On May 3, 1982, a Piper PA-25-235 (registration N7350Z) operated by Charles B. Gregg was involved in an aviation accident near Lubbock, TX. Investigators recorded the probable cause as: The pilot's failure to purge air from the left brake hydraulic system after adding fluid, which resulted in a loss of braking effectiveness and caused the aircraft to veer right upon landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft veered right and flipped over during a test flight landing because the pilot failed to purge air from the hydraulic brake system after servicing.
What happened
Prior to the flight, the operator and pilot performed routine servicing on the aircraft in preparation for the upcoming spraying season. As part of this maintenance procedure, hydraulic fluid was added to the left brake assembly. However, the pilot did not purge the system of air after adding the fluid.
During a short test flight following the servicing, the aircraft landed. Upon touchdown, the aircraft veered sharply to the right. It departed the runway surface and entered a soft field, where it flipped over.
The investigation
The investigation focused on the maintenance activities performed prior to the flight. It was determined that hydraulic fluid had been added to the left brake system. The critical finding was that the system was not purged of air after the fluid was added.
Probable cause
The pilot's failure to purge air from the left brake hydraulic system after adding fluid, which resulted in a loss of braking effectiveness and caused the aircraft to veer right upon landing.