British Vertical Aerospace's VX4 prototype achieves first untethered piloted vertical take-off.

On November 12, 2024, Vertical Aerospace achieved a significant milestone in its flight test program for the VX4, an electric vertical take-off and landing (eVTOL) aircraft. The British company confirmed that its VX4 prototype successfully conducted its first untethered, piloted vertical take-off and landing, marking the start of Phase 2 testing. The focus of Phase 2 is on thrustborne flights, which involve vertical take-offs, landings, and low-speed maneuvering using propeller-generated lift.
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The Vertical Aerospace VX4 could offer a zero-emission, low-noise military platform, with potential applications such as emergency medical services and other defense-related operations. (Picture source: Vertical Aerospace)

The VX4 prototype, powered by a proprietary battery system capable of delivering 1.4 MW of peak power, is undergoing assessments of its stability, battery performance, control systems, aerodynamics, and structural loads. These tests aim to expand the flight envelope established during Phase 1, where the aircraft operated under tethered conditions. Data collection during the program has been extensive, with nearly 90 test points completed and more than 35,000 flight and system parameters recorded.

Phase 1 included 20 piloted sorties involving tethered flight, high-speed taxi tests, and powertrain evaluations. Tests simulated potential failures, including an intentional shutdown of one Electric Propulsion Unit to verify the aircraft’s response and redundancy capabilities. Additional ground tests focused on propeller balancing, structural integrity, and vibration characteristics, using accelerometers to measure aircraft movements under various conditions. These results informed the next stages of the flight test program.

Phase 2 testing is taking place at the company’s Flight Test Centre at Cotswolds Airport in the UK. The testing aims to ensure the VX4 meets stringent safety and regulatory standards. Documentation supporting the Phase 2 Permit to Fly expansion included engineering specifications, operational procedures, and results from Phase 1.

Following Phase 2, the program will advance to Phase 3, which will focus on wingborne flight. This phase will simulate operations similar to conventional fixed-wing aircraft, including take-offs, cruising, and landings relying on wing-generated lift. Testing will prioritize safety by reducing speed from high altitudes rather than increasing speed from low altitudes. Phase 4 will evaluate the transition between thrustborne and wingborne flight modes. To support these efforts, Vertical is developing an identical VX4 prototype to accelerate data collection and refine the production model’s design.

The VX4 is a piloted aircraft designed to carry four passengers, with a range of 100 miles (approximately 160 km) and a cruise speed of 150 mph (more and less 240 km/h). Its design incorporates eight electric motors and Distributed Electric Propulsion to provide redundancy and enhance safety. The aircraft’s high wing configuration, V-tail, and retractable tricycle landing gear contribute to its operational performance. Its large windows, skylight, and dedicated baggage space are designed to meet passenger needs. Vertical’s proprietary battery system was developed at the Vertical Energy Centre in Bristol and has undergone extensive testing, including crash and thermal evaluations.

Vertical Aerospace, headquartered in Bristol, was founded in 2016 with the aim of advancing electric aviation. The company collaborates with partners such as Honeywell, GKN Aerospace, Leonardo, and Molicel. These collaborations support the VX4’s development, including its avionics, composite fuselage, and propulsion systems. As of November 2024, the company has secured 1,500 pre-orders from customers including American Airlines, Japan Airlines, and Bristow Group, with a combined order book value of $6 billion.

Despite advancements in testing, the certification timeline has been adjusted. Initially projected for 2025, type certification is now expected by 2028. This delay aligns with evolving regulatory requirements and industry-wide adjustments in timelines. Vertical Aerospace is pursuing a phased approach to flight testing and development, with the aim of advancing electric air mobility and supporting its commercialization goals.