From rotary, radial and reciprocating gasoline engines used on first-generation helicopters to gas turboshaft engines found on modern helicopters, an engine’s function is to provide power – but the means of producing that power is constantly evolving.
In the first half of the 20th century, helicopters suffered from the fact that engines could not produce more power than their weight in vertical flight. Since then, there have been many upgrades, most notably turbine engines that revolutionized the rotorcraft industry. Today’s turboshaft engines produce the sustained high levels of power required by a helicopter with a low weight penalty.
With traditional helicopter designs fairly static, upgrading rotorcraft performance aside from avionics means boosting the power and increasing the engine’s efficiency. What follows is a review of today’s rotorcraft engine updates from major engine manufacturers.
Pratt & Whitney, headquartered in East Hartford, Connecticut, has a fleet of more than 64,000 engines and more than 13,000 customers in different market segments. The entire P&W engine fleet has flown more than 864 million hours.
P&W Canada alone invests some $500 million Canadian dollars in R&D every year and that number more than doubles for the larger company. Pratt sources said these investments are positioning P&W to respond successfully to the trends it sees in the industry: a focus on the environment, fuel consumption and new technologies, as well as innovative service plans with solutions increasingly tailored to meet the diverse needs of P&W operators.
“It's clear that the engines of tomorrow will need to have ever-lower environmental impact,” Pratt sources said. “By 2029, our engines will have significantly less environmental impact and we will have a zero-carbon footprint in our commercial operations. Our objective is to be the best aerospace company not only for our customers, but also the world.”
P&W is serious about reducing the fuel consumption of its engines and sees a lot of potential in hybrid electric designs. “We are excited to explore this very interesting field,” said Pratt sources. “Using the resources of United Technologies Corporation (UTC), including the Research Center and Digital Accelerator, we are working on technologies that will take us well beyond where we are today.”
One example of Pratt’s innovation is its latest engine, the PW210, which powers the Sikorsky S-76D and the Leonardo AW169. This engine is exceptionally fuel efficient and easy for customers to maintain, providing automated and electronic engine monitoring functionality that results in significantly reduced pilot workload and allows operators to better plan their maintenance activities.
Based in Paris, France, Safran operates worldwide with more than 2,500 customers in 155 countries. Its next-generation engines, ranging from 500 to 3,000 shaft horsepower, power a wide variety of new helicopter models.
Safran’s technological roadmap is built on four main pillars: core engines’ research and development, new hybrid electric systems, new manufacturing processes and innovative digital services. It invests a significant share — around 15 percent — of its revenue in R&D to deliver rotorcraft engines with more power, better fuel consumption and fewer emissions.
Safran’s latest engine, the 1,200-shaft horsepower (shp) Arrano, incorporates cutting-edge technology and numerous innovations. It offers a 15 percent improvement in fuel consumption over competing engines; sources at Safran say this is one reason why Airbus Helicopters chose it to power the H160.
Safran says integrated and optimized hybrid electric propulsion systems (HEPS) combined with the widest power range are a growing trend –and one that is on its roadmap. In June 2018, Safran passed a major milestone for the Bell Nexus and the first ground run of a HEPS. It validated the energy system architecture and was based on a 100 kWe system. Unveiled at the annual technological innovation event known as Consumer Electronics Show (CES) 2019, Bell Nexus VTOL is powered by a Safran HEPS. The 600 kWe system dedicated to the Bell Nexus will be tested in 2020 and delivered a few months later to Bell.
Phoenix, Arizona-based Honeywell has supported military and commercial rotary wing customers since the introduction of the first military turboshaft-powered helicopter: the Lycoming T53-powered Bell UH-1 Iroquois, or Huey. Since that time, Honeywell has delivered over 40,000 turboshaft engines for operators in over 200 countries and territories worldwide.
Honeywell’s science and technology programs in partnership with the U.S. government have advanced the state of the art in both military and commercial applications. Current technology infusion programs across its helicopter engine portfolio include advanced materials and turbine cooling, improved thermal barrier coatings, as well as in-compressor and turbine technologies.
“To complement the advancements in mechanical capability, Honeywell is leveraging in-depth product domain knowledge across its broad engine portfolio, along with advanced data analytics, to develop innovative new customer solutions providing unmatched maintenance and operational savings,” says John Russo, senior director of military turboshaft engines at Honeywell. Russo believes Honeywell’s forthcoming digital solutions will reduce aircraft downtime and improve customer mission readiness by up to 15 percent.
Honeywell is investing in a program on the T55 engine for the CH-47 Chinook and future vertical lift. The T55 entered service in 1961 at 1,760 shp. Through six deliberate, structured spiral development technology infusion programs over the past 50 years, the T55 has grown from 1,760 to 4,800 shp as the Chinook mission and requirements evolved. “Our latest spiral insertion effort, which is currently in development, will provide a 25 percent improvement in power for the T55 rotorcraft engine while improving fuel efficiency by more than 8 percent using low-risk, state-of-the-art technologies,” Russo said, adding that recent conflicts in the Middle East have shown the need for engines to operate in higher, hotter environments.
GE Aviation, based in Cincinnati, Ohio, is a provider of commercial, military, business and general aviation jet and turboprop engines and components as well as avionics, electrical power and mechanical systems for aircraft. Part of the General Electric conglomerate, it offers engines for the majority of commercial aircraft.
GE Aviation’s commitment to technology investment and its understanding of industry trends and customer requirements resulted in its T408 engine. Building on the architecture of the widely-used T700 engine family, the T408 integrates significant features such as sand-tolerant and corrosion-resistant compressors and turbines to provide abundant, reliable power in harsh conditions. Its sturdy, modular design has sealed oil sumps and an accessible gearbox for ease-of-field maintenance.
David Wilson, a spokesman for military systems at GE Aviation, said the T408, 7,500-shp class engine is designed for heavy lift applications. “Three of them power the U.S. Marine’s CH-53K King Stallion, which is scheduled for initial operational capability (IOC) in 2019,” he said. Reportedly, the T408 allows the CH-53K to fly 20 knots (37 km/h; 23 mph) faster than its CH-53E predecessor. And, as previously reported in Rotor & Wing International, the T408 will provide at least 57 percent more power, 18 percent better specific fuel consumption and 63 percent fewer parts.
Wilson cites other GE Aviation technology advancements and engine design updates as:
Wilson said GE Aviation is focused on more than just the engine for future vertical lift. He cites GE’s total systems approach with 5 pillars: Propulsion, Total Vehicle Health Management, Open Systems Architecture, Integrated Electronic Controls, Total Energy Management.
The Improved Turbine Engine Program (ITEP), formerly the Advanced Affordable Turbine Engine (AATE) program, is a U.S. Army project to develop a GE T700 replacement engine for the UH-60 Black Hawk and AH-64 Apache. The program hopes to improve fuel consumption, power, durability and cost.
ITEP is about more than just providing the Army with options; it is also about saving lives. Currently, the Army flies into battle aboard Black Hawk and Apache Helicopters that are underpowered in high and hot conditions —common in places like the Persian Gulf — and that use too much fuel. ITEP’s goal is to have the new engine be 50 percent more powerful, 25 percent more fuel efficient, and provide 20 percent longer engine life over the current engine, while also meeting stringent performance goals in high and hot conditions at 6,000 feet and 95 degrees Fahrenheit.
GE and Advanced Turbine Engine Company (ATEC) have both been in the running to fulfil this. On Feb. 1, the Army selected GE, awarding the company a $517 million engineering and manufacturing contract to continue work on its T901 single-spool engine. ATEC, a joint venture with Honeywell and Pratt & Whitney started in 2006, had submitted its dual-spool T900 engine for consideration.
GE’s T901 single-spool engine’s modular architecture reduces complexity, resulting in lower weight and increased reliability for the warfighter. A single-spool core means that all rotating components in
the compressor and the gas generator are on one shaft and rotate at the same speed. ATEC had designed its T900 dual-spool, 3,000-shp engine so the Army could install it without having to adjust the engine compartment. A dual-spool engine reportedly has the potential to increase an engine's pressure-to-power ratio to fly higher and longer with more soldiers in hotter climates. The Army weight limit for ITEP is 500 pounds, a requirement which both GE and ATEC met.
The Army expects its next-generation GE engine to be completed by Aug. 1, 2024.