• 08 Dec 2022 10:46 PM
• 0

eVTOL on a Desktop

By Frank Colucci
Vertiflite Nov/Dec 2022

A new version of popular flight simulator software helps Beta Technologies develop an advanced air mobility aircraft and might orient and inspire new aviators to electric vertical takeoff and landing.

The latest release of the popular X-Plane flight simulator software enables desktop computer pilots to fly the Beta Technologies Alia-250 electric Vertical Takeoff and Landing (eVTOL) aircraft. The battery-powered Alia transitions from four lifting propellers on takeoff to an efficient propeller and fixed wing in cruising flight and restarts the lift propellers for vertical landing. Beta test pilots in South Burlington, Vermont, already use X-Plane 12 to rehearse real-life test profiles. Changes made in the flying prototypes enable the X-Plane software developers at Laminar Research in Columbia, South Carolina, to update their predictive simulator.

Separately, Mattern Aerospace in Orlando, Florida, sees a business case for an inexpensive simulator to introduce pilots to the subtleties of electric flight, complementing the use of X-Plane by Beta for aircraft development. Founder and entrepreneur Joe Mattern explained, “I am not a certified flight instructor and I cannot legally train pilots in flight simulation. My long term goal is to remotely orient pilots in the Beta Alia-250 X-Plane 12 desktop simulator and prepare them for professional simulator training and in the process, expedite their future flight training curriculum, given their familiarization with the cockpit.”

A 2020 report by McKinsey & Company projected a need for 60,000 eVTOL pilots within the next few years to realize advanced air mobility (AAM) schemes. Some without pilot experience will have to train quickly for short aviation careers, knowing they will be replaced by automation and may not transition to conventional cockpits.

The AAM training picture and pilot pipeline is complicated by the variety of air taxis in development, according to Mattern. “Many of these aircraft are single-pilot-seat designs. As a result, eVTOL manufacturers will have to use simulation as a flight training tool to train pilots before they get into the real aircraft.” So, he asked, “how do you quickly get qualified, safe eVTOL pilots into the airspace, given the fact that this is brand-new aircraft technology?”

With room for 1,400 lb (635 kg) of cargo or five passengers and a single pilot, the 7,000-lb (3.5-t) Alia-250 is bigger and more capable than ultra-short-range air taxis but still poses piloting peculiarities. Mattern logged about 2,000 X-Plane 11 simulator hours in the conceptual aeroG Aviation aG4 ducted fan eVTOL, in which he is still seeking development sponsors. He began learning to fly the Beta Alia-250 in an X-Plane 12 early release and acknowledged, “This airplane flies very differently from either an airplane or a helicopter. Even for a certified pilot, there’s going to be that learning curve… It’s going to be many times harder for someone who has no pilot experience at all.” He noted, “The modulation of the pusher prop and the rotors and learning how to use those together is critical for ascending and descending.”

Beta Technologies and CAE in September 2021 announced plans for an Alia pilot and maintainer training suite including training devices. The SAE International G-35 committee is developing standards for eVTOL flight simulation training devices. Beta’s fixed-base engineering development simulator is already used for pilot training and, according to the company’s spokesperson, “We have designed the simulator in a way that would allow us to develop a certifiable platform that could be used for pilot training credit in the future.” US Air Force and Army test pilots flew Alia-250 evaluations earlier this year after ground school and simulator training.

According to Mattern, the X-Plane 12 professional use edition meets frame rate and other current requirements for a US Federal Aviation Administration (FAA) tabletop simulator. X-Plane developer Austin Meyer explained, “For certified flight simulators at the most basic level, the requirements are so low that my demands and the demands of the customer are way above the legal requirements. Then, when you get to Level-D [simulators], the certification requirements are so high that I don’t think any predictive simulator could hit them. So, yes X-Plane hits some intermediate level of certification quality.”

Fly and Remodel

Beta has been flight testing the Alia-250 aircraft for more than two years. The first prototype is configured for electric conventional takeoff and landing (eCTOL) and the second for eVTOL. The eCTOL aircraft flew 2,400 nm (4,400 km) in stages from New York to Arkansas and back. The eVTOL aircraft has so far collected data in successful hover testing.

Both Alia-250 prototypes have a mix of commercial and custom-developed sensors to telemeter live flight test data to the Beta flight test center. The company’s ground simulators replicate the aircraft’s databus virtually to produce the data fed to actual flight hardware. According to Beta, “This helps put additional operational hours into our flight hardware, such as avionics, inceptors and more. It also enables us to train our test engineers and test conductors on the same software and infrastructure they will use during actual flight test missions.”

The company spokesperson explained, “X-Plane simulator physics are based on blade element theory, which enables the software to respond realistically to changes in the aircraft. This means that as we make tweaks or adjustments to Alia’s features, X-Plane can provide us with a clear picture of how the changes will perform in real-world environments. It also allows us to prepare for flight tests in regions we have not yet collected data for, expanding our understanding of aircraft performance in a safe and calculated manner.”

The Beta spokesperson added, “We feed flight test data back into our simulator in two ways. First, we update the physical characteristics of the aircraft in X-Plane, to ensure the various parameters recorded in real-world test flight are reflected in the virtual program… Second, we developed our own aircraft dynamics model built entirely from flight test data to ensure that, as new data is received from flight test, the simulator model is updated to reflect the data exactly.”

Alia and other aircraft configurations with distributed electric propulsion pose simulation challenges. Austin Meyer noted, “So many of these eVTOLs have vertical-pointing props that wind up blowing propwash down on to the wings in hover… Now we have wings that are not just doing nothing when the craft is in hover. Those wings have a downwards column of air pushing them down. X-Plane 12 now has an airflow-velocity tracker internally that tracks these propwashes, downwashes, and even wing and body wakes to see how each part interacts with the others. This was one of the more challenging parts of the simulation to get right!”

Also challenging is that eVTOL propeller performance needs to be predicted accurately in hover, forward flight, and conditions in-between. Meyer added, “This includes transitions where some up-pointing props are getting dragged through the air sideways as they spin. The math gets tricky on that, but X-Plane 12 has been [readied] for that for about two decades… as we have simulated the full performance envelope of helicopters.”

Under contract to Beta Technologies, Laminar Research developed the Alia-250 model in X-Plane 12 for use on Beta’s own simulators. According to Meyer, “I model the Alia-250 exactly the same way I model all the other planes: I enter the geometry of the airplane and let X-Plane apply the math to predict how it will fly… We enter the shape of the airplane in Plane-Maker, and then let X-Plane read that shape to interact it with the air, and show how the airplane will fly, based on its shape.” Meyer added, “[People] want to see approximately what a huge variety of airplanes will do in the future, and X-Plane is the best sim there is for that mission.”

Meyer offered, “X-Plane at this point really is not going to be surprised by wings. We have the performance on those very well established and dialed-in. As well, X-Plane at this point really is not going to be surprised by props that either lift or push or pull. We have the performance on those very well established and proven as well. Both airplanes and helicopters are represented very well in X-Plane.” Beta and other companies use simulation-trainers for their test-pilots. Meyer observed, “[The] coolest thing is watching them do multi-player X-Plane, where the test-pilot is flying Alia in the sim; the chase-pilot is flying a helicopter in the sim; and they sim the whole test-flight mission in the multiplayer environment.”

The latest X-Plane edition brackets the 120-kt [220-km/h] Alia-250 between the Cirrus SR20 and the little Robinson R22 helicopter. “This falls somewhere in the middle,” said Mattern, “because you’re balancing a pusher prop for the horizontal movement and the [lift props] for the vertical movement.”

Beta has contracts with UPS, United Therapeutics, and other carriers for the Alia-250 cargo configuration. Mattern envisions the X-Plane 12 simulator inspiring and preparing thousands of new pilots to progress to certified flight training devices. “I believe by creating an orientation ahead of time, they’re going to know where every knob, button, every part of the cockpit is, and what it feels like to fly it before they get into the commercial sim… I want to work with the pilots when they’re at home so they can learn about the aircraft and get them ready for the simulator to advance them through the simulator at a faster pace.”