Cessna P210N N210PF accident near Crete, Nebraska

Probable cause

The stuck turbocharger wastegate in the closed position for reasons that could not be determined based on the available information. Also causal was the pilot's failure to reduce the throttle during takeoff when the manifold pressure and fuel flow exceeded the takeoff limitations and the pilot's decision to turn on the fuel boost pump, which exacerbated the excessively rich fuel mixture and resulted in a total loss of engine power.

NTSB analysis

The pilot started the "turbo-normalized" 310-horsepower engine, but then it stopped. He stated that he used the low-pressure boost pump to restart the engine and then turned off the boost pump after it had started. He indicated that he completed an engine run-up before takeoff and that the engine was operating normally. The airplane traveled about halfway down the runway before it became airborne. When the airplane had a positive rate of climb, the pilot raised the landing gear and flaps. He stated that when the airplane was about 500 ft above ground level, he heard the engine "miss," and the engine did not seem to be producing total power. He turned on the low-pressure boost pump and turned back toward the airport, but the engine eventually lost total power. He performed a gear-up forced landing to a cornfield; the airplane impacted the ground hard and slid through the cornfield on its belly.

A witness who watched the airplane take off reported that the airplane sounded like it was full throttle but was "overweight sounding" during the takeoff. He reported that the airplane "finally got in the air at the end of the runway." He stated that it was "running rich" and that he could see "dark exhaust" trailing the airplane during the takeoff. The airplane veered to the right, and he lost sight of it behind a tree line.

An engine monitor installed on the airplane indicated that the manifold pressure reached 37 inches of mercury (inHg) and fuel flow reached 48 gallons of fuel per hour (gph) during takeoff. The pilot operating handbook for the supplemental type certificated engine stated that the full rated horsepower is achieved at 31 inHg of manifold pressure and that full throttle fuel flow during takeoff is 35-37 gph.

The engine was run on the engine manufacturer's test cell and operated within normal operating specifications. There were no mechanical malfunctions or failures with the turbocharger controller, wastegate actuator, pressure relief valve, manifold pressure transducer, and fuel flow transmitter that would have precluded normal operation.

However, a static demonstration run on the same airplane model/engine conversion, with the oil line from the wastegate to the wastegate controller disconnected to simulate a wastegate stuck in the closed position, showed similar indications of manifold pressure as on the accident flight; the manifold pressure far exceeded the design criteria. Sporadic black smoke was observed coming from the turbo exhaust. The engine was rough and lost power as the mixture became richer while the throttle was held fully forward. Reducing the throttle position to reduce manifold pressure allowed more normal operation to resume and the fuel flow to reduce to a less rich mixture. The engine resumed somewhat normal operating conditions except for the wastegate still being fully closed.

Given this information, it is likely that the turbocharger wastegate was "stuck" in the closed position during the takeoff roll for reasons that could not be determined because it was not stuck or binding during the postaccident examination. The stuck wastegate resulted in high manifold pressure and high fuel flow, which caused the fuel mixture to be excessively rich. Instead of pulling back on the throttle to reduce the manifold pressure, the pilot turned on the fuel boost pump, which exacerbated the problem; the fuel mixture became too rich, and the engine stopped producing power.

Text from the NTSB. Open the NTSB docket for CEN18LA363 for the full record.