push/pull cables, and most likely replace. You may also have a weak motor, mis-aligned gear doors, or misrigged doors (especially on a twin). You may also have a weak breaker. The highest current draw is at the last inch of throw. If you have any deficiency in the system, this is where it will show up.
-Zach

[N3322G]

FYI. When it happened to us, the gear was not rigged correctly. The gear up-limit switch had been improperly adjusted by a mechanic. After I flew Matt Kurke in, several other discrepancies were noted.

Zach, of course, gave a much more complete description of possible problems.

[Gus Denovan]

On the subject of gear malfunctions :-
Occasionally when I lower the landing gear I don't get a green light. Even after waiting a long time.
The nose wheel is visible in the side mirror.
Recycling the gear has so far always sorted the problem.
It tends to happen when I lower the gear going a bit fast (around 130mph).

This is the thing that confuses me :-
With the gear lowered and no green light, I pull the throttle back completely to idle but I don't get the "gear not down horn". I then raise the gear and get a steady yellow light. Closing the throttle then yields the "gear not down horn".
Finally, I lower the gear, and get a green light.

So, when I get no green light, no "gear not down horn" at low power, and a nose wheel in the mirror, is it safe to land? ( don't worry I wouldn't ! )
Which sensor is not making a contact ?
Thanks, Gus.

[Zach Grant L1011jock]

Gus,
Do not pass go, do not collect $100...Call Matt Kurke at Comanche Gear www.comanchegear.com, and order a new gear wiring harness. You probably have bad switches and/or broken wires and it is only a matter of time before you will do something bad like burn up the motor, chew up the transmission, do a manual extension, or worse, have a gear colapse.

The simple answer to your question is that the nose gear down limit switch is the only one connected to the gear horn. All three gear down limit switches need to make (and the wires need to be intact all the way in) to turn the motor off, and turn the green light on. Seeing a gear in the mirror is only an approximate indication the the gear has moved, not a confirmation that it is down and overcenter.

HERE IS THE BIGGIE!!!! Your gear may also not be rigged correctly. Before you fly again, get SOMEONE WHO KNOWS how to check gear rigging to look at your airplane on jacks. Not doing this is a $40000 mistake, as it is only a matter of time before you collapse the gear if it is not in rig. When you install the new harness/switches, you will follow the directions showing how to set the switches properly, however the entire gear must also be rigged properly to assure continued operation of the aircraft without a belly skid. When you put the switches in, if the gear is still not simultaneous in its operation, equal in its preload, up snuggly with the doors at proper upload,and vertical when extended with no discernable play ay any pivot point, then you need to do the entire gear rig from the start. This is best done by someone who knows what they are doing!!Where are you located?

-Zach

[N3322G]

Gus,

Had a similar problem in 1996. Could not be reproduced on jacks. Quite by accident found that turning the panel lights on and off after the gear was down but with no green light, brought the green light on.

Replaced the wiring with Matt's harness - still not fixed and called Maurice Taylor. He said change the nose microswitch - that fixed it.

If I were in your shoes, I'd take 100% of Zach's advice. I'd add that you might want to get a dial caliper to check the microswitch settings after the work is done - even the best of mechanics can make mistakes or try to take shortcuts. If these are not adjusted correctly, your plane's gear can and will collapse.

Hope this helps.

[Gus Denovan]

Zach / Pat,
Thanks for the advice.
I will take it to my maintenace firm to be looked at.
I am based in Southern England (EGLK) , and have my maintenance done in the tax free Channel Islands. ( 20% VAT in the UK from Jan ! )
Gus.

[skipsouthernsky]

Dear Scott,

In your particular case, I would first check the status of the bungees. If they haven't been changed recently (within the last year) I would try putting new bungees on and see if the the problem goes away. The bungees help hold the gear down and locked, but they also help with the gear going up and take some stress off the motor. Try it, you might cure the problem simply and inexpensively. Otherwise you will have more complicated problems to address.

Sincerely,
Skip Dykema

[Chief]

Hey Scott,

Happened to us the other night, 16 degrees outside, popped breaker on the way up. I had to do manual extension of gear for landing. Put the 250 on jacks, gear was fine, noticed the breaker was popped. Reset, A &P flew plane, all was well (warmer day). A week later we fly again, 20 degree morning, breaker popped again, reset breaker, did fine the rest of the day.

Pretty good evidence and confidence the cold weather and the grease in the trunions caused it. Our plane has NEVER done any of this before and the two times it happened, it was the two coldest days we have flown the plane.

My two cents, with the backing of a great A&P.

Every plane is different though. Best fix it or have a good idea of what is causing it before it progresses.

[John Wasserburger]

Chief,

I had that happen on my twin on a very cold night in WI. As it turned out, the generator belts were loose and not charging the system at the required rate. In addition, since it was night we had all the lights on and drawing more current from the battery. The breaker tripped because the voltage was insufficient. However, we were able to minimize the electrical demand, reset the CB, and lowered the gear normally.

John W.

[Chief]

Hey John,

Thanks, and like I mentioned every plane and every situation can be different. Glad yours was easily fixed. We have an amp meter readout in our plane, we were drawing 13.8 or so. It could have been the amp load, but I doubt it. We've never had electrical issues at night And I run pretty much whatever I want when we fly at night. Plus, if you have a good alternator, good battery, it is hard to overload a system like we typically fly in a Comanche. There is usually plenty juice. I think when our landing gear motor got to that last throw of the gear, right before the gear retracts and given the "cold grease", it threw the breaker to save the motor, which was working its hardest at that point. We have new bungees also.

Going forward, we live in Alabama, so we don't have a lot of cold days. I did speak with Webco, they have a great replacemnt system where the trunions are teflon. That would fix all this. About 8 -10 hours of labor to install. Maybe someday, if the global warming Gore keeps predicting dosen't kick in, we may go the teflon route. Until then, we'll press on and pray for warm weather.

[Zach Grant L1011jock]

Chief,
Just so there is no confusion, the Webco replacement parts that are teflon lined are not the "trunions", they are the push-pull cable/conduits. Yes, the Conduits are a single point of failure for the entire system. If they jam, you will land gear up.

-Zach

[Chief]

yes, my bad, conduits.