CFM56-7: An In-Depth Look At The New Industry Leader

December 7, 1996

The new CFM56-7 engine for the Next-Generation Boeing 737 family combines proven CFM56 architecture with new technology to lower operating costs dramatically while maintaining industry-leading performance, reliability, and operability.

Through November, firm orders have been announced for 501 CFM56-7-powered 737 aircraft. The CFM56-7 is produced by CFM International (CFMI), a 50/50 joint company between Snecma (Safran Group) of France and General Electric of the United States. CFMI is headquartered in Cincinnati, Ohio.

The CFM56-7's advanced technology, which includes 3-D aero design, a high efficiency wide chord fan, advanced electronic engine control and active clearance control systems, will provide significant cost benefits.

The engine's specific fuel consumption (SFC) is about 8 percent lower than that of the CFM56-3 on current 737s, resulting in better aircraft fuel burn. A reduction of 1 percent in fuel burn can mean an annual savings of up to $15,000 per aircraft.

In addition, CFMI has improved the engine cycle, resulting in increased EGT (exhaust gas temperature) margin, and has incorporated advanced materials and thermal barrier coatings in the high pressure turbine for enhanced durability. CFM56-7 maintenance costs are projected to be 15 percent lower at equivalent thrust than those of the industry-leading CFM56-3C1. Engine reliability, low operating temperatures, and durability features will extend time on-wing up to 20 percent compared to other CFM56 engines. An overview of the CFM56-7 technology features follows:

FAN: The fan, designed with three-dimensional (3-D) aerodynamic analysis techniques, incorporates 22 solid titanium, wide-chord blades and features a 61-inch diameter for maximum specific flow. The resulting 92 percent adiabatic efficiency makes the -7 the best in the industry. The fan also includes a conelliptical spinner which centrifuges hail, water, and debris, thus minimizing the potential for foreign object damage to the core. The aluminum fan casing weighs less than that of the CFM56-3.

BOOSTER: The three-stage CFM56-3 booster has been improved with 3-D aero design tools for the CFM56-7, to increase airflow and enhance efficiency, thereby contributing to the engine's higher EGT margin.

CORE: The CFM56-7 shares a common core with the CFM56-5B/P engine currently in service on the Airbus Industrie A320 family. The 9-stage high pressure compressor has proven its reliability and durability on other CFM56 engine models, but has been further improved with 3-D aero for better efficiency and aerodynamics. The engine is equipped with either a single or an optional double annular combustor (DAC). The DAC, in service on the -5B, lowers engine NOx emissions by as much as 45 percent compared to the single annular configuration. The high pressure turbine also incorporates 3-D aero, active clearance control, and single crystal N5 material in both the blade and the nozzle for improved durability, lower maintenance costs, and longer on-wing life. At entry into service, CFM56-7 rotating parts will have higher declared initial lives compared to other CFM56 engine models.

LOW PRESSURE TURBINE: The high-efficiency low pressure turbine is also common with the -5B/P and features new 3-D airfoils, a new case and shrouds, and improved materials.

CONFIGURATION AND ACCESSORIES: A co-located CFMI/Boeing team designed the configuration and installation of accessories, using digital mock-ups and maintenance access solids. The goal was to simplify on-line maintenance and improve specific line-replaceable unit times. The team validated the process in the first full maintenance demonstration in Cincinnati, Ohio, earlier this year. The -7 incorporates the FADEC II (Full Authority Digital Electronic Control) system originally developed for the CFM56-5C engine.

The CFM56-7 is rated from 18,500 to 26,300 pounds (84 to 117 kN) thrust for the Boeing 737-600/-700/-800 series of aircraft.

More than 7,700 CFM56 engines are currently in service on more than 2,700 aircraft worldwide, and this fleet has logged more than 85 million engine flight hours and 53 million cycles. Overall, more than 11,000 CFM56 engines have been ordered or committed to date at a value of more than $40 billion.

Jamie Jewell

+1 513.885.2282

Charles Soret

+33 (0)

Perry Bradley

+1 513 375 2597