X-57 modified P2006T
As NASA completes tasks for X-57’s functional ground testing at its Armstrong Flight Research Centre in Edwards, California, working towards taxi testing and first flight, assembly and qualification tests are underway on two critical components of the X-
Derived from the Tecnam P2006T which has established itself as the aircraft of choice for not only the world’s most reputable Flight Training Organisations but private owners alike. A firm favourite with leading General Aviation fight-test journalists who praise its styling, handling and very low operating costs. The P2006T is a twin-engine four-seat aircraft with fully retractable landing gear. The superior high-wing configuration offers stability, superior cabin visibility and easy access for passengers and luggage. Tecnam has used its extensive experience with aluminium airframes to create a robust yet very light airframe, resulting in an outstanding payload-to-total weight ratio. The wings are of traditional construction, that is essentially a mono spar configuration. Integral fuel tanks are located outboard of the engines, holding 100 litres each for a total of 200 litres.
Particular attention has been paid to the cabin’s structural design in order to ensure the required crashworthiness as prescribed in recent amendments to the FAA-FAR23 and EASA-CS23 codes.The standard P2006T is powered by twin Rotax 912S3 100 Hp engines that run on either AVGAS or MOGAS automotive fuel. The aircraft has a maximum cruise speed of 150 knots (278 km/h) and a range of 670 nautical miles (1240 km) burning only 9 USG/h (34lt/h) on both engines.
X-57 Maxwell
NASA has selected the Tecnam P2006T twin as the airframe on which it will evaluate the potential of LEAPtech (Leading Edge Asynchronous Technology), with the aim of developing safer, more energy efficient, lower operating cost and greener general aviation aircraft. 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. The 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. Whilst this
configuration features the replacement of the vehicle’s standard combustion, 100-horsepower 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 take-off 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 the X-57 will utilise the same cruise motors. We have taken those cruise motors and we are 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.
Meanwhile endurance testing 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 are really pushing the limits of temperature and power,” said Wilson. “So far, the motors and controllers have performed exceedingly well and we are in the process of getting them to perform even better.”
Whilst 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, whilst the other two will be used for envelope expansion testing and will act as spares to the flight motors. Lessons learned from this testing are helping to pave the way for future Federal Aviation Administration airworthiness standards for electric aircraft. “It’s critical for the success of the project that we achieve the efficiency goals at which we are looking, but also, as we are going through these steps, we are beginning to develop how anyone else in the industry is going to certify or make airworthy motors,” said Foster. “We are taking those first steps.”
As this cruise motor testing directly feeds the effort for X-57 Mod II, currently housed at NASA Armstrong, preparation for Mods III and IV are well underway with the team getting the vehicle’s future wing ready for integration. An additional P2006T fuselage, off the same assembly line as X-57’s fuselage, was acquired, which is acting as a ‘tooling’ fuselage, allowing engineers to assess the best way to integrate the cutting-edge wing, designed by Xperimental LLC, to X-57 for Mods III and IV, whilst troubleshooting any challenges with the attachment.
Amongst the lessons learned from this phase is a better understanding of what physical modifications must be made to the fuselage to allow the wing to be mounted as efficiently and safely as possible. The wing is also undergoing instrumentation development, with engineers working to finalise the positioning of hardware inside the wing,to accommodate X-57’s complex distributed electric propulsion system.
“We are working how to figure out the right positioning for specific instruments and how to mount them,” said Phil Osterkamp, ESAero Vehicle Instrumentation Lead. “It’s a small wing and the challenge is to get all these items fitted onto and inside it, whilst trying to understand how to make this as light and as small as possible. It’s a lot of layout and routing.”
This is being done as a risk reduction for the X-57, which will be the first NASA X-plane in two decades to have a test pilot onboard, but also as a schedule reduction effort. With these activities taking place in parallel to Mod II, the transitions from Mod II to Mods III and IV will require less time. “The work being done now for X-57 is extremely important,” said NASA’s X-57 Project Manager Tom Rigney. “The team is proving out the key electric components that will very soon set the stage for all the parts to come together and for on-aircraft ground testing to begin. This critical step must be completed successfully before the airplane can take its first flight. Although managing this and the wing development simultaneously is challenging, doing both in parallel is proving to be a huge time saver.” As testing on these critical components continues to advance X-57 toward its historic first flight, an approaching milestone in NASA’s effort to help set certification standards for electric aircraft of the future, anticipation for that day grows across the team. “In the beginning, we were trying to push the envelope for this technology and I think now sharing lessons learned along the way, we are providing more benefits to the aerospace community at this stage than we thought we would,” said Foster. “It’s really exciting to see how far we have come and really seeing things start to come together here in these final phases as we approach first flight for Mod II. I am incredibly excited to see this aircraft fly.”