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19 Lockheed Martin F-35B Lightning II Joint Strike Fighter, both of which he found very satisfying. As mentors, he acknowledges Steve Lee and Robert Vaughan at Rolls-Royce. “They guided me on my first experience of theoretical and applied compressor aerodynamics, as well as forced response analysis,” he says. Forced response analysis works out how components such as compressor blades that are subject to aerodynamic forces respond to those forces, so that phenomena such as resonances that might cause engine failures can be avoided. Akanni also acknowledges James Chu, then head of flight physics at Airbus. “In my time there I found him to be very knowledgeable, always approachable and available, and always ready with an interesting personal, historical anecdote about aircraft of years gone by, like the Hawker Siddeley Trident and Vickers VC-10. “Last but by no means least is Willem Toet, who mentored me when I did my PhD research for the Ferrari One team. Willem was the head of aerodynamics at the time. While his aerodynamics knowledge is beyond question, he also has an infinite enthusiasm for science and living life.” With all these mentors, however, what impresses Akanni most is their ethical character. “After some of my life and work experiences, that is of ever-increasing importance to me. You need to have a decent code of ethics in life, otherwise what is the point?” he says. Micro-turbine technology He resigned from his last job in Formula One in October 2017 to set up Sentient Blue, based in Parma, Italy, to develop micro-turbine engines and small, high- performance UAVs. Explaining his motives for doing so, he says, “I wanted to do something different and exciting that would expose me to a variety of engineering disciplines on a daily basis while allowing me to work on projects I deem relevant,” he says. “What we are doing with the drones and engines is more relevant to human beings because it has the potential to help people, improve quality of life and alleviate suffering, whereas motorsport activity is primarily an exercise in conspicuous consumption and ego!” Heading a team of 12 people at Sentient Blue, Akanni is working on micro-turbine engine technology he refers to under the code name Django, after the freed slave turned bounty hunter in Quentin Tarantino’s film Django Unchained . The core engine technology can be applied to a turbojet or a turboprop, or coupled to a generator to provide a purely electrical output. Sentient Blue is working with a number of potential customers on UAV applications. It is also working on its own UAV, called the Quexada, named after a kicking move in Capoeira, an Afro-Brazilian martial art developed in early 16th-century Brazil by Angolan slaves. The Quexada will use an engine based on the same technology, although it won’t compete with customers’ aircraft, Akanni emphasises. “The two engines have very different flight envelopes and therefore different efficiencies,” he says. “We conservatively expect overall efficiencies of 55-65% or more depending on the mission and engine type.” Airflow and software challenges Although the technology has been evolving since 2013, the core has been flight tested and key systems have been through a number of iterations. The definitive Django engine will be fixed in May in response to an existing but confidential customer requirement. However, Akanni says the most difficult part of the development – gaining an understanding of the Reynolds effects on airflows at small scales to achieve stable combustion over the entire flight envelope – is complete. A related challenge has been finding software engineers with relevant expertise in embedded systems, as the company seeks to develop an engine control unit and an entire ‘ecosystem’ around it that can communicate with the engine and aircraft systems such as the autopilot and control surface actuators. All of these have to be modelled mathematically in order to understand the behaviour of the system as a whole, so embedded software experts are vital. Engine versions The outer casing of the engine currently being worked on is 15 cm in diameter, while the overall length, depending on the configuration, will be between 60 cm and 1 m. “We have had interest from certain entities that would mean one version would be a turboprop,” he says, “and we’ve had others that are interested in very high speeds, so that would be a turbojet. Then we’ve had others that are interested in high speeds with greater efficiency, which would mean a turbofan. We anticipate our UAV will be a turboprop.” He anticipates that, depending on the type of mission and its requirements, the engines will use either one or two Saif-Deen Akanni | In conversation Unmanned Systems Technology | April/May 2018 Created with data from a CFD analysis, this shows the compressor section of a miniature turbine engine Akanni and his team are developing for small, high-performance UAVs (Courtesy of Sentient Blue)