Indian Defence Review

CH-47 Chinook

Inarguably, the most ambitious programme to design future battlefield helicopters is the US FVL. However, the Dutch Air Chief, Lt. Gen. Alexander Schnitger reportedly questioned the programme thus, “When I look at the Future Vertical Lift designs, I see today’s technology being incrementally improved toward the future. What I would like to see is a disruptive vision of the vertical-lift capabilities that is ready for any operation in 2040. Instead of extrapolating today into the future, I would like to start with the future and then decide how to get there.” Currently, that suggestion appears impossible to comply with as dramatically new designs seem unattainable. Over the next decade and a half, battlefield helicopters appear destined to be incremental progressions of existing models, with no revolutionary enterprise visible on the horizon.

Etymologically, the word  ‘battlefield’ owes its origin to Latin battualia meaning ‘the fighting and fencing exercises of soldiers and gladiators’. Cavalry introduced a significant element of speed and manoeuvre and in a process of evolution, was, replaced by tanks, but the stalemate on the Western Front during World War I initiated an intense debate in the years that followed about the use of mechanised forces. The debate continued during the 1930s and was supplemented by another element, the emerging developments in rotary wing aircraft, with noteworthy and self-evident advantages as a combat platform in the battlefield. Since then, the helicopter has developed with profound tempering through significant battle experience in Vietnam, Korea and Iraq into a veritable machine that has performed roles encompassing attack, anti-tank, Suppression of Enemy Air Defences, reconnaissance and observation, airlift of troops and cargo resupply, fire fighting and medical evacuation. Indeed, it has performed all roles a fixed-wing aircraft can, excluding strategic strike.

The battlefield helicopter, belonging to the ‘air forces’ by classification, remains tethered to land forces, making significant contribution in the battlefield. However, development in helicopter technology has not been at the same pace as for fixed-wing aircraft, especially those with combat roles. Higher speeds, precise and incisive fire power, superlative agility and manoeuvrability, stealth and self-protection, high survivability and low vulnerability, with the capability to perform designated roles in bad weather and night conditions, are the badgering challenges that accost helicopter manufacturers. The US and Europe, major users of battlefield helicopters, have taken on these challenges and are working on designs to achieve technological enhancements for battlefield helicopters.

Overview of Ongoing Programmes

Experience of the US military with helicopters is perhaps the richest. Wars in Vietnam, Korea, Iraq and Afghanistan have provided invaluable lessons to the US in the tactical employment of helicopters. The ongoing war against terrorism holds its own imperatives in terms of what is needed in the domain of helicopter technology. The US Army, currently operating close to 4,000 helicopters in various roles, is looking at a combination of rotor and fixed-wing as the possible future solution, the Future Vertical Lift (FVL) with the target date set as 2030. Towards this objective, a US Army-led programme, the Joint Multi-Role (JMR) Demonstrator, has drawn up an ambitious wish-list with inputs from the Coast Guard, Special Operations Command and NASA. The final objective is a design with vastly improved avionics, electronics, range, speed of 200 knots, survivability, operating altitudes and payloads. The ‘multi-role’ part of the programme alludes to several roles ranging from attack configurations to cargo, medevac, search and rescue and anti-submarine warfare. Originally, three Capability Sets were planned in 2009: JMR Light (scout version to replace the OH-58 Kiowa), JMR Medium-Light, JMR Medium (utility and attack versions). Later on two more sets were added: JMR Heavy (cargo version to replace the CH-47 Chinook) and JMR Ultra (ultra-sized version for vertical lift aircraft with performance similar to fixed-wing tactical transport aircraft). Eventually, these new designs are expected to replace 25 current rotorcraft types in use with the US military.

The focus so far has been on FVL Medium, seen as the replacement for the US Army’s Sikorsky UH-60 Black Hawks and Boeing AH-64 Apaches. The main contenders are Bell Helicopter and a Sikorsky/Boeing team. Bell is offering a next-generation tilt-rotor, V-280, evolved from its V-22 Osprey, which tilts its huge rotor blades between vertical and horizontal positions to gain both the best features of a helicopter (Vertical Take-Off and Landing) and those of a propeller plane (fuel-efficient speed for long range flight). The Sikorsky-Boeing Defiant looks more like a traditional helicopter, but is based on Sikorsky’s “X2” technique of combining two counter-rotating rotors, one on top of the other, with a pusher propeller at the tail. On September 15, 2010, the X2 Technology Demonstrator had unofficially broken the rotorcraft speed record of 250kts. The Defiant is slated to fly in the first half of 2018 while the V 280 demonstrator is to fly in November this year.

A significant, concrete step that has already been taken in the direction of the JMR is a fifty-fifty partnership between Pratt & Whitney and Honeywell Aerospace for developing the Advanced Affordable Turbine Engine (AATE), aimed at providing a 30 per cent increase in horsepower for helicopters while at the same time cutting fuel consumption by 25 per cent. The US FVL programme’s objective of replacing all US military helicopters with a family sharing common technologies, but not common platforms, is laudable and sure to bring remarkable results over the next two decades.

In Europe, Airbus Helicopters’ X-3, “high-speed long-range hybrid helicopter” has a set of propellers for forward motion instead of a tail rotor and is one of the aircraft that have flown under “high-hot” conditions (6,000 feet at 95 degrees Fahrenheit) like a rotorcraft with airplane-like speed. The X-3 demonstrated a speed of 255 knots in level flight and 263 knots in a shallow dive on June 07, 2013,[beating the Sikorsky X2’s unofficial record set in September 2010, thus becoming the world’s fastest non-jet augmented compound helicopter. On May 21, 2016, Airbus filed a patent for X-3, claiming it as the world’s fastest rotary wing aircraft. Let us now address some of the challenges for helicopter technology.

Speed

Conventional helicopter design has retained its tadpole like shape and remained predicated to a rotor system which restricts maximum speed to around 180 knots due to a phenomenon called “retreating blade stall”. As long as a helicopter design employs a rotor blade system in which the moving rotors in flight manifest themselves as a ‘disc’ lying in a horizontal plane, speed will be limited due to this phenomenon. Helicopter design is different from fixed-wing inasmuch as the airframe drag and engine power are not the important determinants of forward speed; it is the rotor system that limits forward speed. Higher speed envelopes would help military helicopters to achieve their missions more efficiently, helping them to reach critical targets and destinations in shorter times, while giving them a better edge against enemy fire from the air and ground. Realising that a single rotor system with a complementing tail rotor, is unlikely ever to achieve a breakthrough in forward speed, designers are exploring other avenues which are tending to metamorphose not just the shape and silhouette of the helicopter, but also its name to Vertical Take-Off and Landing (VTOL) craft.

VTOL Technologies

The basic helicopter design has other limitations essentially because the rotor system is not as efficient for forward travel as a fixed-wing one and consumes approximately 15 per cent of total engine power available to run the essential tail anti-torque rotor which is an essential part of the design to keep the helicopter from spinning. The helicopter must also deal with high vibration levels. Higher fuel consumption and is maintenance-intensive. New technologies have permitted them to move away from the original shape while retaining the VTOL characteristic of a helicopter. Developing a practical, hybrid aircraft with a VTOL capability and the performance of a fixed-wing aircraft in forward flight, was a daunting challenge with two fundamental objectives. The first was to accomplish controllable vertical flight using the very same mechanisms and equipment that are required for forward flight. Any weight of exclusively vertical flight mechanisms would be useless during forward flight and would represent a reduction in available payload relative to a comparable fixed-wing aircraft. The second goal consisted of achieving “power matching” i.e. a VTOL design that requires the same power in vertical flight as in forward flight. Any mismatch would represent excess capacity which corresponds to excess weight in one mode of flight. Numerous approaches to VTOL aircraft have been explored over the years; the prominent ones are tilt-rotors, tilt-props and tilt-wings, as well as deflected-slipstreams, deflected-thrust, thrust augmenters, ducted fans, tilt ducted rotors and tail sitters.

As the name implies, a tilt-rotor aircraft uses tiltable propellers, or prop-rotors for lift and propulsion. For vertical flight, the prop-rotors are angled to direct their thrust downwards, providing lift. In this mode of operation, the aircraft is essentially identical to a helicopter. As it gains speed, the prop-rotors are slowly tilted forward, eventually becoming perpendicular to the ground. In this mode the wing provides the lift and the wing’s greater efficiency helps the tilt-rotor achieve high speed. In this mode, the machine is essentially a turboprop aircraft. Bell Helicopter has been dominant in tilt-rotor development and partnered with Boeing on the first production tilt-rotor aircraft, the Bell/Boeing V-22 Osprey. Tilt-rotor prop-rotors require all the fundamental parts of a twin-rotor helicopter. They also have a full set of airplane controls and a tilt mechanism that rotates the lifting rotors. The V-280 design is a successor of the V-22 Osprey but with one major difference from the V-22 Osprey, the engines remain in place while the rotors and drive shafts tilt. It has a maximum speed of 275 knots at sea level and 305 knots at 15,000 feet. While these speeds are much higher than helicopters with rotors, they do not compare well with fixed-wing aircraft.

Bell and Boeing are exploring larger Quad Tilt Rotor (QTR) military models for possible use by the US Army. The QTR has two sets of fixed-wings and four tilting rotors mounted at the tips of the wings. The programme has been nicknamed the V-44 Tilt Rotor for the four tilt-rotor version and V-66 tilt-rotor for the six tilt-rotor version. They would use higher rated versions of the tilt-rotor engines used on the V-22 Osprey.

From January 01, 2016, Leonardo’s Helicopter Division absorbed the activities of AgustaWestland which is developing AW609 (formerly known as Bell/Agusta BA609) for civilian use and, in an allied development endeavour, working on the world’s first electric tilt-rotor aircraft, as a technology demonstrator termed Project Zero. Each of its two rotors is driven by an electric motor which is powered by rechargeable batteries. The aircraft’s control systems, flight controls and landing gear actuators are also all electrically powered, so there is no need for a hydraulic system. Besides, the aircraft doesn’t require a transmission as well. A first flight was demonstrated in early 2013, and it has made numerous public appearances since then. Flight testing has been carried out on 1:3 scale models due to the limited endurance it has but, in February 2016, it was announced that a hybrid drive system would be installed on the full-scale aircraft so as to extend the flight endurance from 10 to 45 minutes.

AgustaWestland is looking at the possibility of blades that change effective shape during flight much like a fixed-wing does with the aid of flaps. The VTOL experimental plane or VTOL X-Plane programme of US Defense Advanced Research Projects Agency (DARPA) seeks to cross-pollinate fixed-wing and rotary-wing designs to attain sustained flight speed of 300-400 knots. Aurora’s Phase 2 design for VTOL X-Plane envisions an unmanned aircraft with two large rear wings and two smaller front canards – short winglets mounted near the nose of the aircraft. A turbo-shaft engine, the one used in V-22 Osprey tilt-rotor aircraft mounted in the fuselage, would provide three MegaWatts (4,000 horsepower) of electrical power which would drive 24 ducted fans. Flight tests are expected in 2018.

NASA’s Greased Lightning or GL-10 deserves a mention here. It is a battery-powered, 10-engine remotely piloted tilt-rotor and the prototype has a ten-foot wingspan and can take-off vertically like a helicopter as also fly efficiently in forward flight. It is in design and testing phase and flew a series of test flights during 2015, including transition from vertical to horizontal flight. The final version is expected to have a 20-foot wingspan and be a hybrid machine powered by lithium-ion batteries with a pair of eight horsepower diesel engines which will drive ten electric engines, eight on the wing and two on the stabilizer. The tilting nature of the wing and stabilizer dispenses with the need of either a launch system or a large operation space.

Besides tilt-rotors, VTOL aircraft could have other designs like ducted fans (Bell X 22A, Ryan XV 5A/B), hovering platforms (UrbanAero X-Hawk) or the Elytron design (which combines three sets of wings: one pair of rotary wings called “prop-rotors”, mounted on a single tilt-wing in central position, and two pairs of fixed-wings) or the Disc Rotor (in which for hover, a set of blades are extended from the periphery of the disc much like a helicopter, but forward flight is like a fixed-wing aircraft with the blades either fully retracted into the disc or with two of the rotors sticking out like conventional lift producing wings.

Survivability/ Vulnerability

In a broad sense, all technological enterprise aimed at improving helicopter design has enhanced survivability and reduced vulnerability as the definitive objectives. To avoid detection, most helicopters flying in the battlefield would take place at as low a height as possible, below 100 feet Above Ground Level if design permits. Nap of Earth flying is the lot of some helicopters endowed with the agility and manoeuvrability to perform that very interesting genre of flying, involving flying not above but between obstructions like trees or terrain features. In other words, the envelope in which military helicopters operate is largely hugging the ground and within lethal range of enemy weapons, some of which are optimised for aerial targets and some others (personal arms fire, for example) not designed against helicopters, but yet equally lethal against them due to their inherent vulnerability. As the Soviet helicopter pilots learnt in Afghanistan, even small arms fire from a perch higher than the helicopter could render it unfit to continue the mission. More recently, Operation Geronimo also highlighted the requirement for helicopters to be more agile, manoeuvrable, quiet and stealthy.

Stealth technology enables a helicopter to minimise detection by radar, but is not a foolproof measure against the amazingly sensitive radars that technology has produced. Passive radars are emerging and stealth does not provide total safety against leading edge radars. Survivability in terms of crash resistance, i.e. the ability to allow minimum damage to the helicopter in case of an uncontrolled or partially controlled contact with ground below, is thus an inescapable criterion for designers to consider. Unfortunately, it comes with a weight penalty.

Unmanned Craft

Undoubtedly, the unmanned rotary-wing platform that caught the military planner’s attention first was the K-MAX. A UAS transformed by Lockheed Martin Corporation and Kaman Aerospace Corporation from an existing helicopter model of Kaman, it enabled US Marines to deliver supplies by day or night to precise locations without risk to life in the process. The K-MAX can deliver a full 2,700-kg of cargo at sea level and over 1,800 kg at 15,000 feet. It rendered laudable service in Afghanistan for the US Marines and has proven the concept beyond any reasonable doubt. The future can be expected to see variations of the concept in optionally manned versions as well.

The GL-10 mentioned earlier is a small tilt-rotor, but is a spectacularly successful drone helicopter that has pioneered its way to fame. Another noteworthy helicopter innovation is the Mars Helicopter being developed by NASA. Due to the large distance from Mars, remote control is not technically feasible in real time as it would take minutes for radio waves to travel one way between Mars and any control station on Earth. As such, the Mars Helicopter is being designed as a totally autonomous craft. The project, called Mars Electric Reusable Flyer, is faced with the challenge of getting a rotary-wing craft to fly in three-eighth of Earth’s gravity with 100 times less atmosphere.

China too is pursuing unmanned rotorcraft programmes and its unmanned V-750 helicopter UAV successfully fired anti-tank missiles at targets in June this year. Certified by Chinese aviation authorities in 2014, the 750-kg platform can carry at least two 50-kg anti-tank missiles, such as the HJ-9 and HJ-10 or rocket pods and has a range of 500 km.

The Fire Scout MQ-8B/C based on the commercial Bell 407 can be used for unmanned helicopter system that provides real-time Intelligence, Surveillance and Reconnaissance, target acquisition, laser designation and battle management to tactical users without relying on manned aircraft or space-based assets. It has also demonstrated the ability to operate concurrently with other manned aircraft and, in an offensive role, can carry 8 to 14, 70mm rockets. Meanwhile, Sikorsky is trying to demonstrate that autonomous aircraft can perform complex and life-saving missions with enhanced safety, reduced cost of ownership and superior capabilities through the Sikorsky Autonomy Research Aircraft MATRIX Technology (consisting of a suite of hardware and software systems); a Black Hawk is being converted so that it may be optionally-piloted. The US Army’s next generation helicopter could be “optionally manned” that is, it could be capable of autonomous flight for a full mission or a substantial segment of a mission.

The future of airborne weapon platforms does not only belong to the large but to the very small as well. The Nano Air Vehicle (NAV) programme has an objective of making small airborne vehicles which could be utilised in a variety of applications, including both indoor and outdoor missions. The object is to develop an aircraft smaller than 15 cm in length and 20 gm in weight. Thus in some roles, military helicopters would become invisible to the enemy.

Another variation of the unmanned theme is that in the future, some manned ones could operate in concert with drones. The US Army is already doing this with a Manned-Unmanned Teaming (MUM-T) squadron, combining Boeing AH-64D/E Apache helicopters with Textron Systems RQ-7B Shadow UAVs as a heavy attack-reconnaissance unit as also General Atomics Aeronautical Systems MQ-1C Gray Eagle UAVs. Both UAVs can be operated from the Universal Ground Control Station (UGCS) or by an Apache crew in flight.

Concluding Remarks

Vulnerability and survivability apprehensions fuelled by experience in Iraq and Afghanistan, have rejuvenated the debate on the utility of helicopters on the modern battlefield. However, military helicopter industry plods on tirelessly in pursuit of more capable helicopters for employment in the battle area.

Budgetary considerations have relegated helicopter development to a second position behind fixed-wing combat aircraft and so, some expensive technologies such as Fly-By-Wire (FBW) have been comparatively slow in making their presence felt in helicopters despite the advantages of safety, efficiency and weight. An innovative substitute for FBW is the Active Parallel Actuator Subsystem for Boeing Chinooks which is not FBW, but makes some of its capabilities available at a much lower cost.

Technological advances hold out two interrelated promises, the first being new and innovative changes to rotorcraft design predicated to new projects and enterprises and the other, the increasing capability to upgrade existing models so as to increase their performance, role capability and utilisation for new missions. Needless to say, upgrades cost a fraction of the outlay on a new helicopter although the upgraded helicopter may not turn into a new helicopter in terms of performance.

As an illustration, the Boeing AH-6 Little Bird has been around since the 1960s; but its current version is substantially superior to the original. It flies higher, has a higher speed range, carries a heavier payload and can be used as a potent light attack helicopter for recce and in the Search And Rescue (SAR) role. Another inspired feature of the AH-6 is the commonality of systems it shares with the Apache AH-64. The two cockpits are strikingly similar. In a somewhat similar vein, Boeing is in the process of remanufacturing 117 Apache AH-64Ds into the more capable AH-64E model for the US Army. Likewise, Lockheed Martin is offering two options to potential customers interested in an armed UH-60 Black Hawk: either an all-new helicopter or a weapons kit that can be used to upgrade existing aircraft. At Farnborough, it offered an option with UKM2000, M240 or M134 7.62 mm mini-guns, four Hellfire missiles, a 12.7 mm FN-Herstal HMP and an M261 Hydra 70 19-shot rocket pod in addition to a rescue hoist and either a crashworthy external fuel system or weapons pylon. Lockheed Martin made it a point to stress that any new customer could customise its armed Black Hawk to fit its individual needs. Airbus Helicopters too has developed a Generic Weapon System (being marketed as HForce) consisting of two main components – a Thales-produced, helmet-mounted sight display and a Rockwell Collins Deutschland FMC-4212 General Purpose Computer. It will initially be made available for H125M, H145M and H225M. Options include fixed guns, rockets, guided missiles and air-to-air missiles.

Inarguably, the most ambitious programme to design future battlefield helicopters is the US FVL. However, the Dutch Air Chief, Lt. Gen. Alexander Schnitger reportedly questioned the programme thus, “When I look at the Future Vertical Lift designs, I see today’s technology being incrementally improved toward the future. What I would like to see is a disruptive vision of the vertical-lift capabilities that is ready for any operation in 2040. Instead of extrapolating today into the future, I would like to start with the future and then decide how to get there.” Currently, that suggestion appears impossible to comply with as dramatically new designs seem unattainable. Over the next decade and a half, battlefield helicopters appear destined to be incremental progressions of existing models, with no revolutionary enterprise visible on the horizon.