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1. 1) Most modern swept-wing aircraft use some form of winglet. What is a winglet's purpose?

   Winglets are actually little wings that generate lift. And, just like any other wing, they generate lift perpendicular to the relative wind. Because wingtip vortices bend the relative wind inward toward the root of the wing, winglets are able to produce a small amount of forward lift, which opposes drag. When you draw the lift vector from the winglet, the lift vector points forward a little.

   Winglets are actually little wings that generate lift. And, just like any other wing, they generate lift perpendicular to the relative wind. Because wingtip vortices bend the relative wind inward toward the root of the wing, winglets are able to produce a small amount of forward lift, which opposes drag. When you draw the lift vector from the winglet, the lift vector points forward a little.

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2. 2) Most small single engine aircraft have a best-glide speed for power-out situations. What occurs at best-glide speed?

   Any speed faster than (increase in parasite drag) or slower (increase in induced drag) than your best glide speed (L/D max) will decrease your gliding distance.

   Any speed faster than (increase in parasite drag) or slower (increase in induced drag) than your best glide speed (L/D max) will decrease your gliding distance.

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3. 3) Adding flaps increases:

   Adding flaps increases camber, lift and drag.

   Adding flaps increases camber, lift and drag.

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4. 4) Aircraft that have retractable landing gear encounter a slight increase in total drag while the gear are retracting. What is this due to?

   Interference drag is a form of parasite drag that is a result of mixing airflow between aircraft components. If the angle between the components is 90 degrees or less, interference drag increases. So, as the gear retracts, it'll go from 90 degrees all the way to 0 degrees.

   Interference drag is a form of parasite drag that is a result of mixing airflow between aircraft components. If the angle between the components is 90 degrees or less, interference drag increases. So, as the gear retracts, it'll go from 90 degrees all the way to 0 degrees.

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5. 5) What is skin friction drag?

   Skin friction drag is a form of parasite drag that is created at the boundary layer level. Due to the friction of the wing surface or aircraft surface, the air molecules close to the skin will stagnate creating drag. Contaminants such as frost can increase this drag.

   Skin friction drag is a form of parasite drag that is created at the boundary layer level. Due to the friction of the wing surface or aircraft surface, the air molecules close to the skin will stagnate creating drag. Contaminants such as frost can increase this drag.

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Those questions were a real drag!

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Looks like you know quite a bit about drag...

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Nobody's dragging your score down today!

You scored %. Nice work.