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5 Things You May Not Know About the HTS7500 Turboshaft Engine

5 Things You May Not Know About the HTS7500 Turboshaft Engine

It’s very important to Honeywell, and the U.S. Army.

We’re very proud that the Lockheed Martin Sikorsky-Boeing team chose Honeywell’s new HTS7500 turboshaft engine to power the ground-breaking DEFIANT X® helicopter, the team’s entry in the U.S. Army’s Future Long-Range Assault Aircraft (FLRAA) competition. The FLRAA program is a top priority for Honeywell Aerospace and the DEFIANT X will carry on Honeywell’s 60+ year tradition of support of the warfighter if it is chosen by the Army. The HTS7500, which is setting a new standard for power, reliability and versatility, is the latest in a long line of highly successful Honeywell turboshaft engines that have powered U.S. Army aircraft. The HTS7500 checks all the right boxes for the Sikorsky-Boeing team and the Army, and we are excited to play a part in the future of vertical lift for the Army and Team DEFIANT.

The HTS7500 produces 42% more power, uses 18% fuel and is lighter than the latest T55 model.

Investing in turbine engine technology is critical to innovation, and Honeywell maintains a solid investment strategy. The result is an amazingly efficient and powerful HTS7500. Many of these advancements are carried over from Honeywell’s successful business aviation engine lines, such as the HTF7000. We are also applying lessons learned and best practices from our collaboration with the Army on ITEP, the Improved Turbine Engine Program. Combined, they provide the foundation for the HTS7500 design, which achieves these power and fuel burn improvements. The HTS7500 will give the DEFIANT X the power it needs to fly low, fast and far, land quickly, and evade the enemy in complex terrain.

Acquisition, maintenance and lifecycle costs are lower than ever before.

While this is a new engine for Honeywell, the architecture for the HTS7500 has its roots in the T55 family of engines, which have been powering the Boeing CH-47 Chinook for more than 60 years. That longevity enables a significant knowledge base through interactions with Boeing and U.S. Army maintainers on critical reliability and replacement factors, user experience, and maintenance practices. We overlayed those decades of knowledge with the specific aircraft and mission requirements to develop the HTS7500 configuration to meet the DEFIANT X aircraft and mission needs. 

This engine is full of innovations

Design innovations on the HTS7500 include a reduced part count, implementation of a sand-tolerant design, the use of proven low-cost materials and lower turbine temperatures, which minimize cooling and sand-glassing risk. In addition, we’ve lowered operational and support costs through increased reliability and on-condition maintenance. This is supported by advanced engine health monitoring and a modernized control system that leverages digital thread and on-wing optimization from commercial engines.

This engine was purpose-built to power the DEFIANT X and give the Army what its needs

The DEFIANT X has a dual coaxial rotor system with one set of blades placed above the other and a push prop with clutch. We worked closely with the Sikorsky-Boeing team to understand their specific requirements and intentionally designed the HTS7500 to maximize the DEFIANT X aircraft and mission performance. By focusing on the DEFIANT X’s specific needs, we were able to optimize the power-to-weight ratio, lower turbine temperatures and drive maintainability into the design. The modernized control system operates to optimize the engine cycle performance under varying conditions.


John Russo
Vice President, General Manager, Military Engines

John Russo is the Vice President, General Manager, Military Engines at Honeywell Aerospace.


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