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Brainteasers
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May 18, 2009

Brainteasers
Interactive Quiz #143:
Mommy, Where Does Lift Come From?

Eventually, all pilots face the uncomfortable moment when passengers ask about the facts of flight. Don't blush, stammer or tell them to "Go ask your flight instructor." Instead, tell them to take this quiz.

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. As an airplane pilot increases pitch to increase angle of attack (AOA), lift generally increases. Swell, but what's the definition of angle of attack?
a. The acute angle between the chord line of the airfoil and the direction of the winds aloft.
b. The acute angle between the camber line of the airfoil and the direction of the relative wind.
c. The acute angle between the chord line of the airfoil and the direction of the relative wind.
d. The obtuse angle between the chord line of the airfoil and the direction of the reflexive wind.
2. Flying is all about working the angles. The pilot is able to change the angle of attack, but the angle "formed by the chord line of the wing and a line parallel to the longitudinal axis of the airplane" is determined by the airplane manufacturer. What is that fixed angle called?
a. Angle of incidence
b. Angle of insipience
c. Angle of intercept
d. Angle of variance
3. What statement best describes Bernoulli's Principle?
a. The pressure of a fluid increases at points where the velocity of the fluid decreases.
b. The pressure of a fluid decreases at points where the velocity of the fluid decreases.
c. The pressure of a fluid decreases at points where the velocity of the fluid increases.
d. A short, balding guy with soup stains on his tie
4. Having correctly answered the previous question, you can now apply Bernoullian principles throughout your life ... but that would seriously hamper your social standing. Instead, consider what happens as fuel vaporizes inside a carburetor's venturi, where pressure (_____) and temperature (_____). (Please fill in the blanks.)
a. increases, increases
b. decreases, decreases
c. decreases, increases
d. increases, decreases
5. Air moving past a lift-producing airfoil produces differing pressures. One result is wingtip vortices, which ultimately cause wake-turbulence issues. Complete this thought: "The (_____) and (_____) the airplane, the greater the angle of attack and the stronger the wingtip vortices."
a. heavier, faster
b. lighter, slower
c. higher, faster
d. heavier, slower
6. Drag produced by the wingtip vortices in the previous question is called:
a. Introduced
b. Parasite
c. Induced
d. Interference
7. Of the choices below, in which phase of flight would you expect an airplane to produce the strongest wingtip vortices?
a. Takeoff and climb
b. Rollout
c. Takeoff roll (full thrust)
d. En-route cruise
8. Think back to question #4, the one about carburetors, and consider this: A loss of manifold pressure (MP) is the first sign of carburetor icing in a fuel-injected airplane equipped with a constant-speed propeller (RPMs remain constant).
a. True
b. False
9. The propeller is a spinning airfoil that provides thrust. Like an airfoil, it reacts to the air based on various angles. The "angle formed by the chord line and the reference plane containing the propeller hub" is called:
a. Angle of incidence
b. Angle of attack
c. P-factor angle
d. Blade-twist angle
10. A private pilot (ASEL) buys a 200-horsepower, retractable-geared airplane with electric flaps and a constant-speed propeller. The new owner has flown airplanes with manually operated flaps and fixed landing gear. Under FAR 61.31 (additional training authorization requirements), this pilot needs a one-time endorsement for complex airplane, plus an endorsement for high-performance, because the engine is "at or greater than 200 horsepower."
a. True
b. False

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.

Return to the AVweb Brainteasers page.

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