Boeing today revealed that it has decided to adopt a 20.3cm (8in) nose gear extension for the 737 Max family, in addition to controling the new twinjet's spoilers using fly-by-wire.

The company's announcement clarifies several key design features first discussed by Boeing Commercial Airplanes president and chief executive Jim Albaugh in November.

Albaugh had previously said the nose-gear extension could range between 15.2-20.3cm, accommodating the larger diameter of the CFM Interanational Leap-1B engine. CFM has initially sized the engine with a 1.74m-wide fan, but the precise dimensions could change before the design is frozen in the fourth quarter. Entry into service for the Max is slated for 2017 with launch customer Southwest Airlines.

By using the maximum extension in the trade study, Boeing potentially opens the door to slightly increasing the diameter of the turbofan. The longer nose gear also means Boeing must alter the door.

Meanwhile, the new CFM Leap-1B engine will be integrated into the wing in a design similar to the 787, the company adds.

All flight controls will remain mechanically-driven except for the spoilers, which will be based on fly-by-wire inputs, Boeing says. The 737 Max also will adopt an "electronic bleed air system", which is also used on the Airbus A350. The electronic bleed air system can reduce fuel burn by improving cabin pressurization and anti-icing systems without adopting the 787's bleed-less architecture.

Boeing also is extending the 737's tail cone and thickening the section above the elevator for the re-engined variant.

Finally, Boeing also could slightly change the wingtips of the 737 Max, but the company provided no details. A revised design is being tested in a wind tunnel, Boeing says.

The company has not yet publicly stated whether the 737 Max will carry winglets built by Aviation Partners Boeing, which this year is providing winglets for all commercial 737s in production.

Source: Air Transport Intelligence news