In a letter to investors for public release, Vertical Aerospace has shared an update on its flight test program following an incident last month involving one of its VX4 flight test prototype aircraft. According to the release, Vertical does not expect any significant impact to its certification timeline.
The release stated the VX4 flight test prototype has concluded its remote thrustborne flight test campaign as of July 2023, as the first full-scale VX4 prototype reached its target speed of 40kts (70 kmph), demonstrating exceptional overall stability and control.
Performance targets were generally exceeded by 10-30% during hover and low speed flights. The prototype performed especially well in sustained hover, typically the most challenging regime for a VTOL aircraft, where it maintained level flight for longer than anticipated. The aim of these thrustborne flight tests was to verify acceptable stability, battery efficiency and control characteristics, aerodynamics, structural loads, performance and vibration throughout this speed range – all of which were achieved.
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). Vertical’s investigation 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.

Stephen Fitzpatrick, Vertical Founder and CEO, 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”
Why it matters: Despite the setback of a flight test incident, Vertical remains on track for its certification timeline. The company stated it is also developing a second, more advanced flight test prototype of the VX4 model which will be ready to fly in early 2024. Expect more updates as Vertical progresses toward entry to service of its eVTOL aircraft.
Source: Vertical Press Release
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