On the grainy videotape image, the small delta-winged plane is just visible in the distance, exercising a banking turn some 300m above Salisbury Plain, the chainsaw-like buzz of its two-stroke engine clearly audible over the gusting wind.
Any casual observers would imagine this was a pretty nifty model aircraft, and that somewhere nearby there must be a bloke in an anorak, working the controls.
But as the plane approaches the camera, passes overhead, and then flies on until it is a tiny speck in a grey sky, it is obvious that this aircraft is something different altogether.
The picture fuzzes over as Dave Dyer, an engineer at Cranfield Aerospace, fast forwards the tape to show the landing sequence. ‘We select the landing spot, it circles to lose height, and then…’ He pauses as the video shows the rest: the engine on the aircraft abruptly cuts out, and a parachute emerges from the top of the fuselage. The plane (which Dyer reveals is insured for £100,000) then drops straight towards the ground – surely far too quickly to survive the impact.
But at the last minute an airbag suddenly balloons from under the craft and the whole thing sinks safely onto the grass.
What Dyer has just been demonstrating is a UAV – an unmanned air vehicle, in this case designed for aerial reconnaissance – which has taken the best part of two decades to develop.
Known as the ‘Observer Concept’, the UAV is packed with three video cameras in its nose, angled to provide seamless coverage of the ground beneath and up to around 1000m ahead, relaying these live images back to the person who is flying it.
Dyer is head of control systems at Cranfield Aerospace, a niche technology company that is a spin-off from (but still owned by) Cranfield University in Bedfordshire, where it is based conveniently next to the airstrip. As well as a wide range of the more usual engineering and avionics projects, Cranfield Aerospace has been involved with UAVs for some time. But only now are these aircraft starting to look like a workable concept.
The challenge has been how to make the UAV easy to fly for military personnel: simple enough, as the team likes to say, for someone who can’t even spell UAV. And they seem to have succeeded.
This is how it works. Once the plane is launched (by catapult) it starts sending live video pictures of the terrain ahead of it back to the operator. The route of the UAV is programmed by touch screen, either on an electronic map image, or on the video image that the UAV is sending back.
If the operator wants to get a closer look at something that appears on the video image, he simply touches that point on the screen. The UAV then works out how to get the best view of that point – by circling to lose height, or looping back to make a second pass at something it has just overflown. ‘It’s like a searchlight,’ says Dyer. ‘The operator flies the footprint, rather than trying to fly the plane.’
Added to this, the plane is able to hold a straight course irrespective of wind direction (in the same way that a ferry crossing a river with a strong current will head upstream to reach the jetty opposite), and landing is simplicity itself. The operator just specifies the point on the map, and the aircraft does the rest, as Dyer’s video shows.
If it seems to have taken a long time to get the project to this stage, that is down mainly to money and also to computing power constraints. Only recently have the microchips become available that can get all the complex algorithms required to fly the plane – and its sensor footprint – into a tight space. The next stage will be to make the whole craft smaller still: it is currently powered by a two-cylinder, two-stroke engine, with a single wooden propeller at the rear.
Weighing 42kg, it can fly for a couple of hours at 60-70 knots – but makes too much racket to have any kind of stealth credentials. It also needs to be launchable by one man on a battlefield, rather than being ferried around in a Ford Galaxy with a two-man launch team.
Cracking these problems will be the next challenge for Cranfield, which is working on the project with the government’s military technology agency, DERA. But in many ways, the difficult part – getting the thing to fly itself – has already been achieved.