A helicopter, or chopper, is a type of rotorcraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of VTOL (Vertical TakeOff and Landing) aircraft cannot perform.
A military helicopter is a helicopter that is either specifically built or converted for use by military forces Helicopters are among the most adaptive and versatile weapons system worldwide, integral during times of war and peace. A military helicopter’s mission is a function of its design or conversion. The helicopter provided the military with unparalleled flexibility: its rotors allowing for vertical take-off and landing, and it possessed capabilities to hover and fly in all four directions.
Military helicopters play an integral part in the sea, land and air operations of modern militaries. The most common use of military helicopters is transport of troops, but transport helicopters can be modified or converted to perform other missions such as combat search and rescue (CSAR), medical evacuation (MEDEVAC), airborne command post, or even armed with weapons for attacking ground targets. Transport helicopters are used for transporting personnel (troops) and cargo in support of military operations. The benefit of using helicopters for these operations is that personnel and cargo can be moved to and from locations without requiring a runway for takeoffs and landings.
Specialized military helicopters are intended to conduct specific missions. Examples of specialized military helicopters are attack helicopters, observation helicopters and anti-submarine warfare helicopters. Attack helicopters are helicopters used in the anti-tank and close air support roles. As helicopter technology matured with increased payload and endurance, anti-submarine warfare (ASW) was added to the helicopter’s repertoire. Initially, helicopters operated as weapons delivery systems, attacking with air-launched torpedoes and depth charges based on information provided by its parent and other warships.
Military Aviation today is looking at the next generation of military helicopters and the strategy to modernise vertical lift capability with improved avionics, electronics, range, speed, propulsion, survivability and high-altitude performance. The aim is to improve upon the present limitations by examining emerging technologies within the realm of the possible, with speeds in excess of 170 knots, combat range of 800km, hover with full combat load under high/hot conditions and with a degree of autonomous flight capability. Some of the enabling technology areas being considered are propulsion, airframe materials, rotor systems, engine technology, survivability equipment, mission systems and next-generation maintenance techniques among others.
Another area of future development is helicopter UAVs. Two avenues are already being explored and implemented in different countries, the UAV-helicopter cooperation and development of rotary wing UAVs. Lockheed Martin’s K-MAX helicopter UAV was deployed in Afghanistan for logistic resupply and has proved to be quite a hit. It has been able to fly in adverse weather conditions when manned helicopters could not fly. Northrop Grumman’s ‘Fire Scout’, is another helicopter UAV which is already in service with the US Navy, capable of operating from the deck of a ship. The latest in the unmanned field is the unmanned version of Sikorsky’s UH-60A Black Hawk helicopter modified for both manned and unmanned flights.
The US military has embarked on the most transformative science and technology initiative in decades – the Joint Multi-Role (JMR) technology demonstration effort, where the industry plans to prove the revolutionary capabilities of high speed approaches for a family of future military products. In Russia, the Moscow-based ‘Russian Helicopters’ has been a lead player in the Global Helicopter Industry, with its major thrust being towards design and development of military helicopters.
Special jet engines developed to drive the rotor from the rotor tips are referred to as tip jets. Tip jets powered by a remote compressor are referred to as cold tip jets, while those powered by combustion exhaust are referred to as hot tip jets. An example of a cold jet helicopter is the Sud-Ouest Djinn, and an example of the hot tip jet helicopter is the YH-32 Hornet.
The number, size and type of engine(s) used on a helicopter determines the size, function and capability of that helicopter design. Early helicopter designs utilized custom-built engines or rotary engines designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. Turbine engines revolutionized the aviation industry; and the turboshaft engine for helicopter use, pioneered in December 1951 by the aforementioned Kaman K-225, finally gave helicopters an engine with a large amount of power and a low weight penalty. Turboshafts are also more reliable than piston engines, especially when producing the sustained high levels of power required by a helicopter. The turboshaft engine was able to be scaled to the size of the helicopter being designed, so that all but the lightest of helicopter models are powered by turbine engines today.
Helicopter Engines and Operational Impact In Harsh Environments
The helicopter’s operational versatility means many missions take place in harsh environments in which systems are exposed to airborne contamination including sand, abrasive dust, corrosive salt, and high moisture.
Helicopter turbine engines require massive intake airflows, creating a low-pressure area at the engine inlet that can sweep up sand, dust, and seawater spray driven by main rotor downwash. Desert environments are particularly hostile, with increased wear reducing engine reliability by as much as 50%.
These contaminants are known to cause engine erosion, wear, and damage, requiring more frequent overhauls, as well as unscheduled component removals resulting in increased MTBUR (Mean Time Between Unscheduled Removal), or increased emergency landings.
Engine performance also deteriorates over time, due to compressor blade erosion, which in turn reduces load carrying and hover capabilities. Typically, a leading-edge wear of 1.5 – 2 mm in the first stage compressor blades can result in a 5-8 % engine power loss, which increases with altitude. Accelerated engine wear is a primary reason for premature engine removal, with compressor blade erosion the major cause—accounting for 40% of cases.
A secondary problem occurs during takeoff and landing. A helicopter churns up thick clouds of surface contamination (ground effect). To reduce engine exposure to this cloud, pilots try to minimize operation in ground effect, which often results in high-power takeoffs and hard landings, both of which can take aircraft out of service.
Two primary methods of removing particulate contamination from engine inlet air are Inlet Barrier Filters (IBFs) and Vortex Separation Systems.
IBFs are either dry or oil-wetted filters. Both types trap particles in a filter media. IBF installations require structural attachments and a bypass-air door to let the pilot continue operation if a filter becomes clogged. Typically, barrier filters are not suited for continuous operation in ‘brown-out’ conditions (high concentration of environmental dust resulting in low visibility) due to the high dust concentration rapidly plugging the filter.
Vortex systems discard, rather than trap, particles. They employ a panel of small diameter vortex tubes that spin airborne particulates to the outside of the tube, where they are dumped overboard. Clean air in the center of the tube passes through to the engine. Often available as factory-installed options, vortex filters use either engine bleed air or a scavenge fan to collect and dump particles from the airstream.
Improved Turbine Engine Program
As Apache and Black Hawk helicopters add capabilities and associated weight, they are also required to perform at higher and hotter conditions than they were designed for. This has led to the need for additional power. In response, the U.S. Army launched the Improved Turbine Engine Program (ITEP), formerly the Advanced Affordable Turbine Engine (AATE) program, for improving fuel consumption, power, durability and cost. The objective of the Improved Turbine Engine Program (ITEP) to seek a new turboshaft engine to provide 50% more power, 25% better specific fuel consumption while reducing life cycle costs.
Honeywell and Pratt & Whitney formed the ATEC joint venture to develop the T900, while GE Aviation builds the T901. The U.S. Army has selected GE Aviation’s T901-GE-900 engine for the Engineering and Manufacturing Development (EMD) phase of the Improved Turbine Engine Program (ITEP), the U.S. Army’s endeavor to re-engine its Boeing AH-64 Apaches and Sikorsky UH-60 Black Hawks.
GE has powered Black Hawks and Apaches for the past four decades with its T700 engine, racking up more than 100 million flight hours of combat-proven experience. Through continuous upgrades and technology advancements, GE has doubled the power of derivative engines in the T700 family over its lifetime and reduced its cost to the government by 50 percent.
GE carried over the benefits of the T700 engine’s single-spool core architecture, ensuring that the T901 engine is ready to continue delivering combat readiness to the Warfighter over the next four decades. The T901’s single-spool core design is the key to its low cost, growth, reliability, maintainability and reduced life-cycle costs.
The full modularity of the T901’s single-spool core provides the Army with superior fix-forward maintainability. Combat units can swap out modular parts of the engine in the field and travel with fewer full-sized spare engines, simplifying logistical footprints and supply lines. The fully modular design also offers superior growth potential at a lower cost through incremental improvements to engine modules, a significant advantage to meet the Army’s FVL requirements. The U.S. Army is also expecting the ITEP engine to meet Future Attack Reconnaissance Aircraft requirements for Future Vertical Lift (FVL).
US Army Engine Program Advances to Design Phase
The US Army’s effort to improve the operational capabilities of its rotorcraft fleet through the Improved Turbine Engine Program (ITEP) is heading for preliminary design requests in May as it aims for a 2023 production goal.
Advanced Turbine Engine Co. (ATEC), a 50-50 joint venture of Pratt & Whitney and Honeywell, is competing with GE Aviation to develop a drop-in replacement for the legacy GE T700 engines that power the Boeing AH-64 Apache and Sikorsky UH-60 Black Hawk fleets. The engine is also expected to power light rotary-winged aircraft expected to emerge from the service’s nascent Future Vertical Lift (FVL) program, according to Jerry Wheeler, vice president of programs at ATEC.
The Army’s new engine will be designed to save 25 percent on fuel consumption at 3,000-shaft horsepower, as well as boost the horsepower-to-weight ratio by 65 percent and engine-design life by 20 percent.
ATEC is offering the HPW3000 turboshaft engine for the ITEP competition, which uses a two-spool gas generator architecture that improves specific fuel consumption, according to Madden. The engine successfully completed performance and durability tests and its new inlet particle separator proved effective in sand testing, Madden said. An engine that can cope with dusty, sandy environments is a requirement stemming from the wars in Afghanistan and Iraq.
Aviation and Missile Command’s chief, Maj. Gen. Jim Richardson, recently highlighted the engine’s potential to allow the Apache and Black Hawk to, “carry more armament and more troops further and more efficiently.
“The ITEP will allow our future aircraft to operate with more flexibility while increasing effectiveness on the battlefield. ITEP, when paired with FVL aircraft, provide us the opportunity to see the future of Army aviation,” Richardson told Army Technology magazine.
Helicopter engines market
The market for military helicopters is on the verge of a technological generational leap with next-generation compound helicopters and tilt-rotor crafts heralding the advent of a new era that is likely to witness a significant expansion of the operational spectrum, capabilities and performance threshold of these machines. This is likely to eventually redefine their role besides enhancing overall effectiveness in conducting a wide range of military missions and operations.
The necessity for enhancing the helicopter engine performance has become one of the main areas of concentration for the helicopter manufacturers, as fuel economy is also one of the main factors that reduce the operating costs of the helicopters. This would make way for the manufacturers to produce more efficient new generation helicopter engines in the years to come.
The helicopter engines market is expected to register a CAGR of over 3% during the forecast period (2020 – 2025). Increase in the demand for helicopters for various military and commercial applications is the main driver for the market. Procurements are being done on a large scale in the military for rotorcraft. Additionally, the helicopters find their use in many applications nowadays even in the commercial sector.
In segmentation by application, the military helicopter engines segment holds the maximum revenue share, followed by commercial helicopter engines. The advantages offered by the helicopters in the military, like quick response in transporting personnel and cargo for frontline support, their vertical takeoff and landing capabilities (which eliminates the requirement of long runways), and the ability to be deployed in almost any open area in cases of emergency assistance, increases their utilitarian value in the military. Thus, the usage of helicopters is more in the military compared to commercial applications, and hence, the market for military helicopter engines is expected to increase. The military helicopter engines segment is also expected to continue their dominance in the market during the forecast period
Globally, North America holds the highest market share in the helicopter engines market, with the US being the major market for the helicopter engines. The demand from the US is likely to continue, thereby becoming the driving factor for the helicopter engines market during the forecast period. The US is currently having the largest helicopters fleet in the world, with more than 9000 commercial helicopters in the US alone. The aftermarket and maintenance services, along with the need to replace parts of the engines for these helicopters, may drive the market for the helicopter engines in the years to come. The huge budgets of the US toward military are enabling the procurement of new helicopters by the US military. This may also drive the production of new helicopter engines for the engine suppliers for these helicopters. Thus, the demand from the US is poised to drive the share of the North American helicopter engines market during the forecast period. However, the market in the Asia Pacific is expected to register the highest CAGR during the forecast period. India is taking the deliveries of Chinook and Apache helicopters currently.
China is also ordering new helicopters from various foreign OEMs, in addition to its indigenously manufactured helicopters. Australia is also expected to procure helicopters for commercial and law enforcement purposes in the near future. All these factors are expected to increase the growth of the market in the region during the forecast period.
Safran, United Technologies Corporation, General Electric Company, Rolls-Royce Holding PLC, and The Boeing Company are some of the major players in the market. Efforts are being made by the existing players for increasing the efficiency and time between overhaul of the engines, which may help them to grab new contracts with the helicopter OEMs. In the military, many local manufacturers are trying to produce new generation indigenous turboshaft engines for their military helicopters. For example, Turkey and India are developing their own indigenous helicopter engines.