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Ground School
Chapter 1
Question | Answer |
---|---|
Which force produced by the wings support the airplane in flights? | Lift. |
Which force is produced by the engine propeller? | Thrust. |
Which force resists the motion of the airplane through the air? | Drag. |
Lift and weight are generally how much greater than thrust and drag in straight and level flight at a constant airspeed? | 10 times. |
What relationships exist between lift and weight, and between thrust and drag, when the airplane is flying straight and level at a constant airspeed? | Lift = weight; thrust = drag. |
Which surface is designed to create an aerodynamic lifting force as air flows over it? | An airfoil. |
What do you call a steady airflow around an airfoil in which succeeding parcels of air follow each other? | Streamline flow. |
Where on an airfoil does the smooth boundary-layer flow separate from the airfoil surface and become turbulent? | At the separation point. |
Static pressure in the air is exerted in which direction(s)? | Static pressure in the air is exerted in all directions. |
Which pressure is caused by motion? | Dynamic pressure. |
What is the total pressure energy the sum of? | Static pressure + dynamic pressure. |
In streamline flow, if dynamic pressure increases, what happens to the static pressure | It will decrease. |
What does the expression "1/2pV^2" represent? | Dynamic pressure. |
What line is drawn half-way between the upper and lower surfaces of the wing to give an indication of its curvature? | The mean camber line. |
The wing shape and the angle of attack determine the profile that the airfoil presents to the airflow. What else do they determine? | The lifting ability of the wing. |
True/False: The forces acting on an airfoil in flight, as a result of the changes in static pressure around it, may be considered to act through the center of pressure. | True. |
Describe how the relative airflow relates to the flight path of an airplane. | Relative airflow is parallel to the flight path of the airplane and flows in the opposite direction. |
Define the term "angle of attack." | The angle between the wing chord line and the relative airflow. |
If the angle of attack is gradually increased in normal cruise flight, what will happen to the lifting ability of the wing? | It will increase. |
On a wing, the force of lift acts perpendicular to and the force of drag acts parallel to the : a. chord line b. flight path c. longitudinal axis | Answer b. |
What does the angle of attack of a wing control directly? | Distribution of positive and negative pressure on the wing. |
What happens to the center of pressure as the angle of attack is gradually increased in the normal flight range? | It moves forward on the wing. |
True/False: Beyond the stall angel of attack, the lifting ability of the wing decreases significantly and the center of pressure moves rearward on the wing. | True. |
How will frost on the wings of an airplane affect takeoff performance? | Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting ability. |
What is drag? | Drag is the component of relative airflow which is parallel to the relative airflow. |
True/False: If drag can be kept low, thrust can be kept low. | True. |
Describe the two basic groups of total drag. | The two basic groups of drag are induced drag, which comes about in the production of lift, and parasite drag which is not associated with the production of lift. |
True/False: As airspeed increases, drag caused by skin friction decreases. | False. As airspeed increases, drag caused by skin friction increases. |
How can form drag be reduced? | To reduce form drag, separation of the boundary layer airflow from the wing surface should be delayed by streamlining. |
True/False: The spanwise flow of air on the upper wing surface is toward the wing root. | True. |
When is the formation of wingtip vortices and induced drag greatest? | At high angles of attack and low airspeeds. |
When is the total drag at a minimum? | At medium speed where the parasite drag and induced drag are equal. |
Why is the thrust requirement greater at high speeds and low angles of attack? | Because of the greater parasite drag. |
True/False: Minimum drag means minimum thrust to maintain airspeed. | True. |
What does the lift/drag ratio describe? | The lift/drag ratio describes the aerodynamic efficiency of the wing. |
What effect does extending the flaps have on the camber of the wing? | It increases the camber of the wing. |
Aside from lift, what do trailing-edge flaps increase? | Drag. |
The percentage increase in drag usually exceeds that in lift when the flaps are extended. Do flaps therefore increase the "lift/drag ratio?" | No, flaps decrease the lift/drag ratio. |
True/False: The extension of flaps on a glide approach allows a steeper approach path at a constant speed. | True. |
True/False: With flaps extended, the nose attitude of the airplane is higher. | False. With flaps extended, the nose attitude of the airplane is lower. |
True/False: Slots increase the angle of attack at which the wing stalls by delaying the separation of the smooth airflow over the upper surface of the wing. | True. |
What does a propeller convert engine torque into? | Thrust. |
True/False: At high altitudes, when the air is less dense, a propeller will be more efficient. | False. At high altitudes, when the air is less dense, a propeller will be less efficient. |
Why is a propeller blade twisted? | To ensure that it operates at its most efficient angle of attack along is full length. |
True/False: A fixed-pitch propeller is efficient at only one set of RPM and airspeed conditions. | True. |
True/False: A constant-speed propeller has a variable pitch angle and is efficient over a wide range of RPM and airspeed conditions. | True. |
As the FWD speed of a plane w/ a fixed-pitch prop increases, w/ the RPM remaining constant, the AOA of the propeller blades: a. decreases as forward speed increases b. increases as forward speed increases c. remains unaltered as forward speed increases | Answer a. |
In an airplane with a clockwise rotating propeller, what does P-factor, or asymmetric blade effect cause the airplane to do? | P-factor causes the airplane to yaw left at high angles of attack of the wing. |
During the takeoff roll in a single-engine airplane, the left tire will carry more load. Why? | Because of the propeller torque reaction. |
When is torque effect greatest in a single-engine airplane? | Torque effect is greatest in a single-engine airplane at high power and low airspeed. |
How can you keep the airplane tracking straight down the runway during the takeoff roll in a single-engine airplane? | By applying right rudder. |