Electrical - Gear Retraction

[Lubek]

I'm having an electrical problem in my PA-30 at the very end of gear retraction, when everything else is on during an IFR departure. With everything on (pitot heat, landing lights, beacons, nav lights, fuel pumps - everything required for IFR departure), when I retract the gear, the circuit breaker trips at the very end of the retraction cycle. The red light (full retraction) doesn't come on. If I reset the breaker there is a split second lapse, and the light comes on. I get normal retraction with a VFR departure whether at night or during the day. I put it up on jacks and cycled the gear and the problem doesn't show up, but of course all of the 'extras' aren't on because I was on battery power only. The gear motor didn't get warm with these retractions. Upon inspection the main gear bunges were quite weak and were replaced, but that didn't resolve the CB problem. The CB also trips if I have throttled back on an IFR approach and put on the landing lights before lowering the gear.

I thought it might be an issue of tired alternators (I have the 50 amp.) that weren't putting out sufficient voltage, which would increase the amperage drawn when the gear motor is running and therefore might trip the 30 amp. breaker. I have checked the voltage from the alternators at 1100 rpm and 1600 rpm and there is no difference with rpm or when both alternators are on, or either is on alone. Ample voltage and approximately the same between the alternators.

Now I'm thinking it might be a tired circuit breaker as the gear motor CB is original Piper issue from 1966.

It has also been suggested that I might have a tired battery, but I don't see how that might be the problem because there is ample juice for starting the plane, and on takeoff one is at full throttle and should be able to run on the alternators alone - the condition of the battery at that point shouldn't be an issue. Am I wrong?

Another option might be to install 70 amp. alternators, but insufficient amperage doesn't seem to be the problem. With both alternators working properly, 100 amps. should be plenty. As well, the conditions under which the CB trips may not have common elements.

Suggestions?

[md11flyer]

Barry
I would agree that the circuit breaker could be your culprit. I have heard on previous posts that after the circuit breaker was replaced the problem was solved. Now for the difference with or without all the electrics on, well regardless how good the output devices are, there is a voltage drop when any electrics are drawing power and if the drop is enough the gear motor will draw the gear up slow enough that as it is reaching stowed position, which is where the most torque is needed, the amperage will spike long enough to pop the circuit breaker.
As this condition has just come up, as you mentioned, rule out the circuit breaker first, and if the problem persists, go further with diagnosis. When is he last time the push pull cables were serviced/ replaced? Gear motor brushes replaced/ serviced?
What does the gear transmission sound like during retraction on the ground, on the jacks? normal? or clunky?
My opinion is not to chase batteries and alternators, as I don't think they are your problem.

Gary

[N3322G]

Just chased one of these on my 39. All appeared to be in great condition, fresh 1000 AD within 2 years, new conduits, Matt's wiring, new microswtiches, 3 year old gel battery and the CB popped on the third departure of the day. The gear appeared to be all the way up.

Got the gear down with no trouble and flew it to the shop. On jacks it failed on the first retraction but the next 6 it was fine. The only thing I noticed was it was about an eight count on the way up. In flight the gear up or down count is normally 6.

Swapped gear motor with Matt Kurke of Comanche Gear fame and no trouble since. All movement on jacks or in flight is a count of 6.

Not saying this is your problem, just sharing what seems to be a similar symptoms and what the resolution was for me.

BTW during problem diagnosis the IA noticed the gear up limit switch worked but felt a little sticky. Currently at annual and replaced it on my schedule as opposed to when the switch would decide to fail some time in the future.

Hope this helps.

[Lubek]

Hi all. Thanks for the replies to this point. I have ordered a new breaker, and it will be here in a few days. Today/tomorrow I have the opportunity to borrow a new fully charged battery. I am going to install it and take the plane up to see if eliminating the possibility that my battery either can't accept a full charge or isn't holding a full charge for any measurable length of time. I'm doing this on the theory that with everything on for an IFR departure, the system is taxed, and that under these conditions the battery provides any extra electrical power needed temporarily for the gear retraction and recoups it by charging in cruise when demands on the electrical system are reduced.

I will report on the results. In the interim, additional suggestions/comments remain welcome.

[VANBLADEREN]

If your breaker trips going up, then your up limit switch (in the transmission well) is not set properly. The that micro switch shuts off the gear solenoid. In a twin and all C-model singles, it is easily adjustable. Refer to the service manual for adjustment.

Regards

jvb

[Lubek]

Update: First, my apologies for the delay in reporting, but weather has been a significant factor ( I have to work outside).

I thought about the limit switch, as suggested in the previous posting, but decided that was not likely the culprit, because there was occasionally also a problem with the breaker tripping on gear extension when I put on the landing lights before extending the gear. The battery in the plane was old (>6.5 years) and since it provides the extra juice when necessary, I changed it. The problem of the gear retraction was relieved in most situations, but when under full load in a simulated IFR departure, it tripped on the retraction. So, the next step was to change the breaker - not an easy task because of the position of the breaker in the floor tray. It appeared to be an original breaker, 1966 vintage. Got it changed and was able to test it out in the air yesterday. In all situations tested - simulated IFR departure, simulated approach (low rpm, landing lights and and everything on and then lowering the gear), new breaker did not trip on gear retraction or extension. So, I am guardedly optimistic that the problem is corrected. A few more uneventful flights will help regain confidence that the problem is fixed. I will report after a few more flights.

[VANBLADEREN]

Barry: I would agree with your direction. . I worked with a plane where the breaker would never trip when the plan was on jacks, but when in the air, it did trip. We replaced the breaker and the problem went away. The old standby thought, keep an eye on it.

Regards

jvb

[N3322G]

Barry,

Hope that fixes the problem. Somewhere I read that after a breaker is tripped a couple of times, it is recommended that it be replaced. I can't recall the source but had our original one replaced a few years back after it had been tripped a couple of times due to a mal-adjusted limit switch by a shop I used only once. I'll cross my fingers that between the battery and breaker, you've got it; but like you, I'll be interested in seeing several no-problem flights before declaring victory.

Your sure did get great mileage out of your ship's battery. We replace our gel battery every 4 years just cause we don't want to get caught somewhere. do the same thing on our car batteries ... although I did get 6.75 years out of the Mini Cooper battery and then I had to break out the jumper cables to get it to the service shop.

[Chief]

Barry,

I had this issue, same symptoms, it was our landing gear push/pull conduits. just old, old grease, etc. Cold weather magnified the problem. Bought some new Webco teflon-coated conduits and no issues since. it was putting a load on motor, electrical etc.

Love them.