Answers - Aerodynamics | Aircraft Systems

Answers - Aerodynamics


1. Force, dyne
2. Hg or inches of mercury, barometer
3. Increases, increases, increases
4. Inversely, directly
5. First, inertia
6. Increase
7. upper surface
8. AOA or angle of attack
9. Longitudinal
10. Fluid, pressure
11. High, low, outward, vortex
12. Static
13. Ailerons, elevator, rudder
14. Free‐spinning, upward
15. Down
16. Left, all
17. Dissymmetry
18. Clutch
19. Right, left
20. “Go” and “no‐go”
21. Fairleads, 3°
22. Turnbuckle, left‐hand
23. Position or angle, wing tips
24. Dihedral, incidence
25. Double‐twist, single‐wire


1. true
2. true
3. false; faster at higher altitude
4. false; inversely
5. true
6. true
7. false; lift to drag ratio
8. false; drag, not weight
9. true
10. false; center of gravity
11. false; vertical axis
12. true
13. false; wing fences
14. true
15. true
16. false weight added fore or aft of hinges
17. false; manufacturer provides instructions for fabrication
18. true
19. false; issued by FAA
20. false; flexible and used for pulleys
21. false; not used
22. true
23. true
24. true
25. false; never re‐used


1. It is a substance that has the ability to flow or assume the shape of the container in which it is enclosed.

2. Atmospheric pressure is the force exerted against the earth’s surface by the weight of the air above that surface. It is measured using a barometer in “Hg.

3. Density varies in direct proportion with pressure and inversely with temperature.

4. Absolute ‐ the weight of water vapor in a unit volume of air;
Relative ‐ the ratio (%) of the moisture actually in the air to the moisture it would hold if it were saturated at the same temperature and pressure.

5. The law of action and reaction states that for every action (force) there is an equal and opposite reaction (force).

6. The top part of the wing has a greater curvature than the bottom. This requires the air above the wing to travel farther than the bottom. The air therefore, has a greater velocity and a decreased pressure. The pressure differential creates lift. The high pressure on the bottom of the wing tries to equalize by rising to the low pressure area.

7. There is an area of negative pressure behind the resultant force when AOA is 0°. As AOA increases towards its critical point, the resultant force moves forward. Once critical angle is reached the resultant force falls rapidly until the wing stalls.

8. Drag is the resistance of the air to an object moving through it. There are 3 forms of drag: Parasite drag occurs when an exposed object offers resistance to the air. Profile drag is the parasite drag of the airfoil. Induced drag occurs as lift is created and the air flow spillage over the wing tip creates a vortex. This vortex constitutes induced drag.

9. Control is the pilot action of moving the flight controls, providing the aerodynamic force that induces the aircraft to follow a desired flight path. Controllability means that the aircraft responds easily and promptly to movement of the flight controls.

10. Sharp disturbances generate shock waves that affect lift and drag as well as airflow downstream of the shockwave. A cone of pressure which moves outward and rearward from the shockwave. Also, the energy of the object moving excites the chemical bonds of the oxygen and nitrogen.

11. Each blade can move back and forth in plane, lead and lag; and flap up and down through a hinge independent of the other blades.

12. As the engine turns the main rotor in a counterclockwise direction, the helicopter fuselage tends to turn the opposite direction. The action of the main rotor blade creates an equal and opposite force that turns the fuselage clockwise.

13. It is a mechanical connection between the collective lever and engine throttle. When the collective lever is raised, power increases and when lowered, power is decreased. This system maintains RPM close to the desired value.

14. Loose elevator linkage at swash plate horn, loose elevator, or tail rotor balance and track.

15. The gas producer (compressor turbine) is essentially disconnected from the power turbine. When the engine is started, there is little resistance from the power turbine allowing the gas turbine to accelerate to normal idle without the transmission load dragging it down.

16. Pulleys are used to guide cables and change cable direction. Pulley guards prevent jamming or the cable slipping off when slackened due to temperature changes.

17. Positioning the flight controls in the neutral position and locking them in place. Adjusting the cable tension and maintaining control surface neutral. Adjusting the control stops to the aircraft manufacturer’s specifications.

18. To make minor adjustments in cable length and for adjusting cable tension.

19. Trim tab systems. As the trim tab control moves, the cable drum winds or unwinds to actuate the trim tab cables.

20. Annual, 100‐hour inspection, progressive.