3-13. What  is  an  imaginary  straight  line  from  the leading edge to the trailing edge of an airfoil? 1. Camber 2. Chord line 3. Span 4. Angle of attack 3-14. Which  of  the  following  terms  identifies  the rear edge or surface of the airfoil? 1. Span line 2. Retreating edge 3. Chord line 4. Trailing edge 3-15. What is the curve or departure from a straight line from the leading edge to the trailing edge of the airfoil? 1. Camber 2. Chord line 3. Angle of attack 4. The angle of incident 3-16. What term is used to describe the direction of the airstream in relation to the airfoil? 1. Angle of attack 2. Directional heading 3. Relative wind 4. Chord line 3-17. What is the angle between the chord line and the relative wind called? 1. The angle of attack 2. The resultant angle 3. The control angle 4. The angle of incidence 3-18. The generation of lift by an airfoil is dependent upon which of the following factors? 1. The shape of the airfoil's cord 2. The airfoil being able to create circulation in the airstream 3. The  airfoil  being  able  to  develop  lifting pressure over the airfoil surface 4. Both 2 and 3 above 3-19. As the relative wind strikes the leading edge of an airfoil, the flow of air is split.  What part of the airfoil creates the low pressure area on the airfoil's surface? 1. The camber of the airfoil's upper surface 2. The camber of the airfoil's lower surface 3. The trailing edge of the airfoil 4. The leading edge of the airfoil 3-20. What speed or pressure causes most of the lift of an airfoil? 1. The speed of the air striking the front of the airfoil 2. The difference in air pressure on the upper and lower surfaces of the airfoil 3. The increase in pressure over the airfoil 4. The decrease in pressure over the airfoil 3-21. What is the force that is created by an airfoil? 1. Lift 2. Drag 3. Gravity 4. Thrust 3-22. What force overcomes gravity? 1. Drag 2. Lift 3. Thrust 4. Weight 3-23. What is the force that holds an aircraft to the ground? 1. Lift 2. Drag 3. Gravity 4. Thrust 3-24. What is the force that is created by a propeller, jet engine, or helicopter rotor? 1. Lift 2. Drag 3. Gravity 4. Thrust 3-25. What force overcomes drag? 1. Lift 2. Thrust 3. Weight 4. Momentum 3-26. What is the force that acts against an aircraft in flight? 1. Lift 2. Drag 3. Gravity 4. Thrust 3-27. Aircraft drag acts in what direction in relation to the relative wind? 1. Parallel and in the same direction 2. Parallel and in the opposite direction 3. Perpendicular in the same direction 4. iPerpendicular  and  in  the  opposite  direc- tion 3-10