Primary finding
Probable cause
Leakage of brake fluid from an unknown source onto the brake lining and drum.
Investigator assessment
Analysis narrative
The pilot said that during landing the aircraft began turning to the left. He attempted to correct the turning tendency with right rudder and brake application; however, the aircraft suddenly ground looped and collapsed the main landing gear. The brakes were examined and brake fluid was observed on the brake drum and lining. Disassembly of the left brake cylinder revealed deep corrosion pits on the interior surface of the cylinder. Due to the manufacture date of the airplane, vegetable base (automotive) brake fluid is used. It was reported that unlike mineral base brake fluid used in modern aircraft, 'vegetable base fluid will not tolerate high temperature and will cause a brake lining to 'grab' the drum during heavy brake application.'
Source record
Factual narrative
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