What happened
On 13 September 2015, a Vierwerk Aerollite 120, registration G-OLAS, was involved in an accident during a private flight near Darley Moor, Derbyshire. The pilot had recently acquired the aircraft and was operating it from Darley Moor Airfield.
Following a period of inactivity on the ground, the pilot attempted takeoff from Runway 19. The aircraft lifted off at approximately 30 kt with 12 degrees of flaps applied. The pilot maintained flight within ground effect until the airspeed indicator reached 42 kt. Upon reaching a height of 80 ft, the pilot retracted the flaps. Immediately following this action, the aircraft's climb ceased, and the right wing dipped. The aircraft subsequently entered a nose-down spin to the right, impacting the ground just off the runway. The aircraft sustained damage beyond economic repair, while the pilot escaped with one minor injury.
The investigation
The investigation examined the pilot's flight experience, the aircraft's performance characteristics, and the circumstances surrounding the takeoff. The pilot had only three hours of experience on this specific type and had purchased the aircraft roughly one week prior.
Investigators looked into the pilot's decision-making regarding flap retraction and airspeed. The pilot noted that while the airspeed indicator showed 40 kt, his GPS logs indicated a groundspeed of no more than 32 kt. When accounting for the observed wind, it was possible the aircraft was operating very close to its clean stalling speed of 35 kt at the moment the flaps were retracted. Furthermore, the investigation considered the pilot's lack of formal conversion training and his unfamiliarity with the specific handling characteristics and high-drag nature of this low-powered microlight.