CFM56-2 Performance Upgrade Yielding Big Benefits for USAF

October 29, 2020

WEST CHESTER, Ohio – Through September 2020, the U.S. Air Force (USAF) had installed CFM Performance Upgrade Program (C-PUP) hardware in 770 engines of a planned total fleet of 1,440 CFM56-2 engines.

The engines (military designation F108) power nearly 500 USAF KC-135R Stratotanker aircraft. The program was launched in 2012.

In addition, the U.S. Navy has installed the C-PUP upgrade in 40 of the planned 75 engines in its E-6B Mercury aircraft fleet.

“This program has been a total success, with the hardware yielding even more improvements than we had originally forecasted. As a result, the USAF is getting tremendous benefits from these upgrades,” said Eric Kanaskie, CFM56-2 Military Program manager. ”C-PUP is a prime example of how an operator and a supplier can work together to find a great solution.”

The C-PUP configuration, which also includes diagnostics technology to effectively manage fleet health and enable proactive, condition-based maintenance, incorporates new high-pressure compressor airfoils designed using three-dimensional aerodynamic techniques to improve engine efficiency. As a result, the upgrade is initially expected to provide a 1.5 percent improvement in engine specific fuel consumption. However, the engines are actually exceeding this projection and delivering roughly 1.9 percent better SFC.

In addition, the high-pressure turbine hardware that incorporates the advanced materials technology has been extending engine life by improving the EGT (exhaust gas temperature) margin. The initial forecast of 15 degrees Celsius has been exceed by more than 30 percent. Every degree of EGT margin equates to 1,000 more hours on wing.

The technology in this upgrade is derived from CFM’s highly successful CFM56 commercial engines currently powering the Airbus A320ceo and Boeing Next-Generation 737 families.

Although CFM was responsible for upgrading the engines initially, the USAF has been performing its own C-PUP upgrades at its Oklahoma City Air Logistics Complex since late 2013.

In addition to significant mission benefits, upgraded engines are transparent to both the flight and maintenance crews; there are no field-level technical change orders that drive training requirements for pilots or maintainers on the flight line. Upgraded engines can be intermixed on the wing with the older configuration. As a result, the improved engine configuration is being implemented on an attrition basis when overhauling the original engines – some of which have been on wing for more than 25 years – finally come off wing.

The C-PUP was certified in 2012 following a ground and flight test engine certification program. The U.S. Navy provided the aircraft/engine combination for the flight test program, with the USAF sharing the costs. The flight test engine performed so well that the Navy has kept it installed on the aircraft.

The first re-engined KC-135R tanker entered service in 1984 and nearly 2,000 CFM56-2 engines were delivered for the program.



A 50/50 joint venture between GE Aerospace and Safran Aircraft Engines, CFM International has redefined international cooperation and helped change the course of commercial aviation since its founding in 1974. Today, CFM is the world's leading supplier of commercial aircraft engines with a product line that sets the industry standard for efficiency, reliability, durability, and optimized cost of ownership. CFM International produces the LEAP family of engines and supports LEAP and CFM56 fleets for operators worldwide. .


Charles Soret,


Nathan Hicks,

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