As well as the current and soon-to-enter-service technologies on view all over the air show site, there are a few glimpses of possible futures to be found. One of the most intriguing is buried deep in a sub-menu on a touchscreen installation on the future unmanned systems stand in BAE Systems’ exhibition hall.

In a piece of forward-scanning work that sits at the very low end of the technology readiness level scale, BAE are positing a cranked-kite stealthy UAV that can change shape during flight, deploy retractable fins from internal bays to aid maneuverability and that uses air bled from the engines instead of moving control surfaces.

“These are concepts: we haven’t worked out how to engineer some of these ideas yet,” cautions Martin Rowe-Willcocks, BAE’s future combat air systems (FCAS) business development director. “We’re trying to ask, if you want a vehicle that does more for its shape, how does that work? Would a core aeroplane with disappearing fins, reconfiguration of the shape for different speeds and control regimes, and so on, be something that was worth exploring?”

Perhaps the biggest surprise is that none of these ideas are in themselves unprecedented. Aircraft from the Mirage Milan to the T-144 have had retractable control surfaces; aeroplanes as different as the XB-70 and the B-1 have changed their configuration in flight. And BAE have already demonstrated using bleed air to control flight on an earlier UAV program (see panel). Still, the concept raises far more questions than it answers: but, as Rowe-Willcocks points out, that’s really the point of the exercise.

Take, for example, the shape-changing idea. It implies a flexible outer skin on the aircraft, which will not fold or kink as the structure underneath it shifts, if the airframe is to maintain stealthy characteristics.

“That’s the challenge,” Rowe-Willcocks says. “A traditional aircraft that changes its shape like a Tornado or an F-111 has some fairly sharp corners and quite big gaps. To us, that’s the purpose: to ask, if we wanted to do that, how would we achieve it? I’m not saying we know yet! But what I am saying is, we need to try to test the boundary, so that we’d know if we decided we needed to do that whether we’d have to run an individual technology program that explored that piece of the airframe.”

Another obvious challenge the concept poses is software-related. Current aircraft that change configuration in flight do at least have someone onboard to manage the transition: if the system has to do that itself, some new techniques around reconfigurable autopilots are required. Extant work will also inform this discussion, if and when it takes place.

“We’ve not specifically explored reconfigurability in flight, but we’ve done reconfigurability between shapes,” Rowe-Willcocks says. “If you look at the line of development from [demonstrator aircraft programs] Raven to Corax to Taranis, they have slightly different shapes but a common core architecture inside them. And in the very early concept phases we had a single flight-control system that worked across three very different aeroplanes in Raven, Corax and [still partly classified UAV] Herti, all at the same time, by putting different control laws in there. Of course, you’re not changing the shape of the aeroplane while it’s flying. That’s the next thing: how would you do that?”

Older Project Demon-strates Surface-Free Control

The Demon program, which culminated in flights on Walney Island in September 2010, has already proven one novel capability. Air bled from the engine is routed to openings along the top and bottom of the wing’s trailing edge. Variably controlling the air flow through the four apertures allows the aircraft to be steered.

“We sponsored this work inside the university network to build one of these and see if it worked,” Rowe-Willcocks says. “As a concept, we found it works quite well, but the big challenge would be engineering it into a full-scale aeroplane.”

Another challenge would be incorporating the concept into a stealthy design. Demon’s wing trailing edge had long gaps for the air to flow through, which leave edges that would not be tolerable on a low-observable design.

“So we know flowing air can move the aircraft, but that’s not a stealthy trailing edge,” Rowe-Willcocks acknowledges. “But if you think of the way the conformal air data [system] works on the nose ] of Taranis] – it’s a streamlined nose but you’ve got holes there that you’re using for air-data management – could you do the same thing?

“It’s about building blocks,” he concludes. “It’s not proven – you’re not going to put it in a fighter yet. But it shows it’s possible to do these things.”