N582YBInterplane SKYBOY EX · 2001

On July 27, 2012, at 1830 Pacific daylight time, an Interplane Skyboy EX, N582YB, experienced a partial loss of engine power and collided with a fence during the off-field landing near Sandy River Airport (03S), Sandy, Oregon. The private pilot operated the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot and single passenger were not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed for the local flight, and no flight plan had been filed.

The pilot reported that he had been flying the airplane for about 1 hour before the accident. He landed, shut down the engine, changed passengers, and restarted the engine. The total time from shut down to start up was about 5 minutes. He said that the airplane's engine run-up and takeoff were normal. After takeoff, about 300 to 400 feet above ground level (agl), the engine began to lose power. The pilot made a hard right turn and landed in an open field. The airplane impacted a fence post with its right wing during the landing roll out.

The pilot, age 41, held a private pilot certificate for airplane single-engine land issued January 17, 2012, and a second-class airman medical certificate issued June 22, 2011, with the limitation that the holder shall wear corrective lenses. The pilot reported 338.1 total flight hours, and 1.2 hours in the accident airplane make and model.

The two-seat, high-wing, fixed gear, experimental category airplane, serial number 06192001735, was manufactured in 2001. It was powered by a Rotax 582, 64-horsepower engine, and equipped with a Powerfin 3-bladed fixed pitch propeller. The pilot reported that the airplane had 159.6 hours total time, and the most recent annual inspection was completed on July 9, 2012. The engine was not equipped with a carburetor heat system. The engine manufacturer stated in the Rotax 582 installation manual that, "If the aircraft is to be operated in climatic conditions where carburetor icing is likely to occur, a heating system must be fitted."

Meteorological information collected by a Remote Automated Weather Station (RAWS) located on Firewood Road, 1.7 miles south of Sandy River Airport recorded ambient temperature, dew point, and relative humidity for that location. The data recorded on July 27, at 1848, was the ambient temperature of 63 degrees F; the dew point was 55 degrees F; and the relative humidity was 76 percent. Data for August 9, at 1248, was the ambient temperature of 62 degrees F; the dew point of 56 degrees F; and relative humidity of 81 percent. The ambient conditions at the time the engine was being examined and tested by a Federal Aviation Administration (FAA) inspector on August 9 matched closely with the ambient conditions at the time of the accident on July 27.

Meteorological conditions in Vernon, British Columbia, Canada, on November 12, 2012, when the engine was test run at the manufacturer's technical representative's facility, indicated an ambient temperature of 32 degrees F; a dew point of 31 degrees F; and a relative humidity of 91 percent.

Photographs of the airplane after the accident showed damage to the leading edge of the right wing outboard of the lift strut attach point. The left landing gear main mount and nose wheel were collapsed. The windscreen exhibited a crack across the entire face of the windscreen. No damage to the engine or propeller was evident.

An FAA inspector, assisted by an airframe and power plant (A&P) mechanic, examined the airplane and engine on August 9, 2012. The engine remained attached to the airframe and was test run multiple times. The FAA inspector reported that the fuel, oil injection, and engine control system was checked and appeared to operate properly. The pistons were viewed through the exhaust ports and appeared to have normal wear signatures with no sign of seizure. The engine was started and accelerated to 5,900 revolutions per minute (rpm). After approximately 1 1/2 minutes of operation the engine rpm began to degrade until a total reduction of approximately 1,000 rpms occurred, then stabilized around 5,000 rpms. After the carburetor fuel jets were replaced with ones of a smaller orifice size, as well as the replacement of spark plugs, the engine run was repeated; the results were consistent with the first engine run. Carburetor fuel pressure was observed to maintain 3 pounds per square inch after engine shut down. Under the direction of the National Transportation Safety Board (NTSB) Investigator-in-Charge (IIC), the engine was removed from the airframe, crated, and shipped to the Rotech facility, located in Vernon, British Columbia, Canada, for further examination.

On November 13, 2012, the engine was examined at the Rotech facility under the supervision of the NTSB IIC. The engine was removed from the sealed crate and placed on an engine test stand. A static examination of the engine failed to reveal anomalies. Oil was present in the gear box, both carburetors were closely synchronized, the fuel filter was checked for leaks and held a 15 kilopascals (Kpa) vacuum, all spark plug gaps were 0.032 inches, and the piston heads exhibited normal combustion signatures. The engine was run on the test stand, first for 8 minutes at 3,000 rpm, then to maximum (max) power at 5,500 rpm. The test propeller was re-pitched to 12 degrees in order to produce max power rpm. The engine was run at 6,250 rpm for 2 minutes, 6,000 rpm for 5 minutes, then 4,900 rpm for 5 minutes. The engine was shut down, inspected, and restarted. It was run at idle for 1 minute, then at 6,200 rpm for 2 minutes, then 4,800 rpm for 10 minutes. An engine acceleration test followed by accelerating the engine from 3,150 rpm to 5,800 rpm; this was performed two times. It was then run at 3,150 rpm for 2 minutes, and then shut down and sat for 1 hour. The fuel transducer was removed and the engine restarted; it produced a new maximum rpm of 6,480. In summary, the engine was run for approximately 28 minutes without losing power or rpm, shut down for 1 hour, then restarted and found to maintain normal power rpm.

Carburetor Icing

The carburetor icing chart indicated the possibility of serious carburetor icing at the reported atmospheric conditions. The Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A) states that first indication of carburetor ice in an airplane with a fixed pitch propeller is a decrease in engine rpm. Additionally, it states that when conditions are conductive to carburetor icing that carburetor heat should be applied immediately and should be left ON until the pilot is certain all the ice has been removed. If ice is present applying partial heat or leaving heat on for an insufficient time might aggravate the situation.