Gear Circuit Breaker Popped

hharney · #1 12-11-17, 10:05 AM

Quote:

Originally Posted by tomcomet

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

JamesC · #2 12-11-17, 10:36 AM

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

tomcomet · #3 12-11-17, 07:10 PM

Quote:

Originally Posted by JamesC

My Skymaster pod had a door for the front jack point.

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

tomcomet · #4 12-11-17, 07:15 PM

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???

Red Air Rambo · #5 12-12-17, 12:56 AM

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

JAG · #6 12-12-17, 10:11 AM

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

tomcomet · #7 12-12-17, 01:06 PM

Quote:

Originally Posted by JAG

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.

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...