Electroflight

The ACCEL initiative, short for Accelerating the Electrification of Flight, is a Rolls-Royce-led initiative partly funded by the UK government. It involves a host of partners including electric motor and controller manufacturer YASA and the aviation start-up Electroflight. The project’s focus is officially described as ‘an effort to build, test and commercialize a specially designed aircraft powered by megawatts’ – all within a self-imposed 24-month timeframe.

The ACCEL aircraft is based on a Nemesis NXT racing aircraft airframe. It will have a three-bladed prop, driven by three YASA 750R electric motors sharing a common prop shaft; where YASA is the motor supply partner in the project. The motors will have a combined peak power of 700kW, which is about the same power as the internal combustion engine used on a standard NXT in record run trim. Also, 700kW equates to circa 1,000 horsepower, which is about the same as a Formula 1 racing car.

The source of the electrical power will be 6,000 battery cells, and much of Electroflight’s development focus is around the power management of those cells. The team is working towards what it hopes will be one of the most power-dense flying battery packs in the world. It will have enough power to fly from London to Paris on a single charge and will contain a liquid cooling system to regulate heat.

With a start-as-we-mean-to-go-on attitude, Electroflight is adopting best working practices, is documenting all processes and is aiming for ISO9001 accreditation in 2020, on the road to further aerospace approvals. As part of this journey, Electroflight has invested in engineering toolchain products that support its growth plans. One such tool is Zuken’s E3.series electrical and fluid engineering solutions.

“We evaluated two leading CAD vendors of which Zuken was the clear winner because its E3.Series software also supports the development of hydraulics, which our aircraft has for the cooling of the battery and key powertrain components”, says Joe Holdsworth, Electroflight’s Control Systems Engineer

Another compelling reason for Electroflight’s selection is that E3.series is already popular in the aerospace industry. It is also fast becoming the wiring harness tool-of-choice within the motorsport industry too, where it helps teams meet tight race season deadlines. Electroflight plans to take advantage of E3.series’ aerospace and motorsport synergies, and the team will be using System 25 mil-spec motorsport connectors and harness construction techniques on the ACCEL project.

Because of the nature and compressed timeframe of the project, the Electroflight team is using E3.series to explore a variety of ‘what-if’ scenarios and has built a test rig to evaluate their concepts. E3.series is used for the schematic capture and design of the wiring harnesses (mainly on the low voltage side). To help meet an ambitious development schedule, rigorous version control is place.

The components, sensors, and connectors are tested on a test rig. They are the same ones that will be used for the aircraft. “The test rig on which we’re developing our hardware is completely in sync’ with the E3.schematic, the bill of materials and the wiring loom details, such as pinouts”, comments Holdsworth. “This means when we outsource the build of the loom, we’ll be able to supply everything in one go.” “Also, we’re using CANbus as much as possible, to keep the weight down”, says Holdsworth.

There’s also an ECU as part of the design. Its role is to optimise the aircraft’s performance but, should the unit fail, safety will not be compromised. The aircraft will still fly.

Electroflight is using a battery management system and other modules that are popular in motorsport but the team is also building bespoke PCBs, most of which are needed for data acquisition purposes; i.e. signal conditioning followed by the presentation of data onto CANbus in order to give the ECU visibility.