Defense Media Network

Straight Up, Hands Off

Vertical takeoff unmanned aircraft systems still aim to fill niche warfighting requirements on land and at sea

Though vertical takeoff unmanned aircraft systems (VTUASs) cannot match the endurance of fixed-wing unmanned aircraft systems (UASs), unmanned rotorcraft already fill specific U.S. military requirements. Honeywell’s backpack-portable T-Hawk ducted fan helps the Army scout convoy routes and joint-service explosive ordnance disposal (EOD) teams find improvised explosive devices (IEDs) in Afghanistan and Iraq. A refined version is part of the Army Brigade Combat Team Modernization (BCTM). The Navy’s Northrop Grumman Fire Scout helicopter completed an operational Caribbean cruise in April and will share a frigate deck with a manned Sea Hawk next year in the CENTCOM area of responsibility (AOR). Boeing Hummingbird and Kaman/Lockheed Martin K-MAX helicopters at Dugway Proving Ground, Utah, showed the Marine Corps Warfighting Lab how unmanned systems could resupply forward operating bases in Afghanistan. Both will compete with the Northrop Grumman/Bell Fire-X helicopter for a combat deployment in 2011. While the Army considers its own unmanned cargo demonstration, it too wants a Quick Reaction Capability in theater to exploit the 20-hour endurance of the A160T Hummingbird for reconnaissance, surveillance, and target acquisition.

Predators, Shadows, and other fixed-wing UASs are valued widely by U.S. warfighters, but unmanned vertical takeoff platforms remain niche capabilities. Tim Owings, deputy project manager for UAS in the Army Program Executive Office Aviation, summarized, “What has become the most untradeable asset is system endurance and persistence. People want to stay in the air a long time … You don’t do that with helicopters.” Combat commanders with many ways to strike targets sometimes leave UAS weapons at home to preserve endurance. “That’s why A160 is the one vertical lift platform that’s getting a lot of play – that metric of time and persistence over target.” With funding expected in 2012, the Army intends to buy nine new Hummingbirds and deploy a Quick Reaction Capability to Afghanistan 12 to 18 months later.

For all the emphasis on endurance, vertical takeoff and landing and hover-and-stare performance are themselves valuable to select warfighters. The U.S. Special Operations Command reportedly lost one of its eight YMQ-18A Hummingbirds in Belize testing FORESTER – Foliage Penetration Reconnaissance, Surveillance, Tracking, and Engagement Radar. The long-endurance VTUAS is uniquely adapted to the persistent all-weather sensor. A Hummingbird hovering in a headwind at 15,000 feet gives the UHF radar zero ground speed to spot slow-moving, low-radar cross section troops or vehicles through trees. In Belize, the innovative unmanned helicopter, with its optimum speed rotor, high fuel fraction, and retractable landing gear, flew for 10.5 hours carrying the big radar and afforded the 21-foot-long rotating antenna an all-round field of regard. The test aircraft logged 28 flights in 27 days and flew on 24 consecutive days before the mishap.

A concept rendering of the Fire-X optionally manned helicopter, based on the Bell 407. Northrop Grumman rendering by Kent Rump

VTUAS programs have suffered technical and acquisition setbacks. Hummingbird crashes this year in Belize and California remain under investigation. The Army canceled its Fire Scout order in November 2009 after it de-scoped the Future Combat Systems program into BCTM. (Eight Army aircraft in process were diverted to the Navy program.) A Navy Fire Scout caused unwanted headlines this summer when it violated Capitol airspace after losing its supervisory datalink. Yet despite the complexities and compromises of unmanned rotorcraft, U.S. military customers still intend to transition VTUASs from development to operational systems.

Evolved from an Advanced Concept Technology Demonstration (ACTD) of the Defense Advanced Research Projects Agency (DARPA), the Honeywell RQ-16 T-Hawk enables foot soldiers and EOD teams to launch and recover a UAS in confined areas. The 17-pound micro air vehicle (MAV) flies for 50 minutes at sea level and sends infrared or electro-optical (IR or EO) imagery by digital datalink to ground stations up to 10 kilometers away.

Programmed through a portable Ground Control Station (GCS), the ducted fan takes off vertically and tilts to fly to its target autonomously. The fan inside the duct slows down as the vehicle transitions from takeoff to cruise, and moving thrust vanes steer the vehicle. The MAV and its sensor gimbal are coupled, enabling the operator to aim the camera at points of interest on the GCS display without regard to aircraft or gimbal orientation. Current T-Hawks come with interchangeable IR/EO payloads. Combined EO/IR/laser pointer, short-wave infrared (SWIR), and high-resolution IR and EO sensors are in development.

Honeywell received the original MAV contract in 2003 and delivered 25 ACTD systems – each with a GCS and two air vehicles – to DARPA. The demonstrators were remanufactured for the Army as Block I G-MAVs and still serve in Iraq. The Naval Air Systems Command meanwhile ordered 130 Block II systems, each with two RQ-16B aircraft, for Joint EOD teams in Iraq and Afghanistan. A Foreign Military Sale under the same contract sent six systems with 12 aircraft to the U.K. Ministry of Defence. Despite requirements for safer, more fuel-efficient diesel engines, production vehicles use a gasoline engine from 3W in Germany, modified with a Honeywell Engine Control Unit.

Block III deliveries of 40 T-Hawk systems with 80 aircraft now under way give the Army surrogate UASs for Early Infantry Brigade Combat Teams. Eleven single-aircraft systems also went to Boeing for Brigade Combat Team Modernization Increment 1 tests at Fort Bliss, Texas. The Class I company-level MAV survives the four classes of UASs once planned for the Future Combat Systems. The BCTM Increment 1 Block 0 T-Hawk system will integrate additional networking equipment, including a handheld device that connects the UAS to the BCTM network. First deliveries and Initial Operational Capability are scheduled for late 2011. An objective Class I vehicle with a heavy fuel engine and laser designator will probably be twice the size of today’s T-Hawk.






Fire Scout
Programmed through a Ground Control Station, the 3,150-pound MQ-8B Fire Scout launches and recovers from small, moving ship decks without a pilot. On the first operational deployment aboard USS McInerney, two of the unmanned helicopters logged about 60 flight hours over six months in the U.S. Southern Command/4th Fleet AOR. The VTUAS was generally operated and maintained by SH-60B Sea Hawk pilots and mechanics from Navy squadron HSL-42, overseen by Northrop Grumman technical representatives. “We wanted the maintainers and operators on the Navy side to use it as they saw fit,” said Program Manager Capt. Tim Dunigan at the Naval Air Systems Command (NAVAIR). “This was the first time people not connected with the program got a really good look at it.”

The air detachment aboard the McInerney totaled 32 people to operate two Fire Scouts and a Sea Hawk. UAS aircraft operators were generally H-60 officer-pilots, but one enlisted operator with a commercial pilot license subsequently joined the cruise. “The H-60 pilot is kind of overkill for that kind of job,” acknowledged Dunigan. Mission payload operators were enlisted air systems crewmen. The Fire Scout Ground Control Station occupied an unused room on the McInerney, and real-time imagery from the UAS sensors was piped through the ship. The sea deployment also marked the first time Fire Scout used a Tactical Common Datalink (TCDL) like that planned for the Navy’s coming Littoral Combat Ships (LCSs). The Fire Scout will begin deck interface testing aboard the LCS USS Freedom later this year.

Fire Scout emerged from a 1999 Navy requirement and made its first autonomous shipboard landings in 2006. Northrop Grumman developed the RQ-8A air vehicle from the Sikorsky-Schweizer 333 manned light helicopter. Seven development aircraft preceded 16 low rate initial production (LRIP) vehicles now in service, modification, or assembly. Today’s MQ-8B, with four-bladed main rotor and uprated transmission, carries up to 600 pounds of sensors, relay radios, or other payloads for 2.2 hours up to 110 nautical miles from the ship. Fire Scouts have fired unguided rockets in testing, but the Navy has no requirement to arm the autonomous helicopter.

A successful operational evaluation early next year will clear the way for a Fire Scout full rate production decision. The program of record still calls for 168 helicopters to put two Fire Scouts on guided missile frigates like the McInerney or three aboard an LCS like Freedom. The Coast Guard plans to borrow one or two Navy Fire Scouts for testing next summer on a National Security Cutter. (The Coast Guard abandoned the Bell Eagle Eye tilt-rotor UAS to partner with the Navy on Fire Scout and U.S. Customs and Border Protection on the more conventional Guardian fixed-wing UAS.) Each Fire Scout system includes the helicopters, a Ground Control Station, and payloads. The deployed aircraft were equipped with the Brite Star II IR/EO payload and the Automatic Identification System to interrogate cooperating vessels. Imagery from the UAS helped the Coast Guard intercept a Caribbean drug smuggler.

The operational cruise also underscored the need for a streamlined operator interface with less distracting data, and a radar to complement the existing sensor suite. Dunigan explained, “We have a maritime radar upgrade; the concept is to get the vehicle out, get people comfortable operating it, and then we’ll put the radar on.” The next Fire Scout deployment is scheduled for January 2011 aboard USS Hallyburton, assigned to the Mediterranean and the CENTCOM region.

A Boeing A160T Hummingbird during an autonomous cargo delivery demonstration for the Marine Corps. Boeing photo by Keith Skelton

Cargo Contenders
Afghanistan remains a dangerous place for resupply convoys and aircraft. The Marines plan to demonstrate a cargo UAS capability in theater next year to augment existing logistics chains at forward operating bases and reduce their exposure to IEDs, groundfire, and brownout accidents. NAVAIR expects to award a contract by the end of 2010 to put a VTUAS with two aircraft in Operation Enduring Freedom.

The Marine Corps Warfighting Laboratory at Quantico, Va., sponsored a non-competitive Immediate Cargo UAS demonstration at Dugway Proving Ground, Utah, last February and March. “We just wanted to get an idea of what was out there and how it could be put into theater,” said project officer Capt. Amanda Mowry. The demonstration modeled a company-sized unmanned air resupply system able to haul 10,000 pounds of cargo a day over a 150-nautical mile round trip and deliver external cargo within 3 miles of a set point.

The 6,500-pound gross weight Boeing Hummingbird and 12,000-pound (gross weight with external load) Kaman Aerospace/Lockheed Martin K-MAX helicopters each moved 2,500 pounds within six hours over a 150-nautical mile round trip, sustained beyond-line-of-sight communications, and recovered automatically from a simulated loss of datalink. The Hummingbird with Optimum Speed Rotor and Kaman/Lockheed Martin K-MAX with intermeshing rotors both demonstrated the high-altitude hover performance needed to deliver cargo to mountain landing zones.

A Lockheed Martin/Kaman K-MAX at Yuma Proving Ground, Ariz., January 2010. Lockheed Martin photo by Chad Slattery

Designed for sling load operations, Kaman’s single-seat K-MAX found limited success in commercial logging and construction. With control servos working regular cockpit control links, it first flew autonomous cargo demonstrations with a safety pilot aboard in 1999 for the Marines’ Broad-area Unmanned Responsive Resupply Operations (BURRO) effort and follow-on Army demonstrations. Kaman developed automatic load stabilization technology that integrates precise load weight with center-of-gravity calculations and the rate of load movement to make the autonomous helicopter stable and safe.

Kaman joined with Lockheed Martin Systems Integration in 2007 to market a cargo UAS. For the Dugway demonstration, Lockheed Martin provided software updates and the concept-of-operations, and Kaman integrated redundant flight controls and more responsive actuators. The work-ups for the demonstration were the first K-MAX flights without a safety pilot.

At Dugway, the unmanned helicopter with cargo carousel delivered four 750-pound loads to different locations. The first three loads were delivered automatically, the last under manual control from a TCDL station. The K-MAX previously demonstrated mine-hunting lasers and sensors and offers military users a multi-role platform with up to 6,000-pound payload or better than 12 hours’ endurance. Kaman has 21 K-MAXs available for UAS conversion and stands ready to put the helicopter back into production for new orders.

Frontier Systems (now part of Boeing Advanced Rotorcraft) in Irvine, Calif., flew a piston-engined A160 Hummingbird under a DARPA contract in 2002 and proved that changing rotor speed with airspeed, altitude, weight, and load factor increases lift-to-drag ratios and endurance. The current turbine-engined A160T has since demonstrated 18.5 hours’ endurance and carried a 1,000-pound cargo pod over 600 nautical miles. Boeing engineers are now tying the rotor speed change to the mission profile selected by the UAS operator. A160 Program Manager Ernie Wattham explained, “What we’re trying to do is automate the aircraft as much as possible to make it like driving an automatic transmission in a car.”

At Dugway, the Hummingbird showed it could place loads consistently within 3 meters of a designated point. Boeing developed a portable GCS from the Enhanced Position/Location Reporting System (EPLRS) radio that enabled a landing zone operator to steer the UAS to the delivery point with imagery from nose and belly cameras.

The U.S. Army is invested in manned/unmanned teaming, such as this Boeing AH-64 controlling an AH-6 Little Bird. Boeing photo

Boeing built 10 developmental Block I A160T Hummingbirds at its Irvine, Calif., rapid prototyping facility and committed to building 20 standardized Block II Hummingbirds with better weather sealing and other reliability enhancements at its Mesa, Ariz., plant. The first of the “white-tailed” aircraft will begin flight-testing early in 2011, ready for an unmanned cargo demonstration if selected, or other applications.

Northrop Grumman meanwhile intends to adapt Fire Scout controls to the 6,000-pound gross takeoff weight Bell 407 helicopter and offer the resulting Fire-X UAS for unmanned cargo and other Navy missions. The civil-certified Model 407 aircraft provides about 3,000 pounds of payload that can be allocated to fuel, sensors, or hook loads. Fire-X flight tests are scheduled to begin in October with a safety pilot aboard. Like the Boeing AH-6X Unmanned Little Bird developed around the Army’s Armed Scout Helicopter requirement, the autonomous Fire-X will retain regular cockpit controls. According to Bob Davis, director of business development for Northrop Grumman Advanced Programs and Technology, “What we’re beginning to see in our customer community is an interest in optionally piloted operations.”

VTUAS Concepts of Operations (CONOPS) are in the earliest stages of development. The U.S. Army is notably invested in manned/unmanned teaming and has integrated One System Remote Video Terminal functionality into Apache and Kiowa Warrior cockpits and high-level UAS control into the cockpit of the new Block III Apache Longbow attack helicopter. Networking will enable Apache crews to tap imagery from Class I micro-air vehicles as well as fixed-wing unmanned systems to keep the enemy in sight while they shuttle to and from rearming and refueling points. In June, Sikorsky Aircraft and the Army Aeroflight Dynamics Directorate (AFDD) at NASA Ames Research Center demonstrated autonomous flight following in which one Black Hawk followed another automatically. The technology may one day link mixed formations of manned and unmanned helicopters for resupply missions.

The United States is not alone in exploring unmanned helicopter applications. Little Schiebel Camcopters have operated from German corvettes and SAAB in Sweden now markets the small Skeldar UAS for maritime and land-based applications. Mono-tilt rotors, mono-wings, small fan-craft, and other advanced VTUAS concepts remain under study. Vertical takeoff unmanned aircraft systems nevertheless remain in their infancy, and their value may become clear only when operational systems take off straight up.

This article first appeared in The Year in Defense, Winter 2011 Edition.


As an aerospace and defense writer for more than 30 years, Frank has written in-depth...