Bell is pursuing the development of its urban air taxi with the same rigor and discipline that it applies to a mainline helicopter program. That was the message from Bell director of innovation Scott Drennan at Heli-Expo in March. Drennan said Bell hopes to have a vehicle to market around 2025.
“We're in a full-blown development program. We have a dedicated team that we are ramping up over the course of this year to about one hundred [team members]. We're focused right now on system-level tests at full scale. We're going to take an approach like we do on our full-scale vehicles. They have dedicated systems and full-size system level tests and then we integrate those across a demonstration platform,” Drennan said.
While Drennan is not prepared to say exactly which technologies Bell will be using on the final vehicle, he believes “all of your best learning occurs as you develop your prototypes and demonstrations” and that “lots of people are proving out their concepts” at this phase of development. He did say that early vehicles likely would rely on some form of hybrid electric propulsion. “We are not revealing the propulsion system right now, but we're doing lots of tests on it as we speak and moving through our design cycle. If we also think it's the right pathway to all electric, we will be ready for an all electric vehicle when the mission makes sense, where we're starting out with that four- to five-place vehicle. So it's going to be larger than the early [two seat] electric vehicles that you've seen come out, and we believe in adding range to the equation by having the hybrid electric units. So our vehicle will start out hybrid electric,” he said.
Drennan thinks Uber has set broad vehicle parameters that most market entrants are following, specifically 5- to 10-minute charging turnaround times, the ability to operate at least 2,000 flight hours per year, and direct operating costs that are at least half of those posed by today's light helicopters. Capital costs must also be dramatically lower, and that means adopting lower cost production techniques such as automotive style cellular manufacturing, Drennan said. But keeping costs low will be challenging, Drennan admits, as right now it appears that urban air taxis will need to meet the same safety standards as light helicopters under FAR Part 27. “Those vertical takeoff pieces of the mission, you'd expect it to revolve around Part 27, but we'll see where that goes,” he said. He also said that it is unlikely that Bell will be incorporating whole aircraft ballistic recovery parachutes into the design, as some competitors are.
“We just don't believe that's a tenable solution. I can't imagine these vehicles coming down in the middle of an urban environment [uncontrolled and] under chutes. While these vehicles will not get the baked-in energy of autorotation that you do with a large rotor, we look at it as an energy problem, and we will provide the energy to come to ground via redundant motors, propellers, and power systems. We want to make sure the public knows our vehicle will be able to handle situations like that,” Drennan said, adding that safety and limited external noise signatures are key to building the required levels of public acceptance and urban airspace access that will make urban air vehicles truly economically viable.
“You've got to make a safe vehicle that flies over all kinds of urban environments. Otherwise you just won't get to the yearly usage rates you want. Realistically, they're going to be much quieter than helicopters. Electric propulsion is going to help with that as will distributed propulsion, because you can bring down your [blade] tip speeds. You can also use techniques like shrouding and phasing of the frequencies that you can't do mechanically. Electric motors can phase at different frequencies and you can change the sounds that are perceived. The tones that we've experienced so far are much different, and they can blend in more easily to the background noise of an urban environment,” he said.