Vertical Aerospace remains on track to carry out crucial piloted wingborne flight tests of its VX4 eVTOL in the second quarter, and expects to conduct initial transition flights this year.
Wingborne flight involves the VX4’s taking off, flying and landing like a conventional aircraft – with the lift being generated by its wings.
Chief executive Stuart Simpson says this is “incredibly significant” for the programme. “We’ll be into public airspace,” he says. “[That’s] a huge vote of confidence in us.”
Simpson says the company has submitted some 20,000 documents to the UK Civil Aviation Authority to accompany the piloted wingborne phase. Securing approval has been a “huge, high bar to climb”, he adds.
Initial piloted transition – whereby the aircraft switches between thrustborne and wingborne flight, and back again – is set to take place before the end of the year.
Once these phases are achieved, the company will have two aircraft capable of performing further test flights to generate data for improving modelling and understanding.
Carrying out flights with a test pilot under real conditions is “absolutely critical”, says Simpson, adding that he has “total confidence” in the VX4’s capability.
“We firmly believe passengers will expect these aircraft to be as safe as commercial airliners,” he says, stressing that the company intends to certify the VX4 to the highest standards.
The company views the prototype flight-test campaign as a “mini-certification process” which gives it confidence that it will meet a 2028 certification target.
Engineering director Limhi Somerville says the all-electric VX4’s battery technology has undergone eight iterations since Vertical brought the development capability in-house.
“We haven’t finished,” he says. “We have two more development cycles in the next 12 months before locking down the final battery for production aircraft.”
Between the development of the initial aircraft and the current prototype, he says, the company has saved 10% of battery system mass while also improving its performance.
The company passed a full-pack drop test of 15.2m in early April, which Somerville says is “comparable” to a fuel-tank drop-test for rotorcraft.
He points out that the company already passed this test in 2020, but has repeated the achievement with a refined and significantly lighter pack.
“Passing that test is comparatively easy,” he says. “Passing that test with all functionality present, at the energy and power density we have, is tough. And we’ve done it.”
Somerville adds that, later in April, it passed its latest full-scale thermal-runaway propagation test on a VX4 subpack.
“If battery fire occurred in flight, we’d be able to continue safe flight and landing – either to the destination or an alternative – with full manoeuvrability,” he says.
Vertical has applied high certification standards “rigorously”, says Somerville, and multiple iterations have resulted in a battery which is “exceptionally high in energy and power for the mass, at a cost that makes the business profitable in the future”.
Batteries will be replaced more frequently than the aircraft, he says, and the company is using a “razor-blade” model that will lead to a 50:50 split in revenues between batteries and airframe.
Vertical expects to benefit from reselling batteries taken off VX4s and redirected to a secondary-life market, such as the marine sector.
