What happened
During a local flight, a Cessna aircraft departed from Peterborough Airport with a pilot and one passenger. Shortly after becoming airborne, the aircraft's climb performance faltered. The aircraft initially gained altitude but then experienced a decrease in pitch, descending to nearly ten feet above the runway. While the aircraft managed to climb to approximately 200 feet, it entered a left turn that quickly transitioned into an abrupt increase in bank angle and a sharp nose-down pitch. The aircraft struck the ground in a steep, left-wing-low attitude, resulting in one fatality and one serious injury.
The investigation
The investigation focused on the engine's performance and recent maintenance history. On 10 June 1996, the same aircraft had been used for a training flight where the engine was reported to be running roughly. Maintenance personnel had replaced the carburettor and the engine starter drive unit on 21 June 1996. Following the replacement of the starter drive unit, the engine oil and oil screen were not inspected for contamination.
Physical examination of the engine revealed a significant amount of ferrous material within the engine oil and the oil screen. Laboratory analysis confirmed this material was consistent with bearing metal. It was determined that the needle bearings in the previously removed starter drive gear assembly had failed, causing wear that released metal particles into the lubrication system. These particles became lodged in four of the engine's eight hydraulic lifters, restricting their movement. This malfunction prevented the engine from producing its rated power, reducing output by as much as 30 per cent.
Findings
- The failure of needle bearings in the starter drive unit caused metal debris to contaminate the engine oil.
- This contamination caused four hydraulic lifters to malfunction, reducing the engine's power output.
- The aircraft was operating at an estimated weight of 1,619 pounds, exceeding its maximum takeoff weight of 1,600 pounds.
- The pilot maintained a nose-high attitude after takeoff, which prevented the aircraft from reaching a safe climb airspeed.
- The aircraft entered a stall and an incipient spin at an altitude too low for recovery.
- The pilot's attempt to correct the left bank with right aileron input likely increased the aircraft's tendency to spin.