MicroStrain wireless sensor networks were leveraged by Beta Technologies to inform the development of its electric vertical takeoff and landing (eVTOL) aircraft prototype, intended to transport human organs for critical transplant operations.
Designing new eVTOL types, such as fully electric eVTOL models capable of carrying passengers, demands extensive data collection and precise measurements across diverse conditions.
Sensors play a crucial role in acquiring this data. Beta required advanced sensor systems to meet the stringent requirements of its design and testing process.
Building the eVTOL Prototype
Beta sought a sensor system capable of monitoring temperature, vibration, and strain for both component bench tests and in-flight evaluations. Additionally, accurate monitoring of pitch, roll, angular rate, position, and velocity required an inertial measurement unit.
MicroStrain sensors, with a proven history of supporting flight tests for helicopters, fixed-wing aircraft, and unmanned systems, were an ideal match for Beta’s testing and validation efforts.
The prototype, designed to carry a 4,000-pound aircraft over distances of up to 150 miles on a single charge, incorporates a range of innovative features. It is piloted and optimized for lightweight efficiency while storing and converting energy.
The aircraft boasts a 35-ft wingspan and eight 75kW motors for takeoff and landing. To achieve lift, four counter-rotating propellers, driven by the motors, handle vertical ascent. Upon reaching the appropriate altitude, the propellers tilt, transitioning the aircraft to conventional flight.
Powering this system are two 124 kWh lithium-ion battery packs. In over 180 FAA-approved test flights, the prototype has achieved a top speed of 72 knots and an altitude of 100 feet.
Data Monitoring with MicroStrain Sensors
MicroStrain’s sensors played a pivotal role in Beta’s prototype development. Among the key components used were the:
- G-Link-200 rugged IP-67 wireless accelerometer
- V-Link-200 8-channel analog input node
- TC-Link-200 12-channel wireless thermocouple node
- WSDA-2000 wireless gateway
- 3DM-GX5 GNSS/INS-aided AHRS
Flight Control Monitoring
Beta utilized three GX5-25 inertial sensors to capture pitch, roll, and angular rate values, ensuring redundancy in the flight control loop.
Data from these sensors was transmitted to the flight computer, which controlled the eight propeller motors during hover-mode operations. Inertial sensor outputs, including position and velocity, were also logged on an SD card and onboard computer for detailed analysis of flight metrics.
Test Stand Evaluation
MicroStrain sensors were employed to monitor propeller thrust, vibration, strain, and load characteristics on the test stand. A load cell measured upward lift at various propeller speeds, while accelerometers assessed vibration on the stand. This allowed Beta to evaluate propeller balance across different designs.
To track revolutions, a tachometer synchronized with vibration sensors, correlating accelerometer signals with propeller blade phases.
Strain gauges on the propeller blades measured centrifugal and bending loads at speeds up to 1200 RPM and loads ranging from 10,000 to 20,000 pounds. These measurements were recorded using V-Link-200s in synchronized sampling mode with high sample rates.
Structural Static Load Testing
For static load assessments, strain gauges were applied to the airframe structure. Hydraulic pumps applied loads at critical structural points, with load cells referencing the applied force. Data was captured at low sample rates using V-Link-200 systems.
Battery Temperature Monitoring
Beta’s prototype integrates 1,500 pounds of cylindrical lithium-ion battery cells organized into six packs. Since thermal runaway can pose a fire risk at approximately 70°C, Beta closely monitored battery temperatures using probes inserted into the battery packs.
During peak sustained hover power of around 500 kW, two MicroStrain TC-Link-200 nodes transmitted real-time temperature data.
Hover Motor Vibration Testing
To measure aerodynamically induced vibrations and identify resonant frequencies, Beta deployed MicroStrain G-Link-200 wireless accelerometers operating at high sample rates.
Advancing the Prototype
MicroStrain sensors provided essential data for Beta Technologies’ prototype development. Monitoring and testing presented challenges, including interference from nearby high-power RF devices and accessing hard-to-reach areas like rotating components. Despite these obstacles, MicroStrain sensors delivered the reliable feedback Beta required to refine and advance its eVTOL design.
