What happened
On 21 August 2004, a Pegasus Quik microlight, registration G-STYX, departed Rochester Airfield for a flight intended as a training lesson. Approximately 35 minutes into the flight, while cruising at 500 feet along the north coast of the Isle of Sheppey, the aircraft experienced a sudden and violent pitch-up. The aircraft entered a near-vertical climb and began a series of intense tumbling manoeuvres. During this sequence, the trike unit, carrying the pilot and one passenger, detached from the wing assembly and fell vertically to the ground. The impact resulted in two fatalities.
The investigation
The investigation focused on the structural integrity of the aircraft's upright fittings. It was established that the aircraft's upper fittings had previously undergone modifications to comply with Service Bulletin 116. However, the investigation found that the additional rivets required by this bulletin were incorrectly installed and did not match the manufacturer's specifications. Furthermore, the inspector who performed the work did not refer to the specific Service Bulletin, and no independent duplicate inspection was performed to verify the work. The investigation also examined the maintenance records, noting that a 100-hour inspection and wing overhaul had not been documented, which meant the incorrect rivet installation went undetected.
Findings
- The primary cause of the accident was the failure of the right upright upper fitting, which triggered a sudden change in wing reflex and applied full nose-up trim.
- The failure of this fitting initiated a tumbling sequence from which the aircraft could not recover.
- The modification to the upper fittings was performed incorrectly, with rivets placed in the wrong locations.
- There was a lack of independent oversight, as no duplicate inspection followed the structural modification.
- The inspector involved did not meet the required engineering qualifications and experience.
- Maintenance records were incomplete, specifically regarding the 100-hour inspection and wing overhaul.