NTSB Factual Report

On November 19, 2015, about 1400 Pacific standard time, a Cessna P210N, N9824G, experienced a partial loss of engine power and was substantially damaged during a forced landing near the Harris Ranch Airport (3O8), Coalinga, California. The airplane was registered to and operated by the private pilot as a 14 Code of Federal Regulations (CFR) Part 91 personal flight. The pilot and two passengers were not injured. Visual meteorological conditions prevailed at the time and a flight plan was not filed. The proposed cross-country flight, which was originating at the time of the accident, was destined for Shafter-Minter Field (MIT), Shafter, California.

In a written report submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that during the takeoff roll he advanced the power to 70 psi torque, and rotated at 70 knots (kts); he then lowered the nose to maintain his target climb speed. The pilot stated that when the airplane reached about 200 to 300 feet above ground level the engine experienced a partial loss of power; he did not observe any abnormal fuel system indications. The pilot then advanced the throttle and condition levers, however, there was not sufficient power to climb and maintain altitude. During the forced landing, the airplane impacted multiple power lines, before making a gear up, soft field landing to an open dirt field. The airplane came to rest in an upright position, with substantial damage to its undercarriage and left wing.

On January 7, 2016, under the supervision of the NTSB IIC, accompanied by two Federal Aviation Administration (FAA) airworthiness aviation safety inspectors, a Rolls-Royce field technician performed an examination on the subject engine, a Rolls-Royce model 250-B17F/2. The technician's examination revealed that the compressor intake exhibited crushing damage to the compressor front support, however, the compressor could still be rotated by hand. Rotational continuity from the compressor to the gas-generator turbine and starter/generator was confirmed. There was no evidence of rotational damage to the compressor blades. Soil was present around the front of the engine and compressor intake, but there was no evidence of foreign object ingestion by the compressor. The compressor bleed valve was operated manually. The poppet valve cycled easily by hand and exhibited radial movement. Additionally, N2 drive continuity was established from the power turbine to the sun gearshaft. Rotation by hand was smooth and quiet. Visual examination of the 4th stage power turbine revealed no evidence of damage to the turbine blades.

A visual examination of the gas-generator turbine revealed no evidence of abnormal combustion, turbine failure or thermal degradation of the turbine. Rotational continuity was verified from the compressor to the turbine.

Compressed air was applied to the engine control pneumatic system via the Pc air fitting. A soapy water solution was liberally applied to the pneumatic system's tubes and fittings in order to check for air leaks. A minor air leak was noted at the Pc air filter, and a larger air leak was found on the propeller overspeed governor Py air inlet B-nut. This leak produced an approximate 1" bubble every ten seconds. As observed, according to the technician, this leak was not significant enough to affect engine performance. A similar leak was also discovered on the impact-damaged Py line connecting the propeller overspeed governor to the propeller/power turbine governor.

Fuel was present in the fuel spray nozzle supply line, fuel pump filter bowl, and the fuel supply line fitting at the firewall. The fuel spray nozzle was disassembled and examined. The internal filter screen was free of debris.

Compressed air was applied to the aircraft's fuel system, which resulted in a flow of clean fuel from the fuel supply line to the engine-driven fuel pump.

The airframe oil tank contained ample clean oil. The #1 magnetic chip detector was removed and examined, and found free of any ferrous debris.

The technician concluded that based on his examination, there was no evidence of a mechanical engine failure. (Refer to the Rolls-Royce Field Observation report, which is appended to the docket for this investigation.)

On February 18, 2016, under the supervision of an FAA airworthiness aviation safety inspector, the airplane's propeller governor (serial number 16251527), was examined and functionally bench tested by a Woodward Inc. technician at the Woodward facility in Rockford, Illinois. The technician reported that the unit was test run in accordance with a production Acceptance Test Plan. The results revealed that there were no anomalies during the testing of the unit that would have caused the reported loss of engine power.

On February 18, 2016, under the supervision of an FAA airworthiness aviation safety inspector, the airplane's overspeed governor (serial number 16222036), was examined and functionally bench tested by a Woodward Inc. technician at the Woodward facility in Rockford, Illinois. The technician reported that the unit was installed on a test stand and run to production acceptance test limits. Tests revealed that the pressure for the set point of the overspeed limiter was 3.0 psid, approximately 0.2 psid below the minimum range of the manufacturer's test specifications. The test point was run at a nominal differential pressure of 4.0 psid, and the speed was 4,769 rpm, which indicated that overspeed occurred at 113.60% instead of 113.58%. All other data points were within acceptance test point limits. Woodward stated that none of the shifts in data support a conclusion that the overspeed governor could cause a loss of power. (For both of the above tests, refer to the Woodward Inc. Investigation Report, which is appended to the docket for this investigation.)

The investigation failed to reveal what precipitated the reported loss of engine power.

NTSB Probable Cause

A partial loss of engine power during takeoff for reasons that could not be determined, because postaccident examination revealed no mechanical malfunctions or failures that would have precluded normal operation.