Is the aerospace industry on the cusp of widespread electrification? This chief technology officer thinks so, and physical tests have begun on a revolutionary new craft. Jon Lawson takes up the story.
The drive towards certification of eVTOLs is accelerating. Michael Cervenka, CTO at Vertical Aerospace says, “The key catalyst in this industry has been Uber setting up its Elevate division. This created an excitement and awareness that has enabled the industry collectively to gain investment from serious companies, and it made the wider aerospace ecosystem sit up and take notice of the possibilities offered by eVTOLs. The other thing that was very helpful in the early days was that a set of specifications was laid out, giving the industry something to work on.”
The outcome was that craft need to carry four passengers and a pilot, with a range of around 100 miles. For dimensions, to fit in most of the existing heliports, width must be less than 15 metres. The company took this and, in combination with a study of what potential users needed, came up with the initial design criteria.
That started the genesis of the VX4. When Cervenka joined around five years ago, there were designs on the table, but nothing practical. His first task was to split the engineers into two teams: red and blue. “I had them competing against each other,” he explains. “I gave the same specification to both, to see who could come up with the best architecture. At that stage we undertook a lot of spreadsheet work, setting out important elements like payload, but alongside that a lot of concept studies were done with pen and paper. Part of the challenge is that it has to do very different things – taking off vertically places different requirements on the design compared to efficient flight. We wanted a high wing, to give good access to the cabin and we wanted a competitive passenger cost-per-seat-mile, with eight propellers to give us the most efficient hover. Once we had those elements in place, we moved onto lots of simulation (with MATLAB) and CFD.”
Cervenka decided to quickly move to testing physical prototypes. “You can do all the computer, lab and wind tunnel testing you like but with a project like this it all comes together with the plane itself. Because what we’re doing is new, the best way to test our ideas is to build the thing. One of the key opportunities we have is that we can build in a huge amount of safety, which if you compare that to helicopters for example is not possible due to the large number of single-point failure parts. In fact, there are about 60 components in a helicopter where the failure of any one will bring it down. With our eight propeller design we can build in lots of redundancy as electricity is so easy to transport around the craft.”
Another area where full-size prototypes are so useful is demonstrating handling characteristics, a lot of which is dependent upon correctly sizing powertrain components, like motors and batteries. Three different prototypes have been flown so far, and another couple are on the horizon. “A lot of the challenge is how to get the thing to behave when it is close to the ground,” observes Cervenka. “The last one we flew was a winged vehicle, and all future examples will be too. In August, during one of our tests we had an incident with a propeller blade. Our investigation showed that it was an old design, and the adhesive failed during a deliberately challenging test where we switched off a motor. The software stepped in as expected, but when the part let go it broke a pylon and caused a short circuit which triggered a communication issue, meaning some of the other propellers ran at the wrong speed. Fortunately, it was right at the end of the session so we had already bagged a huge amount of useful data, and it proved to be a bit of a bonus for testing the other systems. So, despite the heavy landing, the battery didn’t catch fire and we learnt a huge amount about the communication systems and the new prototypes have a totally different design and manufacturing method for the propellers.”
The company has a different philosophy to most of its competitors. Instead of becoming a manufacturing hub, a strategic partnership approach has been adopted. Cervenka notes, “We chose established and knowledgeable suppliers such as GKN, Rolls-Royce and Honeywell because of the technology and certification experience that they bring. Also they have spare capacity because of supply chain disruptions stemming from the pandemic. Battery systems aside, much of the manufacturing will be carried out within their existing footprints.”
Considering numbers, the company forecasts a production run of hundreds per year by the end of the decade, which is well within the supplier’s range. Around 1,500 conditional orders have already been received, with plans to start series production by the end of 2026.