Vertical Aerospace’s investigation into a flight test incident on 9 August has identified the root cause to be a fault with a propeller. This early generation propeller had already been redesigned prior to the incident, with the issue fully resolved ahead of the next phase of testing. Further recommendations by the investigation are being implemented by Vertical.
Vertical founder and CEO Stephen Fitzpatrick commented: “We are pleased with our flight test progress to date and the data, insights and invaluable learnings we have collected.
“While a fault of any sort is disappointing, it is not wholly unexpected at this stage of testing a novel aircraft. I am pleased that as a result of our expert team we have isolated the cause of the fault and been able to provide the AAIB with our report within 14 days of the incident.
“Our planned second upgraded prototype, which will include most of our top tier partners’ technology, will have us in the air early next year and we remain on track for our certification timelines”.
During one of these test flights, an unexpected fault occurred causing the aircraft to enter a stable descent, before being damaged on impact with the ground. Vertical completed a swift and thorough investigation and submitted a report to the Air Accidents Investigation Branch (AAIB).
One of the aircraft’s electrical propulsion units (EPU) had been intentionally disabled and one of the front propellers connected to a separate EPU was released, resulting in an excessive out of balance load, which caused the failure of one of the supporting pylon structures.
Vertical’s Core proprietary technology unique to the aircraft, including the high voltage and battery systems, was said to have ‘performed well during the incident’. Voltage, current and power all stayed within acceptable limits and cell temperatures were considered normal during and after the incident.
Vertical’s investigation identified the root cause to be a bonding issue within the propeller blade itself. This generation propeller design will not feature on any future VX4 prototype and prior to the incident, it had already been redesigned and manufactured with a different process. The aircraft involved in the incident will be used in further ground tests but will not be repaired to an airworthy standard.
Vertical has continued further uncrewed flight tests following the completion of the remote thrustborne flight test campaign. The purpose of these was to understand how the aircraft performed outside of its expected operating conditions before the aircraft’s planned retirement.
Vertical intends to provide a further full update on the incident once the AAIB’s investigation has concluded. The VX4 certification programme remains on track with no changes to timelines.
The assembly of a more advanced full-scale VX4 prototype is underway at GKN Aerospace, and expected to be ready to fly early next year. Its components will include technology from most of Vertical’s certification partners: Honeywell, GKN Aerospace, Hanwha, Solvay, Leonardo and Molicel.
An additional, identical full-scale aircraft has also now been approved and will require rigorous regulatory oversight, including a Permit to Fly from the UK Civil Aviation Authority, to progress to piloted flying.
Vertical Aerospace’s experimental prototype aircraft crashed during a test flight at Cotswold Airport, home to Vertical’s flight test centre. The company confirmed the aircraft was remotely piloted and there were no injuries during the accident.