At the sharp end of Accel - The Spirit of Innovation, the fastest project in flight Venice, 30th March 1928. Italian Mario de Bernardi (the winner of the 1926 Schneider Trophy) becomes the first pilot to achieve a world speed record above 300mph. His Macchi M.52R racing seaplane is powered by a 400kg, 1,000hp Fiat V-12. Boscombe Down, Wiltshire, 16th November 2021. Powered as much by the synergy of several British organisations as its innovative powertrain, The Spirit of Innovation smashes its 300mph target: their initial aim in accelerating the electrification of flight. Bernardis record took 93 years to recreate in sustainable form. Humankind has spent most of this period unwittingly creating a sustainability issue; resolving it now becomes the final part. The aims of the project: clearly tell the world how serious we were about sustainability and prove it, explains Rolls-Royce Head of Flight Operations Phill ODell, one of two record-breaking pilots. Interest had begun to build since its 15-minute maiden flight, two months prior ODell and colleague Steve Jones sharing these four firsts. That was how we divided it: Id do the first flight and 3km, and Jones would do 15km and the climb to height. Evidence of claim was submitted to the FAI (Fdration Aronautique Internationale) for three record-breaking flights: at 345mph (3km distance), 331mph (15km distance) and climb to 3,000m (202 seconds) subsequently ratified in January 2022. By Captain Robin Evans, Senior Log Contributor Pedigree Rolls-Royces aero engine pedigree stretches from the V-12 Eagle of World War I, through the Schneider-winning Type-R and Merlin to the globespanning Trent. The airflow control and compression of Merlin superchargers was itself a step towards the Jet Age. In 2018, they began collaborating with Gloucester Airport-based start-up Electroflight, already working on a battery prototype with contra-rotating propellors. The novel partnership cast aside traditional silos and was heavily influenced by the motorsport and automotive sectors exploring supply chains that were new, agile and fast, adds ODell. While most visibly about a record, their efforts were ultimately to accelerate a market beyond legacy combustion engines. Rolls-Royce would manage project and flight operations, a safety case defined under the CAAs E Conditions. Steve and I actually did a fraction of this, says ODell, crediting wider team synergy. That was a massive part of the programme. I hope Electroflight learnt from us our learning how to work with start-ups was really powerful. We learnt as much about teamwork as we did about engineering. To build an aircraft and powertrain, Electroflight turned to an unusual source. Spirit began life as a Sharp Nemesis NXT, a Sport Class Reno Racer and the first Reno homebuild to exceed 400mph, the domain of Unlimited Class warbirds. The slippery design was an obvious starting point, but with other purposes: a long nose, containing a single fuel tank close to its CG, where efforts would be focused. A rare aircraft, an unbuilt kit had to be sourced for bespoke modification, a damaged model used as a static rig (dubbed the ionBird, a nod to Iron Bird test rigs). It would become a single seater, wings bonded directly to the fuselage, but beneath the modified cowling is where this flying battery differs dramatically. Three-hearted beast From the front and, despite the highest of tech, the constant speed propeller is wooden. Its driven directly, spun individually or in combination by three independent 750v, 133Kw powertrains (the combination of power source and corresponding drivetrain). Automotive powertrain supplier and project partner YASA supplied their 750R motors (see box, Axial flux motors, below left). These resemble silver platters: 368mm in diameter, 98mm across and 37kg apiece. Each has a separate inverter and battery channel, nine components in all, delivering about 160wh/kg. The motors attach directly to the structure of the Energy Storage System (ESS), a carbon-fibre box of upper and lower parts. This arranges and secures more than 6,000 Murata VTC-6 cylindrical li-ion cells (as used in power tools) into three compartments, separated by composite dividers. Each compartment has six battery modules with vertical cooling plates. The ESS uses inerting and flame-retardant Portuguese cork insulation. The whole point of the ESS is to provide a 10-minute resilience to thermal runaway, reveals ODell. From the cockpit, the ESS is 1.8m long, 0.8m wide and 0.4m tall. If this appears short, beneath sits the solution to the challenge of temperature regulation. Two intakes supply multi-core radiators, coolant pumps driving nine cooling loops, one per battery channel, motor and inverter component. ODell says this also serves to pre-condition battery temperatures. We were trying to get half a per cent state of charge gains because tiny percentages meant we could get another knot or two. This approach extended to refuelling: The slower, to a degree, you refuel the more charge youll get. Immediately in front of the pilot is an avionics bay containing the engine control unit (ECU), power distribution unit (PDU) and telemetry, key for realtime system monitoring. The Spirit airframe weighs 295kg, versus 300kg of batteries plus powertrain (200kg), ESS (175kg) and cockpit systems (175kg) for a total 1,145kg. ODell also reveals that pilots were not spared from team commitments to weight reduction. READ MORE Axial flux motors The perfect aeroplane for going fast A hard aeroplane to fly, but monumentally rewarding. I now would much rather fly an electric aeroplane Unlocking READ MORE Record rules Precise and understated in manner, ODell has flown many types (including the A380, 787 and Vulcan) but, positioned on the cusp of this third era of flight, he is candid about how Spirit tested him. A hard aeroplane to fly, but monumentally rewarding, he says. I now would much rather fly an electric aeroplane. He asserts: Its a perfect aeroplane for going fast, and Jon Sharp, who [originally] designed it, and Electroflight, who built it, have done a remarkable job. The focused design permits handling adequate for a safe record attempt in qualified hands, minimal concessions made towards aerobatic purity, comfort or mass production. Any dilution of this vision a bigger tail, rudder trim or less raked seating position could have compromised margins. Sharps piston engine Nemesis was analysed abroad several years ago. We took extensive notes, collaborated, talked as a team and documented all of that; it was very valuable, declares ODell. It has interesting stall characteristics. Its a very thin, high-performance, laminar flow wing. When you lose the lift, you lose it all. Despite common origins, they treated Spirit as an entirely new machine. Our C-of-G is quite a bit further forward, inside the theoretical envelope, but further forward than a Nemesis had flown, so that made for some handling differences throughout. The team used an Extra 300 and CAP10 to drill 150kt record profiles at half scale (see box, Record rules, below left) for identical cadence, to keep our hands, feet and mouth in close formation, adds ODell. These were also used for finessing the landing technique. With such little forward visibility, but great peripheral vision from aft of the wing, Spirit is flown on, avoiding the classic tailwheel three-pointer. Rolls-Royces Mk.XIX Spitfire also became a training aid. It was useful to practise turn techniques where I needed to look, how I needed to react, how I needed to think which was a big part of preparation, reveals ODell. They look very similar, but clearly are at entirely opposite ends of the technology spectrum. Alongside innovation, heritage was important, Spirits stripes a nod to the longitudinal radiators of the Schneider-winning Supermarine S.6B, displayed in the Science Museum. Operations Initial flight-testing targeted stall speed calibration and assessment of flare characteristics. Thirty scheduled flights would explore only the necessary parts of the flight envelope for the record. We progressed very incrementally: up to 150kts on the first flight, then we pushed that a little bit, pushed that a little bit more. Quite rapidly wanting to move, but, equally, quite thoughtfully. Analytics aside, ODell comments on Spirits personality, hinting at the challenges confronted. Spirit built its own romance over time; it wasnt a romance at the beginning. The first couple of flights were very interesting first dates. The powerplant throughout was spectacular I say that very genuinely. We had some issues with parts of the flying envelope and it was hard work to fly at times. One of the big takeaways for me was how, in a short space of time, you can change your opinions of an aeroplane materially. The throttle response is so linear, its the nicest throttle-to-motor tempted to say engine integration Ive ever worked with in an aeroplane. ODell relates early ATC confusion over the perception of taxi readiness without a turning propeller. Theres a big debate in electrical do you turn the prop or not? Zero thrust is a very low current drawing, prop-stopped setting, but we are a millimetre of nudge away from turning the propeller. Personally, I think you should turn the propeller at a very slow speed, it draws a fraction more current, but sends a very clear visual indication. We always gravitate, particularly in test and evaluation, towards risks at whatever level, and clearly in electric aviation there are uncertainties its new. We make a big thing of thermal runaway, but need to put it in proportion. There are strong ways to mitigate it by protection, by manufacture. But, ultimately, if you keep its temperature below certain levels, around 80-90oC depending on how hard you want to push, you can very successfully reduce the risk and I think you reduce it beyond the levels of current combustion and jet engines. Future The programme cost was around 6m, half from Aerospace Technology Institute (ATI) geared funding, 1m/year the balance to Rolls-Royce. While the record was key, its the wider value derived that is most valuable. To put it into production, its got to be fit for purpose and theres clearly work to be done there, advises ODell. There are choices do you charge batteries, reload batteries, charge the aeroplane? But the really strong point is we didnt see anything in this programme that would stop the electrification of aerospace, operationally or mechanically. I took a bit of a risk two years ago when I said electric aviation is going to stay, he reveals. That was a very early shout, but Im more convinced than Ive ever been. Rolls-Royces recently announced partnership with Vertical Aerospace in the eVTOL urban air mobility market will most immediately benefit. Rolls-Royce is also developing complete electric propulsion systems for the passenger aircraft market. I also believe there will be small commuter aeroplanes running all-electric in specific environments hopping around the islands of northern Norway [Wideres Tecnam P-Volt] and Loganair in the Scottish Isles, says ODell. We have to have vision and attitude because this is the most incredible time in aviation its a third generation, he explains. You dont fix world climate change by fixing aviation, but you do more than the percentage that aviation is within world climate change, because you change attitudes. As only pilots appreciate, coupled with power, performance soon follows. Spirit built its own romance over time, it wasnt a romance at the beginning READ MORE RECORD RULES The Fdration Aronautique Internationale (FAI) absolute speed record is the average of four passes of a reciprocal 3km leg with a 1km approach, conducted below 500m agl. The debut benchmark of 201 mph was set in 2013 and pushed to 213 mph in 2017 by a Siemens-powered Extra 330LE. Spirit is visually very different from the legacy Extra (built for manoeuverability first) hence the desire to smash, rather than nudge the record. Spirits powertrain is built to discharge its battery energy most efficiently inside the short period of time the record attempts dictate. READ MORE AXIAL FLUX MOTORS Oxfordshire-based YASA is named for its proprietary yokeless and segmented armatures. Segmenting into identical pieces aids mass production and economies of scale. Axial flux motors have rotors that spin alongside, not within, flattened stators. As the stator no longer supports (yokes) the rotor, removing it saves weight. The gap between rotor and stator causes a flux aligning parallel to the rotational axis, not radially like a legacy motor. The design turns motors inside out, offering significant increase in torque and power density. These are not bespoke aerospace products, also fitted to Ferraris hybrid SF90 Stradale.