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Locked brake causing brake defects on tires?


M252

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I have been flying my 252 for 7 years and several hundred hours across Europe.

From time to time I have seen brake defects on the left main gear/tire and blamed myself that I pushed the brake paddle too hard. However, recently I have seen more significant defects on the very same left tire, which prompted a tire replacement too soon after replacement. I have been exceedingly careful not to apply any brake power during and after landing. My hypothesis is that the left brake is somewhat locked during landing causing the fast erosion of my tires (with a typical "brake plate" on them).

This could be a malfunctioning brake system keeping the left wheel locked after take-off (after which I apply brake pressure before moving gear up). I always check the parking brake before landing that it is not engaged, I also do not use main brakes during landing, but potentially the left is slightly engaged when I use rudder?

Has any one seen this in a Mooney? Any idea what the culprit might be?

Thanks,

Udo

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5 hours ago, M252 said:

I have been flying my 252 for 7 years and several hundred hours across Europe.

From time to time I have seen brake defects on the left main gear/tire and blamed myself that I pushed the brake paddle too hard. However, recently I have seen more significant defects on the very same left tire, which prompted a tire replacement too soon after replacement. I have been exceedingly careful not to apply any brake power during and after landing. My hypothesis is that the left brake is somewhat locked during landing causing the fast erosion of my tires (with a typical "brake plate" on them).

This could be a malfunctioning brake system keeping the left wheel locked after take-off (after which I apply brake pressure before moving gear up). I always check the parking brake before landing that it is not engaged, I also do not use main brakes during landing, but potentially the left is slightly engaged when I use rudder?

Has any one seen this in a Mooney? Any idea what the culprit might be?

Thanks,

Udo

A few things to check.  Mil H 5606 hydraulic oil get very thick over time and can cause the piston to become stiff in the calliper, fill the reservoir with fresh fluid and pump it out the bleeder fitting on the calliper until it runs freely, be sure to keep the reservoir full to avoid air entry.

The piston may be stuck stuck in the calliper bore due to corrosion, disassembly is required to polish the bore, install a new O ring and bleed the brakes.

The brake pressure plate can get stuck on the calliper guide pins and you can get a build up of dirt and dust behind the pressure plate, disassemble to inspect and clean as required.

Clarence

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3 hours ago, M20Doc said:

A few things to check.  Mil H 5606 hydraulic oil get very thick over time and can cause the piston to become stiff in the caliper, fill the reservoir with fresh fluid and pump it out the bleeder fitting on the caliper until it runs freely, be sure to keep the reservoir full to avoid air entry.

The piston may be stuck stuck in the caliper bore due to corrosion, disassembly is required to polish the bore, install a new O ring and bleed the brakes.

The brake pressure plate can get stuck on the caliper guide pins and you can get a build up of dirt and dust behind the pressure plate, disassemble to inspect and clean as required.

Clarence

The only item I could add to what Clarence said would be that even though you run new clean fluid through the caliper there can still be thick 5606 jelly inside the brake caliper. I've seen this a couple of times. I would suggest taking the wheel caliper off, disassemble it, clean and hone the puck seal area with 300 - 400 black sandpaper and reassemble with a new oring, clean the 2 slider pins with 300-400 paper and run a gun brush (brass) through the pin mounting holes. Reinstall and bled it and your problems will probably go away.

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2 minutes ago, mike_elliott said:

my bad, I was thinking it was the newer synthetic stuff that doesnt congeal.

Indeed you were thinking of Royco 782 MIL-PRF-83282, which is still compatible with 5606 systems , and which is a synthetic superior to 5606 since it will not congeal over time and fireproof. https://www.aircraftspruce.com/catalog/lgpages/anderolr782hf.php

I don't believe we ever needed permission from Mooney to use it, since the mil standard identifies it as compatible with 5606 brake systems, but recently Mooney did issue a SB saying they approved of its use. I've been using it for years. 

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