PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 10th Dec 2019, 18:04
  #4375 (permalink)  
MechEngr
 
Join Date: Oct 2019
Location: USA
Posts: 133
Originally Posted by answer=42 View Post
Some posters on airliners.net assumed that, due to the new undercarriage, that the MAX-10 would not need MCAS. Then the story got picked up by the media ... The following reference (in French!) confirms the presence of MCAS:
https://www.air-journal.fr/2019-11-2...x-5216417.html
Apologies for the wild goose chase.
I suppose that the original question more or less stands:
Could a taller undercarriage permit a revised pylon and changed engine position to be used to eliminate MCAS as a last best option?
This SLF thanks you for many hours of safe flying.
The "taller" undercarriage is a temporary extension capacity used during take-off and probably landing. It squats back to the original height at all other times, placing the engines close to the pavement just like always. The main effect doesn't seem to be from the forward placement, but from the larger diameter which presents a far larger frontal area (radius-squared). There are overlays of the NG vs MAX and the difference in engine longitudinal placement is slight.

Making that increase permanent isn't likely. The landing gear tucks into the fuselage and any increase in length changes the wing structure by placing the upper mount farther out, increasing the bending loads on the wing, especially during landing. It would also raise the fuselage, making the low-impact ground support more difficult to do; baggage handling, fueling, food delivery, and I'm sure others. Longer escape chutes might require increases to the storage areas in the fuselage. It seems like a small change, but it snowballs pretty quickly. And the airlines, the customers, don't like snowballs.

To put the engines where they would be neutral to pitch response is likely to require a substantial increase in landing gear length making for a large snowball.
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