What happened
On 18 July 2006, a Denney Kitfox Mk 2, registration G-BWHV, departed Cardiff Airport for a local flight. The aircraft, carrying a pilot and one passenger, initially climbed to 2,000 feet as part of a planned flight pattern over the Rhondda Valley. While the pilot was communicating with Cardiff ATIS and initiating a turn back toward the airport, the engine began emitting loud bangs and screeching noises.
Following this, the engine suffered a substantial loss of power. The pilot noted that the engine could only maintain 4,000 rpm, significantly lower than the 5,000 to 5/500 rpm required to sustain altitude. After searching for a suitable landing site, the pilot attempted a forced landing at the Hawthawn playing fields near the Treforest Industrial Estate. The initial approach was too fast and too high; the aircraft bounced twice on the grass. In an attempt to clear nearby trees, the pilot applied full throttle, but the engine failed completely during the turn.
The aircraft descended toward industrial buildings, where the left landing gear struck a roof. This impact caused the aircraft to spin, ultimately coming to rest inverted on the A4054 road near a brick wall. The aircraft was destroyed, though both the pilot and passenger escaped with minor injuries.
The investigation
Investigators examined the Rotax VL 582 engine at an overhaul agency. They identified a major failure within the hydrodamper, a component designed to reduce vibration. The outer flange of the cylindrical body had separated, leading to a loss of the viscous fluid required for damping. While the exact cause of the initial separation was unconfirmed, the loss of fluid may have led to engine contamination.
A metallurgical analysis of the fracture surface revealed that the failure originated from fatigue points on the inner surface of the flange. The engine manufacturer noted that they had not previously encountered similar failures of this specific flange design.
Findings
- The primary cause of the engine failure was a fatigue-induced fracture of the hydrodamper flange.
- The separation of the flange resulted in the loss of viscous fluid from the damping unit.
- The pilot's inability to complete a successful forced landing was influenced by a lack of recent practice in glide approaches to a full landing.
- The approach to the playing fields was characterized by excessive speed and altitude, partly due to the pilot's concern regarding the engine's condition and the proximity of industrial structures.