Primary finding
Probable cause
the pilot's improper planning/decision, which resulted in loss of engine power due to fuel exhaustion. A factor associated with the accident was: the erroneous (false) indication of the fuel sight tubes.
Investigator assessment
Analysis narrative
The pilot stated that he had approximately 4.5 hours of fuel on board. He indicated that he tried to conserve fuel during his flight by operating the airplane at a reduced power setting, because he knew that the flight time would be close to the airplane's fuel flight time limits. The engine began to sputter as he was crossing Knik Arm. He applied carburetor heat and noted a small improvement in engine RPM. The engine then lost all power. The pilot stated he attempted to land on water, but was unable to reach the water. He landed on mud flats, and the right float struck a gully during the landing. The float strut collapsed, and the airplane dragged the right wing and elevator. During repair of the airplane after the accident, a mechanic found that the fuel sight tubes would show a greater quantity of fuel than was available.
Source record
Factual narrative
On September 16, 1996, at 1545 Alaska daylight time, a float equipped Piper PA-12 airplane, N7658H, registered to and operated by the pilot, experienced a loss of engine power during cruise flight and was forced to land on the mud flats of Knik Arm near Anchorage, Alaska. The personal flight, operating under 14 CFR Part 91, departed Lake Louise, Alaska, and the destination was the Lake Hood Seaplane Base in Anchorage. A visual flight rules flight plan was in effect and visual meteorological conditions prevailed. The certificated private pilot and the passenger were not injured. The airplane received substantial damage. During a telephone conversation with the pilot on September 17, 1996, he stated that he had approximately 4.5 hours of fuel on board. He was trying to conserve fuel during his flight by operating the airplane at a reduced power setting because he knew that the flight time would place him close to the airplane's fuel flight time limits. The engine began to sputter as he was crossing Knik Arm. He applied carburetor heat and saw a small improvement in engine RPM. The engine then lost all power. The pilot stated he was attempting to land on the water but was unable to reach the water. He landed on the mud flats and the right float struck a gully during landing. The float strut collapsed and the airplane dragged the right wing and elevator. According to the owner, during the repair of the airplane, the mechanic checked the fuel sight tubes against the quantity of fuel in the fuel tank. He found that the fuel sight tubes showed more fuel available than actually in the fuel tanks. -