[NSRCA-discussion] Airplane angle of attack

[chris moon]

The optimum AOA  on airliners is a function of wing design.  It's the 

operator's job to try and stay near the optimum AOA for maximum 

efficiency.  Lighter gross weights require either higher altitudes or 

lower true airspeed to be most efficient. Likewise, heavier weights will 

have you faster and or lower.  I guess what I'm saying is that the 

optimum AOA is essentially dictated by wing design and we juggle the 

other variables in order operate the wing as efficiently as possible.



I have rolled the 737, 757, 767 and A320 in the simulator and they make 

poor pattern planes.  I'm sure there is a significant downgrade for a 

single roll that loses 5000+ feet of altitude.  Don't even ask about 

knife edge performance.



Chris



Bob Richards wrote:

> That makes sense to me. The AOA depends on the load. In an extreme 

> case, very lightly loaded, I don't think you would want to fly with 

> the fuselage in a nose down attitude, that would probably be 

> inefficient. Better to have it slightly nose up in cruise with a full 

> load. JMHO.

> Of course, the reason WE would trim wing incidence would have more to 

> do with overall flight characteristics during aerobatics, particularly 

> with pitch coupling in knife edge flight.

> Bob R.

>

>

> */chris moon /* wrote:

>

>     Tried to post this before but it did not go through.

>

>     The optimum cruise angle of attack for jetliners is somewhere between

>     2.5 and 5 degrees nose up. Usually closer to 2.5 or 3 degrees for an

>     econ cruise. As fuel burns off and the gross weight goes down, the

>     airplane will need a lower angle of attack to maintain flight which

>     will take us away from our optimum angle (lower). So, we will either

>     climb to where the air is "thinner" and require a higher aoa

>     (angle of

>     attack) to get us back to the 2.5 or 3 degrees or, slow down and

>     maintain the lower altitude thus requiring us to increase the aoa

>     back

>     to optimum. The answer to your question is yes, a jetliner flies at a

>     nose high aoa in cruise. Lift from the fuselage would probably be

>     negligible other than "impact" lift - the force of the relative wind

>     against the raised fuselage bottom.

>

>     Chris

>

>

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