Manufacturing defect caused blade release in Vertical prototype crash, says AAIB

The Vertical Aerospace prototype which was written off in August, 2023 crashed due to an adhesive bond failure in a propeller blade.

The Aircraft Accidents Investigation Branch (AAIB) report supports Vertical’s findings which it published in the month following the incident. The OEM’s investigation identified 36 product and process improvements. 

Vertical, at the time, was also in the process of introducing a revised propeller blade design with a new supplier that eliminated the bonding failure mode. All remaining blades have been withdrawn and will only be used for ground testing. 

The aircraft was being tested by a remote pilot when a propeller blade detached from one of the electric propulsion units forward motor due to a failure of the adhesive bond between the propeller blade sheath and spar. 

Loads generated by the blade release caused structural failure of the right inboard pylon, resulting in damage to the eVTOL’s wiring harnesses. This caused a loss of thrust from the remaining motors. The aircraft’s flight control system was initially able to maintain a level attitude, but the high rate of descent caused by the loss of vertical thrust resulted in substantial damage when it struck the ground.

Vertical spent a significant amount of its investigation on the aircraft performance after the rotor propeller blade release, according to crash investigators. The aircraft was designed to be able to continue to operate with one electronic power unit inoperative, so the investigation focused on the root cause of the propeller blade failure as well as the aircraft response following the failure of the blade. 

See the full AAIB report here.