NTSB Identification: SEA02LA059.
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Accident occurred Monday, March 25, 2002 in Shoup, ID
Probable Cause Approval Date: 09/09/2002
Aircraft: Potts KitFox, registration: N139SP
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot attempted a takeoff in an experimental aircraft who's engine/propeller combination had not produced the expected rpm since the pilot/builder changed the engine but did not change the propeller. Prior to the attempted takeoff, the pilot experienced a 250 rpm drop on each magneto during the engine run-up check. During the takeoff roll, the pilot realized that the aircraft was not performing as desired, and momentarily thought about aborting, but instead continued. After liftoff, the pilot was unable to get the aircraft to climb, and as he was making a turn over a river situated off the departure end of the runway, the aircraft stall/mushed, and one wing drug in the water. Immediately after the wing contacted the water, the aircraft cartwheeled along the river's surface, coming to rest upright in about 30 inches of water.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot’s failure to maintain a speed above stall speed, and the resulting inadvertent stall/mush. Factors include the pilot's failure to abort the takeoff when he realized the aircraft's performance was not as expected, his decision to attempt a takeoff after experiencing an unacceptable rpm drop on each magneto during the engine run-up check, and the failure of the magnetos to maintain an acceptable engine rpm when operated individually.

Full narrative available

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