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Odd Brake Failure

Tim-NJ

Active Member
After some routine maintenance which did not include anything at all with the brakes (I did an oil change), I uneventfully taxied out to the runway for a short test flight. Winds were something around 12G18 and coming from a direction that favored the far end of the runway when coming from my hangar. The taxing was uneventful. I line up and go full throttle when I do notice some unusual squirreliness staying on the centerline that I dismissed as xwind.

I flew for a half hour and landed only to find out my right brake was completely out. Lucky for me the runway was 3500ft and a the last third is uphill, 2nd stroke of luck the FBO was a left turn :) I got a tow back to my hangar and found this! I'm wondering if I picked up some FOD on the taxiway or runway?

Photo's:

https://photos.app.goo.gl/N66p62FsPBoUmLLv6

Ordered about $300 in parts. Hope the weather is as nice next weekend as this one.
 
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Look like the pant hit something that forced it top side outward and the mount bent and made contact with the rotor. Could also have hit something head on that was on the inboard side of the pant front (deflecting to fwd tip outward). The spinning steel rotor eventually ate a slot out of the alum bracket. Likely when the mount finally severed, the tension was released and the object holding the pant there was released. Also possible it just bent from hitting something.

This would have caused that wheel to initially drag, like the brake was partially stuck on. Then likely alum fragments got stuck in the pads and the brake became ineffective.

You can see the slight chamfer on the rotor where the contact was made.

Just speculation from the pics.

Larry
 
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Look like the pant hit something that forced it top side outward and the mount bent and made contact with the rotor. Could also have hit something head on that was on the inboard side of the pant front (deflecting to fwd tip outward). The spinning steel rotor eventually ate a slot out of the alum bracket. Likely when the mount finally severed, the tension was released and the object holding the pant there was released. Also possible it just bent from hitting something.

This would have caused that wheel to initially drag, like the brake was partially stuck on. Then likely alum fragments got stuck in the pads and the brake became ineffective.

You can see the slight chamfer on the rotor where the contact was made.

Just speculation from the pics.

Larry

I didnt notice any wheel pant damage but will look closer.
 
It looks like the brake disk was touching the pant bracket and it took that time to crack and fail.

I replaced all those nylock nuts with metal locknuts some time ago. The reason is that they get warm and loosen due to the heat from the brake rotor. Once they loosen, the bracket is free to move around.
 
My guess is someone stepped on your wheel pant and cracked the attachment. It was touching the brake disc and eventually was worn through. That thing coming apart caused the brake failure. But, thats just a guess based on the pictures.
 
I bet the bracket distortion was forced by the wheel fairing. Either somebody stepped on it or it hit something. Could even touch the tarmac in a strong xwind if the pant sits too low. Also Tim while redoing it check for other bracket integrity could be some micro cracks there. Once upon a time I drove through the brush of Wild West and observed similar symptoms :)

 
Thx Vlad, I think I?ll also check the pilots side before I disassemble anything to see if I reassembled incorrectly after the last relining.
 
Brake Failure

Perhaps one of the brake pads came loose and it tore the bracket on it's way around. No brake pad, no brakes.
 
It looks like the brake disk was touching the pant bracket and it took that time to crack and fail.

I replaced all those nylock nuts with metal locknuts some time ago. The reason is that they get warm and loosen due to the heat from the brake rotor. Once they loosen, the bracket is free to move around.

Bill - I've been thinking about your post a lot because the nylock nuts were loose enough to allow play and I thought that was purposeful. They were loose enough to allow the bracket to slide around a bit. Bit = a little fore/aft but no noticeable lateral movement. When I checked the pilot side yesterday, they were also slightly loose to allow some movement.

I'll get some locknuts, I assume you got the ones with a star washer attached and not the ones with a distorted thread.
 
My guess is someone stepped on your wheel pant and cracked the attachment. It was touching the brake disc and eventually was worn through. That thing coming apart caused the brake failure. But, thats just a guess based on the pictures.

I did have it in the shop last month for a new radio and an ADS-B install.
I cleaned up the wheel pants yesterday after reading Vlad's post and didn't find any physical damage although I don't think stepping on it would leave obvious physical damage. Brackets are all damage free.

One thing I'll mention is that when I relined last fall, this side was missing safety wire on the two bolts that go through the brake assembly. I don't remember consciously looking for broken safety wire that could have been stuck somewhere (Amateur lesson on my part) but there isn't really any place for it to hide either.

Anyway, I'm off today and think I will celebrate Presidents Day by disassembling the brake and wheel.
 
Bill -

I'll get some locknuts, I assume you got the ones with a star washer attached and not the ones with a distorted thread.

Except for some electrical applications (where you want a washer to bite thru any oxidation layer) most people use the distorted thread locknuts. The star washer may set up corrosion issues down the road.
 
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