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Old 18 April 2018, 02:52 PM
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GenYus234 GenYus234 is offline
Join Date: 02 August 2005
Location: Mesa, AZ
Posts: 26,695

Originally Posted by jimmy101_again View Post
Hint #3: Most planes are aerodynamically capable of flying upside down.
I get what you are saying about wing design, but I'm not sure this entire statement is accurate, especially with regards to larger aircraft like jumbo jets. First, the aircraft would have to adopt an exaggerated nose up attitude* in order to get an appropriate angle of attack. From some quick Google searches, Boeing aircraft have an angle of incidence like 2 (727) or 3.2 (757). Other searches say they fly with something like 3 of nose up for an overall angle of attack of 5 to 6.2 angle of attack. To get that same AOA inverted would require a nose up attitude* of 9 to 12.6. That would severely increase the drag. Also, there are a number of design elements on the wing such as vortex generators and winglets that are designed to maximize lift and minimize drag in the upright flight positions, they could be useless or even counterproductive in inverted flight.

Secondly, an upside down jumbo would be quite unstable**. The now negative dihedral and inverted wing twist would cause major roll instability and severe danger of spinning the aircraft in a stall. Worse than that would be the fact that in the high angle required for inverted flight, the horizontal stabilizer would probably be at a positive AOA meaning it would also be producing upward lift instead of the downward lift it would normally produce. This would shift the center of lift far beyond the normal range, making pitch severely unstable, possibly so unstable as to be unflyable.

* As seen by an outside observer.
** Not sure if you consider stability part of aerodynamics.
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