Boeing has outlined the specification of it's longest version of the MAX, to compete with the Airbus 321 NEO and fill the gap in the market left by the 757. The design will be finalised by the end of 2017. Entry into service could be 2020 depending upon orders,
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.
*** Updated 17 Jan 2017 ***
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.
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.
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.
Boeing 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,"
So will it happen?
These relatively minimal changes from the original proposals should allow entry into service as soon as 2020, thereby allowing the MAX to compete wiith the A321NEO sooner.