CFM56

Overview

The CFM56 is the most produced jet engine in aviation history, with more than 35,000 units delivered since its entry into service in 1982. A joint venture between GE Aerospace and Safran Aircraft Engines (formerly Snecma) under the CFM International partnership, the CFM56 family powers two of the most ubiquitous commercial aircraft families ever built: the Boeing 737 Next Generation (NG) and the Airbus A320ceo. Its combination of reliability, fuel efficiency, and low maintenance cost made it the dominant narrowbody powerplant for four decades.

The CFM56 traces its lineage to the early 1970s, when GE and Snecma signed a joint-venture agreement in 1971 to develop a new commercial turbofan for the narrowbody market. The core technology derived from GE's F101 military engine, while Snecma contributed fan and low-pressure turbine expertise. After a lengthy certification program driven partly by US export-control regulations on military-derived technology, the CFM56-2 entered airline service on the DC-8-73 in 1982. Successive variants — the -3 for the 737 Classic, -5 for the A320 family and A340, and -7B for the 737NG — continuously improved thrust, efficiency, and reliability.

Technical Specifications

Variants

The CFM56 family spans five major variants across fifty years of development. The CFM56-2 (22,000–24,000 lbf) re-engined the Douglas DC-8-73 and powers some Boeing E-3 Sentry and E-6 Mercury military aircraft. The CFM56-3 (18,500–23,500 lbf) was developed for the 737 Classic (−300/400/500), featuring a smaller fan to maintain ground clearance. The CFM56-5A/5B/5C (22,000–34,000 lbf) powers the entire A320ceo family and the A340-300/200. The CFM56-7B (19,500–33,000 lbf) is the exclusive engine for the 737NG (−600/700/800/900ER) and remains the most numerous variant, with over 15,000 units delivered. Each successive variant brought improvements in OPR, SFC, and on-wing reliability.

Aircraft Applications

• Boeing 737-300: CFM56-3B1/3B2 (20,000–22,000 lbf) — 737 Classic launch variant
• Boeing 737-400: CFM56-3C1 (23,500 lbf) — stretched Classic
• Boeing 737-500: CFM56-3C1 (20,000 lbf) — shortened Classic
• Boeing 737-600: CFM56-7B18/22 (18,500–22,700 lbf) — smallest 737NG
• Boeing 737-700: CFM56-7B24/27 (24,200–27,300 lbf) — 737NG standard single-aisle
• Boeing 737-800: CFM56-7B26/27 (26,300–27,300 lbf) — best-selling 737 variant
• Boeing 737-900ER: CFM56-7B27A (27,300 lbf) — longest 737NG
• Airbus A318: CFM56-5B5/9 (23,300 lbf) — shortest A320 family member
• Airbus A319: CFM56-5A4/5B5/6 (22,000–27,000 lbf) — A320 family smallest narrowbody
• Airbus A320-200: CFM56-5A1/5B4 (25,000–27,000 lbf) — the defining narrowbody
• Airbus A321-200: CFM56-5B3 (33,000 lbf) — high-thrust variant for heaviest A320 member
• Airbus A340-300: CFM56-5C4 (34,000 lbf) — four-engine long-range application

Development History

First run in 1974 at GE's Evendale facility, the CFM56 program was nearly cancelled multiple times due to US ITAR restrictions on the F101 core technology — the US DoD initially refused to allow export of the military core to a French partner. A landmark 1979 agreement cleared the path for commercial sales. The −3 variant for the 737 Classic required a novel accessory gearbox repositioning to the side of the engine (from beneath) to preserve the 737's low ground clearance — a design decision that would echo in the LEAP-1B decades later. The CFM56-5B introduced a dual-annular combustor (DAC) option to reduce NOx emissions on the A320neo's predecessor. The −7B for the 737NG, certified in 1997, achieved unprecedented dispatch reliability rates above 99.98%, cementing CFM56's reputation. Production continues for aftermarket support and spare engines, with the LEAP family serving as the direct successor.