NTSB Identification: CHI07LA205.
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Accident occurred Monday, June 18, 2007 in Southern Pines, NC
Probable Cause Approval Date: 03/31/2008
Aircraft: Harpster Hawk Aero Tandem, registration: N4022P
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 experimental amateur-built Hawk Aero Tandem airplane sustained substantial damage during an emergency landing following a loss of engine power during cruise. The pilot stated that he had lost engine power after restarting the engine twice. He impacted a mound with his nose landing gear. A witness saw liquid in the fuel tank when the airplane was disassembled. The airplane was powered by a Hirth 2706 fuel-injected engine. The Blue Max two cycle oil's recommended fuel and oil ratio was 100:1. An engine manual supplement noted that the recommended fuel and oil mixture was 90:1 for fuel injected engines. The pilot reported that he used a 100:1 fuel/oil ratio. A representative of the engine repair facility stated, "This engine experienced a piston seizure of the mag[neto] end piston. ... The PTO side piston is undamaged and from inspection of this cylinder it appears that possibly there was too lean of an oil mix in the fuel."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The loss of engine power during cruise due to the piston seizure for undetermined reasons and the unsuitable terrain the pilot encountered during the forced landing. A factor was the rising terrain of the mound that the airplane impacted. Full narrative available
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