What happened
On 9 August 2011, a Pegasus Quantum 15-912, registration G-BZOD, was conducting a refresher training flight near Ballyduggan, Co. Tipperary. The flight was intended to help the pilot revalidate a Weight-Shift Flex-wing Microlight rating. The crew consisted of an instructor and a pilot.
During a specific training exercise designed to simulate an engine failure following takeoff, the pilot closed the throttle and aggressively lowered the aircraft's nose. This maneuver caused the aircraft to adopt a steep nose-down attitude, leading to a rapid increase in airspeed. The aircraft subsequently entered a partial tumble maneuver. The forces involved were so violent that the instructor, seated in the rear, was unable to reach the controls to attempt a recovery.
As the aircraft inverted, the structural integrity of the trike front strut failed due to the opposing forces between the wing and the trike unit. This failure caused the propeller to strike the wing keel. The resulting damage to the starboard wing leading edge created asymmetric lift, causing the aircraft to enter an autorotation in yaw until it impacted the ground. Both crew members sustained serious injuries.
The investigation
Investigators examined the wreckage and the flight history to determine the sequence of events. The aircraft was found to be in an airworthy condition prior to the flight, and all regulatory requirements for the training facility and the aircraft's operation were met.
Analysis of the wreckage revealed that the trike front strut had failed in bending and tension. Evidence of the propeller striking the wing keel was present, and the starboard leading edge had failed. The investigation also reviewed the mechanics of the "tumble mode" in flex-wing aircraft, noting that while the maneuver is typically unrecoverable, the specific nature of this impact—specifically the asymmetric lift caused by the wing damage—led to a yawing motion that reduced the vertical descent rate enough to make the accident survivable.
Findings
- The accident was triggered by an aggressive nose-down pitch during a simulated engine failure exercise.
- The aircraft entered a partial tumble maneuver.
- The structural failure of the front strut led to the propeller striking the wing keel.
- Asymmetric lift from the damaged starboard wing caused a continuous autorotation in yaw until impact.
- The instructor was unable to intervene due to the extreme G-forces and violence of the maneuver.
- The pilot's lack of recent flying currency was identified as a contributing factor.