Sikorsky Demos Autonomy As Key To Its Urban Air Vision
Sikorsky is declaring its interest in urban air mobility (UAM) but stopping well short of unveiling a vehicle designed specifically for the nascent market. Technologies it has been developing for the past decade are maturing to support urban air taxis, but the issue that must be tackled first, the company believes, is developing the infrastructure to provide a travel experience the public will embrace.
Adoption is a key challenge facing UAM and, in addition to showcasing technologies it thinks are key to enabling safe and efficient urban air transport, Sikorsky is presenting its vision of the passenger experience at the Helicopter Association International’s Heli-Expo show in Atlanta on March 5-7. In parallel, the company provided Aviation Week with unique insight into the technology behind the vision.
Sikorsky likens its envisioned travel experience to a three-dimensional elevator, with the passenger simply pushing a button to select their destination and a multimodal transport network deciding how best to get them there. To flesh out its vision, the Lockheed Martin-owned helicopter manufacturer is working with former United Technologies sister company Otis Elevator and Richard Branson’s The Spaceship Co., manufacturer of Virgin Galactic’s suborbital-tourism SpaceShipTwo.
A decade ago, Sikorsky launched a research plan focused on three areas it saw as fundamental to the future of vertical lift: speed, autonomy and intelligence. The speed initiative has resulted in the S-97 Raider and Sikorsky Boeing SB-1 Defiant demonstrators. The intelligence pillar is producing advanced analytical tools now being used to improve support for its S-76 and S-92 commercial helicopters.
The Matrix Technologies autonomy program is developing certifiable capabilities that Sikorsky plans to introduce incrementally across its commercial and military product lines. Along with advanced analytics and electric propulsion for future vertical-takeoff-and-landing (VTOL) vehicles, the company sees autonomy as foundational to enabling safe, reliable and affordable urban air mobility on a large scale.
The autonomy effort is reaching a crucial stage, as Sikorsky works with potential customers on how to begin deploying the capabilities being developed. The technology is being used in an optionally piloted UH-60A Black Hawk testbed that is expected to fly this spring, while the U.S. Army is installing the Matrix kit in a UH-60M for flight testing this year.
The technology has matured to the point where the company is allowing people other than its test pilots—including this non-pilot Aviation Week editor—to fly its Matrix testbed, the S-76 Sikorsky Autonomy Research Aircraft (SARA). The current development effort with SARA is focused on refining the human-machine interface (HMI) that enables pilots and other operators to interact with Matrix.
“So far, only experienced pilots have interacted with the autonomy. But the level of maturity and HMI now enables us to put inexperienced people on board,” says Chris Van Buiten, vice president of the Sikorsky Innovations research organization. Matrix enables the 12,000-lb. SARA to be flown, by pilots and non-pilots, via a tablet computer or control inceptors after little more than 30 min. of training.
“The intent always was to have people on board the aircraft operate it in a fundamentally different way and to move beyond sticks and pedals,” he says. In a UAM vehicle, Matrix would enable a passenger to push a button and fly fixed routes between fixed locations. In other vertical-lift applications, autonomy could enable a helicopter to be operated with two, one or even zero crew, depending on the mission.
Matrix is focused on safety and on reducing controlled flight into terrain and crew-related issues that account for three-quarters of helicopter accidents. “Rule No. 1 is not to hit stuff,” says Igor Cherepinsky, chief engineer for autonomy programs. But in addition to preventing the vehicle from colliding with obstacles, the autonomy system reduces workload on the crew throughout a mission.
“We give them more tools to be more successful,” says Van Buiten. “We shift the burden of flying the aircraft onto the machine and let them think about the full context of the mission.” On a demanding emergency medical mission, for example, the autonomy will fly the aircraft while the crew determines the best place to land next to the ambulance or which hospital to head to, he says.
“If we earn the right to go to single pilot it will be very valuable,” he says, because of the growing helicopter pilot shortage. Van Buiten also sees “a real opportunity for performance” with autonomy. A single pilot would allow an additional passenger to be carried, and the accuracy and repeatability with which autonomy performs procedures would increase payloads on Category A takeoffs.
“Autonomy fundamentally changes safety, reduces cost, increases flexibility and enhances performance,” says Van Buiten. Autonomy is also key to making the interface with urban air mobility “as simple as an elevator.” The passenger will not have to decide the vehicle’s route or altitude, but “just hit the button that says Rockefeller Center.”
For Sikorsky, autonomy is also a key to enabling its vision of UAM “at the right level of safety,” he says. At scale, air taxis around the world could be logging 150 million flight hours a year. At the accident rate now achieved by the S-92, around one per 1 million flight hours, that would mean an unacceptably high 150 accidents a year. “We need to be 100 times safer than the S-92,” says Van Buiten.
The ability of the autonomy system to perceive and react to the world around it is essential to improving safety. At the core of Matrix is a world model built from digital terrain and obstacle databases. This is updated in real time with data from lidar and camera sensors. As the system plans and executes flight trajectories, it is always aware of any potential hazards and will not permit the helicopter to fly into an obstacle, even in response to a pilot command.
The S-76 SARA is a flying laboratory. The helicopter has been converted to an optionally piloted vehicle (OPV) by installing a fly-by-wire system with servos and clutches that drive the existing mechanical flight controls in response to commands from the Matrix autonomy management system. A safety pilot is always on board and can disengage the OPV system if needed to take back mechanical control.
The servos, triple digital flight-control computers and triple GPS/inertial navigation units, sensor pre-processors, a compact supercomputer and other equipment are mounted in the cabin. In the cockpit, the pilot in the right seat has a knee-mounted tablet as well as left and right control inceptors. The safety pilot in the left seat has a door-mounted tablet and conventional controls but does not have the inceptors.
Aviation Week was invited in late February to fly the SARA. The flight with Mark Ward, chief pilot for Sikorsky’s Stratford, Connecticut, flight-test center, was preceded by a short training session in a simple simulator inside the modified recreational vehicle that is the Matrix ground control station.
Matrix is a research project, and the user interface is a work in progress, says Cherepinsky, but Sikorsky has reached the stage where it is working with commercial and military customers to evolve interfaces specific to how they operate. “The whole point is reduction in workload and moving from piloting to mission management by taking care of the things that take up the pilot’s bandwidth,” he says.
The autonomy system is normally controlled via the touch-screen tablet. Its display shows an image of the area around the helicopter. This can be two- or three-dimensional, and during flight it continuously shows terrain close to the aircraft and potential landing zones detected by the lidar system.
Tapping a “Fly To” icon on the screen brings up three connected circles. Using these “super Mickey Mouse ears,” the operator can enter an airspeed, altitude and heading and move crosshairs over the map image to set a location. These become fly-to goals for the autonomy system.
Set an altitude and heading, tap “Execute,” and SARA will lift off autonomously and come to the hover pointing in the desired direction. Enter a sequence of goals to define a flight plan, and the autonomy system will create and execute a trajectory that avoids known hazards, replanning on the fly if the three lidars constantly scanning a volume around the helicopter detect any obstacle not in the database.
For our flight, the autonomous takeoff to hover was loaded by the ground station, demonstrating the ability of the Matrix system to accept inputs from anyone on the network. This can be the pilot, copilot, a loadmaster in the rear cabin or someone on the ground guiding the helicopter to pick up a load. Once in the hover, Ward asked me to maneuver the helicopter over the airfield using the inceptors.
The second mode of interacting with Matrix, these controls mimic the functions of the conventional helicopter cyclic stick, collective lever and anti-torque pedals, but work in a fundamentally different way. Instead of pilot commands being sent directly to the fly-by-wire computers, they go to the autonomy system, where they become voting inputs to the motion-planning algorithms.
The inceptors give the pilot the ability to change the planned trajectory, perhaps to deviate from the planned flight to look at something of interest, but they do it through the autonomy system, so the modified flightpath always avoids obstacles and keeps the aircraft safe. Release the inceptor, and the helicopter will safely return to the trajectory required to meet its original goals.
The right-hand inceptor is a small sidestick. In the hover, moving it side to side commands SARA to translate left or right; fore and aft makes the helicopter move forward or backward. In forward flight, sideways movement commands a banked turn; fore-aft increases or decreases speed.
The left-hand inceptor is a throttle-like grip: Pull back, and the helicopter climbs; push forward, and it descends. On the right edge of the grip is a thumbwheel: In the hover, this is rotated forward to turn left and backward to turn right. In forward flight, it is disabled.
With SARA in a stable hover, I played with the 3D-printed inceptors and quickly found I could easily move the helicopter around the airfield, looking only at a small display showing the target and actual groundspeed, altitude and heading to achieve the task.
After I repositioned us into wind, Ward asked the ground station to construct a departure flight plan. This would take us north along a river. Once the plan was uploaded, I hit “Execute” on the tablet, and SARA accelerated into a climb away from the airfield.
A modified S-76B, SARA has only partial fly-by-wire, and its safety system puts tight limits on the servo rates. As we repositioned over the airfield and again as we climbed out, gusts pushed the rates past the limits and the OPV system disengaged, Ward briefly taking back control before reengaging the servos. The optionally piloted Black Hawk is fully fly-by-wire and more robust, Ward says.
But the unexpected disengagements did show two things: that the system is safe and the transition between OPV and manual control is smooth, something on which the team has had to work, Ward says.
The Matrix system generates an idealized flight trajectory that the real helicopter strives to follow. This allows development of an autonomy system that is agnostic to the platform, Cherepinsky says, allowing the same algorithms to be used with different types of aircraft.
This was apparent during the preflight simulation training, where the helicopter’s flightpath could be seen to be following as closely as possible a “rabbit” that moved along the ribbon in space representing the ideal trajectory generated by the Matrix system.
Under DARPA’s Alias program, Sikorsky demonstrated the technology could fly both the rotary-wing S-76 SARA and fixed-wing Cessna Caravan, Ward simply carrying his tablet between the two Matrix-equipped aircraft. The system is being transitioned to the UH-60 under Phase 3 of Alias.
After the autonomy system had taken us north of the airfield to about 2,500 ft. at 80 kt., Ward told me to select and circle a landmark using the inceptors. Orbiting a point on the ground is normally a relatively high-workload piloting task, he says, but SARA’s control system made it surprisingly easy. There was no apparent concern that I would exceed any of the S-76’s limits in my ignorance as I increased bank angle to tighten the circle, the autonomy system keeping the aircraft safe.
An approach flight plan was then uploaded and executed, and we headed back to the airfield. It was still gusty, and Ward was poised on the controls in case of an OPV disengagement, but SARA successfully held to the inbound path following the river, then executed a surprisingly smooth and precise approach to the hover, then a gentle landing, all autonomously.
Sikorsky’s original “2-1-0” crew concept for autonomy will be achieved with the two optionally piloted Black Hawks in the graduation demonstration under Alias. “Two crew will fly highly augmented, then one will get off, and finally the last crewmember will get out and turn the switch to 0,” says Van Buiten.
“In parallel, we are working on commercial certification. It will be ‘crawl, walk, run,’” he says. “Day 1 will not be a zero-pilot S-92 with 19 people on board. But there will be a lot of functionality in there that we will turn on as we earn the right to with regulators and operators.”
Rigorously certified, high-integrity autonomy software is one key to Sikorsky’s UAM vision. Another is the simplicity and redundancy of electric propulsion. Sikorsky built an electric helicopter demonstrator, the Firefly, in 2010-11, but it never flew because available batteries enabled only a short flight time. But the company set “tripwires on how industry would have to develop to get us interested again,” says Jonathan Hartman, disruptive technologies lead for Sikorsky Innovations.
A third piece of Sikorsky’s vision is the artificial-intelligence-driven prognostic maintenance capability the company is developing and fielding to support the S-76 and S-92. By applying advanced analytics to data downloaded from aircraft, Sikorsky’s Customer Care Center in Trumbull, Connecticut, has gained approval to extend the lives of some parts based on how they are being used. The ultimate goal is to manage parts based on a “health bar,” not a life limit, and an advanced health and usage monitoring system will be part of the Matrix offering. It also will be a key to safe, high-utilization UAM operations.
For now, Sikorsky’s UAM vision features the S-76, already being used for urban on-demand service in New York. “The long-term vision of thousands of vehicles will need to see a change in aircraft. But the UAM mission is happening today, and we need to find ways to expand it,” says Hartman. “It is easy to look at this as a technological challenge, but it is fundamentally about adoption. Until we crack that code, all these [electric VTOL] development programs could be academic exercises.”
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