As NASA completes tasks for X-57’s functional ground testing at its Armstrong Flight Research Center in Edwards, California, working toward taxi testing and first flight, assembly and qualification tests are underway on two critical components of the X-57 vehicle at NASA’s prime contractor for the project, Empirical Systems Aerospace, or ESAero, of San Luis Obispo, California.
These components include the electric cruise motors, which will power X-57 in flight, and the future high-aspect ratio wing that will fly on the aircraft in X-57’s final configuration.
X-57, modified from a Tecnam P2006T airplane, is currently in its first of three configurations as an all-electric aircraft, called Modification II, or Mod II.
While this configuration features the replacement of the vehicle’s standard combustion, 100hp Rotax 912S engines with 60-kilowatt electric cruise motors, X-57’s test flights in this phase will be flown using the vehicle’s standard wing.
The following phase, Mod III, will see this replaced with the high-aspect ratio wing, greatly reducing overall vehicle area, and relocating the cruise motors out to the wingtips, before the aircraft flies in its final Mod IV configuration, which will feature the addition of 12 smaller high-lift motors along the wing’s leading edge to be activated during takeoff and landing.
The constant throughout these configurations, meanwhile, will be the electric cruise motors, which have begun tests at ESAero to verify that they are ready before they are installed in the X-57 vehicle itself.
“All three mods of X-57 will utilise the same cruise motors. We’ve taken those cruise motors and we’re putting them through functionality tests, acceptance tests, and qualification tests to ensure their airworthiness for the X-57 vehicle,” said Trevor Foster, ESAero vice president of operations. “As part of the NASA airworthiness process, these are the verification and validation steps to reduce risks and increase the safety and reliability of the components on the vehicle.”
These steps include endurance and high power testing of the cruise motors and cruise motor controllers, with a focus on monitoring overall system efficiency. To do this, engineers use a dynamometer to measure current and voltage, taking in data at a rate of two million times per second. From there, the performance of these components can be recorded, analysed, and augmented as necessary to achieve maximum efficiency.
The goal of this high power testing is to ensure that the cruise motors and their controllers can perform, with overhead, any of the steps of a flight mission.
Endurance testing, meanwhile, involves a wider spectrum of activities, according to ESAero Cruise Motor Acceptance and Qualification Lead, Colin Wilson.
“The endurance testing involves everything from doing small checks and low power checks, making sure that the motor spins and communicates and gives us the information we need, all the way up to running full mission profiles, and even taking it beyond mission profiles, where you’re really pushing the limits of temperature and power,” said Wilson. “So far, the motors and controllers have performed exceedingly well, and we’re in the process of getting them to perform even better.”
While X-57 will always fly with a pair of cruise motors in each configuration, five motors in total have been built for the project. One was disassembled and used for evaluation of the unit’s construction as a safety measure, two will be used as flight motors on the X-57 aircraft, and the other two will be used for envelope expansion testing, and will act as spares to the flight motors.