What happened
On February 24, 2000, a Velocity (homebuilt) aircraft, registration N111KE, was conducting a test flight originating from Lelystad. The aircraft had not flown for approximately three years prior to this flight. While en route near Halle, in the municipality of Zelhem, the engine experienced several instances of near-stalling. As the engine power fluctuated, the crew was unable to maintain the necessary altitude. Consequently, the pilot executed an emergency landing in a pasture. During the descent, the aircraft struck a ditch, which caused the landing gear to break off. The two occupants, a pilot and a technician, sustained light injuries, while the aircraft suffered heavy damage.
The investigation
The investigation focused on the mechanical cause of the engine's intermittent power loss. Technical examination of the engine's air intake system revealed that the induction hose consisted of two separate segments. These segments were joined simply by sliding one piece approximately 10 cm into the other. Following the accident, investigators found this connection had become detached. It was determined that the connection likely failed during the flight. Once the segments separated, the engine's suction pulled air from the engine compartment. The resulting vacuum caused the intake hose to be sucked against the interior of the engine compartment, obstructing airflow and causing the engine to nearly stop. As the engine's RPM dropped, the suction force decreased, allowing the hose to release and the engine to regain power, creating a repeating cycle of power loss.
Findings
- The primary cause of the engine instability was the failure of the air intake hose connection.
- The method of joining the two hose segments—sliding them over one another—was insufficient to withstand the engine's suction.
- The aircraft lacked an alternate air intake option, which prevented the crew from bypassing the obstructed primary intake to maintain engine operation.