What happened
On 12 March 2000, a Europa aircraft, registration G-KWIP, was performing a private flight from Hollyme and near Ashbourne to Tatenhill, Staffordshire. The flight was intended to facilitate the inspection and calibration of a newly installed Light Aircraft Glass Cockpit (LAGC) system.
Shortly after takeoff from a grass runway at Hollymeadow Farm, the aircraft experienced an uncommanded reduction in engine power. Witnesses observed light grey or blue smoke emanating from the engine cowling as the aircraft climbed to an altitude of approximately 25 to 50 feet. While the aircraft initially maintained a nose-up attitude and began a gentle left turn, the left wing and nose subsequently dropped. The aircraft descended rapidly and struck the ground in a steep, nose-down attitude with a severe left wing drop. The impact resulted in two serious injuries and the total destruction of the aircraft.
The investigation
Investigators examined the wreckage and the engine's cooling and fuel systems. While the fuel system was found to be functional, the cooling system showed evidence of significant overpressure. The coolant expansion bottle was heavily deformed, with a ruptured seam weld, indicating it had inflated due to internal pressure.
Crucially, a section of the radiator hose had disconnected from a metal joiner tube. This connection was particularly vulnerable because the hose bore was significantly larger than the joiner tube diameter, reducing the effectiveness of the hose clamp. The investigation also noted that the aircraft's stall strips had been removed to improve takeoff performance, which may have contributed to the wing drop during the stall.
Findings
- The primary cause of the power loss was the discharge of coolant into the engine cowl and its subsequent ingestion into the engine.
- This coolant discharge was caused by a hose disconnection and a rupture in the expansion bottle, both resulting from overpressure within the cooling system.
- The overpressure was triggered by a boiling event, likely caused by the engine temperature rising during an extended period of ground running while stationary, followed by the increased demand of takeoff power.
- A significant contributory factor was the low concentration of glycol in the coolant (approximately 50%), which lowered the boiling point and reduced the safety margin between operating temperatures and the boiling threshold.
- The removal of stall strips from the wings may have contributed to the aircraft's inability to maintain control during the stall.