Brake Master Cylinders

The following information is derived from the FAA's Service Difficulty Reports and Aviation Maintenance Alerts.


Beech C90GT King Air 90

Manufacturing Defect

After a new master cylinder was installed, attempts to bleed the system failed. Instead, it pulled fluid from the reservoir and returned it through the same line—internal bypass not functioning properly. Disassembled and found bypass valve stuck. Parts were unable to slide smoothly on shaft; metal shavings were found inside. Metal shavings were found inside cylinder. Unit removed and replaced with new master cylinder.

Part total time: 0.0 hours

Beech B300 King Air 300

Leaking Brake System

The crew experienced left main brake failure during taxi. Examination revealed left main tires were flat-spotted. Replaced the #1 and #2 wheel/tire and brake assemblies. Pilot side left brake master cylinder was also replaced.

Part total time: 171.0 hours

Cessna 172M Skyhawk

Internal Damage

While taxiing for takeoff, the right brake failed, resulting in the propeller contacting a taxiway light. Visual inspection of the right brake master cylinder revealed the cover’s chamfer was damaged and not allowing the piston rod end to fully seal when the brake was pressed, resulting in a decrease in hydraulic pressure and loss of directional control.

Part total time: Unknown

Cessna TU206G Turbo Stationair

Sheared Piston Rod

Pilot lost right brake on landing. Examination revealed brake master cylinder piston rod (p/n 0541143) was broken at base below clevis check nut (p/n 0541140). Upon further inspection, the clevis and check nut was found to have bottomed out on the piston rod, causing contact with the brake pedal shaft attachment horn, shearing the shaft below the check nut and causing the subsequent loss of brake capabilities.

Part total time: 5661.0 hours

Cessna 402C

Worn Master Cylinder

Pilot reported right brake failure while making right 180 turn. Left main gear exited runway, but no damage noted. Re-sealed pilot’s right brake master cylinder, serviced and bled. 

Part total time: Unknown

Pilatus PC-12-47E

Faulty Master Cylinder

Pilot reported right brake pedal went to floor. The right pilot-side brake master cylinder (p/n 959.47.51.132) was found faulty. It was removed and replaced.

Part total time: Unknown

Piper PA-31-360 Navajo

Failed Master Cylinder

The pilot experienced total failure of the left brake system during landing. No external leaks were detected following inspection and the reservoir was full. Air was noted in the reservoir during the bleeding procedure.

Part total time: 5412.0 hours


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