Gear Circuit Breaker Popped
 

On today's flight to four airports I had the gear breaker pop twice upon selecting gear down. The gear "looked" to be down but no green light (obviously). Both times I was able to manually reset the gear breaker and cycle the gear UP then DOWN to get a green light and a successful and happy landing.

I have read through some of the older posts here RE gear problems. Tomorrow I will attempt to pump the gear doors open on the ground and have a good look inside to see if I have any frayed wires or dirty switches or contacts etc. Any other ideas??

Maybe try replacing the circuit breaker first as it's cheaper than the second option would be the pump motor. Doesn't sound like a gear or door issue. Did you have a heavy electrical load at the time?

Electrical load was not heavy. Daytime VFR flight.
Yes to new circuit breaker!! I like cheap fixes IF they work!

TC

Motor
 

Hi Tom,

I am not an expert on the Skymaster, but an AME/A&P for quite a few years, so I will offer a couple other spots to look at that are even cheaper than a CB.

If the gear pops its CB, it means that it is drawing a higher current as it works against electrical resistance, and will not be dependant on any other system. Things that can cause it to work harder to heat up and pop the CB:
- corrosion on connector (or bad connection)
- corrosion in a crimp of a connecter
- bad or loose ground (I always check grounds first - it is the simplest and most often the offending party).

Check the wires on the motor and at the CB. It may take a bit of work, but is cheaper than replacing any parts.

I think you already filled the system too - so that would eliminate any pump cavitation issues (I am really stabbing in the dark here, as I am not well studies on the power pack).

Anyway, hopefully some of this may help.
Jeff

Im a big fan of punting the 40+ year old circuit breakers.
Like Herb said, it's a good place to start. I've found a bunch of CB's that were no bueno. Punt the lot of them. Go to the Klixon's.


The emergency proceedures in the operators manual specifically state to pull the CB if you have to. The Cessna CB's don't allow that.




Leighton.

I like the idea of being able to disable circuits as I wish and I too noticed how most of my CBs do not currently allow this. I will look into upgrading to the Klixon's for sure. Thanks!

Gear Issues Continue...
 

After my initial gear issues things cleared up for a couple of flights but today the problem came back. Today when I went to put the gear down I popped the breaker near what should have been the end of the gear down cycle (12-15 seconds in). Like the previous time I tried cycling the gear but this time I could not get a green light and was not able to reset the breaker right away in order to cycle UP even. Eventually I manually pumped the gear DOWN and got the green light and landed fine. When I look at the mirrors the gear appeared to be down and locked. To me it seems like the gear cycle may in fact be complete and perhaps one of the switches that tell the system that the gear is down and locked might not be functioning which would cause the motor to continue running, heat up and overload the circuit. This is my current best guess.

Obviously this little snag goes to the very top of my list of things to fix!

Low Voltage ?
 

Could it be caused by low voltage in the system creating higher amp draw by the power pack ?

This is a good suggestion. We will look into it. She is going in to my AME tomorrow for a gear swing. Will keep you all posted...

Baggage Pod & Gear Swing..??
 

So, I have the baggage pod which I LOVE. My folding ladder and folding bike live in there 24/7 and it makes my travels so much easier and better while exploring distant lands. However, tomorrow I go in for my first ever gear swing (first since I bought her). I see the two jack points on the wings however the one behind the front wheel is inside the baggage pod. Hum... That can't be good.

The front gear point is not normally used for full lift of aircraft. It's more of a safety and allows you to just lift the nose if desired. Jacking the wings will cause the tail to go down and nose to go up so it should be fine. Check the service manual on jacking aircraft for sure

Except that if while the gear are swinging the aircraft comes off it’s wing points due to inadequate nose point support you will trash your wings, gear and belly, and someone might die…
My Skymaster pod had a door for the front jack point. I have also seen a Skymaster with a pod and no front pod door jacked by partially removing the wings and hoisting the aircraft using straps around the wing attachment points (the shop had an overhead hoist on rails). I have also seen it done using the usual wing points and for the front of the aircraft a strap from a hoist around the the front prop shaft...Whatever way you choose best of luck and stay far away from anywhere underneath the aircraft :)

I was thinking about that very option and how it would be pretty handy. Perhaps a future project.

Gear Swing Results
 

So they jacked her up today and, of course, she totally behaved herself, or rather misbehaved, as the gear worked flawlessly during over 15 cycles. It didn't pop the circuit breaker even once and everything appeared totally normal (of course). Tomorrow they claim to have a technique for putting simulated wind resistance on the gear as it is going down to be better representative of real life. I am going over to supervise (and video) and hope that we find something.

Here is a thought - it was -5C when I was out last time with the dual gear breaker failures. How does temperature affect such things???

Tom, I had a similar problem with my gear. Mine is a 1973 P model and if it is the same gear there are service bulletins on the pump and actuators that I highly recommend if not previously done. You might want to call Rick Cox at Cox Airparts. 316-945-0737

Brent

Cold Temperatures
 

Tom,

Regarding your question around temperatures and the subject of wind loading. Temperature certainly has an effect on a rotating component that is greased, and in addition, the wind loading from airspeed does provide an amount of resistance to the hydraulic system. It could be that with just a little cold grease and some airspeed provides enough resistance on the hydraulic system to make that pump work that much harder and draw more current. These are not your root cause however, just possible contributing factors in my opinion.

I used to be a crew chief on a L382 Hercules (commercial version of the C-130) and we operated in the Canadian Arctic. Ground temperatures were often below 40 C. We kept everything greased and clean on the gear and never had problems. One winter we were working out of Amsterdam - was a nice break from the cold. Of course in Holland, it seemed like it rained every day, and instead of a parka, I wore a rain suit to maintain the aircraft. We had to come back to Canada at Christmas to do a few fuel-hauls. This was the first time I discovered how grease can hold water in suspension, and when it gets cold, it can loose its flexible properties. We had to stop in Iqaluit (Frobisher Bay for the old-timers) for gas, and when the crew went to put the gear down, it was frozen! The hydraulic system could not overcome the drag of the moisture laden grease in the gear screw jacks. I took meticulous care of this landing gear - never had a problem until this day. Anyway - we ended up getting the gear down...I had to hand crank the mains down on both sides. That is a whole other story.... The problem was solved once I was able to purge all the old grease out of the ball nuts.

So the point of my rant is this - landing gear (in my experience) needs constant TLC. Cleanliness in areas that need to be clean, and consistent fresh lubrication where it is required. Old Grease and lots of grease is not good. Actuators need to be clean, and pivot points free from dirt and build up.

Cheers!
Jeff

Our Progress Today...
 

I wouldn't call that a rant but it is a pretty great story and a really good way to get your point across. Thanks for sharing that!

I visited the shop in order to witness the gear swing today so I got so see up inside areas not previously accessible. There was a little bit of very clean, non-contaminated looking grease in all the areas where I would expect it and everything was neat and tidy. The good news is they managed to pop the breaker a couple of times by putting the gear down while someone else applied back pressure on it to simulate the wind. We discovered a couple of things after that...

The gear actuator on the left side was much easier to "overpower" then the right one so the thought is that the actuator needs new seals or to be rebuilt entirely. The thought is that this was caused by the next issue.

We a wear point was discovered near the left gear hinge top. It appears that during the final stages of the lock process something is not aligned properly and this is causing the hinge to not seat. The actuator would continue to PUSH and maybe that is how it wore itself out. On those last few flights when I cycled the gear up and down it eventually seated itself and locked.

I am trying to not be terrified by the ramifications of all of this. The possibility of there being some sort of damage to the gear and just how much money this could cost to fix it. Also, how did this happen in the first place. So many mysteries. Perhaps not so much holiday flying for me...

Gear Swing Video
 

This is what it looked like in the shop this morning - https://vimeo.com/247046941

Hi TC

During my ground up restoration, we removed every hydraulic component and flexible line.

The main gear actuators were the last to overhaul as I waited until the plane was assembled and on jacks. The actuators are fairly straight forward to remove once you have access after taking off all those floor panels. Being careful it took me 2hours to removed both. Removing some of the hydraulic piping helped (as per SM), also make sure you take off the plastic cap, they just clip in.

Once out we dissasembled, cleaned, inpsected, conducted a die penetrant test and then reassembled with new seals and packers. All up the cost of seals for both actuators was approx $20, labour well that is a different story.

At the same time we did the main uplock and down locks, again about $25 in seals and a few hours labour.

In essence during the project we rebuilt every hydraulic component in the plane and replaced every flexible hose. Which I would strongly recommend if they have not been done in recent years, I bought a kit from PHT.

When it comes to the gear, a bit of PM and some $$ is good peice of mind. Also I open the doors regulary to look around the gear.

With any luck I will get a bit of stooging around in mine next week, I will time the cycles and let you know.

Dave