On August 11, 2001, a Grumman G-164B (registration N6774Q) was involved in an aviation accident near Quincy, WA. Investigators recorded the probable cause as: The failure of the impeller assembly as a consequence of impeller rub and binding within the impeller collector case for undetermined reasons. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An Agcat spray plane experienced engine power loss and oil spray after takeoff. The pilot dumped the chemical load and executed a forced landing in a field, during which the aircraft nosed over. Post-accident engine examination revealed metal contamination and impeller damage.
Accident Summary
Just as the Agcat spray plane broke ground during takeoff, the engine experienced a power loss, with an oil spray appearing on the windscreen. The pilot reacted by dumping the chemical load and continuing straight ahead, performing a forced landing in an agricultural field. During the landing, the aircraft nosed over.
Investigation
The accident investigation included a post-accident examination of the engine. This examination revealed substantial metallic particles in the oil filter and on the magnetic sump chip detector. Further disassembly of the engine disclosed substantial rubbing and abrasion damage to the engine impeller. The impeller and its associated collector case were sent to the Engineering Branch Laboratory of the Canadian Transportation Safety Board for a detailed metallurgical analysis. The laboratory examination found no signs of any progressive failure mechanism; the degree of damage was so extensive that a conclusive determination of the initiating event could not be made.