page_title: Boeing 737 MAX
section_title: Engines
hierarchical_section_title: Boeing 737 MAX / Design / Engines
caption_attribution_description: == CFM International LEAP
context_page_description: The Boeing 737 MAX is the fourth generation of the Boeing 737, a narrow-body airliner manufactured by Boeing Commercial Airplanes. It succeeds the Boeing 737 Next Generation.
  It is based on earlier 737 designs, with more efficient CFM International LEAP-1B engines, aerodynamic changes including its distinctive split-tip winglets, and airframe modifications.
  The new series was publicly announced on August 30, 2011. It took its maiden flight on January 29, 2016 and gained FAA certification in March 2017. The first delivery was a MAX 8 in May 2017, to Malindo Air, with whom it commenced service on May 22, 2017.
  The 737 MAX series has been offered in four variants, offering 138 to 204 seats in typical two-class configuration and a 3,215 to 3,825 nmi range. The 737 MAX 7, MAX 8, and MAX 9 are intended to replace the 737-700, -800, and -900, respectively. Additional length is offered with the further stretched 737 MAX 10. As of December 2019, the Boeing 737 MAX had received 4,932 firm orders and delivered 387 aircraft.
  In the aftermath of two fatal accidents, Lion Air Flight 610 and Ethiopian Airlines Flight 302, the 737 MAX was grounded worldwide in March 2019.
context_section_description: In 2011, the Leap-1B was initially 10–12% more efficient than the previous 156 cm (61 in) CFM56-7B of the 737NG. The 18-blade, woven carbon-fiber fan enables a 9:1 bypass ratio (up from 5.1:1 with the previous 24-blade titanium fan) for a 40% smaller noise footprint. The CFM56 bypass ranges from 5.1:1 to 5.5:1. The two-shaft design has a low-pressure section comprising the fan and three booster stages driven by five axial turbine stages and a high-pressure section with a 10-stage axial compressor driven by a two-stage turbine. The 41:1 overall pressure ratio, increased from 28:1, and advanced hot-section materials enabling higher operating temperatures permit a 15% reduction in thrust specific fuel consumption (TSFC) along with 20% lower carbon emissions, 50% lower nitrogen-oxide emissions, though each engine weighs 849 lb (385 kg) more at 6,129 lb (2,780 kg).
  In August 2011, Boeing had to choose between 66 in (168 cm) or 68 in (173 cm) fan diameters necessitating landing gear changes to maintain a 17-inch (43 cm) ground clearance beneath the new engines; Boeing Commercial Airplanes chief executive officer Jim Albaugh stated "with a bigger fan you get more efficiency because of the bypass ratio [but also] more weight and more drag", with more airframe changes. The smaller Leap-1B engine will weigh less and have a lower frontal area but a lower bypass ratio leading to a higher thrust specific fuel consumption than the 78 in (200 cm) Leap-1A of the A320neo.
  In November 2011, Boeing selected the larger fan diameter, necessitating a 6–8 in (150–200 mm) longer nose landing gear. In May 2012, Boeing further enlarged the fan to 69.4 in (176 cm), paired with a smaller engine core within minor design changes before the mid-2013 final configuration.
  The nacelle features chevrons for noise reduction like the 787. A new bleed air digital regulator will improve its reliability. The new nacelles being larger and more forward possess aerodynamic properties which act to further increase the pitch rate. The larger engine is cantilevered ahead of and slightly above the wing, and the laminar flow engine nacelle lipskin is a GKN Aerospace one-piece, spun-formed aluminum sheet inspired by the 787.
  To mitigate the pitch-up tendency of the new flight geometry from the engines being located further forward and higher than previous engines, Boeing added the new Maneuvering Characteristics Augmentation System.
caption: Nacelle with chevrons for noise reduction
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