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rf7.egg

manual-slack

• when choosing airframes, try challeging one such as Goldberg, which is

• wing load

• wing configuration

• wing location / high/ mid /low wing

The lift formula is rearranged to determine speed as a function of wing loading and the lift coefficient. If we assume that the lift coefficient is approximately constant between the two aircraft during cruise (this is an acceptable assumption here to demonstrate the concept of wing loading), then we can compare the effect that wing loading has on the resulting cruise speed.

An increased wing loading corresponds to a smaller wing at a given mass, and results in an increased cruise speed. Of course the Legacy has a much larger engine which allows it to reach a far higher cruise speed (drag is proportional to V^2), but the point still stands that an aircraft that is designed to cruise at higher speeds will do so most efficiently with a higher wing loading. The highly loaded wing also results in a higher stall speed (clean), and a more complicated flap arrangement (greater increase in lift coefficient) is thus required to reduce the stall speed.

wing-area

Lift is an aerodynamic force which is produced as a consequence of the curvature of the wing and the angle of attack of the relative velocity flowing over the surface. It follows that larger wings of a greater planform area are able to produce more lift; this is easily shown mathematically from the lift formula:

L

1 2 ρ V 2 A C L L : Total Lift Force ρ : Air density V : Velocity A Planform Wing Area C L : Lift Coefficient The total lift force is increased in proportion with the wing area.

Higher aspect ratio wings result in a lower lift-induced drag coefficient. This is why gliders have long slender wings (high AR) as drag minimization is paramount to obtain the best glide ratio. A high aspect ratio wing is more structurally challenging to design, as the wing will flex more in flight, creating larger bending stresses and a damped roll control response. Structural flutter is also more prevalent in higher aspect ratio wings.

• control surface

The flaps and ailerons are attached to a rear spar which runs along the span. The spar is designed to resist and transfer the loads generated by the deflection of the control surfaces.

Trailing edge flaps are one of two devices used to extract additional lift from a wing at low speed. Slats modify the camber at the leading edge, performing a similar roll to the flaps. High-lift devices are a large topic on their own and are discussed in detail in Part 4 of this mini-series.

Ailerons are used to provide roll control and do so by generating a large rolling moment through asymmetrical deflection. The figure below demonstrates a roll to the left. The aileron on the right wing deflects downwards which produces additional upward lift on the right wing. The left aileron deflects upward which modifies the flow field, generating a downforce at the left wingtip. Together these deflections generate a rolling moment which forces the right wing up, and the left wing down.

link-above

[aerodynamicsEngineeringForStudents(https://github.com/aiegoo/uas-reference/blob/master/drone-dev/aeroEngineering.pdf)

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