NTSB Identification: ANC09LA100
14 CFR Part 91: General Aviation
Accident occurred Thursday, September 17, 2009 in Anchorage, AK
Probable Cause Approval Date: 10/21/2010
Aircraft: GRUMMAN G-44A, registration: N86627
Injuries: 2 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 commercial pilot reported that he was landing his tailwheel-equipped amphibious airplane on a dry, paved runway at the conclusion of a local area postmaintenance flight operated under Title 14, Part 91 after a local facility had completed repairs to the right brake assembly. After landing, the pilot applied the brakes to slow the landing roll, and while depressing both brake pedals, the right brake pedal unexpectedly "went to the floor" and the airplane swerved to the left. The airplane ground looped to the left, sustaining substantial damage to the right wing and right aileron. A postaccident investigation revealed that a hydraulic supply line fitting on the airplane's right brake assembly had broken. The maintenance technician that did the repairs on the airplane's brake reported that the hydraulic supply line fitting was not removed during his work. He also said that he strongly suspected that the broken fitting might be an unapproved or "bogus" aircraft part due to an atypical thread pattern. An NTSB metallurgical examination revealed that the fractured fitting had failed due to a fatigue fracture. A Safety Board mechanical engineer noted that the broken fitting was marked with the "AN" (Air Force-Navy standards) identification stamp, signifying that it was approved for use in aircraft. Further investigation revealed that the fractured fitting was consistent in appearance to that of a fitting manufactured to meet the standards of a Joint Industrial Council (JIC), which is not intended for use in aircraft. The Safety Board mechanical engineer also noted that the two types of fitting are nearly indistinguishable except for the "AN" identification stamp. He added that without the aid of magnification, the "JIC" fittings and the "AN" fittings look identical. The "AN" fitting is reported to have a 40 percent increase in fatigue strength over the identical "JIC" fitting. There was no logbook entry which disclosed replacement of the hydraulic fittings, and the airplane's owner said that he was unaware when the brake line fittings had been replaced, but assumed it had been done prior to him purchasing the airplane. On July 22, 2008, the Federal Aviation Administration (FAA) issued an Advisory Circular (AC) 21-29C, change 1, which provides updated information and guidance to the aviation community for detecting suspected unapproved parts and reporting them to the FAA.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A fatigue fracture of an unapproved hydraulic brake line fitting, which resulted in a loss of control during the landing roll. Contributing to the accident was the installation of an unapproved part by an unknown maintenance personnel. Full narrative available
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