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Old 05-30-2017, 11:47 PM
Richard Pearse Richard Pearse is offline
Join Date: Aug 2001
Location: On the outside looking in
Posts: 10,072
Originally Posted by eschereal View Post
The reality is that a cruising airplane flies with a slight positive pitch of a couple degrees or so all the time. I believe this is probably in order to offset mach tuck, which affects subsonic airplanes. The level was registered to the cruise attitude, which does not correspond to ground plumb.
It is more simple than that. The wing needs to fly at a positive angle to the relative airflow (angle of attack), otherwise there is no lift. The angle of the fuselage then is the wing angle plus or minus any rigging angle between the wing and fuselage (angle of incidence). You can design a plane that has zero body angle but it will only be level at one speed, any faster and it will be angled down, any slower and it will be angled up.