Since the Wright Brothers first developed wing warping, flight controls have been subject to mechanical constraints. Their design has been less about what is optimal for the pilot and more about what is physically possible — which particular arrangement of rods, wires, and linkages can successfully translate the pilot’s gestures in the cockpit to desired motion of the control surfaces.
With the advent of fly-by-wire systems — which replace traditional manual flight controls with an electronic interface — that’s no longer the case. And while most fly-by-wire systems to date have been designed to minimize the cost of transitioning conventionally trained pilots, for the next generation of eVTOL aircraft, that won’t be such a priority. The designers of most of these aircraft are eventually aiming for full autonomy, but recognize that until autonomous aircraft gain regulatory and public acceptance they’ll need human pilots — potentially tens of thousands of them. Flight training today is slow and expensive, so if aircraft can be redesigned to be radically easier to fly, the savings in training new pilots will justify the departure from convention.
That’s the logic behind one of the highest-profile efforts to rethink flight control design, Bell’s Future Flight Controls program. Since debuting the initiative at the CES 2019 trade show in Las Vegas, Nevada, in January, Bell has put thousands of people in VTOL flight simulators with three different control configurations. By collecting data on how they interact with the simulators, Bell hopes to gain insights into how to design novel flight control systems that are simple and intuitive for more people to use.
“We don’t really have a great idea of what the general public has in terms of experience and abilities that would allow them to control an aircraft,” explained Bell experimental test pilot Jim Gibson, a former U.S. Marine Corps V-22 pilot who is leading the program. “We’re looking to see what kinds of skill sets we can capitalize on . . . and looking to ask the participants what actions are intuitive to them.”
For the initial phase of the study, Bell developed two unconventional control systems. One of these has two control inceptors: a joystick in the right hand for lateral and longitudinal control, and a power control in the left hand, with auto-yaw functioning behind the scenes. The other has just a single inceptor for the right hand, which can be twisted to command yaw and has a thumb control for power. The third simulator in the study has conventional helicopter controls: cyclic, collective, and yaw pedals.
As they enter each sim, participants don virtual reality goggles, then use the controls to guide their vehicle down the Las Vegas Strip, following a line of glowing green balls that requires them to navigate in three dimensions. The goal is to follow the defined path as closely as possible while also reaching the end of the Strip before a specified time limit. It is essentially a video game, and Bell has been very consciously leveraging its entertainment value at events including CES and the South by Southwest (SXSW) conference in Austin, Texas, in March.
Even at this early stage, however, Bell has been collecting extensive data on user experiences by sampling 75 parameters at a rate of 20 times per second. Users are also asked to complete exit surveys that evaluate their perceived workload and performance using a modified version of the Bedford workload scale used by test pilots. Already, there have been some surprises.
“The most interesting thing we’ve learned during the research study is people believed they performed well on one particular sim when in fact they actually performed better on a different configuration,” said Gibson, explaining that most people tend to do best with the single inceptor. Moreover, experienced aviators haven’t necessarily had an advantage in the sims: “Trained pilots didn’t always perform to the level that they expected to, and that was very entertaining for us as we watched it,” he said.
Phase two of the study, which is expected to start later this year, will involve further refinement of the flight controls and more rigorous data collection at a higher level of fidelity. “That’s where the real valuable data will come,” said Gibson, noting that he would like to expand this testing to as broad of a cross-section of the population as possible, ideally matching the study’s data set to U.S. census data. The second phase of the study will also explore how much of the pilot’s workload can be successfully automated.
In phase three, which is not yet associated with a firm timeline, Bell will incorporate advanced cueing and artificial intelligence to arrive at an ideal model for simplified vehicle operations — the model that will be necessary to recruit and train thousands of new pilots for urban air taxi operations. Reducing the training burden for these pilots will be an important goal, but just as critical will be determining how to task their attention in ways that meaningfully contribute to the safety of flight; after all, no one wants their pilot watching TV shows on their mobile phone when they should be flying. Consequently, the third phase will also involve more line-oriented observation, looking at how pilots actually behave on operational flights. “I think some of the things we’ll see in our research is how to keep them mentally engaged,” said Gibson.
While Bell is pursuing its Future Flight Controls program in the context of urban air mobility, it sees potential to apply its findings to conventional aircraft designs, too. According to Gibson, “Fly-by-wire is really what allows all this to happen. . . . We really see this as applicable to all of our fly-by-wire vehicles at Bell.” Not surprisingly, the Future Flight Controls program has also been gaining insights from the development of the Bell 525, which is on track to be certified by the U.S. Federal Aviation Administration (FAA) as the first commercial fly-by-wire helicopter.
Gibson pointed out that the Bell 525 already incorporates some advanced features that reduce the demands on the pilot, such as the ability to automatically enter autorotation in response to a dual engine failure. These, he said, are not speculative capabilities, but “proven technologies that are approved by the FAA.” Which means that even conventional aircraft are evolving to better accommodate human capabilities and limitations, rather than forcing humans to adapt to the capabilities and limitations of their machines.