How and why Boeing re-engined the 737 to create the Max

Circumstances preceding Boeing’s 2011 launch of the 737 Max programme share similarities with the situation the company now finds itself in.

Today, and for several years, Boeing has been tossing around the idea of developing a new jet – reportedly a 757-sized aircraft for the so-called mid-market.

However, today’s market environment – and Boeing – differ significantly from when the company was considering the 737 Max a decade ago. The airframer now faces the concurrent challenges of recovering from the Max grounding and the pandemic.

Ten years ago Boeing was deep in consideration of a new narrowbody aircraft. Choices were either a 737 replacement – a pricey proposition – or another update of the long-running single-aisle.

At the same time, Airbus was weighing an update for its rival A320.

Eventually, Airbus moved first, launching in late 2010 its re-engined A320neo. That event set in motion circumstances that essentially forced Boeing’s hand, pushing it to launch the 737 Max.

First from the gate, Airbus accumulated impressive early orders for its A320neo – some 918 by the middle of 2011. Notably, those included a landmark order from American Airlines, placed in July 2011.

Until then, American had been an all-Boeing airline, but its 2011 Airbus order included 130 A320s and 130 A320neos.

But the Texas-based airline had not given up on the 737. On the contrary, alongside those A320s American ordered 100 737NGs and, critically, pledged to buy a re-engined 737. “American also intends to order 100 of Boeing’s expected new evolution of the 737NG, with a new engine,” it said at the time.

American hedged that commitment on “final confirmation of the programme by Boeing”.

The die was cast. Official word came from Boeing on 30 August 2011 when the company launched the 737 Max programme with 496 orders from five airlines. The Max was meant to counter the A320neo and fit seemlessly into the fleets of Boeing’s existing 737 customers.

The backlog filled quickly. By December 2011, Boeing held commitments for 948 of the CFM International Leap-1B powered jets from customers including American, Lion Air, Southwest Airlines and lessor Aviation Capital Group.

The Max was a hit.

Boeing initially aimed to begin deliveries in 2017 – a conservative six-year development effort that was several years longer than the company had initially planned for the 787, which, due to delays, subsequently required seven years before first delivery.

“We want to make sure that any date that we quote is the date that we can meet. And I’d rather under-promise and over-deliver, rather than over-promise and under-deliver,” Boeing’s then-commercial aircraft chief executive Jim Albaugh said in September 2011.

Boeing touted the 737 Max’s efficiency as being 16% better than A320s and 4% better than A320neos. And it would require minimum “differences training” for pilots transitioning from the 737NG to the Max. With a few hours of study, pilots could hop from the older 737 to the newer version.

But hanging modern high-bypass turbofans on the 1960s-era 737 posed different challenges than Airbus faced with its re-engining effort.

Boeing’s narrowbody sits lower to the ground than the A320. That is because, as initially designed, relatively low bypass Pratt & Whitney JT8Ds powered the 737. Those engines have smaller diameter fans than modern engines, meaning the 737 originally needed less ground clearance.

Airbus, however, designed its A320 in the age of high-bypass turbofans; as a result, it sits higher.

Boeing added high-bypass CFM56 turbofans to 737s starting with the 737 Classics, solving the ground-clearance issue by flattening the bottom of the nacelle. Those unique CFM56s also power 737NGs.

But Leap engines have a larger diameter than the CFM56s. So, in designing the Max, Boeing moved the Leaps forward and higher.

That configuration, however, caused the jet to pitch nose-high during some flight configurations. Boeing addressed that issue by equipping the Max with the Maneuvering Characteristics Augmentation System (MCAS), which, when activated, pushes the nose down.

MCAS malfunctions played a major role in the crashes of Lion Air flight 610 in October 2018, and of Ethiopian Airlines flight 302 in March 2019. The pilots were unable to recover. Both jets crashed, killing a combined 346 people.