Besides being quiet, eVTOL air taxis will need to be three things: safe, cheap to operate, and comfortable for passengers. The health and usage monitoring system (HUMS) developer GPMS thinks it can help with all three.
Based in Cornwall, Vermont, GPMS has been focusing on HUMS for light helicopters, but is now entering the eVTOL market through an agreement with another Vermont startup, Beta Technologies. GPMS announced in October that its Foresight MX HUMS will be installed for a demonstration pilot on Alia, Beta’s yet-to-be-revealed successor to its first eVTOL aircraft, Ava XC.
HUMS is used today especially in large rotorcraft to monitor the condition of bearings and other critical components. By providing advance warning of failures, these systems allow operators to proactively replace components during other scheduled maintenance activities, enhancing safety and reducing downtime.
“Everything requires maintenance,” explained GPMS CEO and chief engineer Eric Bechhoefer. “But if you can tell when something is going to break, then you can move that unscheduled event into a scheduled event, and that allows you to better control the management of that asset.”
That kind of optimization will be key to the success of many urban air mobility business models, he continued, since “functionally these things are trucks — they’re only going to get paid when they’re flying. So the key is reducing unscheduled maintenance so that the aircraft, when scheduled to fly, can fly.”
Moreover, Bechhoefer pointed out, if HUMS is designed into an aircraft from the beginning, then there are “opportunities to change how maintenance is done, which lowers operations and maintenance [O and M] cost. Which is really where eVTOL is going to be successful, based on its lower O and M cost.”
According to GPMS, the Foresight system installed on Alia will provide engine performance and component health monitoring, exceedance monitoring, flight regime recognition, and optimization solutions for rotor track and balance. Beta’s engineers and the operator will be able to monitor Alia remotely, accessing data and analytics for advanced diagnostics and predictive maintenance.
The system that GPMS is developing for Beta shares many elements with its distributed systems for light helicopters, since “whether it’s an electric motor, permanent magnet synchronous motor, or a turbine, they still have rotating components, which have bearings, and we do a pretty good job of monitoring” those for temperature and vibration anomalies, Bechhoefer said.
“I think the real uniqueness is that typically on a traditional helicopter you have one or two engines, but typically on an eVTOL aircraft you have many engines. So there’s not one gearbox or one big drivetrain, there’s multiple drivetrains. So it’s a little bit different architecture, but basically it’s just the same thing, just multiplied by n.”
Compared to helicopters, the multiple asynchronous rotors on most eVTOL aircraft also create some “additional problems that the software has to solve” with respect to analyzing vibration, he added. Here, the goal is to provide operators with guidance for regular tuning of the rotors to keep vibration to a minimum.
“Every time the aircraft flies, we’ll get this data, so it gives the opportunity to do smaller adjustments over time, and maintain in general a much lower overall vehicle vibration,” Bechhoefer said. “Which enhances safety because there’s less pilot fatigue; enhances the experience of the customer because it’s smooth and quiet.”
The Foresight system can offer other safety advantages, too, he pointed out. Because the system is collecting a range of vehicle and flight data, it can also be used for flight data monitoring (FDM) — analyzing how the vehicle is being flown to identify opportunities for improvements in training and standard operating procedures. FDM has been credited with helping to improve the safety record of commercial airline operations, and, along with safety management systems (SMS), could conceivably become a regulatory requirement for large-scale air taxi operations.
“When we talk about HUMS we predominantly think about condition monitoring,” Bechhoefer said. “But really, we support a bunch of other functionalities that reduce risk in the aircraft operation.”
For all of the benefits that HUMS can provide, Bechhoefer is keenly aware that keeping the weight of the system to a minimum will be critical to its successful deployment on eVTOL aircraft. Facing similar concerns in light helicopters, GPMS developed a bussed system where “you can run one wire and daisy chain it around as opposed to multiple wires going to each sensor,” he said.
On the Foresight installation in the Bell 407 helicopter, this architecture has resulted in a system weight of just 8.8 pounds (4 kilograms). For eVTOL aircraft, Bechhoefer said, “I’m really working hard to get it less than that.”
While GPMS is focusing on its collaboration with Beta for the time being, the company hopes to develop solutions for a variety of eVTOL platforms in the future.
“I think our strategy in eVTOLs is similar to how we’re approaching the traditional rotorcraft market,” said GPMS head of marketing Andrew Swayze. “We’ve got an STC [supplemental type certificate] in the Bell 407 family, but we’ll shortly be complete on the AStar, an Airbus platform. So it’s our intent to be multi-OEM and work for multiple aircraft and multiple companies.”