737 Max

The Boeing 737 MAX is a new series of aircraft being developed by Boeing Commercial Airplanes. It is the successor of the Boeing 737 Next Generation. The 737 MAX is the fourth generation of the 737 family. The primary change is the use of the larger and more efficient CFM International LEAP-1B engines and modifications to the airframe. As of December 2015, Boeing has 3,072 firm orders for the aircraft. The 737 MAX first flew on January 29, 2016, nearly 49 years after the maiden flight of the 737 on April 9, 1967; the MAX is scheduled for first delivery in 2017.

## Development

Since 2006, Boeing has discussed replacing the 737 with a "clean-sheet" design (internally named "Boeing Y1") that could follow the Boeing 787 Dreamliner. A decision on this replacement was postponed, and delayed into 2011. In November 2014, it was reported that Boeing intends to replace the 737 by 2030 with a new airplane, possibly with a composite airframe, dubbed as the Boeing Y1.

In 2010, Boeing's competitor, Airbus, launched the Airbus A320neo, which boasted new engines which improve fuel burn and operating efficiency. The decision was met with positive reaction by many airlines and they began making major orders for the aircraft. Pressure from airlines for more fuel efficient aircraft forced Boeing to shelve plans for developing a replacement aircraft, the Boeing Y1, and instead focus on upgrading the 737. On August 30, 2011, the company's board of directors approved the 737 MAX project. Boeing predicted that the 737 MAX will provide a 16% lower fuel burn than the current Airbus A320, and 4% lower than the Airbus A320neo. Boeing expects the 737 MAX to meet or exceed the range of the Airbus A320neo. The first 737 MAX aircraft is scheduled to be delivered in 2017.

There are three main variants of the new family, the 737 MAX 7, 737 MAX 8 and 737 MAX 9 which are based on the 737-700, -800 and -900ER, respectively, the best-selling versions of the 737 Next Generation family. Boeing has stated that the fuselage lengths and door configurations from the Boeing 737 Next Generation family will be retained on the first three 737 MAX variants. On July 23, 2013, Boeing completed the firm configuration for the 737 MAX 8. In December 2013, Boeing stated that a recent internal audit forecasts a 14% lower fuel burn than current 737NG series aircraft. In September 2014, Boeing launched a high density version of the 737 MAX 8, named the 737 MAX 200. The MAX 200 is named for its seating for up to 200 passengers in a single-class high-density configuration with slimline seats. An extra exit door is required because of the higher passenger capacity. Three of eight galley trolleys are removed to accommodate more passenger space. Boeing states that this version will be 20% more cost efficient per seat than current 737 models, and will be the most efficient narrow body on the market when delivered, including 5% lower operating costs than the 737 MAX 8.

Boeing has increased 737 production to 42 per month in 2014, and plans to increase rates to 47 per month in 2017 and 52 per month in 2018.

Spirit Aerosystems manufactures the 737 MAX's thrust reversers. A shortage of a critical component for the thrust reverser has developed; supplier GKN PLC has had difficulty producing the titanium honeycomb inner wall. While early test components met Boeing's specifications, GKN is unable to ramp up production, threatening Boeing's goal of producing up to 52 MAX versions per month by 2020.

The first 737 MAX fuselage completed assembly at Spirit Aerosystems in Wichita, Kansas, on August 13, 2015. It will be a test aircraft and eventually be delivered to launch customer Southwest Airlines. On December 8, 2015, the first 737 MAX was rolled out at Boeing's Renton, Washington, factory; this 737 MAX 8 is named "Spirit of Renton". The first flight took place on January 29, 2016.

## Costumers

Initially, the customers for the 737 MAX were not disclosed, except for American Airlines. On November 17, 2011, Boeing released the names of two other customers – Lion Air and Aviation Capital Group. At that time, Boeing reported 700 commitments from 9 customers for the 737 MAX. On December 13, 2011, Southwest Airlines ordered 150 737 MAX aircraft with 150 options. Southwest will be the launch customer when deliveries begin in 2017.

By December 2011, Boeing had 948 commitments and firm orders from 13 customers for the 737 MAX. On September 8, 2014, Ryanair signed an agreement with Boeing to purchase up to 200 new Boeing 737 MAX 200 "gamechanger" aircraft - comprising 100 firm orders and 100 options

## Design

As production standard, the 737 MAX will feature the Boeing Sky Interior with overhead bins and LED lighting based on the Boeing 787's interior, as well as winglets.

### Improving fuel efficiency

Boeing's design improves fuel efficiency in a number of ways. The most significant improvements are to the wing, the interface of wing and engine, and the use of winglets. The 737NG's wing creates transonic shock waves on the inboard wing at the interface with the CFM-56-7B engine. The 737 MAX wing's integration of the Leap engine's nacelle reduces this drag by 0.5%. In addition, the Leap engine is mounted higher and farther forward of the wing's leading edge than the CFM-56-7B is on the 737NG's wing.

The 737 MAX is to introduce Boeing's Advanced Technology Winglet featuring a split tip. Boeing designed the device to maximize lift specifically on airplanes with wingspans that fit airport gates dimensioned to ICAO Annex 14 code letter C. The device is a direct descendant of the winglet designed for the McDonnell Douglas MD-12. Resembling a three-way hybrid between a blended winglet, wingtip fence, and raked wingtip, Boeing states that this new design should deliver an additional 1.5% improvement in fuel economy over the 10–12% improvement already expected for the 737 MAX. Aviation Partners Boeing is offering a similar "Split-Tip Scimitar" winglet for previous 737NG models. The fuel savings could be even higher if a laminar flow surface treatment being applied meets expectations. Boeing stated in 2013 that the 737-8 MAX with the new winglet can have a 1.8% better fuel burn than a blended winglet-equipped aircraft on flights of 3,000 nautical miles (5,600 km) with 162 passengers. The advantage increases with flight length, but a short flight of 500 nmi (930 km) has a 1% lower fuel burn with the aircraft flying at Mach 0.79.

### Flight deck and flight controls

Boeing plans no major modifications for the 737 Max flight deck, as it wants to maintain commonality with the 737 Next Generation family. The 737 Max will, however, feature four new large-format display screens supplied by Rockwell Collins. These are 15.1-inch (380 mm) landscape LCD displays, in use on the 787 Dreamliner, that will increase pilots' situational awareness and efficiency. Boeing also plans to add more fly-by-wire control systems to the 737 MAX family, although Boeing Commercial Airplanes CEO Jim Albaugh said that changes would be "very minimal." Boeing has confirmed that fly-by-wire controls will be added to the spoilers.

### Engines

Boeing spent most of 2011 evaluating two fan diameters of the CFM International Leap-1B engine: 66.1 in (168 cm) or 68.1 in (173 cm), both of which would require few changes to the landing gear to maintain a 16.9 in (42.9 cm) ground clearance beneath the engines. Albaugh stated the larger fan diameter would produce less fuel burn, but because it is bigger, it produces more drag and is heavier, and would need more extensive airframe changes.

Both fan diameters are an increase from the 61.8 in (157 cm) CFM56-7B engine on the Boeing 737 Next Generation. The updated airliner is also expected to feature external nacelle chevrons for noise reduction, similar to those on the 787 and 747-8. While the smaller Leap-1B engine would have a lower bypass ratio and higher specific fuel consumption (SFC) than the baseline 78 in (198 cm) Leap-X and 80.7 in (205 cm) Pratt & Whitney PW1100G engine options for the A320neo, the smaller engine will weigh less and create less drag on the airframe. The 66.1 in (168 cm) engine integrated on the airframe would offer an SFC improvement of 10–12% over the current 737NG CFM56-7B engine. Industry sources report that assessments are underway to revise the tail cone, natural laminar flow nacelle and a hybrid laminar flow vertical stabilizer for additional fuel burn decrease and drag reduction.

In November 2011, Boeing selected the 68.1 in (173 cm) fan diameter. Because of the larger fan diameter compared to the 737 Next Generation family, the nose landing gear will have to be lengthened by 6–8 inches (15–20 cm) to maintain the required ground clearance. Firm configuration for the 737 MAX is currently scheduled for 2013. On May 17, 2012, Boeing further modified the fan diameter with an increase to 69.4 inches (176 cm). The larger fan will be paired with a smaller engine core than previously identified as part of a series of minor design changes before the final configuration is set in mid-2013.

There will also be a new digital regulator for the engine bleed air systems which should improve its reliability.