What happened
A training flight departed St. John's, Newfoundland, en route to the Bell Island training area. During the flight, a chief flight instructor was conducting a type check-out for a right-seat instructor in a Zenair CH2000. While performing a coordinated sideslip maneuver, the aircraft experienced an abrupt nose-down pitch. During this maneuver, the crew noted a noticeable smell of fuel in the cockpit. Following a second, more aggressive sideslip involving full rudder and aileron input, the aircraft experienced significant negative gravitational forces, and the fuel odor intensified.
Upon recovering from the descent, the pilot attempted to advance the throttle, but the engine failed to respond. Despite adequate fuel indications and normal fuel pressure, the engine would not restart. The pilot initiated a forced landing at the Bell Island airport. Due to darkness, the instructor, who had taken control for the landing, lost sight of the unlit runway, causing the aircraft to strike a grassy knoll approximately 700 feet short of the runway threshold. The impact destroyed the aircraft, and both pilots sustained minor injuries.
The investigation
The investigation focused on the cause of the engine power loss and the mechanical condition of the aircraft. Investigators examined the fuel system and the carburettor, discovering that a broken boss within the carburettor float chamber had been present for some time. This damage was traced back to the installation of the inlet air box, where an excessively long bolt likely caused the internal breakage. This defect caused the float and needle valve to malfunction, flooding the engine with fuel during the abrupt maneuvers of the sideslip.
Additionally, the investigation looked into the aircraft's safety equipment and documentation. It was determined that the emergency locator transmitter (ELT) failed to activate because it had not been armed. The investigation also identified issues with the aircraft's door latch wear, exhaust leaks into the cabin heat box, and ambiguities in the owner's manual regarding alternate static source usage and airspeed corrections.
Findings
- The engine power loss was likely caused by pre-impact carburettor damage that interfered with fuel scheduling during the sideslip.
- The internal carburettor damage was likely caused by the application of an incorrect bolt length during the inlet air box installation at the Zenair facility.
- The ELT was not armed, preventing activation during the impact.
- The aircraft's owner's manual contained confusing instructions regarding the use of the alternate static source and airspeed adjustments.
- The side-slip maneuver itself can result in a steep nose-down pitch even at speeds above normal approach speeds.