GREELEY, CO, USA
N950AW
Townsend KITFOX
The pilot was test flying his experimental airplane in the local area when the engine lost partial power then seized. The airplane landed hard, shearing off the right main landing gear and buckling the fuselage. Post accident disassembly of the engine revealed evidence of high heat distress and a lack of lubrication. The builder said he had adjusted the fuel-oil metering system on previous occasions because the engine was difficult to start and operated erratically. Operating temperatures were also high. The engine was further examined by an independent repair facility. They found that the engine did not have a harmonic balancer, which allowed the crankshaft bearings on the magneto end to move within the crankcase. Extreme internal heat build up and oil starvation damaged the crankshaft bearings, rotary valve, disk, and gear, and caused the connecting rod to eventually fail.
On May 10, 1997, at 1357 mountain daylight time, a Townsend Kitfox, N950AW, was substantially damaged when it collided with terrain during a forced landing near Greeley, Colorado. The commercial pilot, the only occupant aboard, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under Title 14 CFR Part 91. The flight originated at Greeley approximately 1300. According to the pilot, he was in level cruise flight approximately 800 to 1000 feet above ground level when the engine suddenly lost power and seized. The only field available for a forced landing was surrounded by houses and trees. The pilot was able to land in a small field, but the airplane landed hard and sheared off the right main landing gear. The right wing tip contacted the ground and the airplane spun around 180 degrees, buckling the rear fuselage. The Bombardier-Rotax 582 LC engine, s/n 3971294 (a liquid cooled, two cycle, two cylinder, in-line engine with an automatic fuel-oil metering system), was later disassembled at Beegles Aircraft Services in Greeley. The airplane builder was in attendance. Power to the propeller is routed through a gear reduction gearbox. Inside the reduction gearbox, rust and corrosion were found on the output shaft near the rear support bearing. The input gear could be turned by hand with difficulty. After removal of the cylinder head, corroded bolts were found in the cooling jacket. The top inside of the cylinder heads were pitted and burned. Both piston heads, particularly no. 2, were severely burned, and there were metal filings inside no. 2 cylinder. The top of no. 2 piston was pitted and filed down to the compression ring. The sides of no. 2 piston were scored. The exhaust gas temperature probe was discolored. The rotary valve was scarred, and there was a small piece of metal lodged between the valve and its guide. No. 2 main rod bearing and thrust washer were fused together with the rod exhibiting heat damage and discoloration. The rear main bearing was dry. The airplane builder said he adjusted the fuel-air mixture on previous occasions because the engine was difficult to start and operated erratically. Operating temperatures were also high. The engine and fuel-oil metering system was taken to Leading Edge Airfoil in Peyton, Colorado, by the owner's insurance company for examination. According to their report, the engine did not have a harmonic balancer. This allowed the crankshaft bearings on the magneto end to move within the crankcase. Extreme internal heat build up and oil starvation damaged the crankshaft bearings, rotary valve, disk, and gear, and caused the connecting rod to eventually fail.
The engine manufacturer's inadequate quality control by failing to install the harmonic balancer, causing the engine to fail catastrophically. A factor was the lack of suitable terrain on which to make a forced landing.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
