What happened
On 28 April 1999, a Rans S10, registration G-BTJX, was performing a private flight from Welshpool toward its home base near Newark. While cruising at approximately 3,300 feet over Annesley village, the Rotax 582 engine suddenly lost power. Prior to the failure, all engine instruments had indicated normal operation, and the pilot confirmed that fuel was available in both tanks.
In response to the loss of power, the pilot executed a forced landing into a field at Mosley Farm. The terrain was notably soft, which caused the aircraft to decelerate abruptly. This rapid deceleration resulted in the distortion of the right-hand landing gear and caused the right wing tip to strike the ground. The pilot escaped the incident without injury.
The investigation
Investigators examined the engine and determined that one of the two pistons had seized. This failure was attributed to a lack of lubrication, as only about 0.75 pints of two-stroke oil remained in the engine compartment's reservoir. The pilot had been under the impression that the oil supply would last significantly longer than the fuel supply, given the standard consumption ratios.
Further investigation revealed that the pilot was unaware of Rans Operational Alert No 105. This mandatory alert warned that Rotax 582 engines could experience oil starvation during sustained climbs of 16 degrees or more if the oil level was at or below half capacity. It also recommended filling the tank to capacity before takeoff.
Additionally, the investigation looked into the possibility that the aircraft's flight attitude had caused the oil outlet pipe to become uncovered as the level dropped, as the aircraft lacked a slip indicator to monitor lateral balance. The investigation also noted that the pilot had no in-flight method to monitor the oil level, as the cockpit was only equipped with a fuel gauge.
Findings
- The engine failure was caused by piston seizure due to oil starvation.
- The pilot was unaware of a mandatory operational alert regarding oil levels during steep climbs.
- There was no cockpit instrumentation available to monitor the remaining oil quantity during flight.
- The pilot had not been provided with the relevant Rans Operational Alert by the PFA following the aircraft's purchase.