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Why your maintenance company should GREASE bearings and not just oil them

That is a typical airframe part, not legally serviceable (supposedly). When one of the bronze bushes wears out (which it will, rapidly, once it loses the lube), it’s a thousand quid or so… and people then get a suprise Annual bill costing a few k more than they expected.

This small (95mm long) part is incidentally from the back end of a TB20 and when it wears out, it causes a lot of people to change the elevator trim hinges, which is a thousand quid in parts, plus labour, but rarely does very much because actually it is the elevator trim linkage (of which the above part forms a part) that is shagged.

Very few engineers will lube or even look at those bearings. To get proper access, to remove this part for the required cleaning and greasing, you need to remove the elevator, which is a “massive effort” requiring 3 people and about 35 minutes… (so 3hrs of labour because you get billed for six 0.5hr units) but which is anyway necessary to grease the elevator bearings. Cheap at twice the price, as they say

Last Edited by Peter at 23 Jan 18:53
Shoreham EGKA, United Kingdom

Not a great design if you need need such an effort to get there I’d say. Does the MM mention this procedure or is this field knowledge?

There isn’t anything on the 182RG that is hard to get to. The seats have to go out anyway during annual and there are access doors for the gear which take 3 minutes to remove. The whole elevator/rudder/trim mechanism is easy to access and if you’re halfway slim, you can climb inside the tailcone all the way to the back for the control linkages. Particularly nice on a hot and humid summer day.

If you look at the evolution of the 182, I would say that about 50% of the changes are for improved maintenance, learned from experience in the field. Just like when Soccata had the wonderful idea of installing external avionics access covers in addition to the already smart tilting center console (which in reality is sabotaged by bad avionics wiring).

I absolutely love when product designers focus on maintainability. It is a delight to open an old King radio and see how the boards are laid out together with complete schematics of the circuitry. They are built to be repairable for the next 500 years. Not many products are designed that way anymore. The best you get today is a component swap approach for example with modern cars. Diagnostics device gives you the list of components and you swap them.

You probably could got to that part if you climbed inside the tail; that’s a good point.

But going in from the outside is a lot easier, especially as the elevator bearings ought to get fully cleaned and re-greased anyway.

Also the tail section is full of ACF50 from the previous post-Annual spraying

Last Edited by Peter at 23 Jan 20:56
Shoreham EGKA, United Kingdom

Regarding climbing inside the tail: as A&Ps got fatter over time, Cessna added a huge inspection cover on the tailcone (I believe ca. 1982) which allows you to access everything from the outside. I remember that my avionics shop had a gorgeous looking petite engineer who had to do all the tailcone work. Shortly thereafter she resigned and I think I do know why

Not wishing to be controversial: but looking at the picture it looks like these could oil-lite type bearings in which case oil would be more appropriate than grease. Caution should be used if using grease has it will accumulate dirt which can be harmful if it gets into bearings. It appears that the part has rust on it, in which case it should have plated or painted with a good etch primer and top coat.

EGHI, United Kingdom

They are straight bronze bushes, in an aluminium housing which is prob99 CNC milled.

The problem with oil is that the bearings are very short (around 8-10mm) so any oil you put in there lasts about 5 minutes. Also the bearing is more or less in the open air (certainly it is exposed to a lot of draught) so will be collecting a lot of dirt, and if a lot of grease is applied in and outside the bearing that will keep the dirt out. With oil, these bearings don’t last lubricated for more than a year or so, and just keep accumulating dirt. The shafts that run in them are steel and tend to go rusty (actually rusty) unless protected.

The reason for the fashionable paintwork is that Socata (along with most painters) spray the final paint scheme all over anything that sticks out

Last Edited by Peter at 24 Jan 17:40
Shoreham EGKA, United Kingdom

Agree with jxk, be carefull on these. A lot of them are sintered and take oil when warm.

If they are straight bronze bushing, be sure to select the correct grease. A lot of grease additives can damage red metals (copper / bronze). Therefore the choice of the correct grease on these metals is much more important than with many other metals.

I would stay with Socata’s lubrication plan, maybe increase the frequency of it, or that of the aftermarket bearing manufacturer.


It is to be done with grease. TB04-004A is AeroShell #7 which is what I have always used. It is used almost everywhere on the TB20.

Shoreham EGKA, United Kingdom

In that case, grease it is… I would always follow the aircraft manufacturer recommondations in these cases


The point which I probably didn’t make very well is that it is self evidently impossible to get the grease into the bearing (with a brush as suggested, or using any other way) unless you dismantle the parts. Just brushing grease onto the outside is no good.

Which almost nobody is going to do, because they won’t do it within the “£2500 fixed price Annual” – or whatever.

That’s why maintenance people far prefer to just squirt some oil in there. It won’t last long – because the bearing is short and relatively exposed. The real bills (a few k for replacement parts) will start to arrive some years later, long after any blame can be assigned.

Incidentally I wonder how those bronze bushes were inserted. It is apparent that they were inserted after the aluminium part was primed, so they are probably a press-fit. They may also have used some glue.

Last Edited by Peter at 25 Jan 07:19
Shoreham EGKA, United Kingdom
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