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A recent panel discussion by the NASA AAM Ecosystem Aircraft Working Group highlighted several issues passenger eVTOL vehicle developers must consider for flyers to feel safe and comfortable.
As Tom Edwards, CTO of Crown Consulting, observed: “Passengers are going to be making a value judgement about the flight experience. Manufacturers want to avoid surprises that might inhibit people wanting to climb on board and fly.”
Key concerns about eVTOL flying identified by viewers of the NASA discussion included ride quality, pitch/roll angles, acceleration, turbulence/gusts, g-forces, noise, climb and descent trajectories, and the impact of turns, avoidance maneuvers and wind.
“If you control a vehicle in multiple axes as opposed to just one, you will find completely different effects of motion,” said Peter Zaal, principal systems architect at NASA Ames’ SimLabs, whose simulation and modelling facilities are researching these and other issues. “It’s really important to simulate the cues, looking at acceleration, vibration and noise all at the same time.”
Different simulators are required to accurately simulate these cues in a way relevant to eVTOL vehicles, Zaal said. “If we want to look at vibrations in cruise we could just [use] a small motion system, but if we are looking at dynamic phases of flight, or the take-off and landing, then we need a simulator with a larger motion capability such as a vertical motion simulator.”
Complexity is added to this research because stimuli characteristics change depending on the vehicle. “We see different jerk criteria for different modes of transportation. Those can be based off of how a person is seated or standing within a vehicle,” Zaal said.
And different simulators “each give different understanding [and] data points in terms of that person’s experience,” noted Shawn Kimmel, director of engineering at QS-2 consultancy. “Numbers don’t fully encapsulate the person’s experience. You need to think about something that might not be measured by the motion sickness dose value; things like dizziness, cold sweats, eye strain.”
Individual eVTOL vehicles’ varying performance and dynamics create corresponding differences in trajectories and airframe behavior. Kimmel said there is “a lot of work to do” to understand more, and Zaal believes building a complete profile of all the motions and vibrations during a flight is “very important to investigate.”
What are manufacturers doing?
Developers in the urban air mobility segment are working on comfort aboard eVTOLs in their own projects.
During the Working Group discussion, Embraer Eve CEO André Stein said his organization would use knowledge of anti-turbulence logics accrued by its parent company during the development of commercial airliner fly-by-wire flight control systems. A static flight simulator will be developed to assess logics for an eVTOL platform, Stein added.
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