What happened
On 11 December 2016, a Rotorsport UK Cavalon, registration G-EVAA, was performing a private flight from Wolverhampton Halfpenny Green Airport. During the takeoff roll from Runway 28, the pilot noted that the aircraft was slower to accelerate than usual and heard an unusual noise originating from the right side of the engine compartment.
Shortly after the aircraft became airborne, Air Traffic Control notified the pilot of debris present on the runway. Following the removal of this debris, the pilot performed a flypast of the control tower to check the aircraft for damage. While no immediate issues were observed during the flypast, the aircraft landed normally. Upon inspection on the ground, it was discovered that the right-hand section of the engine cowling had detached from the aircraft.
The investigation
Investigators examined the engine cowling and the fastening mechanism. The Rotorsport UK Cavalon utilizes a single-piece cowling secured by 16 fasteners, split into two groups of eight on either side. The procedure requires all fasteners to be correctly positioned before any are locked into place.
Findings revealed that during the pre-flight inspection, the pilot had successfully secured the left side of the cowling. However, the pilot was interrupted by a bystander during the process. While the pilot completed the remaining items on the pre-flight checklist, he failed to lock the fasteners on the right side of the cowling.