NTSB Identification: LAX95LA166.
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Accident occurred Saturday, April 22, 1995 in CHINO, CA
Probable Cause Approval Date: 11/11/1996
Aircraft: WACO UPF-7, registration: N20971
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE PILOT EXPERIENCED A DIRECTIONAL CONTROL PROBLEM DURING THE LANDING ROLL. IN HER INITIAL ORAL STATEMENT, SHE INDICATED THE DIFFICULTY WAS DUE TO THE WIND CONDITION. REGARDING HER ATTEMPT TO CONTROL THE AIRCRAFT, SHE SAID SHE THOUGHT SHE MIGHT HAVE INADVERTENTLY APPLIED THE BRAKES, WHICH HAD CAUSED THE AIRCRAFT TO NOSE OVER. A POSTACCIDENT INSPECTION OF THE AIRCRAFT REVEALED THAT THE ATTACHMENT LINK OF THE RETURN SPRING FOR THE LEFT MASTER CYLINDER HAD FAILED. ACCORDING TO THE MAINTENANCE MANUAL FOR THE HAYES NO. D-87-36 BRAKE MASTER CYLINDER, THE ASSEMBLY WAS DESIGNED SO THAT SOME BRAKE FLUID WOULD BE ADDED TO THE PRESSURE SIDE OF THE PISTON DURING THE RETURN STROKE. HOWEVER, IF THE RELIEF PORT WAS NOT OPENED BY A COMPLETE RETURN OF THE PISTON, WHEN THE BRAKE WAS RELEASED, PRESSURE COULD HAVE BUILT UP IN THE SYSTEM, CAUSING THE BRAKE TO DRAG OR LOCK.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

failure of the attachment link for the master cylinder return spring, which allowed the left brake to lock.

Full narrative available

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