Frozen trim

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Matthew Rogers

Ejection Handle Pulled
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Matt R
I have a 1966 C150f. One time recently I flew and must have had a drop of water in the trim push rod bushing that comes out of the elevator. Everything was working on the ground, as temps were just over freezing, but after 20 minutes and 5000’ later, the trim was now completely frozen and unable to turn in either direction. Back on the ground, it was again free. It had rained the night before and there was plenty of dripping water on the plane, so certainly water present. The plane is tied down outside, so lots of opportunity for water to enter the area.

Question is, what should I spray onto that rod to displace water/lubricate it? Is there something I can keep in the hangar to spray and displace any water in the area if I expect similar conditions to occur? I mean, sounds like WD-40 (water displacing lubricant) is made for this, but I know that is not the answer.
 
Do you think that will prevent it from holding water that could freeze the mechanism in the future? Does water bead up on LPS2 like it does on a silicone lubricant?
 
My guess the freezing is in the hinge so give that a squirt also.

There is a small panel on the bottom of the Stab.

Remove and you have access to Trim Actuator.

Put a hair dryer on it to boil out entrapped water.

Note there is a procedure to lube the Actuator that is seldom done.
 
Magman said:
Note there is a procedure to lube the Actuator that is seldom done.
Click to expand...
Yup. Seldom. It is a 1000-hour or three-year thing. The actuator comes out, it comes apart, and everything is cleaned thoroughly. Everything gets inspected for corrosion and wear. A corroded shaft can break and let the tab flutter and you are dead. There are specs for wear on the bearing that the shaft passes through; wear allows more free-play of the tab, not a good thing. The actuator is lubricated with the correct lube as specified in the maintenance manual, NOT LPS or silicone or anything else.

I'd bet that there's water laying inside that thing that ain't gonna come out. Heating it will just dry the lube out even more than it is and maybe damage the O-ring seals at both ends. In fact, those seals will be shot, which is why the water is getting in there. Water mixes with the oil in the grease and forms acids, which eat the actuator. Get it serviced properly.

http://www.aeroelectric.com/Referen.../Cessna_100_Series_1962-1968_MM_D637-1-13.pdf

Trim system, section 9. Overhaul times, Section 2, page 2-25.

It's not owner maintenance, either.
 
Oh good, another part on my plane that probably hasn't been checked in 70 years... :) Thanks.
 
Looking at the diagrams, I think that it is water in the actuator, or at least just a bit in the outer bushing where the push rod actuator exits the actuator housing. I will quickly know the answer on the first truly cold day, I assume. It will either be frozen up, or it was an isolated occurrence related to water outside the mechanism.

As GeorgeC said, oh great, another part on my 54 year old airplane that is ready to fail.
 
Matthew Rogers said:
Looking at the diagrams, I think that it is water in the actuator, or at least just a bit in the outer bushing where the push rod actuator exits the actuator housing. I will quickly know the answer on the first truly cold day, I assume. It will either be frozen up, or it was an isolated occurrence related to water outside the mechanism.

As GeorgeC said, oh great, another part on my 54 year old airplane that is ready to fail.
Click to expand...
Old airplanes are fun. Too many owners expect them to last forever. They've been spoiled by modern motor vehicles that are built with seals on everything, with factory lube that lasts for a long time. Still, after 50 years even they would be falling apart, if not much sooner.

I have also found frayed trim cables in the belly, where annual "inspectors" seldom go. Fraying primary control cables, too. Or rusted. Seized cable pulleys. Lots of nasty stuff. FAR 43 Appendix D lists the minimum level of inspection, and we find samples like this in it:

(b) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the fuselage and hull group:

(2) Systems and components—for improper installation, apparent defects, and unsatisfactory operation.

(c) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the cabin and cockpit group:

(5) Flight and engine controls—for improper installation and improper operation.

(7) All systems—for improper installation, poor general condition, apparent and obvious defects, and insecurity of attachment.

(g) Each person performing an annual or 100-hour inspection shall inspect (where applicable) all components and systems that make up the complete empennage assembly for poor general condition, fabric or skin deterioration, distortion, evidence of failure, insecure attachment, improper component installation, and improper component operation.

Now, based on the complaints we see on this forum nearly every day, I know it ain't getting done in many cases. Many, many cases. I've seen it myself here in Canada, and we have a similar minimum level of inspection. Shocking, sometimes. How does one comply with the requirements without getting under that floor and into the tailcone? You can't.
 
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