ANC03LA040

The commercial certificated pilot was landing at a remote gravel airstrip. During final approach to the gravel bar/airstrip, the pilot said the airplane encountered a minor downdraft, and as he began to add engine power to arrest the resulting descent, the engine did not respond with any increase in power. He said he pumped the throttle without any response. The airplane continued to descend and touched down in an area of low brush, about 50 yards short of the airstrip. During the touchdown, the right main landing gear collapsed and the right wingtip struck the ground. The pilot, who holds an aircraft mechanic certificate, reported that the engine was overhauled and reinstalled on the airplane three days before the accident. At that time, he installed an overhauled carburetor. He indicated that during attempts to run the engine, after the accident, the engine would start and run at idle power. He noticed a binding of the carburetor's throttle cable or internal carburetor linkage. He replaced the throttle cable, but still felt a binding in the throttle mechanism. The pilot said he disconnected the throttle cable from the carburetor, and hand operated the throttle arm. It had binding only when the engine was running. The NTSB IIC conducted an examination of the carburetor at an aviation maintenance facility. No mechanical malfunctions were discovered during the examination.

On March 31, 2003, about 1800 Alaska standard time, a tundra tire-equipped Piper PA-18 airplane, N8106Y, lost engine power during an approach to landing and sustained substantial damage when the airplane touched down short of a remote gravel airstrip, about 45 miles west of Port Alsworth, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country business flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by Lake Country Lodge, Inc., Port Alsworth, to transport a client to a hunting camp along the Mulchatna River. The commercial certificated pilot, and the sole passenger, were not injured. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect. The flight originated at Port Alsworth, about 1715.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on April 10, the pilot/lodge owner reported that he was on final approach to a gravel bar/airstrip location that is adjacent to his hunting camp. The gravel bar is oriented northeast/southwest and is about 800 feet long and 75 feet wide. The pilot said that during the landing approach, the airplane encountered a minor downdraft, and as he began to add engine power to arrest the resulting descent, the engine did not respond with any increase in power. He said he pumped the throttle without any response. The airplane continued to descend and touched down in an area of low brush, about 50 yards short of the airstrip. The pilot indicated that during the touchdown, the right main landing gear collapsed and the right wingtip struck the ground. The airplane received damage to the right main gear, the right wing lift strut and spar, and the aft fuselage longerons.

The pilot, who holds an aircraft mechanic certificate, reported that the engine was overhauled and reinstalled on the airplane on March 28, 2003. At that time, he installed an overhauled carburetor. He indicated that during attempts to run the engine, after the accident, the engine would start and run at idle power. He noticed a binding of the carburetor's throttle cable or internal carburetor linkage. He replaced the throttle cable, but still felt a binding in the throttle mechanism. The pilot said he disconnected the throttle cable from the carburetor, and hand operated the throttle arm. It had binding only when the engine was running.

On April 15, 2003, the NTSB IIC conducted an examination of the carburetor at a maintenance facility in Anchorage, Alaska. The examination revealed that hand activation of the throttle arm produced fuel spray in the throat of the carburetor. The accelerator pump assembly operated normally without binding. The plastic float assembly was intact and the float shut-off valve operated normally. Fuel pressure at 5 psi was applied to the inlet fuel line. No leaks were observed and all check valves operated normally.