Sometime in the next few months, the U.S. Army will make an award in one of its most critical modernization efforts: the Improved Turbine Engine Program (ITEP). In 2006, the Army began an effort with the aerospace industry to design and develop a new engine primarily intended to replace the existing power plant in its fleets of 1,300 Blackhawk and 600 Apache helicopters. The winning candidate may also power some or all of the products of the Future Vertical Lift (FVL) program as well as a number of Navy and Marine Corps helicopters.
A major impetus for ITEP was the Army’s experience operating rotary wing platforms in Afghanistan and Iraq. The combination of flying in hot-high conditions and operating from rough landing fields put tremendous strain on the engines of Army helicopters.
In addition, both the Apache and Blackhawk have been gaining weight since they were first introduced as additional sensors, weapons and defensive capabilities were added. The result has been enormous strain on the engine and a reduction in mission capabilities. According to Major General William Gayler, commander of the Army’s Aviation Center of Excellence:
“We’ve been growing and gaining weight for all the rights reasons. Every new technology, everything designed to protect a crew or its passengers, but we’ve given maneuverability at the objective away. We’ve given away payload, we’ve given away ammo, we are limiting options to a commander, we are not giving options. We do give options if the weather’s right but if the weather’s not right, we can’t give options.”
ITEP is about more than just providing the Army with options. It is also about saving lives. In many ways, ITEP will mean the difference between life and death for the soldiers involved. There have been a number of crashes in Afghanistan resulting in the loss of life as Blackhawks struggled to operate in the high-hot climate.
As the Army shifts the focus of its investment strategy from counterterrorism to the enormous challenge posed by near-peer militaries, ITEP’s importance, if anything, will increase. Not only will Army Aviation continue to face a wide range of environments and stressing mission profiles, it also will have to operate in a highly contested air environment.
Dealing with near-peer adversaries will require aviation platforms that can go farther and faster while carrying more and yet economize on fuel consumption. Improved fuel consumption and better maintainability also will impact budgetary outlays at a time when the demand on Army financial resources is increasing.
The current engine powering both Blackhawks and Apaches is the T700, first produced in 1978. Over the decades, the T700 has undergone a number of product improvements, most particularly an increase to some 2,000 horsepower. Unfortunately, both the weight and drag of the Blackhawk and Apache has increased beyond what the T700 can fully support. A new engine is now imperative for Army Aviation.
The driving impetus for ITEP is to reclaim the maneuverability, range and payload capacity for Army Aviation assets that has been lost over the past two decades. This translates into a requirement that the new engine be 50 percent more powerful and 20 percent more fuel efficient than the T700. Recognizing that both the Blackhawk and Apache are likely to remain in service for decades to come, the Army also wants an engine that is easier to produce and maintain than the T700. The requirements for the new engine include significantly improved power-to-weight, reduced fuel consumption, greater design life and lower procurement and sustainment costs.
The outcome of the competition between the two companies vying for the ITEP award, General Electric and the Advanced Turbine Engine Company (ATEC), a joint venture of Honeywell and Pratt & Whitney, rests largely on the answer to a single question: is a two-spool turboshaft engine better than one with a single spool?
For those not steeped in the design details of aircraft engines, a spool is a turbine-compressor combination connected by a shaft. A single spool means there is only one turbine-compressor combination connected by a single shaft powering the engine. A two or dual spool engine has two turbine-compressor sets connected by two separate shafts.
The T700 is a single spool engine. So is the ITEP offering by General Electric, the T901. It represents a design approach that was cutting-edge for its time. But the single spool design by definition must compromise on engine performance and, hence, speed and power in order to remain stable. Whatever advances industry can make with respect to the components of a single spool engine, they cannot make up for the fundamental limitations of the basic design.
The T900 dual-spool engine designed by ATEC takes advantage of some 40 years of advances in engine design. In particular, it is an outgrowth of the demand from the aviation industry for greater performance, responsiveness and fuel efficiency. Dual-spool engines power virtually all of this country’s advanced military aircraft. The two-spool arrangement gives more thrust with better fuel economy because each spool can operate at an optimum speed.
Compared to a single-spool design, the T900 runs cooler, uses less fuel and creates less stress on parts requiring maintenance intervention. This allows the pilot to better match engine performance to environmental conditions such as heat and altitude. As a consequence, a two-spool engine also uses less fuel than a single-spool.
In selecting a new engine, the Army must also think about the future. In addition to the introduction of new platforms as a result of the FVL program, it is likely that Army Blackhawks and Apaches will take on new missions and have to carry additional equipment. The dual spool T900 has more power to support growth than a single spool engine. Army leaders stress that their modernization plan is focused on putting capabilities in the hands of the warfighter. ITEP is an example of giving the warfighters what they need now and will require in the future.
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