On February 29, 1992, a Grumman G-164A (registration N5408) operated by Trinkle & Boys Agricultural was involved in an aviation accident near Vernalis, CA. Investigators recorded the probable cause as: THE OPERATOR'S FAILURE TO PROPERLY COMPLY WITH AN AIRWORTHINESS DIRECTIVE AFFECTING THE SECOND-STAGE TURBINE WHEEL ASSEMBLY. CONTRIBUTING TO THIS ACCIDENT WAS THE UNCONTAINED FAILURE OF THE SECOND-STAGE TURBINE WHEEL AND THE ROUGH/UNEVEN TERRAIN. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An agricultural airplane experienced an uncontained second-stage stator turbine wheel separation during a turn. Low altitude prevented alignment with furrows. Landing was normal but wheels dug into furrows, causing the airplane to nose over. Engine logbook revealed non-compliance with an airworthiness directive.
Incident Description
During an aerial application procedure turn, the airplane experienced an uncontained separation of the second-stage stator turbine wheel. The pilot was unable to align the aircraft with the cultivated furrows due to insufficient altitude. The separation occurred while the airplane was maneuvering at low level.
Landing and Nose-Over
The subsequent landing was normal; however, during the landing roll, the wheels dug into the furrows. This caused the airplane to nosed over onto its back. The aircraft came to rest inverted on the agricultural field.
Maintenance Findings
Examination of the engine logbook disclosed that the operator had not properly complied with Airworthiness Directive (AD) 86-08-06. This AD mandates radiographic inspection of the second-stage stator turbine wheel assembly. The lack of proper compliance was identified during the post-accident review of maintenance records.