Accident Overview
On July 19, 2016, at about 1000 Alaska daylight time, an Aeropro CZ A220, registration N151J, sustained substantial damage during a takeoff from an unimproved airstrip approximately 5 miles south of McCarthy, Alaska. The airplane was tail-wheel equipped and operated by the private pilot under 14 CFR Part 91 as a personal cross-country flight to Wasilla Airport. Visual meteorological conditions prevailed, and a VFR flight plan was filed.
Pilot Statement
The pilot reported that shortly after raising the tail during the takeoff roll, a partial power loss occurred. While attempting to maintain directional control, the power loss ceased and full power returned. The pilot could not apply sufficient rudder pressure quickly enough to counteract the increased left turning tendency, resulting in the airplane impacting terrain. Damage included substantial damage to the wings, tail, and fuselage. The pilot was not injured.
Video Evidence
A video of the attempted takeoff shows that during the takeoff sequence, as the tail lifts, sound changes consistent with engine surging can be heard. This occurs three times before directional control is lost.
Postaccident Examination
The aircraft was equipped with a Rotax 912 ULS engine with dual carburetors. Examination revealed that the throttle valve lever on the 1/3 carburetor (associated with cylinders 1 and 3) was bent inward and contacted the carburetor chamber top. When the throttle was actuated inside the cockpit, the lever would eventually push past the contact point but traveled just off the idle stop before contacting the top. The 2/4 carburetor throttle valve lever was in good condition and operated normally.
Engine Testing
A postaccident engine test run on the accident aircraft (with the damaged propeller) showed no anomalies in ignition, fuel, oil, and coolant systems, but the effect of the bent lever was inconclusive. A second test on February 2 in Vernon, B.C., Canada, under NTSB direction used a different Rotax 912 ULS engine with a modified lever to replicate the condition. When the modified lever stuck against the chamber top, the engine ran rough and would not accelerate to maximum RPM. Manually pushing the lever past the contact point resulted in a burst of power followed by smooth operation at maximum RPM, consistent with video evidence.
Weather
The closest weather reporting facility was Valdez Airport, about 98 miles southwest. At 0956, a METAR reported wind from 080° at 16 knots gusting 21 knots, clear sky, visibility 10 miles, temperature 77°F, dewpoint 48°F, barometric pressure 29.88 inHg.