On Thursday, November 30, 2017 at 8:44:24 AM UTC-7, Dan Marotta wrote:
While studying for my Flight Engineer license back in the 70s (do they
have Flight Engineers any more?), it was explained that the max weight
of non lifting components had to do with the strength (bending moments)
of the wing spar.Â* Help us out here, Steve L.

MTOW has, I believe, to do with landing gear, brakes, tires, etc. Think
MV**2 during an aborted takeoff.Â* Higher weight - higher takeoff speed
- WAY higher energy to dissipate, that V squared component.
Dan,
No more flight engineers. You have to go back to 727s or early 747s to find a Flight engineer panel and all of those have been retired in this country years ago. MTOW is based on 5 different Performance charts (4 of which are based on engine out performance). MLW is based on Landing Gear and brake energy. Zero Fuel Weight is based on bending moment just like you said. I checked with the factory on my glider and yes, Non Lifting is just like Max Zero Fuel WT is on a jet. Everything beyond this must be wing ballast.