Virginia Tech Mid-Atlantic Aviation Partnership test site is collaborating with Virginia-based companies NAVOS Air and UAV Pro, and Textron Systems, to design and flight test an instrument approach system for uncrewed aircraft systems (UAS). The project is one step toward integrating new types of aircraft smoothly alongside existing traffic by adapting strategies with a proven track record of ensuring airspace safety.
NASA’s newest “research roadmap” for developing the technological infrastructure that will be required to manage larger uncrewed aircraft identified a need for tools that can be used by air traffic control to keep these aircraft separated from each other and transition safely between higher and lower altitudes. Flying safely in inclement weather also has been flagged as an area to address. That raises the question of whether traditional instrument procedures could be used by — or adapted for — drones.
Instrument procedures are typically tailored for a particular type of aircraft and airport. In this case, the team focused on approach procedures at the Allen C. Perkinson Blackstone Army Airfield in Blackstone, Virginia, using a Textron Systems fixed-wing Aerosonde UAS. UAV Pro provided airport coordination and operations and safety management for the project flights. The research was funded by the Commonwealth of Virginia through a program designed to promote applied research in autonomous systems and commercialize existing research.
The team began by assessing whether the Aerosonde UAS could theoretically follow the same instrument approach path that a helicopter would use at the Blackstone airport. An extensive analysis determined that the speed, climb rate, and other performance markers the Aerosonde UAS had demonstrated in previous flights indicated that it was capable of flying the helicopter approach. Flight tests verified the conclusions.
“While flying an instrument approach is a new concept with a UAS, it is not much different to the way flight operations happen on a daily basis from the operator’s perspective. The operator relies on flight instruments on a workstation computer similarly to that of a manned cockpit,” said Doug Shick, operation manager of Textron Systems, Air Systems Service and Support Center.
In fact, the team found, instrument approaches for drones can theoretically be more efficient and versatile than traditional ones. “We’ve learned that the approaches can be designed to take advantage of the capabilities of drones,” Jones said.
An instrument approach is typically designed to wind up with pilots in a position where they can safely use visual references to land.
“That’s traditionally something like a 3-degree glide slope, so that they’re coming in nice and shallow as they transition from looking at the instruments out at the runway,” said Jones, a certified airplane and helicopter pilot himself. “They’re not turning or in some type of attitude that could be dangerous.”
To work for conventional aircraft, those long, gradual approaches require clear swaths of airspace uncluttered by obstacles such as trees, tall buildings, or powerlines. That limits the environments where they’re feasible, and totally excludes, for example, urban centers crowded with tall buildings.
But the risk of disorienting a human pilot isn’t an issue for a drone.
“The drone doesn’t use visual references anyway. So the approach can actually be very different. It doesn’t have to be this long shallow descent,” Jones said. “The drone could fly right over the point it’s trying to descend to and do a spiraling turndown, for example, which would be extremely dangerous for a traditional pilot. A place that’s almost in a hole and would never be safe for a traditional pilot could be very safe for a drone.”
Condensing an instrument approach into a smaller volume of airspace means that they can be used in a broader range of environments, potentially including dense urban areas. It also will help decrease congestion in airspace that may need to accommodate more aircraft.
“Part of the goal is to maximize airspace efficiency and safety,” Burton said. “If you tailor the flight procedure design to the aircraft performance profiles, they can be made to use a smaller volume of airspace.
(Image: Aerosonde UAS, Textron Systems)
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