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Brake Caliper falling apart

I know Beringer has an EASA STC for the PA28. Do you know if this kind of upgrade makes sense in terms of reliability and reduced maintenance ? Or does it just improves the braking action ?

It seems to me that those auxiliary systems of GA aircraft were/are designed cheap and support is ahem limited

LFOU, France

According to the Cleveland manual for the 30-55 brakes it’s 75-80 inch pounds (or 8.5 to 9 Nm if you have a metric torque wrench) – dry.

The manual also warns that “Overtorquing can cause depressions in the brake cylinder leading to dragging or bound up brakes”

Last Edited by alioth at 21 Aug 09:55
Andreas IOM

The “wet or dry torque” discussion continues here

Administrator
Shoreham EGKA, United Kingdom

That would explain it! 7.5 foot pounds sounds better – I was being a bit thick there!

United Kingdom

I have Loctite 278 in the workshop. Red bottle, the stuff is green, and it is high-temp. Never used it on the plane however. Wire locking is much better, and drilled bolts cost only very slightly more.

90 foot lbs is mentioned above seems huge for that tiny bolt!

It is 90 inch-pounds. 7.5 foot-pounds. It’s a pretty standard torque for 1/4" bolts in aviation, which are normally “high tensile”. The max is about 100 and that is e.g. the value for the bolts which hold the crankcase halves together.

Administrator
Shoreham EGKA, United Kingdom

Thanks for all of the replies. My maintenance organisation were very surprised about this. They routinely throw bolts away which have signs of thread wear & they are diligent with the torque wrench.

I’ve yet to read the manual for torques; 90 foot lbs is mentioned above seems huge for that tiny bolt!

What do people think about using copper grease to lube the threads and I wonder what an appropriate torque would be? If copper grease was used then perhaps the bolts would need wire locking?

United Kingdom

The Loctite I have used is blue (243). It comes in a red bottle, hence my confusion. I understand the red stuff is stronger and the green stuff criminal tight.
Simon

Sounds like over the years they were over torqued too many times and failed. It does happen. Don’t beat yourself up about this, things will and do fail, sometimes without explanation. Every annual/100 hr inspection I would make sure the calipers studs and retaining plate are cleaned thoroughly. If the studs of your caliper do not move freely when pressure is applied, the bolts holding your pads together will be under abnormal tension.

For a brake caliper and given the fact you maintain your aircraft thoroughly, Loctite is way overkill. For piece of mind, buy a set of AN bolts with safety holes drilled in the head and safety them together. If not standard torque for those bolts is more than adequate.

There is yet another technology to lock the threads while maintaining the right tension – green (wicking) Loctite 290. Unlike the regular purple, blue and red grades, it is much thinner, applied after assembly, and penetrates the engaged threads.

LKBU (near Prague), Czech Republic

For my (relatively new) Cleveland brakes, the dry bolt torque is marked on the caliper ID plate and in the manual. After 40 years the markings on the caliper may not be legible, and as Peter says, some technicians may be better at using a torque wrench than others..

Glenswinton, SW Scotland, United Kingdom
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