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18 In conversation | Bill Fredericks Greased Lightning’s target markets are initially military, with commercial linear infrastructure inspection in prospect once beyond-line-of-sight regulations are enacted. This aircraft, he argues, is a true no- compromise VTOL machine. “What’s nice about the Greased Lightning is that it has a lift-to-drag ratio of 15, which is on a par with other small UAVs. It has the aerodynamic efficiency of a fixed wing but has vertical take-off and landing,” he says. The Greased Lightning is a swept- wing UAV with four electrically driven propellers on each wing and two on the tailplane, for a total of ten. In the transition from vertical to horizontal flight and back, the entire wing and tail surfaces pivot. They do so independently because the flow field that the tail sees is different from the one the wing sees. Fredericks says, “There is a non-linear rotation schedule for the tail. In the hover, the wing and tail point leading edge up, and as the Greased Lightning goes through the transition corridor the tail must get ahead of the wing. “Then, once it gets back to wingborne flight, the wing and the tail come back to similar angles. The reason is to keep the aircraft trimmed at every point in the transition corridor.” The future’s electric In the longer term, his ambitions are to combine his love of private flying with his knowledge of autonomous systems and hybrid/electric propulsion. He regards these strands as complementary and revolutionary. “I believe the electric motor will change aviation more dramatically than the switch from the reciprocating engine to turbines,” he says. “What I find most exciting about electric propulsion is that it is scale-invariant – a 1 hp electric motor has the same power- to-weight ratio and efficiency as one producing 1000 hp.” He says this is a new variable for designers because they can now do things at the system level that previously didn’t make sense, citing NASA’s X57 research aircraft (on which he did design work) as an example. The X57 will feature a distributed electric propulsion system with 14 electric motors driving propellers along the leading edges and at the tips of the wing, which has a short chord and a high aspect ratio for cruise efficiency. Normally, such a wing would perform poorly on take-off and landing. With the X57 though, the six propellers on the leading edge of each wing will ‘supercharge’ the airflow over the wing to increase lift, while the tip propellers will provide all the thrust in cruising flight when those on the leading edges stop and fold. The redundancy that comes from multiple motors would improve safety, while the automation expertise built up in unmanned systems would make such an aircraft easier to fly, both normally and in emergencies. As an engineer and a pilot, Fredericks admits to being torn between pride in a skill and awareness of human limitations. “Computers do deterministic tasks way better than human beings,” he says. “If you are trying to shoot an instrument approach and follow needles down to a runway, a computer is so much more capable than a human being. Where we are much better though is with non-deterministic tasks such as devising the best strategy to get through weather. “We need to start delegating a lot of the deterministic tasks to the machine, but a lot of the high-level decision-making should stay with human beings for a very long time.” April/May 2017 | Unmanned Systems Technology Bill Fredericks’ airline pilot father kindled his enthusiasm for aircraft as a child, and Bill soloed a glider in 1996 at the aged of 14, earning his private pilot’s licence two years later (again in a glider) and a single-engine rating the year after. However, his father nudged him away from flying professionally towards aircraft design, which he pursued via a degree in aeronautical engineering from Purdue University, Indiana, from where he graduated in 2006, and a cooperative programme with NASA that started in 2003. NASA gave him a job in its aircraft design division in 2007. At NASA he worked on several innovative aircraft concepts, including a dynamic soaring UAV and the electric, multi-propeller X-57 manned aircraft. He took military leave from NASA in 2008, joining the US Marine Corps Reserve as an artillery officer. In 2011 he returned to NASA to lead its long-endurance VTOL UAV effort that became the Greased Lightning, and formed the Advanced Aircraft Company in 2015 to commercialise it. Bill Fredericks