PA32 gear failure. Possible causes?

[drotto]

I was not in the plane when it happened, in fact I had just finished up my HP and Complex sign-off, and the owner was taking the plane home when the failure occurred. The nose gear failed to light, and after cycling the gear several times would not go on. The decision was made to pull the emergency gear extender. The mains dropped right into place, but still the light for the nose gear would not come. The typical yaw the plane, etc. were tried an no light and a gear failure warning continued. A few fly byes were done at a towered airport, the tower said the gear appeared down, but possibly not at the right angle. So without any other option he made the decision to attempt to land, luckily the green light came on while he was turning final, and landing happened no issues.

I have talked to a mechanic at the school I use, and the plane is currently with its usual mechanic. The general consensus is a small hydraulic leak, because the plane had made 4 landings that day. I had notice in retrospect that the gear did seems slow to come down the final landing I had done about 45 minutes before the failure. Anyone have any other ideas or possible causes for a gear failure like this?

Possible reasons that the nose gear did not initially lock after the emergency release, but luckily did on the base to final turn?

 

[Henning]

Finally got enough load factor and slow enough to get the gear to lock in. Gravity doesn't pivot well into the wind.

 

[Jimmy cooper]

Worn out.

 

[drotto]

Worn out.

Plane was just in annual about 3 months ago, mechanic said it is one of the better 30 year old airframes he has seen. Not evidence of previous gear failure, gear up landing, corrosion, etc.

I also thought that the nose gear had a tensioning spring on it. From what was described to me landing gear is designed to always want to be down, and the hydraulics basically actively hold it up. I had talked to my CFI and his suggestion was get the plane very slow (basically slow flight) at altitude before you pull the emergency extension. The mechanic I talked to also said a common gear issue he sees is that the bolts where the gear is attached will sometimes rub or get over tightened so they do not swing as freely as they should.

 

[James331]

I was not in the plane when it happened, in fact I had just finished up my HP and Complex sign-off, and the owner was taking the plane home when the failure occurred. The nose gear failed to light, and after cycling the gear several times would not go on. The decision was made to pull the emergency gear extender. The mains dropped right into place, but still the light for the nose gear would not come. The typical yaw the plane, etc. were tried an no light and a gear failure warning continued. A few fly byes were done at a towered airport, the tower said the gear appeared down, but possibly not at the right angle. So without any other option he made the decision to attempt to land, luckily the green light came on while he was turning final, and landing happened no issues.

I have talked to a mechanic at the school I use, and the plane is currently with its usual mechanic. The general consensus is a small hydraulic leak, because the plane had made 4 landings that day. I had notice in retrospect that the gear did seems slow to come down the final landing I had done about 45 minutes before the failure. Anyone have any other ideas or possible causes for a gear failure like this?

Possible reasons that the nose gear did not initially lock after the emergency release, but luckily did on the base to final turn?

I thought the PA series used pressure to hold the gear UP.

Yaw is more for the mains, lowering airspeed will help the nose gear.

I'd check the bushings and everything, make sure there is nothing dragging, also check the sensors for the lights.

Glad it turned out ok.

 

[wilkersk]

Finally got enough load factor and slow enough to get the gear to lock in. Gravity doesn't pivot well into the wind.

Yeah, emergency procedures call to "fish-tail" the airplane after actuating the emergency gear down lever for this reason.

 

[Criitter7]

What was airspeed before the nose came down? Maybe too fast?

 

[drotto]

What was airspeed before the nose came down? Maybe too fast?

Came down on base to final when the airspeed was 85 to 90 k.

 

[Henning]

Yeah, emergency procedures call to "fish-tail" the airplane after actuating the emergency gear down lever for this reason.

That's good for the mains, the nose will be helped with a extra pull of some load factor and slowing down. Best thing to do if the nose doesn't lock on a PA -28/32/34 is to pick it back up, slow way down, then re drop it.

 

[Dan Thomas]

Lots of possibilities, but worn seals in the actuators are prime suspects. In many airplanes they're left alone until they fail, not the best practice. A worn-out O-ring on an actuator cylinder piston will start letting fluid past it and the piston won't get pushed where it's supposed to go, especially in any system that has to fight against wind and/or gravity, which is in most systems. I recently rebuilt the actuators on an airplane; one had the wrong seal entirely in it, causing it to bypass and occasionally the gear wouldn't move, and another had a worn-out seal in it. Rubber parts don't last forever.

A leaking seal in one main gear actuator could cause pressure loss in the whole system and make the nosegear unable to extend fully. The mistake would be to assume it's just the NLG actuator.

The gear is worked both up and down by hydraulic pressure.

Dan

 

[drotto]

That's good for the mains, the nose will be helped with a extra pull of some load factor and slowing down. Best thing to do if the nose doesn't lock on a PA -28/32/34 is to pick it back up, slow way down, then re drop it.

Would doing a stall maneuver with recovery serve this purpose? Get the nose high almost stall the plane, then do a relatively aggressive nose down recovery?

 

[Henning]

Would doing a stall maneuver with recovery serve this purpose? Get the nose high almost stall the plane, then do a relatively aggressive nose down recovery?

You don't really want to stall, you want to have enough energy that you can pull 2g for a moment and still not quite stall.

 

[hindsight2020]

The gear is worked both up and down by hydraulic pressure.

Dan

It is worked both ways, but the down cycle hydraulic is not necessary to lock it on the PA-28 and 32s. Gravity suffices and is designed with gear gravity locked down as the failure mode.

You don't really want to stall, you want to have enough energy that you can pull 2g for a moment and still not quite stall.

Yep. Slow it below 100kias, and give the yoke a good 1-1.5 second pulsed pull. Works both ways; I do the opposite too on the Arrow to get the yellow light to go out after a long flight in turbulence. Unload the fick out of it and the main presses the microswitch back to the off position

I'd check that spring assist on the nose gear. It's probably all weak and worn. I love my Piper gear system. You keep up with the seals and all is well. Pump is cheap and easy to procure/overhaul. So far so good on 200 hours. If they had made a Dakota RG I'd be over that thing like white on rice.

 

[Datadriver]

bad limit switch in the nose

 

[ahkahn]

For those that said the hydraulics hold the gear up, you are correct. I saw a couple of posts that said the hydraulics push it down, as well, and that is false. It is a gravity-loaded drop through a release of hydraulic pressure through the pump. All the emergency gear down does is release the hydraulic pressure through different manual valve.

My suspicion is that it was down and locked the whole time (even though the controllers wouldn't confirm). I've had this happen to my plane and it has either been a sensor or the indicator light was loose. I now make it a habit to push in all 3 lights when I lower the gear... just to save me that potential heart-stopping moment again. It probably vibrated back on when he turned base/final.

I've also gotten under the nose and cleaned off the sensors. There is one that you push in, and sometimes it gets sticky. I'd push/clean that one, as well. Make sure you clean everything under off with CorrosionX.

It is extremely difficult for a Piper gear to not come down due to the design of the system. The only thing that can keep it up is if it gets jammed or off-kilter, but chances are it wouldn't go up to begin with if that were the case. If it swings clean, it won't stick. If it were a hydraulic issue, it won't go all the way up.

Watch that the mechanic doesn't chase the yeti... they enjoy doing that. Just jack it up, swing it several times, and if it works consistently, you're good.

 

[Checkout_my_Six]

bad limit switch in the nose

yeah....that.

 

[Cpt_Kirk]

I've had two issues with the landing gear on the PA-32. The first one was similar to your scenario, except it was the left main gear. Nothing I did got the light to illuminate.

It ended up being some sort of broken wire.

 

[bnt83]

Lots of wiring out there that is beat to death and/or flexed with landing gear operation. Ask yourself, how reliable is 30 to 50 year old wiring and gear switches going to be?

Here's some examples...
http://www.comanchegear.com/landing gear wiring harnesses.php

 

[jbrrapa]

I had the identical situation in my Seneca II. Turned out (as previously stated) to be a bad limit switch for the nose gear. You can verify (at least in a Seneca) if the gear is completely down and locked by pulling the throttle to idle. If, assuming the gear horn is working properly, the gear horn remains silent and the gear unsafe light is not lit, the gerar should be down and locked.

 

[drotto]

I had the identical situation in my Seneca II. Turned out (as previously stated) to be a bad limit switch for the nose gear. You can verify (at least in a Seneca) if the gear is completely down and locked by pulling the throttle to idle. If, assuming the gear horn is working properly, the gear horn remains silent and the gear unsafe light is not lit, the gerar should be down and locked.

From what I was told the gear unsafe light did come on at some point. Funny you mention that the gear was likely down despite the light being on. Apparently, the mechanic that now has the plane said in his opinion the gear was likely down and locked despite what the warning lights were indicating.


Still waiting to here more, because I really want to fly again next week, and need about 8 more hours for the insurance company to sign off on the transition training.

 

[Jimmy cooper]

Has your mechanic jacked it up and cycled the gear several times? I would take it somewhere else, get this done by real good shop. Second opinion much better than Internet troubleshooting. What year was the airplane built? How many hours? Etc. Not to mention, how many hacks worked on it or work put off.

 

[Henning]

Look, landing gear is very simple and straight forward, including inspection for worn parts and out of rig switches.

 

[drotto]

Has your mechanic jacked it up and cycled the gear several times? I would take it somewhere else, get this done by real good shop. Second opinion much better than Internet troubleshooting. What year was the airplane built? How many hours? Etc. Not to mention, how many hacks worked on it or work put off.

Its on jacks as we speak, was the following day. As for internet, it is what it is, never hurts to get more ideas. Plane is an 82, with about 4500 hours, fully "restored" (new paint, interior, stripped fully down, corrosion checked, new engine, new panel) about 2 1/2 years ago, and gets taken to the shop every time something seems even slightly off. Hacks from previous owners have been found, and when found were corrected. The primary pilot is very cautious with this plane, and does not let anything slide. Basically will refuse to fly it with any squawks.

 

[gitmo234]

^^ When are we going up in a PA-32? I have my eye on a couple (6/260 and a lance). If everything goes right it could be sooner than later, but we'll see. I'd like to try one out for an hour or two

 

[Henning]

^^ When are we going up in a PA-32? I have my eye on a couple (6/260 and a lance). If everything goes right it could be sooner than later, but we'll see. I'd like to try one out for an hour or two

Either is a good plane. Like a Cherokee with a long fat nose. The 6-260 always had a Low Rider feel to it taxiing around nose high.

 

[drotto]

Either is a good plane. Like a Cherokee with a long fat nose. The 6-260 always had a Low Rider feel to it taxiing around nose high.

Lol, when I have people in the back who are pilots, they comment about how they can't see crap out the front, and the flair feels like you are pointing the nose straight up.

 

[Henning]

Lol, when I have people in the back who are pilots, they comment about how they can't see crap out the front, and the flair feels like you are pointing the nose straight up.

That long nose really pushes the illusion too, although you land them fairly nose high, especially since people set them up nose high with low mains to make loading and unloading that much easier.

 

[ahkahn]

Not sure if you guys are talking about the Cherokee Six only, but coming from Cessnas, it seems like I'm landing flat in my Lance. Sometimes I don't pay attention and revert to a Cessna-style flare and it blows the entire landing. If I land "flat" then they grease every time. I've never had issues seeing over the nose, even in a flare, and I'm pretty darn short.

I did see a boatload of Cherokee Six's in OSH, and it appeared that those suckers really do sit like a low-rider.

 

[Henning]

Not sure if you guys are talking about the Cherokee Six only, but coming from Cessnas, it seems like I'm landing flat in my Lance. Sometimes I don't pay attention and revert to a Cessna-style flare and it blows the entire landing. If I land "flat" then they grease every time. I've never had issues seeing over the nose, even in a flare, and I'm pretty darn short.

I did see a boatload of Cherokee Six's in OSH, and it appeared that those suckers really do sit like a low-rider.

Usually the retract guys put more gas in their main struts, and the geometry is slightly different than with the fixed gear. I still land the Lance or Saratoga at the same nose high attitude as anything. Even my 310 I was stalling as I was rolling on. Flat landings are high energy landings. That's just wear, tear, and stress.

 

[tmyers]

For those that said the hydraulics hold the gear up, you are correct. I saw a couple of posts that said the hydraulics push it down, as well, and that is false.

Then why does the pump run when you extend the gear?

 

[Anticept]

Any time there is a failure of a major component, and an airplane has only been seen by one mechanic, I personally recommend that people get an opinion from a specialized shop or other, unassociated mechanic experienced with that component. Now, if it's only a worn limit switch or busted wiring (and can replicate consistently) then I would let this go, as I wouldn't call this a "major failure", just a good scare .

I really do not like only having one mechanic working on an aircraft. Even personally, my own planes go to other shops for at least one of the yearly inspections. I catch just about everything, but I'm not perfect. It's a lot of peace of mind, plus when it comes back with a clean bill of health or only an item or two, it's a big ego boost too!

 

[Checkout_my_Six]

Lol, when I have people in the back who are pilots, they comment about how they can't see crap out the front, and the flair feels like you are pointing the nose straight up.

Not sure if you guys are talking about the Cherokee Six only, but coming from Cessnas, it seems like I'm landing flat in my Lance. Sometimes I don't pay attention and revert to a Cessna-style flare and it blows the entire landing. If I land "flat" then they grease every time. I've never had issues seeing over the nose, even in a flare, and I'm pretty darn short.

I did see a boatload of Cherokee Six's in OSH, and it appeared that those suckers really do sit like a low-rider.

They can feel like a low rider....and seeing over the nose takes some getting use to.

 

[drotto]

Just an update, mechanic put the plane up on jacks and found that the gear was not retracting 100%. So there is a hydraulic leak somewhere in the system. The fluid reservoir and system fluid levels were good. Top suspect old O-rings. Found out a little bit more about the flight and it seems there was an intermittent gear warning when the gear was up, and the breaker for the gear did pop. It seems the gear was slowly lowing during flight and the pump came on to keep it up. Eventually it overheated and popped the breaker. Then the system cam on as full failure.

 

[Henning]

If it turns that the problem is the valve in the pump leaking by (it happens), this exact, zero differences, pump is available through National Aircraft Parts Agents under a Sierra number as a Mercruiser trim pump. There is also a possibility a pump shop can repair for $50.

 

[ahkahn]

Then why does the pump run when you extend the gear?

AFIK, it is running the pump in reverse to accelerate the pressure release. Even without the pump, the emergency gear valve release allows it to lower the gear, albeit slower than with the pump functioning.

 

[Henning]

AFIK, it is running the pump in reverse to accelerate the pressure release. Even without the pump, the emergency gear valve release allows it to lower the gear, albeit slower than with the pump functioning.

Other way around, it comes down way faster on the emergency drop.

 

[tmyers]

I have a video of the gear cycle on my Arrow. Pretty sure the gear is dropped by the pump. Totally different than an emergency drop. I will look it up in the maintenance manual when I get back from vacation.

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[Dan Thomas]

I have a video of the gear cycle on my Arrow. Pretty sure the gear is dropped by the pump. Totally different than an emergency drop. I will look it up in the maintenance manual when I get back from vacation.

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The pump runs the gear both up and down. IIRC, the emergency opens a bypass between the up and down lines and lets the gear drop.

 

[Henning]

The pump runs the gear both up and down. IIRC, the emergency opens a bypass between the up and down lines and lets the gear drop.

Correct, same bypass the auto extend system operates.

 

[tmyers]

That's what I have been saying.

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