Newman Lake, WA, USA
N2684A
PIPER PA18
The private pilot performed two low passes to the snow-covered airstrip, during which the airplane's flaps were extended and carburetor heat was on. After completing the second low pass, the pilot retracted the wing flaps, turned off the carburetor heat, and applied engine power to go around. The engine subsequently experienced roughness and a partial loss of power. The pilot turned the carburetor heat back on, but engine power was not restored. Unable to maintain altitude, the pilot elected to land on the airstrip he had been overflying. During the landing, the airplane nosed over due to the depth of the accumulated snow, which resulted in substantial damage. A postaccident examination of the carburetor revealed full control continuity to the carburetor heat/air box, the butterfly valve reached full travel, and full control continuity from the cockpit throttle and mixture controls to the carburetor was confirmed. An engine run revealed no anomalies. Although the airplane was operating in conditions that were conducive to a serious risk of carburetor ice accumulation at a descent power setting, the engine was operating at a takeoff/go-around power setting at the time of the loss of power, and it is unlikely that carburetor ice would have accumulated during this time. Therefore, the reason for the partial loss of engine power could not be determined.
On January 1, 2016, about 1530 Pacific standard time, a Piper PA18-150, N2684A, was substantially damaged during a precautionary landing to a private dirt airstrip following a partial loss of engine power near Newman Lake, Washington. The private pilot, the sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the local flight, which was being operated in accordance with 14 Code of Federal Regulation Part 91, and a flight plan was not filed. The local flight departed Felts Field (SFF), Spokane, Washington, about 1500, with the destination being a private airstrip about 13 nautical miles northeast of SFF. In a statement submitted to the National Transportation Safety Board investigator-in-charge, the pilot reported that after departing SFF, his intention was to make several slow, low passes over the private airstrip, which was located about 13 nautical miles northeast of SFF. He initially climbed to 6,000 ft mean sea level, cycled the carburetor heat while on descent to the airstrip, then made an initial low pass with full flaps and carburetor heat applied, followed by a go-around with carburetor heat off. The pilot opined that he subsequently made a second low pass in the same configuration, but during the go-around experienced engine roughness, a loss of power, the engine backfiring, and a loss of engine rpm from 2,400 to 2,200. He then applied carburetor heat, but there was no increase in rpm. Unable to maintain altitude, the pilot elected to make a precautionary landing on the private airstrip, which was covered with what the pilot described as covered with snow. Upon touchdown the airplane nosed over, which resulted in substantial damage to both wing struts and the rudder. A postaccident examination of the airplane and engine overseen by a Federal Aviation Administration aviation safety inspector, which included an engine run, revealed no preimpact malfunctions or failures that would have precluded normal operation. During the examination the inspector noted that the carburetor heat/air box had full continuity, the butterfly valve reached full travel, and full continuity of control was confirmed from the throttle and mixture controls in the cockpit to the carburetor. At 1450, the weather reporting facility located at SFF reported wind calm, visibility 10 miles, sky clear, temerature -7 C, dew point -9 C, and altimeter reading of 30.52 inches of mercury. The carburetor icing probability chart from the FAA Special Airworthiness Information Bulletin (SAIB), CE-09-35 Carburetor Icing Prevention, indicated that the airplane was operating in an area associated with a serious risk of carburetor ice accumulation at descent power.
A partial loss of engine power for reasons that could not be determined because postaccident examination of the engine did not reveal any anomalies that would have precluded normal operation.
Source: NTSB Aviation Accident Database
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