PA22 brakes

[Mike Welsh PA22]

l recently bought into a PA22 Colt and am looking for answers on the standard drum brake system. Specifically how to get them to work! Even with fine adjustment they only vaguely work. Does machining and matching the drums and shoes work?

 

 

[djpacro]

From a previous life many years ago - just a suggestion, consider changing to Cleveland via http://www.univair.com/piper/piper-pa-22/view-all/199-27600-cleveland-conversion-kit-piper/ or http://www.aircraftspruce.com/catalog/lgpages/cleve_piperconv.php

 

My mechanic would want a Form 8130 for something like that per CASA regs - see https://www.aircraftspruce.com/terms_conditions.php for additional cost.

 

 

[planedriver]

I have read of similar cases caused by a bit of air in the system and that the PA22 system can be a bit of pain in the butt to bleed.

 

The linings themselves may be old and hard, and also glazed.

 

I'd be checking the condition of the drums and the surface of the linings as well. If they are heavily glazed they will not have as much bite.

 

Have you tried physically checking the brake resistance by turning the wheels by hand, with the wheels raised off the ground.

 

Is it during the run-up they don't hold, or after landing which is the problem?

 

 

[facthunter]

I presume they are hydraulic. If the cylinders are corroded they will not actuate effectively. Drum brakes can be improved by removing some of the lining in the right places. I think I would fit Clevelands if you really need brakes. Nev

 

 

[Mike Welsh PA22]

Thanks for those suggestions. It has just had 100 hourly and brakes have been bleed and adjusted. It is the original lever and cable mechanism connected to master cylinder under the seat. I have priced the Cleveland disc brake option at around $4,500AU fitted, but that is only for wheels and discs and STC but I would like to see if there is a way to get the originals to work before spending that much money.

 

There is a high spot on each drum but I haven't had them off to inspect yet. The adjustment goes from a touch on the high spot to full lock in a whisker. It was a ground up restoration in 2006 and very well built so I assume it is in good order internally.

 

It won't hold on run up over 1,500 rpm.

 

I was hoping someone might have had the same issue?

 

 

[old man emu]

The plane might have had a ground-up restoration ten years ago, but machining the drums and/or fitting new brake shoes might have been overlooked. Another thing to consider is how much use the plane has had since 2006. If it has spent a lot of time sitting on its Dunlops, it is possible that the brake shoes have hardened, so the amount of friction between them and the drum is reduced.

 

Your comment that there is a high spot makes me suspect that the drums could do with machining. If you can, whip them off and take them to an auto shop - but tell the operator that the drums are off a post-WWl vintage car.

 

While the drums are off, inspect the surface of the brake shoes. If they are shiny, then the judicious application of a fine-toothed metal file will get rid of the degraded surface and expose good friction material.

 

The braking system does not work independently on each side. It's both or none. The brakes are only supposed to be used to slow the airplane to walking speed during its landing run. Even with brand new shoes and drums, the engine will produce enough Force to overcome brake friction above 1500 RPM and off you'll go.

 

If you are looking for a simple, low cost fix, then machining the drums and filing the surface of the shoes is the way to go.

 

YOu might like to join this forum:

 

http://www.shortwingpipers.org/forum/showthread.php?6276-Drum-brakes-on-my-lovely-pa-22-Colt

 

OME

 

 

[Mike Welsh PA22]

Thanks OME. You are confirming my suspicions. I'll take them off and get them machined and matched. Makes me wonder how you are supposed to do a mag check at 1,800 rpm as per the Owners Handbook if the brakes were never good enough to hold it.

 

 

[old man emu]

Chocks, my boy. Chocks.

 

Who ever decreed that mag checks had to be done on the edge of the runway? Why can't they be done at your parking spot before you taxi off to the runway holding point?

 

OME

 

 

[Mike Welsh PA22]

Better than chocks, I've found a slight uphill part of the taxi way to do the run up. On your own, getting in and running up, then shutting down, removing the chocks and getting in again, is just a little tedious! But good suggestion. Thanks.

 

 

[kaz3g]

Mike

 

If you are filing the surface of the linings then please wear a good dust mask. They are more than likely of an age where they are made of an a serous compound material.

 

Geoff Williams has a very nice Tripacer at Tyabb when he's not flying choppers up here. He did the restoration of this himself and would be a great source of information for you and Chris. He is also a great guy and you would enjoy meeting him.

 

The Auster starts creeping at around 1500 rpm but the type's brakes were never known for their effectiveness.

 

If you decide to fit Clevelands, you should also get rid of the training wheel and make it a real aeroplane!

 

Cheers

 

Kaz.

 

 

[facthunter]

You don't have to buy the clevelands new. If you are machining drums don't get them too thin and make sure they are concentric. (Run true to the bearings). Nev

 

 

[planedriver]

Thanks OME. You are confirming my suspicions. I'll take them off and get them machined and matched. Makes me wonder how you are supposed to do a mag check at 1,800 rpm as per the Owners Handbook if the brakes were never good enough to hold it.

Good luck with overcoming your braking problem Mike. Keep us informed as to your progress.

 

Whilst many of us have our own theories as to what the problem actually is, we'd all like to hear what the final prognosis is.

 

Kind regards

 

Planey

 

 

[Mike Welsh PA22]

Thanks Kas and others. I'll chase up Geoff Williams. Will keep you posted on the progress.

 

 

[Mike Welsh PA22]

We found the problem. The filler cap on the master cylinder was leaking. Our LAME nailed it with a new brass tapered fitting into the cylinder and the filler cap into that. Bingo. Brakes are now rock solid at 1800rpm! All the rabbits we followed down burrows were interesting, but all wrong. It is such a simple system it had to be a simple answer.

 

Thanks for all the input people.

 

 

[old man emu]

It always ends up being the two bob solution to the million dollar problem.

 

OME

 

 

[facthunter]

If the reservoir loses oil the brakes will go spoungy, go down too far and need bleeding to get the pedal up and with a firm feel again. Nev