Accident Summary
On August 11, 2017, about 1200 eastern daylight time, a Navion G airplane, registration N249KC, impacted trees after a loss of engine power near Adrian, Michigan. The flight instructor and private pilot were seriously injured, and the airplane sustained substantial damage. The airplane was registered to Kalea Co. LLC and operated by Sky Walker Flying under 14 CFR Part 91 as an instructional flight. Visual meteorological conditions prevailed at the time, and no flight plan was filed. The local flight had departed Lenawee County Airport (ADG) in Adrian, Michigan, about 1000.
Pilot Statements
The flight instructor reported that the engine lost power about 1,000 ft above ground level (agl) while over a wooded area. She was unable to glide the airplane to a nearby field. After the accident, she walked to a nearby road and waited for a car to pass by for help.
The private pilot stated that he was flying the airplane and they were returning to the airport after completing training maneuvers. He reported a partial loss of engine power about 1,500 ft agl, adding that the engine still had a little power available during the event.
Postaccident Examination
A Federal Aviation Administration (FAA) inspector reported that the airplane was found wedged between trees, with the empennage separated from the rear fuselage and the engine separated from the firewall. A smell of aviation fuel was present at the accident site.
An examination by the FAA inspector and a technical representative from Continental Motors revealed that more than 4 gallons of fuel drained from the left wing tip tank, which remained intact. The right wing tip tank was breached and had separated from the wing, with no fuel present. The fuel gascolator, the low point of the center main fuel tanks, contained no fuel, and fuel stain marks were observed underneath it. The gascolator was removed for further testing.
The engine sustained impact damage concentrated mostly to the left rear side, but the crankcase remained intact. All six cylinders were attached, with the left side cylinders more damaged. The induction and exhaust systems showed impact damage but no signs of leaks. The fuel pump and several fuel line fittings were impact damaged. The throttle and mixture arms were broken. The fuel manifold valve and all fuel nozzles remained installed. Both magnetos produced sparks when rotated. The ignition harness showed impact damage, and one propeller blade was damaged. No pre-impact anomalies were found that would have prevented normal operation or rated horsepower.
Gascolator Testing and Maintenance Records
The gascolator was subjected to postaccident testing as prescribed in Navion Service Bulletin No. 106 A, issued by Sierra Hotel Aero, Inc. (SHA) in May 2007. The bulletin required a one-time inspection of the entire fuel system, including a vacuum test of the gascolator: apply 24 inches of vacuum and verify bleed down does not exceed 4 inches over one minute. During testing, the gascolator was filled with clean 100LL fuel, and foreign debris was observed floating. The inspector applied 24 inches of vacuum pressure, but the gascolator failed to hold it for any amount of time, leaking from the top seal, bottom seal, and the drain valve.
A review of the airplane maintenance logbooks found no record of compliance with Navion Service Bulletin No. 106 A and no mention of gascolator maintenance from December 2006 to July 2017.