The Future of Advanced Air Mobility

Vertical Provides More Details on eVTOL Accident with Flight Testing To Resume in Early 2024

With the UK’s Air Accident Investigation Branch still probing the August 9 crash of Vertical Aerospace’s first full-scale VX4 eVTOL aircraft prototype, the company has discussed details about the incident in recent weeks. During the recent Royal Aeronautical Society’s Future of Flight Summit in London, Vertical’s leadership team said it is confident of having a second prototype ready to resume flight testing in the first quarter of 2024, with a third example of the four-passenger vehicle to follow by the middle of next year as the company works toward its type certification target in 2026.

For the remotely piloted flight at Cotswold Airport in southwest England on August 9, the left outboard electric motor was set to zero speed when the aircraft took off in ground effect and climbed out. It had just reached forward flight when the propeller on the opposing wing failed.

According to Vertical, the ensuing imbalance caused a shock load, breaking the pylon in front of the wing, and triggering the high-voltage protection system to successfully isolate the failure. However, despite spinning up the non-operational motor, electrical interference from an unexpected short-circuit resulted in several other motors now de-powering. With these running at less than 57 percent power and the aircraft unable to maintain altitude, a level attitude was held until an inevitable "heavy landing" occurred. Although asymmetric forces asserted on the chassis resulted in a broken wing at the point of the inner pylon, the chassis remained intact.

“The prop that failed is an early standard," Vertical’s CTO, Michael Cervenka, told AIN. He explained that the initial central composite spar design has since been upgraded to an optimized co-bonded design, manufactured by a new, as-yet-undisclosed supplier.

The crash occurred as the first phase of VX4 flight testing drew to a close, with the program having been extended to encompass more than initially planned. “The point of these vehicles is to learn,” Cervenka said.

More Purpose-built Components in Next VX4 Prototypes

The second and third VX4 prototypes will include around 60 percent of components provided by leading industry partners including Leonardo. This contrasts with the first iteration of the eVTOL built three years ago using mainly commercial, off-the-shelf hardware. According to Cervenka, this means the new prototypes will be “very much a stepping stone towards certification.”

The aircraft will be assembled at its partner GKN’s Aerospace Global Technology Centre near Bristol, where Vertical is based. It also intends to scale up production of its proprietary batteries.

The start-up would like to establish a site for mass production of the eVTOL model somewhere close by, indicating that this decision may hinge on getting financial support from the UK government. However, in recent weeks, the country's Conservative government has reversed some commitments made to achieving net zero carbon targets, raising concern about whether incentives for green aviation will be available in the future.