Recent ground testing on NASA’s first all-electric X-plane, the X-57 Maxwell, successfully demonstrated the aircraft’s ability to transmit its telemetry signal, allowing the team the capability to track mission-critical data during flight.
This data will be received on the ground during X-57’s flight tests, where it will be monitored in real time by the project team during flight operations, and recorded for post-flight analysis to measure X-57’s success in meeting its objectives, as NASA seeks to help set certification standards for future electric aircraft.
Completion of this round of tests, which took place at NASA’s Armstrong Flight Research Center in Edwards, Calif., marked continued progress on X-57’s functional ground testing phase — a necessary step toward taxi and flight tests.
“We are doing telemetry testing to confirm that we will be able to monitor data on the ground during future flights,” said X-57 Deputy Operations Engineering Lead Kirsten Boogaard. “It is important to make sure that everything works on the ground before we begin flight testing, first to ensure the safety of the flight, and also to ensure that our mission data will be received by the control room during flights.”
This mission data will help NASA researchers validate whether X-57, which is a converted Tecnam P2006T aircraft, successfully meets its “design drivers” — technical challenges to drive lessons learned and best practices. These design drivers include demonstration of an increase in energy efficiency, zero in-flight carbon emissions, and flight that is much quieter for communities on the ground.
The success of X-57’s ability to meet these objectives will be measured by comparing data from the electric aircraft’s future flight tests to the performance of a baseline, combustion-driven P2006T aircraft.
“This is important research data to monitor during flight. We need to be able to track the X-57’s position, speed, and altitude to see if we’re reaching our flight conditions,” said X-57 Flight Systems Lead Yohan Lin. “At the same time, the system needs to transmit sensor information such as cruise motor traction bus voltage, current, and propeller speed so that the electric aircraft’s performance can be assessed.”
Telemetry testing was conducted by establishing a Radio Frequency (RF) link between the aircraft and the downlink equipment of a NASA telemetry van. The X-57’s two antennas, a top and a bottom antenna, were tested together first in the flight configuration, and then each antenna individually.
The transmitter was operated by an avionics technician in the X-57 cockpit, based on instructions from the test conductor. The instrumentation engineer and telemetry technician monitored the downlink signal in the van, and was able to confirm that the data messages were being received as expected.
Among the data monitored throughout the tests, the X-57 team specifically looked at RF power. This measurement allowed engineers to observe the signal strength of the overall transmission. The team also looked at the bandwidth and center frequency of the signal pattern, to determine if the system is operating within the bounds of the allocated frequency range.
The testing indicated no major anomalies in the X-plane’s ability to transmit data.
“This checkout verifies that we are operating at the right specifications,” said Lin. “The next step will be functional testing of the cruise motors at high voltage, and we’ll be monitoring certain critical parameters using this telemetry system.”
As X-57 Operations Engineering Lead Michael Quinton points out, this functional ground testing phase was indicative of things coming together over multiple areas for the X-plane, and was a big step in leading toward taxi and flight tests.
“One of the best parts of our recent testing was getting an opportunity for all of our discipline engineers and technicians to come together, and support a single, real-time event.”