Gear Circuit Breaker Popped

[JAG]

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]

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...

[tomcomet]

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

[SkyMac]

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