Did CFM International Make The Boeing 737 MAX's Engines Too Big?

Did CFM International Make The Boeing 737 MAX's Engines Too Big?

The Boeing 737 MAX became the subject of intense global scrutiny following two catastrophic crashes that resulted in the loss of all passengers and crew aboard. These tragedies prompted the Federal Aviation Administration (FAA) to ground the aircraft worldwide, severely undermining public confidence in Boeing and inflicting significant damage on the company’s stock value and market standing. Central to the controversy was the aircraft’s engine—specifically its size, placement, and the engineering decisions that ensued.

The Engine Behind the 737 MAX

The 737 MAX is powered by the CFM International LEAP high-bypass turbofan engine, developed by CFM International, a joint venture between GE Aerospace and France’s Safran Aircraft Engines. The LEAP engine is highly regarded within the aviation industry and is also employed on other contemporary aircraft, including the Airbus A320neo and the COMAC C919. The A320neo, as the 737 MAX’s direct competitor, adopted larger, more efficient engines, creating competitive pressure that influenced Boeing’s decision to follow a similar path.

The Challenge of Larger Engines

Modern commercial aircraft increasingly utilize larger turbofan engines to enhance fuel efficiency. High-bypass engines like the LEAP improve performance by directing a substantial volume of air around the engine core, thereby reducing emissions and fuel consumption. The optimal diameter for such engines is approximately 13 feet, striking a balance between efficiency gains and aerodynamic drag.

However, integrating these larger engines onto the 737 MAX presented a significant engineering challenge. The original 737 design features a relatively low ground clearance, restricting the space available for larger engines. To accommodate the LEAP engines, Boeing engineers repositioned them further forward and higher on the wing and redesigned the landing gear. These modifications altered the aircraft’s aerodynamics, increasing its tendency to pitch upward under certain flight conditions.

Engineering Compromises and Their Consequences

To mitigate the altered flight characteristics, Boeing introduced the Maneuvering Characteristics Augmentation System (MCAS), an automated system intended to push the aircraft’s nose downward if a stall risk was detected. However, flaws in MCAS—compounded by erroneous sensor data and inadequate pilot training—contributed directly to the fatal crashes.

While the larger size of the LEAP engine necessitated these design changes, industry experts concur that the engine itself was not to blame. The LEAP has demonstrated reliable performance on other aircraft, including the A320neo. The critical failures stemmed from Boeing’s integration of the engine onto the 737 MAX airframe and the subsequent dependence on MCAS to compensate for the resulting aerodynamic challenges.

Impact on the Aviation Industry

The aftermath of the crashes and the FAA’s grounding of the 737 MAX had far-reaching effects across the aviation sector. Boeing encountered production restrictions, substantial financial losses, and a tarnished reputation. Meanwhile, Airbus leveraged the situation to bolster its market position with the A320neo.

The decision to equip the 737 MAX with larger, more efficient engines was driven by competitive and environmental imperatives. Nonetheless, the engineering compromises required to fit these engines onto an aging airframe—and the flawed solutions that followed—were central to the 737 MAX crisis. Ultimately, responsibility lies with Boeing’s design and safety decisions rather than with CFM International’s engine.