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Brainteasers
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Sep. 7, 2006

Brainteasers
Interactive Quiz #111:
Flapped, Foiled and Dragged

The Earth's atmosphere is composed of 78 percent nitrogen and 21 percent oxygen, leaving only one percent for airplanes. Let's see what we can force into that airspace with a few aerodynamic questions and controversies.

INSTRUCTIONS: Answer the questions as best you can, then click on the "Score my quiz answers" button to see your score and read the explanations. If you don't like your score the first time around, you can change some of your answers and resubmit. To get the most out of this quiz, we suggest you keep trying until you get a perfect score.

NOTE: When more than one answer is true, only the most complete, correct answer will be scored as correct. The answers are assumed to apply within the United States unless otherwise noted.

1. Wings -- the title of a 1928 Paramount Pictures flying/romance movie starring Clara Bow and Charles "Buddy" Rogers -- set the standard for principles of flight and cheesy romances. Wings -- the airfoils, not the film -- are shaped to produce lift as they move through the air. Generally, low pressure forms on the wing's upper surface and high pressure beneath. The high-pressure air beneath tends to move toward the low and curls around wingtips, creating rotating vortices. When viewed from behind, this creates ... (Complete the statement with the best answer.)
a. Counterclockwise rotation about the right wingtip.
b. Clockwise rotation about the left wingtip.
c. Counterclockwise rotations about both wingtips.
d. Clockwise rotation about both wingtips.
e. Both a and b.
2. The four forces acting on an airplane in flight are (all together, class): lift, weight, thrust, and the FAA ... OK, not the FAA (that's a reactive force) but, instead, drag. Thrust and drag are usually considered as opposing forces, but perhaps we should think of them as two forces in search of balance. We'll get to thrust in a later question, but for now please identify the two basic types of drag:
a. Form and interference
b. Induced and vortex
c. Skin friction and flappage
d. Parasite and induced
3. A wing's curvature is called its:
a. Camber
b. Chord
c. Carma
d. Airfoil
4. You can probably name the three axes about which your airplane (and ours, for that matter) rotates, and what those motions are called: It pitches around the lateral axis, rolls around the longitudinal and yaws about the vertical. Yaw is a two-faced force. Adverse yaw occurs when applying aileron to bank the airplane: The (_____) aileron on the rising wing produces (_____) drag than the (_____) aileron on the lowering wing. Picture where the ailerons are pointed in a bank and fill in the blanks while thinking about how to keep the ball centered.
a. Raised, greater, lowered
b. Lowered, greater, raised
c. Lowered, less, raised
d. Raised, less, lowered
5. Let's talk flaps. You, hiding behind the computer screen, please name the four basic types of trailing-edge flaps:
a. Plane, slit, slotted, fouler
b. Plain, slip, slotted, fowler
c. Plain, split, hinged, fowler
d. Plain, split, slotted, fowler
6. Controversy abounds on the subject of flap usage and particularly on deploying flaps in a crosswind. Your POH may have good advice on this topic, but it's tough to read the manual while landing a Cessna 170 in a 20-knot crosswind. Plus, older airplanes lack detailed how-to-fly information. Years back, it was expected that pilots knew how to fly and not just how to read. Pick the most correct statement regarding "flapped" wings and crosswinds:
a. The "flapped" wing on the upwind side is more affected than the downwind wing.
b. Crosswind effects on the "flapped" wing become more pronounced as the airplane comes closer to the ground
c. Both a and b.
d. Only a but never b.
e. Only b but never a.
7. The propeller is an airfoil (honest!) with wing-like terminology such as chord line, angle of attack and bug guts. Look down a prop blade (when it's not spinning) and you'll see an airfoil. Unlike a wing, however, as the prop blade moves through the air it produces thrust, not lift. The amount of thrust depends upon -- among other things -- the propeller's pitch. Think fixed-pitch prop and explain what a "74-48" propeller designation means:
a. 74 degrees in blade pitch with 48-inch length each blade
b. 74 inches in length with 48-degree blade pitch
c. 74 inches in length with 48-percent mean chord pitch
d. 74 inches in length with 48-inch pitch
8. You just bought an airplane with retractable tricycle gear, electric flaps, plus a 300-hp engine swinging a three-bladed, constant-speed propeller. Sweet -- midlife crisis complete. Time to upgrade your pilot's license from Sport Pilot to Private, so you'll need some additional training (lots of additional training). Part of that training will be dictated by FAR 61.31, which requires additional training/endorsement for complex and high-performance aircraft. "Complex" and "high performance" are two separate, but easily confused, labels. The FAA's definition for single-engine, land, "complex" is, "An airplane equipped with a retractable landing gear, wing flaps, a controllable-pitch propeller, or an engine of more than 200 horsepower."
a. True
b. False
9. Constant-speed propellers increase engine efficiency and overall aircraft performance. Plus, the pilot looks cool exercising the propeller during run-up. (Hint: Usually cycling once does the trick; too much and you sound like someone on a Harley revving the engine at a light -- it gets annoying.) On take-off, the pilot achieves maximum power by moving the constant-speed propeller control lever (_____) to the (_____) position. (Fill in the blanks.)
a. Forward, low pitch/high rpm.
b. Aft, low pitch/high rpm.
c. Forward, high pitch/high rpm.
d. Aft, low pitch/high manifold pressure (in inches Hg).
10. The Brainteaser author will now don his protective gear, pull the pin on this question and leave the room as discussion no-doubt ensues: Flaps (trailing edge) produce what type of drag?
a. Form and interference
b. Induced and vortex
c. Skin friction and flappage
d. Parasite and induced
e. None of the above

If you enjoyed taking this interactive quiz and would like to see more like it, go to the AVweb Brainteaser page. And if you thought it was unfair, confusing, or a waste of time, we'd like you to tell us that, too. And if you have an idea for a subject that you think would make a good future Brainteaser quiz, be sure to let us know.

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