Weak Areas

Question 1

What is lift?

Answer 1

Lift—is a force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the center of lift (CL) and perpendicular to the lateral axis. In level flight, lift opposes the downward force of weight.

Question 2

What is thrust?

Answer 2

Thrust—the forward force produced by the powerplant/ propeller or rotor. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis. However, this is not always the case, as explained later.

Question 3

What is drag?

Answer 3

Drag—a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.

Question 4

What is weight?

Answer 4

Weight—the combined load of the aircraft itself, the
crew, the fuel, and the cargo or baggage. Weight is
a force that pulls the aircraft downward because of
the force of gravity. It opposes lift and acts vertically
downward through the aircraft’s center of gravity (CG).

Question 5

What is drag?

Answer 5

Drag is the force that resists movement of an aircraft through
the air. There are two basic types: parasite drag and induced
drag. The first is called parasite because it in no way functions
to aid flight, while the second, induced drag, is a result of an
airfoil developing lift.

Question 6

What is parasitic drag

Answer 6

It is the
drag that is not associated with the production of lift. This
includes the displacement of the air by the aircraft, turbulence
generated in the airstream, or a hindrance of air moving over
the surface of the aircraft and airfoil.

Question 7

What are 3 types of parasitic drag?

Answer 7

Form drag is the portion of parasite drag generated by the
aircraft due to its shape and airflow around it.
Interference drag comes from the intersection of airstreams
that creates eddy currents, turbulence, or restricts smooth
airflow. For example, the intersection of the wing and the
fuselage at the wing root has significant interference drag.
Skin friction drag is the aerodynamic resistance due to the
contact of moving air with the surface of an aircraft.

Question 8

What is induced drag?

Answer 8

Drag caused by the same factors that produce
lift; its amount varies inversely with airspeed. As airspeed
decreases, the angle of attack must increase, in turn increasing
induced drag.

Question 9

What is ground effect?

Answer 9

The condition of slightly increased air pressure
below an airplane wing or helicopter rotor system that increases
the amount of lift produced. It exists within approximately one
wing span or one rotor diameter from the ground. It results
from a reduction in upwash, downwash, and wingtip vortices,
and provides a corresponding decrease in induced drag.

Question 10

What is Bernoulli’s Principle?

Answer 10

Principle that explains how the
pressure of a moving fluid varies with its speed of motion.
An increase in the speed of movement causes a decrease in
the fluid’s pressure.

Question 11

What is angle of attack?

Answer 11

the angle at which
relative wind meets an airfoil. It is the angle that is formed
by the chord of the airfoil and the direction of the relative
wind or between the chord line and the flight path. The
angle of attack changes during a flight as the pilot changes
the direction of the aircraft and is related to the amount of
lift being produced.

Question 12

What is Static Stability?

Answer 12

Static stability refers to the initial tendency, or direction of movement, back to equilibrium. In aviation, it refers to the
aircraft’s initial response when disturbed from a given pitch, yaw, or bank.

Question 13

What is positive static stability?

Answer 13

The initial tendency of the aircraft to return to the original state of equilibrium after being disturbed.

Question 14

What is neutral static stability?

Answer 14

The initial tendency of the aircraft to remain in a new condition after its equilibrium has been disturbed.

Question 15

What is negative static stability?

Answer 15

The initial tendency of the
aircraft to continue away from the original state of
equilibrium after being disturbed.

Question 16

What is Dynamic Stability?

Answer 16

The aircraft response over time when disturbed from a given pitch, yaw, or bank. This type of stability also has three subtypes

Question 17

What is positive dynamic stability?

Answer 17

Over time, the motion of the displaced object decreases in amplitude and, because it is positive, the object displaced returns toward the equilibrium state.

Question 18

What is neutral dynamic stability?

Answer 18

Once displaced, the displaced object neither decreases nor increases in amplitude. A worn automobile shock absorber exhibits this tendency.

Question 19

What is negative dynamic stability?

Answer 19

Over time, the motion of the displaced object increases and becomes more divergent.

Question 20

What is Newton’s First Law of Motion?

Answer 20

The Law of Inertia, states that an object at rest or moving in a straight line remains at rest or continues to move in a straight line until acted on by some other force.

Question 21

What causes left-turning tendencies

Answer 21

P-Factor - When an aircraft is flying with a high AOA, the “bite” of the downward moving blade is greater than the “bite” of the
upward moving blade. This moves the center of thrust to the right of the prop disc area, causing a yawing moment toward the left around the vertical axis.
Torque - Torque reaction involves Newton’s Third Law of Physics — for every action, there is an equal and opposite reaction. As applied to the aircraft, this means that as the internal engine parts and propeller are revolving in one direction, an equal
force is trying to rotate the aircraft in the opposite direction
Spiraling slip stream - The high-speed rotation of an aircraft propeller gives a
corkscrew or spiraling rotation to the slipstream.