gear stuck in transit

[rick bell]

departed kprc enroute to kyum selected the gear handel up and the gear started to retract, at the 1/2 point the gear stuck. looked at the side mirror and it indicated the gear was only 1/2 way up and the nose wheel was turned sideways (making a extra rudder goiing to the right. recycled the gear handel many time, nothing. checked the ckt. breaker it had poped. reset the breaker and recycled the gear several times again, nothing. pulled the cover off the lower consul and felt the motor (very hot) so i pull ed the breaker out, then checked the pummp for fluid and the dip stick showed oil. decided to leave it alone until reaching kyum. 20 miles out decended and slowed down and put the breaker back in and cycled the gear again, nothing (during all this time the green light stayed on and the horn kept beeping). decided to pump the gear down, the hand pump built up pressure and became to hard to pump (5miles out). on short final retried the pump and was able to get four or five more pumps and the gear moved about 6 inches outboard. laned and the gear moved the rest of the way out and locked (lucky ducky). has anyone experienced this or something simular and if so what action was taken tofix the problem. my concern the shop at yuma will recycle the gear 10 times or so and not be able to determine the cause without some help. if anyone knows please let me know. thank's rick

[Jim Rainer]

I have a1976 337G. This is not the same scenario but I had a problem where the gear would do nothing after putting the gear handle up after takeoff. I pulled the breaker and pumped the gear doors open (they may ahve been open all along) and then pushed the breaker back in and the gear retracted normally. This happened intermittently so I had the shop put it on jacks and run the gear several times. They checked the fluid which was OK but added a little bit. It hasn't done it since.

I doubt this is much help to you.

Next time try some strong pull-up G maneuvers and sometimes this will shake the gear loose. Maybe pumping it at the same time.

[Damon Banks]

Did I read correctly in that the green light stayed on the entire time? That is, even though the gear by visual inspection wasn't in the extended position?

One thing I would have tried given your description, was to turn off the master (and alternators) and then pumped the gear down manually. This is a method described in the handbook and will help in the case of mis-rigged downlocks.

Need a little more precise description of exactly what happened to get much closer to the cause, though on the face of it, the fact that the gear motor kept blowing the circuit breaker says that it was drawing a high current...

[rick bell]

the gear light never came off green. it is a 73 p. never did turn off the master, read the book while in flight, i don't thhink it said turn off the master, but it may have and i miss read it. the breaker only blew once, the other times inreset it it stayed in (but i also let the motor cool before resetting it) i do not understand the logic of turnig off the master and alternators, i'm a little confused to how they play a part, i'm not second guessing what you are saying, only that i don't understand.

[Damon Banks]

No Probs, perfectly ok to question.

In my handbook (74 P), under section III - emergency procedures, landing gear malfunction procedures, extension malfunctions (page 3-10) it says:

"A visual cheek of landing gear position after extension should become a habit for every pilot. Illumination of the gear down indicator light is not always a sufficient check of gear position since a damaged or improperly adjusted landing gear system or switching could cause a malfunction which would not be evident unless gear position was checked. As an example of this type of malfunction, an improperly adjusted down lock switch which actuated before gear extension was complete would allow hydraulic pressure to be diverted prematurely from gear actuation to door closing, resulting in proper gear indicator light operation but leaving one main gear in an intermediate trailing position after the system had shut off. Attempts to retract and then extend the gear again would result in the same condition. Also, use of the emergency hand pump would not permit further extension of the gear since pressure is diverted to the door system in the final phases of gear extension and any additional pressure applied to the system would be recirculated. To relieve the pressure which is holding the doors closed, and complete the extension of the trailing gear, electrical power must be removed from the door control valve solenoid which is trapping pressure to the gear door actuators. Turning off the battery and alternator switches will allow the door control valve to recycle to the gear actuator position, permitting hand pump pressure to be applied to complete extension of the trailing main gear. Once extension is complete, the battery and alternator switches should be turned on again to actuate the door control valve and close the doors."

Now, that's for an extension malfunction, and so may have helped to get the gear down for your landing. As to why the green light stayed on during your retraction, I'm at a loss...One idea I do have is that you may have a faulty pressure switch on the hydraulic power pack, allowing the pump to start and unlock the gear, but then failing to complete the cycle any further...still can't figure why your green light stayed on on though, and that shouldn't have caused the circuit breaker to pop.

I'm always picking up the handbook and finding little pearls in there - for such a thin book it takes a lot of reading...I'm sure there's someone who keeps putting extra information in there when I'm not looking!

[Ernie Martin]

Good advice, Damo. My 1973 337G POH did NOT have that text, so I copied it and inserted it in my POH. Thanks.

Ernie

[rick bell]

yes that is great advice and also my poh did not have that information (but it will now) also thank you for the other information i will pass it on to the shop

[Guy Paris]

Hi All, The statement from Damon is in my 77 G normally aspirated 337 POH in section 3 Emergency Procedures on pages 3-24 and 3-25, word for word. FYI.... Guy, old72driver....

[Damon Banks]

Some more thoughts on your problem Rick...

I'm thinking that the problem is electrical, so I tend to suspect the gear switch itself...some of its poles are common to either supplying power to the green light, and power to the gear motor - seems a logical starting point for some testing for high resistance.

First though, I'd be keen to check your charging system voltage during gear retraction - a bit hard to do on jacks though!! Should do a load check on your alternators - if the system isn't coping with the current draw during gear motor operation, then you'll get the gear system doing some strange things...including popping the breaker for the pump (as the system voltage drops, the current draw increases, and pops the breaker). Maybe your alternators are needing brushes or a diode has died? I think the first stop should be testing your charging system...then look a little deeper - preferably without arbitary replacement of expensive bits!

I'd be keen to see if the problem shows itself while you've got the plane on jacks - and being driven by a ground power supply.

I'm still perplexed about the green light though!

Cheers,
Damon

[Ernie Martin]

Rick:

I had a problem with my '73 337G where the gear wouldn't come up at all. It turned out to be, as Damon has suggested, an electrical POWER problem where the battery was very weak and the alternators could not handle the huge load demanded to charge the battery AND drive the powerpack.

BUT, for your case, I like better Damon's earlier thought that it may be a faulty pressure switch on the hydraulic power pack, allowing the pump to start and unlock the gear, but then failing to complete the cycle any further.

Why? Because it didn't work when you tried the manual handle.

If it was due to insufficient electrical POWER (battery, alternators, too-high resistance), then one or both of your alternators would have switched off, as it did in mine. Also, you said the breaker popped, so that suggests that you had all the electricity which the powerpack could handle.

Ernie

[rick bell]

the shop has indicated the problems lies with an overflated nose strut with air and not nitrogen(i had the nose strut raised by another shop so that i could get additional prop clearance when landing on a sand strip) they say the safety lock would not open so the gear wouldn't work, when i go pick it up i will get a better discription as to the problem and cure. thank's all for you imput and help. rick

[WebMaster]

I had my gear not go up, though we could override the little solenoid under the dash, and it was traced to the front strut not having enough nitrogen, and the switch (mental blank) on the front strut didn't make contact, because the gear wouldn't extend enough.

[Damon Banks]

Rick this doesn't make sense for all the symptoms you described!

When the weight comes off the nose wheel the strut extends (or drops) to it's maximum, and the squat switch allows the gear to move...the same thing happens whether the strut is over OR under inflated! So merely changing the inflation of the strut will make no difference to whether the squat switch stops retraction (unless there is zero strut pressure and you're inverted when you retract the gear - or like Larry there wasn't enough pressure to extend the strut far enough to activate the squat switch).

I discounted the thought that your problem lies in the squat switch because a faulty squat switch will allow the gear doors to open, but not allow the gear to move - your description of the gear half way retracted gear doesn't fit that description.

However with a faulty squat switch, the green light staying on would be correct (the gear won't move) and the pump would continue to cycle after opening the doors, eventually shutting down due to overtemperature or popping the circuit breaker (also similar to your description).

Are you SURE the undercarriage was trailing (with the green light still on)?

Even if the squat switch proves to be faulty (I hope it does, because it would work out much cheaper to fix), changing the strut inflation is unlikely to fix it - you'd have to replace the switch or the mechanical device used to activate it.

I'm keen to hear the further details from the shop when you pick the plane up. I would also operate very carefully when you do fly it, because if all they did was service the strut, then I don't think your problem is solved!

These gear problems can be real bears - I've experienced several that magically go away when the aircraft is up on jacks, and then reappear intermittently in the air. Unless you find a smoking gun, I'd assume that it isn't solved.

[rick bell]

got the a/c back this wed. the shop said that they could find nothing wrong except for the front strut had no air only fluid. the place nitrogen in the struct and inflated it to the proper hieght. was place on jack and cyled 10 time with no problems. flew it back home with one stop and it worked as advertised. so we will wait for another indication to what it may be, and hopefully it will not be invisable. thank's to all for your immput. rick