'Eureka' moment results in innovative long endurance drone design

Written by: Graham Pitcher | Published:
Electric motors are the most efficient propulsion system for small (typically unmanned) aircraft. ...

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There is something authentic about a design which came about following a 'Eureka moment'. That is what happened to Ashley Bryant, who is on the point of taking an innovative long-endurance drone to market.

Bryant's 'Eureka' moment came nearly a decade after necessity had forced a hobby to become business, albeit a business that had the rug pulled from under it.

Building a Harrier jump jet was Bryant's hobby whilst working at a commercial airline, a business that effectively collapsed after 9/11. This was when Bryant looked at the advantages of combining vertical-take-off-and-landing (VTOL), as found on the Harrier jet, with the emerging drone technology. He won a £1.5million contract with a defence prime to the American military to develop a maritime platform based on a 'Harrier drone'. Unfortunately, in 2008, the budget to the prime was cut and the programme was axed, although all the IP was retained by the military. Bryant was left high and dry.

This was when Bryant woke up in the night with his brainwave – springing out of bed to write it all down, lest he forgot. The idea was to remove the fuselage, essentially have a flying wing, and put a rotor on each corner, each falling outside the boundaries of the airframe. "When I started to research flying wings, I realised it was the most stable aircraft architecture going," said Bryant.

An obvious comparison, for someone who knows their aircraft, is the Boeing V-22 Osprey, whose rotors can be oriented vertically for take-off and horizontally to provide forward thrust in flight. The equally obvious difference is one of scale – with a 14m wingspan, the V-22 is an order of magnitude bigger than the Flying Wing that Bryant's company VTOL Technologies has subsequently developed. A more subtle difference is that the rotors on the flying wing, of which there are four rather than two, are outside the airframe, whereas in the V-22, when in the vertical position, they overlap the wing. This means that downward thrust goes straight into the wing, causing disturbance and no lift, so proportionally more power is required to take-off.

The Flying Wing developed by VTOL will, in some cases, be used in the same environments as helicopters, although not for cargo or passenger duties like the V-22. More commonly, it will compete with drones.

Main applications will be repeatable automated operations, principally inspection duties for the utility, network and infrastructure sectors. Bryant said: "We are developing brand-new techniques for inspection, so we're combining the capabilities of new camera technologies with the advanced technologies that this platform delivers and that is above and beyond what other platforms deliver."

These new technologies mean that sensors are shrinking in size and weight. Reduced weight means technology that may previously needed a helicopter can now be installed on a platform like this. Regulations allow lightweight unmanned aircraft to fly beneath 400ft, getting closer to the inspection target, so the sensors may not need to provide as high definition and can again be made smaller. It is a virtuous circle. Lighter payloads also result in reduced power consumption and therefore longer air time.

Comparisons will be made with the existing drone technologies – rotorcraft and fixed wing. A typical rotorcraft will require an operator to control the platform, possibly another to control the payload sensor, and will require line of sight operation.It also will be limited in terms of its flight time (usually about half an hour) and speed – and therefore its range. Fixed wing aircraft can be in the air longer, three to four hours, but launching can be a problem as is load balancing with the fuselage, and also they have a minimum air speed – in other words they cannot hover.

Bryant, believing his aircraft could take the positives and remove the negatives for each drone type, took his idea to DLR, the German aerospace research centre. He commented: "The Germans are very, very clever at small wing design – high lift, low drag wing design. It is an advanced aerofoil shape that means we can create high lift at low speed. So if, for example, we are flying at 10 knots, we can reduce the amount of power by 50%. If we fly at 15 knots, it is a 75% power reduction, just because the aerofoil is providing the lift." It also means the Flying Wing can hover into the wind while using very little energy

Bryant continued: "A key feature is that it is a fly-by-wire aircraft. Unlike many other small light unmanned aircraft, we have decoupled the command input from the actual control of the aircraft. We have teamed up with National Instruments and are using its myRIO, which is a phenomenal bit of kit for us. We are fully exploiting all the FPGA capabilities on that platform."

Although initially aimed as a project tool for students, myRIO is a hardware device that has provided all the control functions needed on the Flying Wing. Bryant continued: "We are using all of the NI LabVIEW software development tools to develop the flight control system and other elements of the system, and use it for hardware in the loop testing."

However, the main design environment is Solidworks. "We also use its finite element product to do the stress analysis," said Bryant, "and we have used specialist CFD companies for other parts of the design."

The simulation capabilities VTOL has developed for product design has been extended into a virtual reality environment so potential customers can compare different inspection technologies and determine if the Flying Wing is suitable for their application. The company already has a virtual overhead cable inspection simulation aimed at helping its first tranche of customers this year.

Bryant said that while expertise in house was building in order to deliver on such projects as the simulation tools, the company was still happy to look elsewhere. "As we have gained more experience, we have been able to resolve more issues in house. But we have used –and continue to use – best in class subcontractors."

Brick Kiln composites, an F1 subcontractor, makes the airframe. "Wherever we can, we leverage all the research effort that has gone into the Formula 1 industry to help us," commented Bryant. "We are using advanced foam cores inside certain elements of the design that are going to make the structures incredibly strong, but also incredibly light."

Other contributors are Rutherford Appleton on the electronics side, which has developed a specialist power board. For vision systems, the company is working with Varioptic, which has developed liquid lens technology that allows ultra-fast autofocus. Hydrogen fuel cells research is underway with Cella Energy for the next generation models – the first ones are powered by rechargeable (and replaceable) lithium-polymer batteries. And E2E is working on satellite communications.

"Designing an aircraft like this is a huge challenge," concluded Bryant. "There is a huge number of technologies and we have had to develop some specialist design tools. But it is all part of the design process – it is a bit like we have to go round the spiral time and time again."







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Electric motors are the most efficient propulsion system for small (typically unmanned) aircraft. As they grow in size alternative propulsion systems come into their own regarding improved efficiencies. With regards to a wingspan of 10m and chord of 1.5m this is an extremely large wing to support such a small payload.
It is interesting to note the development of a flying wing with electric motors. Is it possible to do it for a 10m span 1.5 m chord wing ,and 5Kg payload. We are interested.

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