Boeing launched it's longest version of the MAX on 19 Jun 2017, to compete with the Airbus 321 NEO and fill the gap in the market left by the 757. The MAX-10 already has over 361 firm orders and commitments.
Boeings Randy Tinseth has said that the 737 Max 10 will offer the same capacity as the slightly longer Airbus A321neo, but will be 2.8 tons lighter, have lower fuel consumption and slightly greater range. He went on to say that "We aren't looking to simply build something on par with the A321neo. We're bringing a better airplane to the market - and that's our focus."
*** Updated 10 Feb 2018 ***
More details from United...
Shortly after United airlines placed an order for the MAX-10 to replace their -900 and -900ERs, Howard Attarian, the SVP Flt Ops issued a letter to pilots giving a few more details including:
Two extra fuselage barrel sections forward and aft of the mid-section will give an overall length of 43.8m / 143 feet 8 inches which is 66 inches (1.68m) or 2 seat rows longer than the MAX-9, giving it a single class passenger capacity of up to 230, or a two class capacity of 189, still 4 less than a two-class A321 NEO.
There will also be an improved body contour to reduce the risk of tail strikes.
There is to be an “improved flap design” that enables more approaches and landing at Flaps 40. Also, autoland will be certified for lower landing flap settings to improve go-around climb performance following enroute icing conditions.
The MTOW will have to be increased by at least 1,200kg to take the extra 12 pax. Plus any additional fuel/range capability that might be desired.
The idea of using the LEAP-1A or 1C has been abandoned. The advantages of continuing with the LEAP-1B are that the fan diameter remains the same and this greatly reduces development and certification time.
The quick option is using the “thrust bump” capability of the LEAP-1B. Rated at just over 29,000 lb. for takeoff, the Leap 1B28 is expected to be capable of a “throttle push” to over 31,000 lb. This would save the problems of an increased fan diameter.
Main Landing Gear
Although the engine is unchanged, the fuselage is lengthened so the main landing gear must be modified to enable adequate clearance of the longer body for rotation on takeoff and landing and to ensure the aircraft remains stall rather than pitch-limited.
The original plan was to lengthen the MLG however since the fan diameter is unchanged an easier solution which requires less changes to the wheel welll has been adopted, namely a "semi-levered" design which is more commonly known as a trailing-link, similar to that used on the 777-300ER and 787-10, that shifts the rotation point slightly aft. It is also believed that the gear will also be telescopic and contract during retraction to fit into the existing wheel well.
737 MAX vice-president and general manager Keith Leverkuhn said in Feb 2017 ."Boeing has been evaluating multiple “good ideas”, including a shift from the 737’s traditional oleo strut to a trailing link landing gear design, A key criteria in the final decision (of the MAX-10) later this year will be the inherent reliability of the landing gear design,"
Keith Leverkuhn said on 2nd May about the -10 MLG: “The design focus is on the upper portion of the gear as it integrates with the actuator. In this area, within the tight confines of the existing wheel well, Boeing’s new design will do some “clever folding using a link mechanism at the top,”
"The lower section of the leg is also modified with an additional shock strut that fits inside the same forging. This moves the contact point aft a little bit. That’s fundamentally what we are doing and yes, it will look like a trailing link gear. We want to make it maintainable, reliable, and we are going to need that gear to get the performance we want out of the -10 but I’m confident in the solution set,”
When talking about testing Leverkuhn says: “The kinematics are tricky. How do we take this fundamentally longer gear and make sure it folds up nicely in the gear well. So we do drop tests to understand the structure we have sized is appropriate and another rig test around the function of the new gear. We will spend most of the year doing that, but we are really zeroing in on it,” Boeing is constructing two gear test rigs, one for functionality and the other for robustness.