Military, Products, Services

The UAV Revolution: Rotorcraft UAVs

By By Richard Whittle | August 1, 2009
Send Feedback

Unmanned aerial vehicles of the fixed-wing variety have proven their worth to the military beyond doubt during the past 15 years or so, especially since U.S. troops went to war in Afghanistan and Iraq. Now, with a lag time less dramatic but still reminiscent of the four-decade gap between the dawn of powered flight and the debut of the first useful helicopters, interest in rotorcraft UAVs is clearly taking off.

"In a perfect world, I would have the capability of a Reaper or a Predator but not be tied to a runway," said Maj. Thomas Heffern, whose job at the U.S. Marine Corps Combat Development Center is to study how the Corps can best exploit the explosion in UAV technology. Being "runway independent," Heffern noted, means "vertical lift."

The U.S. Air Force’s fixed-wing MQ-1 Predator and newer MQ-9 Reaper, perhaps the most famous UAVs in the U.S. military inventory, have become technological stars in the wars in Afghanistan and Iraq. The Defense Department, especially under Secretary Robert Gates, can’t seem to get enough of them. Equipped with reconnaissance gear and weapons, Predator and Reaper provide military commanders — and the CIA, reportedly — the ability to search out and track insurgents and terrorists around the clock and attack them with missiles and bombs before they know what’s about to hit them.


A UAV that could do all that but take off and land anywhere, rather than relying on runways, would be a hot item, Heffern ventured. "Whoever can crack the code on that, that’s going to be interesting to an expeditionary, amphibious organization" like the Marine Corps.

A Brief Background

Small observation helicopter UAVs, such as Japanese firm Yamaha Motor Co.’s RMAX, have been flying industrial missions for years, and the Defense Advanced Research Projects Agency (DARPA) has been working just as long on advanced UAV rotorcraft concepts for the U.S. military. DARPA has studied concepts as futuristic as an unmanned rotorcraft gunship that could fly as a "wingman" for manned U.S. Army helicopters, whose pilots would control the UAV by voice command.

Rotorcraft UAVs aren’t quite there yet, and may not be for a while, but defense contractors are increasingly busy working on medium-sized helicopter UAVs that can conduct intelligence, surveillance and reconnaissance (ISR), carry air-to-ground weapons, and perform a range of other missions, from serving as communications nodes to carrying cargo. In the not-so-distant future, vertical lift UAVs may even perform combat search and rescue operations, some experts predict.

Vertical lift UAVs and concepts for them come in all sizes, and the military is seriously interested. The U.S. Navy, as the service that leads Defense Department Joint Explosive Ordinance Disposal programs, gave Honeywell a contract in 2008 for the company’s Tarantula Hawk, a video camera-equipped micro UAV that can fit into a backpack. The T-Hawk, which looks more like an appliance than an aircraft, will be used by bomb disposal teams to hover over and examine suspected bombs before the teams set about defusing them. Under the $65-million contract, Honeywell will provide 180 T-Hawks, 90 ground control units, training, spare parts and other support.

The military is eager to start using larger vertical lift UAVs, too. The Navy earlier this year conducted sea trials with Northrop Grumman Corp.’s MQ-8B Fire Scout, a 30-foot-long unmanned helicopter, and plans to deploy Fire Scout aboard ships as an ISR and targeting aircraft. The service scheduled operational test and evaluation of the Fire Scout this summer.

The Navy eventually plans to arm Fire Scout as well, but cargo transport may be the next military mission vertical lift UAVs take on. The Office of Naval Research asked industry this past January to propose cargo-carrying vertical lift UAVs for the Marine Corps. "The ideal candidate," the ONR said, "would be a shipboard compatible, high speed VTOL platform that is autonomous, affordable, rugged and reliable."

The agency said it was interested in UAVs that might be fielded within five, 10 or 15 years. The ideal long-term solution, it added, would be a vertical lift UAV that could carry 1,600 pounds of cargo to four separate locations at speeds of 250 knots or better and to a radius in excess of 285 nautical miles, or 328 statute miles. Those distances and speeds would rule out a UAV that flew like a conventional helicopter, and such goals may challenge industry for years to come. With thousands of additional Marines being sent to Afghanistan this year, the Corps decided the time had come to buy an unmanned helicopter for resupply missions.

Getting supplies to remote Forward Operating Bases, or FOBs, in Afghanistan has proven a challenge for all armed services deployed to that rugged country. "There’s no doubt that this is the most difficult terrain that I’ve ever seen in 33 years to actually walk across, operate in, or to fight in," Army Maj. Gen. Jeffrey Schloesser, commander of Combined Joint Task Force 101 in Afghanistan, said in a recent teleconference with Pentagon reporters. Schloesser’s command, he noted, leases donkeys from local Afghans to get supplies up some difficult mountain peaks.


For those reasons, the Marine Corps War- fighting Laboratory at Quantico Marine Base, Va., issued a Request for Proposals on June 1 for what it calls the Immediate Cargo Unmanned Aerial System. The requirements make it clear that the winner will be an unmanned helicopter.

The winning UAV will have to deliver at least 10,000 pounds and ideally 20,000 pounds of cargo within 24 hours to a round-trip distance of 150 nautical miles, or 172.5 statute miles. It will have to fly at 15,000 feet density altitude and be able to hover at 12,000 feet density altitude either in or out of ground effect. How many trips the UAV might make to deliver all that cargo within the 24-hour time limit wasn’t specified, but the RFP said the "smallest element in a cargo package shall be equivalent to at least a standard wood pallet" measuring 48 x 40 inches loaded with at least 750 pounds of cargo and preferably 1,000 pounds. The aircraft also will have to operate autonomously but be equipped to let Marines on the ground control it "beyond line-of-sight" when delivering supplies, meaning it will need to carry a satellite communications dish.

The goal of the program is to "get Marines off the road" by delivering supplies to small units by air instead of by truck convoy, explained the Combat Development Center’s Heffern, who had no role in evaluating bids but has worked on the resupply problem. Given the demand for helicopters in Afghanistan already, using a UAV for such jobs also should ease the burden on manned Marine Corps rotorcraft that can be used to deliver supplies but are needed for a variety of other missions, too.

"There also could be some other areas where it may potentially be a game-changer," Heffern said. "There may be situations where the risk of ground fire or weather may be so elevated that we’re unable to take manned aviation into particular areas." The Marines "may be more willing to assume that risk with an unmanned system," he continued. The Marines got at least three responses to their RFP, with major differences among the entries.


Lockheed Martin Corp.’s Systems Integration division at Owego, N.Y., partnered with Kaman Helicopters of Bloomfield, Conn., to offer the beefiest entry, an "optionally manned" version of Kaman’s K-MAX. The manned version of the K-MAX has been used since the 1990s for logging and other medium-lift jobs, but Kaman has sold only a few. The K-MAX’s empty weight is 6,000 pounds, and with its two intermeshing "synchropter" rotors, which cancel out torque, and no tail rotor to bleed power from its single engine, Kaman boasts that the aircraft can lift its own weight in payload.


Boeing Co. also bid on the Marine Corps contract with its A160T Hummingbird, a 35-foot-long helicopter UAV whose claim to fame up until now has been its ability to stay aloft for long periods — 18.7 hours in a 2008 test. The Hummingbird was developed by the ever-inventive Abe Karem, who also devised the fixed-wing UAV that evolved into the Predator. The Hummingbird uses Karem’s rigid Optimum Speed Rotor, whose revolutions per minute can be adjusted for maximum efficiency at different altitudes and cruise speeds. DARPA and the Army funded the development work and Boeing took over Hummingbird when it bought Frontier Systems Inc. in 2004. Designed for endurance, the Hummingbird is light — about 2,500 pounds empty — and according to Boeing can carry up to 2,500 pounds of cargo in addition to its fuel.

Game On

Going into the competition, Lockheed and Kaman officials were confident the K-MAX’s superior lifting ability would give their entry the edge needed to win the Marine Corps contract. "They require that you have to deliver 20,000 pounds of cargo over a 24-hour window," said Dan Spoor, vice president for rotary wing programs at Lockheed’s Owego division. "That’s the key requirement. We can handily meet that requirement." The K-MAX also has a carousel cargo hook that allows it to carry four separate loads and drop them at four locations, said Salvatore Bordonaro, president of Kaman Helicopters. "We actually call it the ‘aerial truck,’" Bordonaro explained.

The companies tested a K-MAX flying autonomously in June 2008 for the Army, whose Aviation and Missile Research, Development and Engineering Center at Redstone Arsenal, Ala., is very interested in the optionally manned K-MAX, though that service has no plans as yet to buy a helicopter UAV for cargo hauling. The Army tests were flown with a "safety pilot" aboard because Federal Aviation Administration regulations severely limit unmanned aircraft flights in domestic airspace.

In those tests, Lockheed and Kaman proved that an operator on the ground using a ruggedized laptop computer with a joystick could control the K-MAX through a data link. Team K-MAX, as the companies are calling their partnership, also showed that the aircraft could take off autonomously, pick up and deliver a 3,000-pound sling load, and change its preplanned route in flight. For the Marine Corps competition, Lockheed is installing a satellite communications system in the K-MAX to allow ground operators to control the aircraft when it gets beyond line of sight.

A typical mission for the Marines, Spoor said, might be to deliver food, water, ammunition and medical supplies to a FOB located 75 miles or so from a hub base. A ground operator at the hub would put the aircraft into a hover at around 50 feet and hold it there while Marines hooked cargo loads to the K-MAX. The aircraft then would fly a preprogrammed route autonomously at 12,000 to 15,000 feet to one or more FOBs. At each FOB, a Marine on the ground with a handheld control station would take control of the K-MAX as it approached, put it into a hover, release one or more of the cargo loads, then return control to the aircraft’s mission management computer.

"They can proceed back to other FOBs or to the hub with a series of ground controllers operating it along the way," Spoor said. "It has the full capability to be flown unmanned autonomously," he added, but because the K-MAX has a cockpit, "if you want to ferry it between locations with a pilot, you could do that. You kind of get the best of both worlds."

Boeing officials said they were confident their Hummingbird could do what the Marine Corps wants. The requirement, observed Boeing’s Mike Lavorando, A160T deputy program manager, breaks down to delivering at least 2,500 pounds and ideally 5,000 pounds of cargo every six hours, and the 150-nautical-mile round-trip requirement is no problem for an aircraft that has shown it can fly literally all day and much of the night, on one tank of gas.

The Hummingbird, Lavorando added, offers its own advantages. Should the Marines decide they want their UAV to carry cargo faster than 70 – 80 knots, the top speed most any helicopter would be able to fly hauling a sling load, he said, the A160T can be fitted with an aerodynamic cargo pod that would let it fly as fast as 140 knots. Lavorando said the company was still designing a system to carry sling loads but already had flown the A160T with a cargo pod, though not to 140 knots. A 40 x 48-inch pallet loaded with 750 pounds of cargo won’t fit into the pod, but in principle "the Hummingbird offers the faster podded resupply capability," Lavorando said. "Getting cargo delivered in half the time, basically, that you could do with a sling load would be a big advantage."

The Hummingbird has flown a mission profile such as the Marine Corps wants autonomously, but as the competition began, Boeing was still working to equip it with handheld and beyond line-of-sight control systems. John Groenenboom, Boeing’s A160T program manager, said the company would meet the beyond line-of-sight requirement by attaching a satellite dish to a static mast above the Hummingbird’s rotor.

Lavorando said the Hummingbird could have an edge in the competition because it was designed from the ground up as a UAV. Boeing has been able to flight test the Hummingbird in the high desert near Victorville, Calif., under an authorization given to DARPA by the FAA. "All the development done has been unmanned and all the lessons learned from that have been incorporated into the aircraft and into the control system," Lavorando said. "Starting with a manned platform and trying to unman it is very difficult."

The Hummingbird also would offer the Marines more than just a way to get cargo to remote FOBs, he added, though supply delivery is all the Corps is officially seeking. The aircraft has internal storage capacity that could be used to carry other payloads, such as sensors and communications gear, Lavorando said, "So it could be conducting a resupply mission, at the same time providing a communications relay capability for the troops, and it could be conducting ISR missions while it’s hauling cargo."

Beyond that, the U.S. Special Operations Command has tested a Hummingbird carrying a foliage-penetrating radar called FORESTER to detect ground troops moving beneath jungle canopy, confirmed Maj. Wesley Ticer, a spokesman for the command. The radar works best when used from a hovering platform, which enables it to distinguish the speed difference between the hovering aircraft and the troops as they move on foot.

Boeing’s Groenenboom said the company also has begun experimenting on its own with arming the A160T by flying it with three dummy Hellfire missiles attached to one of two stub wings added to the fuselage. "That is one of the visions our customer has eventually" for helicopter UAVs, Groenenboom said.

Fire Scout

With the Marine Corps still evaluating the bids, Northrop Grumman declined to release any details about how its Fire Scout could meet the program’s requirements. In an e-mailed response to questions from Rotor & Wing, Mike Fuqua, business development manager for Fire Scout, would say only that the aircraft can "carry a significant amount of cargo" in "pods that have been designed for this increased requirement." How much cargo the Fire Scout could carry, he added, would depend on time, speed and "environmentals."

Fuqua also noted that, in addition to being chosen by the Navy as a vertical lift UAV for ISR missions at sea, Fire Scout was the Army’s choice as a helicopter UAV to perform ISR, targeting and communications relay missions under that service’s Future Combat Systems program. The Defense Department ordered the Army to cancel Future Combat Systems on June 24, but Fuqua — commenting before that — said the fact that Fire Scout had been "a mature program of record in two services" should make it "the obvious choice" for the Marines.

A Version of the AH-6

Another arm of Boeing, its Rotorcraft Systems unit in Mesa, Ariz., has been developing an unmanned version of the company’s AH-6 Little Bird helicopter, whose manned and armed version is flown by the Army’s elite 160th Special Operations Aviation Regiment. Boeing considered but decided against entering the AH-6U, as the unmanned Little Bird is designated, in the competition for the Marine Corps cargo resupply contract.

"It was the company’s decision to bid only one platform, and then the decision was made that the platform to be bid was the A160T," said Boeing Rotorcraft Systems spokeswoman Carole Thompson.

Even so, Dino Cerchie, Unmanned Little Bird program manager for Boeing, said it wasn’t inconceivable that the Marines could decide later that the AH-6U would be a good choice for cargo resupply missions. "We’ve been working with the Marine Corps Warfighting Laboratory, helping them develop their CONOPS (concept of operations) for precision delivery and resupply," Cerchie said. "They’ve already seen us demonstrate this capability."

Boeing has been developing the unmanned Little Bird since 2003, and in recent years has demonstrated various UAV missions, such as communications relay using a high bandwidth link with phased array antennas. That gave the AH-6U the ability to communicate with multiple aircraft and ground units simultaneously, Cerchie said. The unmanned Little Bird, which weighs just under 2,000 pounds empty, has carried cargo loads up to 870 pounds and could carry as much as 2,000 pounds, he added. The company also has studied arming the unmanned Little Bird with missiles, rockets and even.50-caliber machine guns. "In 2005 – 2006, since it was such a new concept, we had a pretty broadband approach to demonstrating anything and everything to everyone," Cerchie explained.

Since then, under an Army contract, Boeing has been using the unmanned Little Bird in AH-64D Apache Block III tests as a stand-in for the Sky Warrior, a new Army version of the General Atomics Aeronautical Systems fixed-wing Predator flown by the Air Force. Boeing’s Apache Block III gunship helicopter is being equipped to allow its crew to control Sky Warrior and the UAV’s sensors and communications relay gear in flight. Sky Warrior isn’t far enough along to be used in tests of that capability, so Boeing has flown the unmanned Little Bird as a "surrogate."

"I think all current and future variants of all manned (military) aircraft are going to have some level of UAV interoperability," Cerchie said. "The Apache, being the cornerstone, is probably going to have a little more than most."

Other Contenders

American companies are not alone in moving to cash in on vertical lift UAVs. Schiebel Group of Vienna, Austria flew its little Camcopter S-100 unmanned helicopter at Le Bourget this year — the first time a UAV had flown in that storied venue, according to a company news release. Other companies playing include Saab of Sweden and Swiss UAV of Niederdorf, Switzerland, which in May announced that they would collaborate in developing and marketing unmanned helicopters.

"VTOL UAVs are the future," said VTOL historian and vertical flight consultant Michael Hirschberg. "It’s not a matter of ‘if,’ it’s a matter of ‘when.’"

Receive the latest rotorcraft news right to your inbox