What happened
On 21 April 2015, a Pulsar XP, registration G-PLSA, was conducting a private flight at Fife Airport. The pilot had previously noted engine irregularities and intended to test the aircraft's performance at various engine speeds. During the flight, the pilot encountered difficulty reducing engine RPM below 3,500 during the downwind leg, making it difficult to decelerate the aircraft.
Following an initial approach where the aircraft remained too fast, the pilot initiated a go-around. A second approach was similarly high-speed, necessitating another go-around. On the third attempt, the pilot aimed to land further down the runway to allow for a longer stopping distance. During the flare, as the pilot attempted to reduce power, the engine unexpectedly surged to full throttle. This caused a violent leftward yaw. In an effort to regain control and reduce power, the pilot's nose dropped, leading to an impact on the grass to the left of the runway. The pilot sustained minor injuries and was able to exit the aircraft independently.
The investigation
Investigators examined the aircraft's engine and throttle mechanism following the accident. An inspection by an LAA Inspector revealed that the rear nut, which secures the throttle lever to the angle bracket on the instrument panel, had become detached. This allowed the lever to move freely on the throttle shaft. Because the shaft was stepped with a larger diameter on the engine side, the loose nut prevented the throttle from closing completely, effectively limiting the pilot's ability to reduce engine speed.
Findings
- The primary cause of the accident was the unintended application of full power caused by a mechanical failure in the throttle assembly.
- A loose nut on the throttle lever allowed the throttle to remain partially open, preventing the engine from dropping below 3,500 rpm.
- The pilot did not consider shutting down the engine prior to the landing attempt.