Accident Overview
On September 1, 2018, at about 0900 central daylight time, a Cessna P210N, registration N210PF, sustained substantial damage during a forced landing to a cornfield after a partial loss of engine power following takeoff from the Crete Municipal Airport (CEK) in Crete, Nebraska. The pilot and right seat passenger received serious injuries, and the two rear seat passengers received minor injuries. The airplane was owned and operated by the pilot under Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and the flight was not on a flight plan. The flight was en route to the Cozad Municipal Airport, Nebraska.
Pilot and Witness Statements
According to the pilot, the airplane had flown normally the night before. On the morning of the accident, the engine started but then stopped. The pilot used the low-pressure boost pump to restart the engine and turned it off after it started. An engine run-up was completed and was normal. The airplane departed runway 17 and required about 2,000 ft of runway to become airborne. At about 500 ft above ground level, the pilot heard the engine "miss" and noted it was not producing full power. He turned on the low-pressure boost pump and turned back toward the airport, but the engine continued losing power until it stopped. At about 200 ft agl, he decided to conduct a gear-up forced landing to a cornfield. During the final approach, he saw an irrigation pivot and pulled up to clear it, causing a loss of airspeed. The airplane impacted the ground hard and skidded through the cornfield on its belly.
A witness waiting for his airplane to be fueled observed the takeoff. He reported that the airplane sounded like it was at full throttle but "overweight sounding" and that it "finally got in the air at the end of the runway." He noted it was "running rich" and saw "dark exhaust" trailing during the takeoff. The airplane veered to the right and disappeared behind a tree line.
Examination Findings
A Federal Aviation Administration inspector examined the turbocharger wastegate and found it was not stuck or binding. Representatives from the airplane and engine manufacturer examined the wreckage. Flight controls exhibited continuity. The fuel system revealed no abnormalities. The propeller remained attached; two of three blades were bent aft and loose at the hub, with no leading edge damage. The spinner was undamaged.
The engine crankcase was intact with no signs of catastrophic internal failure. There was minor damage to the induction and exhaust. All six cylinders were attached and undamaged. Magnetos and ignition harness were undamaged. All spark plugs were installed; bottom spark plug electrodes displayed black color and significant soot deposits.
The engine was a Continental IO-550-P, serial number 1009768-R, converted from normally aspirated to turbo-normalized by Vitatoe Aviation under Supplemental Type Certificate SA02918CH on March 1, 2014. The last annual inspection was on May 16, 2018.
Data from the JPI 830 engine monitor showed that during takeoff, manifold pressure rose from 15.4 to 37.1 inches of mercury in about 18 seconds, and fuel flow rose from 5.5 to 48 gallons per hour. MP and fuel flow remained steady at about 37" Hg and 48 gph for about 42 seconds, then fluctuated and decreased. The last MP reading was 33.3" Hg, and the last fuel flow was 33 gph. Exhaust gas temperature for all cylinders began dropping 12 to 22 seconds before the MP and fuel flow fluctuated.
The engine was examined at the manufacturer's teardown facility. Damage was minimal and the engine could be run on a test cell. After installing an induction scoop on the turbocharger, the engine started and ran without hesitation. It achieved full power at 2,676 rpm, 32.54" Hg MP, and fuel flow of 201.68 lbs/hr (about 33.61 gph). Quick throttle advances did not cause stumbling.
The turbocharger controller, wastegate actuator, and pressure relief valve were tested by Hartzell Engine Technologies and operated normally. The manifold pressure transducer and fuel flow transmitter were tested by JP Instruments and operated normally.
Engine Conversion Specifications
The Vitatoe STC specified a maximum manifold pressure of 31.0" Hg (±0.2), full throttle fuel flow of 35-37 gph, and unmetered fuel pressure of 19-23 psi. The pilot operating handbook supplement for the conversion stated takeoff power at 2,700 rpm, 31.0" Hg MP, and 35 gph fuel flow. It noted that cold oil could cause momentary overboost to 33" Hg but not to be exceeded. The handbook advised checking takeoff power early and discontinuing if rough or sluggish.
A static demonstration conducted on December 5, 2019 by the STC owner on another similarly converted aircraft simulated a wastegate stuck closed. With the wastegate fully closed, manifold pressure reached 37" Hg, fuel flow increased, and the pressure relief valve opened above 34" Hg, causing a rich mixture, loss of power, and black smoke. Reducing throttle below 33" Hg allowed more normal operation.
The emergency section of the pilot operating handbook supplement did not contain information on turbocharger failures.
Safety Recommendation
In 1994, the National Transportation Safety Board issued Safety Recommendation A-94-81 to the Federal Aviation Administration, recommending that pilot operating handbooks for turbocharged aircraft be amended to include emergency procedures for turbocharger failure, including loss of engine power and fire hazards.