WASHINGTON — In a future war against a technologically advanced peer like China or Russia, U.S. Air Force special operations forces will need aircraft that is faster, more survivable and capable of traversing longer ranges than the aircraft currently available, while still being able to launch from austere locations without a runway.
The answer to the problem, according to Maj. Gen. David A. Harris, the Air Force’s director of innovation and integration, might be found in the nascent high-speed vertical takeoff and lift aircraft being developed by industry.
“If you look at the time and distance problem that [U.S. Indo-Pacific Command] presents to us, I have to be able to get to someplace fast,” he said during an Aug. 24 interview with Defense News.
“Speed is also survivability,” he added. “I want something that can land off of the runway, but yet have enough useful cargo space where I can offload a runway repair kit, fuel, more base defense munitions [or] more armament.”
The Air Force is looking for a high speed vertical takeoff and landing aircraft that can achieve similar speeds to jet aircraft, with systems such as active/passive threat detection and countermeasures that can make it more survivable in a combat environment. The aircraft should also be large enough to rapidly transport cargo and be capable of plugging into the service’s wider battle network.
Longer endurance and the ability to fly long ranges is also a plus.
“[It’s] something that could fly maybe 800 miles,” Harris said. “It’s low visibility, it’s low signature, but it can get in and it can get out.”
High-speed VTOL aircraft technology is still relatively immature, and the Air Force has no program of record to fund the development of such technology.
However, companies like Bell Flight and Lockheed Martin’s Sikorsky have presented concepts to the Air Force that have generated some interest, Harris said.
“There’s a lot of different designs out there,” he said. “We’re still trying to get through and to figure out what’s going to be the most beneficial for us when it comes to the requirements we have to operate and specifically support logistics under attack.”
In August, the service’s innovation hub AFWERX conducted a showcase of 35 high-speed VTOL concepts, with entrants from longtime defense contractors like Bell and newcomers such as Horizon Aircraft.
With that event now over, the companies are waiting to hear whether the service will award money for further development activities.
“We’re working pretty aggressively to prepare for what we believe is the true proof of concept, which is an air vehicle in flight,” said Jeff Nissen, senior manager for advanced technology at Bell Flight. “This is an aircraft that’s doing something that’s never been done before. We feel that that is the aha moment or the critical milestone event to really showcase what this technology can do.”
Longer ranges, tougher adversaries
Special operations forces were often the tip of the spear during the wars in Afghanistan and Iraq, flying in on AC-130 gunships or CV-22 Ospreys during the dark of night, inserting troops to conduct covert operations, providing close air support to troops on the ground, or rescuing an injured servicemember stuck in an austere location.
“Coming out of the war on terror, we had a bias toward action,” said Harris, who served as a master navigator for Air Force Special Operations Command onboard AC-130s and MC-130s. “At the end of the day, you’re still going to kill terrorists on the battlefield.”
But with a potential adversary like China, AFSOC will face an a much more advanced foe with long-range weaponry capable of disrupting operations at most of the U.S. Air Force’s major airbases in the Asia-Pacific and holding most of its current aircraft inventory at a distance.
High speed VTOL technology could enable special forces to conduct missions such as personnel recovery and aeromedical evacuation, as well as to quietly insert and retrieve special operators, he said.
The technology could also be key outside the SOF community for implementing the Air Force’s “agile combat employment” concept, which calls for small packages of aircraft to be able to distribute to austere airfields inside friendly nations, where they can refuel, reload weapons and take off again.
“At some point, you run out of fuel, and at some point, you run out of munitions, and you have to be able to go into that contested environment to resupply,” Harris said. “And if your runways are bombed, or cratered, and you can’t land things in there, how do you do it?”
In early August, Bell unveiled conceptual designs for a high-speed VTOL platform, which could come in light, medium and heavy-lift variants. The company hopes to develop a rotorcraft that can fly at more than 400 knot speeds — far beyond what tiltrotor technology can currently accomplish — and achieve a mission radius of 500 miles.
Survivability is also a key characteristic of the design concept, and it’s attained through concealing the rotor blades after the aircraft takes off, folding them inward, and relying on jet thrust when flying forward, Nissen said.
“If you look at our aircraft in its cruise mode configuration, you won’t see any spinning rotors and that’s what predominantly drives the radar cross section of a rotorcraft, is the rotor disc,” Nissen said. “Look at that aircraft concept in its jet mode configuration. It sure does look a lot like a jet. That means it will have the signature like a jet in radar.”
Bell has begun doing risk reduction on what is sees as the three main areas for technology development: the vertical lift component, flight controls and engine technology.
Propulsion is particularly challenging due to the requirements to generate shaft horsepower for the rotor system and then transition to jet thrust to enable high speeds and high cruise altitudes. An flight demonstrator for the light variant would use two different commercial engines to achieve that capability, Nissen said.
“Other variants, you might be able to combine that into a single engine,” he said. “There’s work that we’ve been doing — especially with our supplier Rolls Royce Libertyworks — on what is called a convertible engine that has both the ability to generate shaft horsepower as well as turbofan thrust.”
While Harris mentioned Sikorsky has also presented information on its future rotorcraft concepts to the Air Force, the company declined to provide further information.
“While it’s too early to comment on specific conversations and/or possible solutions, we look forward to working with the U.S. Air Force as it refines its needs,” Jay Macklin, Sikorsky’s business development director for future vertical lift, said in a statement.
Aerospace startups and other nontraditional vendors have also shown interest in working with the Air Force on high-speed VTOL.
AFWERX’s showcase event included entrants such as Horizon Aircraft’s Cavorite X5 — which the company claims will fly at speeds of 275 miles per hour over 340 mile ranges — and Jaunt Air Mobility’s hybrid-electric MAV55.
Other contenders include a Northrop Grumman-Jetoptera team, which collaborated on a concept that will use “adaptive fluidic propulsion” to create an aircraft that can fly like a jet and hover like a helicopter, all while using less fuel.
Ultimately, how fast high-speed VTOL technology can be matured will depend on whether the Air Force is ready to buy into a development program, Nissen said.
“We’ve developed plans to demonstrate this quickly and create an opportunity to field it quickly,” he said. “But it’s really going to be driven by a future, to-be-disclosed acquisition and program of record timeline.”
Valerie Insinna is Defense News' air warfare reporter. She previously worked the Navy/congressional beats for Defense Daily, which followed almost three years as a staff writer for National Defense Magazine. Prior to that, she worked as an editorial assistant for the Tokyo Shimbun’s Washington bureau.