ANC93LA151

The modified PA-12 collided with terrain during an attempted emergency landing following fuel starvation. The airplane had been modified with a 160 HP engine requiring extensive upgrade of the fuel system. The airplane had a history of sudden and complete starvation engine stoppages without associated mechanical, ignition or carburation anomalies.

On August 17, 1993, at approximately 2015 Alaska daylight time, a wheeled equipped Piper PA-12 airplane, N123TL, experienced total power loss during a climb after a full stop practice landing. The private pilot was operating under 14 CFR Part 91 and had made two uneventful touch and go landings at the unattended Goose Bay airstrip near Elmendorf AFB, Alaska, when at 100 foot altitude, abrupt cessation of engine power occurred. While attempting to return for a runway landing, the airplane entered aerodynamic stall and impacted off-runway in a brushy level area. Visual meteorological conditions existed and no flight plan was filed. The pilot, as sole occupant on board, was seriously injured and the airplane was substantially damaged.

The pilot told investigators that he believed it to be "fuel starvation," and related that he learned of previous sudden stoppages of the engine when the history of the airplane was reviewed with previous operators of that aircraft. The owner/pilot told the NTSB that despite a previous carburetor change and a subsequent engine replacement, the modified aircraft (upgraded from its original Type Certificated [TC] 100 HP to a Lycoming 160 HP O-320) had experienced yet another sudden stoppage, while FAA-Certificated inspectors found no mechanical anomalies to have pre-existed the stoppage.

FAA inspectors found an undetermined amount of fuel on board the airplane at the accident site and evidence that the impact had compromised the fuel system at the wing roots. The pilot produced a copy of a fueling receipt in his name on the day of the flight which indicated that he had uploaded 31.06 gallons of aviation fuel.

In a review of the events with investigators and engineers at the Piper Aircraft Corporation, the NTSB was told that "in Piper's opinion, the PA-12 fuel system was never designed or capable of providing fuel at a rate beyond which was required for 100 HP." The accident airplane, as modified with both after-market STC's (structural changes for mounting higher horsepower engines) and parts from other Piper airplanes (such as the PA-18 header tank) is different in system and structure to the original type- certificated PA-12 "Super Cruiser" with its 100 HP engine.

An STC (Supplemental Type Certificate) (SA644AL) exists to upgrade the PA-12 to the Lycoming 160 HP engine. That STC is a multiple authorization. The STC stipulates that extensive modifications to the fuel system of the airplane be completed in order to satisfy the requirements of the STC changes in order to supply adequate fuel pressure throughout the test range specified and with the stipulated minimum fuel levels.

The NTSB was not able to determine to what extent the fuel system of the accident airplane had been modified to satisfy the fuel flow requirements stipulated by the STC. Some of the changes, but not all, to the basic airplane include the addition of a certain size header tank, fuel line sizes, modifications to the valves and fuel switches. Subsequent to the accident the airplane was sold, as is, and is reportedly being rebuilt with a Lycoming 160 HP engine installed.