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Can the lift of a plane be increased by increasing the Angle of Incidence (angle between the chord line of the main wing and the axis of the fuselage)? Meaning, can more lift be generated while the plane is in a horizontal position (i.e. not pitching nose up or down) if the wings are angled leading edge up.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Federico Mar 31 at 7:30
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Yes. Angle of Attack is included in the Lift formula. Lift generally increases with angle of attack in a linear fashion until AOA reaches stall. This is why it is not a good idea to fly at too high an AOA. Better to increase Velocity. Lift increases with Velocity squared.

The Navy Vought F-8 Crusader had a "variable incidence wing" that was raised to a higher pitch relative to the fuselage for take-off and landing. Interesting to note the variable incidence wing would also improve forward visibility on landing because the fuselage nose would have a lower pitch to the horizon while the wing was at a given angle of attack. Trailing edge flaps also raise the wing chord incidence to the fuselage with similar benefits.

While in flight, most planes simply pitch the entire plane with the elevator to increase Angle of Attack.

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Yes, it is possible and variable-incidence wings have been used.

The only production example was the Vought F-8 Crusader, used primarily by the US Navy. It had a variable-incidence wing, which tilted nose-up by about 7 degrees to give increased lift for takeoff. The conventional solution of a lengthened nose undercarriage was deemed impractical for the design.

An earlier prototype was the German Blohm & Voss BV 144 transport of WWII, which was built in France and seems to have flown a few times around the end of hostilities. Variable incidence was provided because the tail was too close to the ground for conventional rotation of the whole plane at takeoff.

Another rather obvious application is the tiltwing V/STOL configuration, of which several prototypes have also flown. The additional lift provided by increased incidence can significantly ease the transitions between vertical and forward flight modes.

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If I am thinking about this correctly, increasing angle of incidence would increase lift because you would also be increasing angle of attack. Increasing the angle of attack would increase lift until you reach the critical angle where you have airflow separation and aerodynamically stall the wing. It’s the angle of attack that’s important.

A better question is what are the advantages and disadvantages of increasing angle of attack by increasing angle of incidence. One advantage that I can think of is a reduction of drag generated by the fuselage and empennage at low speeds such as slow flight. However, there will be an increase in drag created by the wings at high speeds such as cruise flight. Intuitively, you would also assume there would be an increase in stall speed. How would an increase in incidence angle affect maneuvering such as banking for turns. Wouldn’t the increased angle of incidence exacerbate stall characteristics even when the turn is coordinated?

Just throwing some thoughts out there.

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  • $\begingroup$ Consider what were the specific advantages motivating the design of the variable-incidence wing on the F-8 Crusader... a nice chance to exercise one's google-foo... $\endgroup$ – quiet flyer Mar 27 at 23:58
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In short, no. But it depends... Angle of incidence does not increase or decrease lift, only angle of attack and airspeed affect lift.

Let me explain - If you had an aircraft with a variable angle of incidence you could fly at a constant angle of attack while varying the incidence and have no effect on lift. Picture the wing steady with respect to the airstream, while the fuselage tilts up and down; all you would affect is drag.

Now, if the fuselage remained constant while you varied incidence then lift would be affected, but it would be affected because the angle of attack was changing!

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  • $\begingroup$ But, if the attitude of the fuselage is constrained to stay horizontal as was stated in the question... $\endgroup$ – quiet flyer Mar 27 at 23:56
  • $\begingroup$ Then it seems the answer is yes, as per your last sentence, which possibly might better have served as the main thrust of the answer... $\endgroup$ – quiet flyer Mar 28 at 0:03
  • $\begingroup$ I'm not so sure that the no-pitch constraint was in the wording that I answered to, but whether it is or not, my point is that it is the AoA that increases lift, not incidence. This question is really a mess... $\endgroup$ – Michael Hall Mar 28 at 0:15
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All it means is the deck angle of the fuselage will be lower for a given speed. Weight being the same, the wing will fly at the AOA it needs to fly at to support the weight. By increasing the incidence, the fuse will just be pointing down more because AOA will be the same for a given flight condition.

You have a downstream problem as well because the decalage with the horizontal tail has also increased so you have to modify it (move it LE up) to maintain the same decalage angle you had before to maintain the same pitch authority and trim behaviour.

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