LEAP-1B
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Technical Specifications
- Thrust
- 130.0 kN (29,317 lbf)
- Bypass Ratio
- 9.0:1
- Fan Diameter
- 1.763 m
- Pressure Ratio
- 40.0:1
- SFC
- 0.2760 lb/lbf·h
- Dry Weight
- 2,780 kg
- Length
- 3.154 m
- First Run
- 2014
- In Service
- 2017
Overview
The LEAP-1B is the sole powerplant for the Boeing 737 MAX family, sharing the same advanced core technology as the LEAP-1A but adapted to the 737's dimensional constraints. The 737's famously low ground clearance — a legacy of the original 1960s design with its underwing main landing gear — forced CFM engineers to reduce the fan diameter to 69.4 inches (1.763 m) compared to 78 inches on the LEAP-1A, and to position the engine accessories to the top and sides of the nacelle rather than beneath it. The resulting bypass ratio of 9:1 is lower than the LEAP-1A's 11:1, yet the LEAP-1B still delivers approximately 14% better fuel burn than the CFM56-7B it replaces.
The LEAP-1B shares the same CMC high-pressure turbine shrouds, 3D-woven composite fan blades (18 blades), TAPS II combustor, and additive-manufactured fuel nozzles as its sibling variants. Boeing selected LEAP-1B as the exclusive engine for the 737 MAX, unlike the A320neo which offers a choice between LEAP-1A and the Pratt & Whitney GTF. This sole-source arrangement created significant operational risk when the 737 MAX was grounded worldwide from March 2019 to November 2020 following two fatal accidents linked to the MCAS flight control system — a software and design issue unrelated to the engines.
Technical Specifications
| Parameter | Value |
|---|---|
| Maximum Thrust | 130.0 kN (29,317 lbf) |
| Bypass Ratio | 9.0:1 |
| Fan Diameter | 1.763 m (69.4 in) |
| Dry Weight | 2,780 kg (6,129 lb) |
| Length | 3.154 m (124.2 in) |
| Overall Pressure Ratio | 40.0:1 |
| SFC | 0.276 lb/lbf·h |
| First Run | 2014 |
| Entry into Service | 2017 |
Variants
LEAP-1B variants cover the full 737 MAX thrust range. The LEAP-1B27 (27,000 lbf) powers the 737 MAX 7, while the LEAP-1B28 (28,000 lbf) is the standard for the 737 MAX 8 and LEAP-1B28E1 covers the MAX 8-200 high-density variant. The LEAP-1B28BBJ1 serves the Business Jet derivative. The LEAP-1B28/B1 (up to 29,317 lbf) powers the larger 737 MAX 9 and MAX 10. All variants share common line replaceable units (LRUs) and maintenance procedures, minimizing fleet complexity for 737 MAX operators.
Aircraft Applications
- Boeing 737 MAX 7: LEAP-1B27 (27,000 lbf) — smallest MAX variant
- Boeing 737 MAX 8: LEAP-1B28 (28,000 lbf) — highest-volume MAX variant
- Boeing 737 MAX 9: LEAP-1B28B1 (29,317 lbf) — stretched MAX
- Boeing 737 MAX 10: LEAP-1B28B1 (29,317 lbf) — longest 737 ever built
Development History
Development of the LEAP-1B began formally when Boeing launched the 737 MAX program in August 2011. The first LEAP-1B engine run took place in June 2014, with FAA certification achieved in May 2016. The 737 MAX 8 entered revenue service with Malindo Air in May 2017. Following the two fatal crashes (Lion Air 610 in October 2018 and Ethiopian Airlines 302 in March 2019), the 737 MAX fleet was grounded globally. LEAP-1B engines accumulated significant time during the 20-month grounding with engines stored on the aircraft or in warehouses, requiring re-certification of airworthiness upon return to service. The MAX returned to service in the US in December 2020. By 2024, LEAP-1B had powered the 737 MAX family to over 30 million flight hours. Introduction of the 737 MAX 10 in 2023 represented the highest-thrust application of the LEAP-1B platform.