Aerodynamics

Question 1

What are the four dynamic forces that act on an airplane during all maneuvers?

Answer 1

“Lift - the upward acting force
Gravity - the downward acting force, or weight
Thrust - the forward acting force
Drag - the backward acting force”

Question 2

What flight condition will result in the sum of all opposing forces being equal?

Answer 2

In steady-state, straight and level, unaccelerated flight. There can be no unbalanced forces (Newton’s Third Law). There can be no unbalanaced forces during straight and steady flight even while climbing or descending. all Opposing forces are equal thereby cancelling the effect of each other.

Question 3

What is an airfoil? Name some examples.

Answer 3

“a device that gets a useful reaction from air moving over its surface, namely LIFT. Examples: wings, propeller, horizontal and vertical tail surfaces”

Question 4

“What is the “angle of incidence?”””

Answer 4

The angle formed by the longitudinal axis of the airplane and chord of the wing. Angle at which wing is attached to the fuselage. Cannot be changed, is fixed.

Question 5

What is “relative wind?’

Answer 5

The direction of airflow with respect to the wing. When a wing is moving forward and downward the relative wind moves backward and upward. Path and relative wind are always parallel but travel in opposite directions.

Question 6

“What is the “angle of attack?”””

Answer 6

The angle between the wing chord line and direction of the relative wind. The pilot can change this.

Question 7

What is “Bernoulli’s Principle”?

Answer 7

The pressure of a fluid decreases at points where the speed of the fluid increases. In the case of airflow, high speed flow is associated with low pressure and low speed flow is associated with high pressure. The airflow of an aircraft is designed to increase the velocity of the airflow above its surface, decreasing the air pressure below its surface. The combination of pressure increase below and decrease above procedures lift.

Question 8

Which several factors which will affect both lift and drag?

Answer 8

“wing area - lift and drag acting on a wing are roughly proportional to the wing area. A pilot can change this by using different types of flaps.
Shape of airfoil - as the upper curvature of the airfoil increases, to a certain point, the lift produced increases. Lowering ailerons or flaps can accomplish this. its why ice and frost are bad.
Angle of attack - as AOA increase, both lift and drag are increase to a certain point.
Velocity of the air - in crease in velocity of the air passing over the wing increases lift and drag
air density - lift and drag vary directly with the density of the air. As air density increases, lift and drag decrease. Air density is affected by these factors: pressure, temperature, and humidity.”

Question 9

What is “torque effect”?

Answer 9

Newton’s third Law of physics - for every action there is an opposite and equal reaction. As the airplane internal parts and propeller are revolving in one direction, an equal force is trying to rotate the airplane in the opposite direction. It is greatest at low speeds with high power settings and high angle of attack.

Question 10

What effect does torque effect have on an airplane on the ground and in flight?

Answer 10

“in flight - torque is acting around longitudinal axis tending to make plane roll.

Question 11

What are the four factors that contribute to torque effect?

Answer 11

“torque reaction of engine and propeller
gyroscopic effect of the propeller - deflection of a spinning object when force is applied to the outer rim of its rotational mass.
corkscrewing effect of the propeller slipstream - slipstream strikes the vertical tail surface on the left side pushing the tail to the right and yawing it to the left
asymmetrical loading of the propeller (p-factor) - airplane flying with a high angle of attack, the bite downward moving propeller blade is greater than the bite upward moving blade. the moving blade meets the oncoming relative wind on downward side with greater AOA than upward. yawing to left.”

Question 12

what is centrifugal force?

Answer 12

the “equal and opposite” reaction of the airplane to the change in direction and it acts “equal and opposite” to the horizontal component of lift.

Question 13

what is “load factor”?

Answer 13

the ratio of the total load supported by the airplane’s wing to the actual weight of the airplane and it’s contents. it’s the actual load supported by the wings divided by the total weight of the airplane.

Question 14

for what two reasons is load factor important to pilots?

Answer 14

“a. because of the obviously dangerous overload that it is possible for a pilot to impose on the aircraft structure
b. because an increased load factor increases the stalling speed and makes stalls possible at seemingly safe flight speeds.”

Question 15

What situations may result in load factors reaching the maximum or being exceeded?

Answer 15

Level turns
Turbulence
Speed

Question 16

what causes an airplane to stall?

Answer 16

the direct cause of every stall is an excessive AOA.

Question 17

What is a spin?

Answer 17

controlled (recoverable) or uncontrolled (possibly unrecoverable) maneuver in which the airplane or glider descends in a helical path while flying at an AOA greater than the critical AOA.

Spins result from aggravated stalls. If a stall doesn’t occur a spin cannot occur.

Question 18

What causes a spin?

Answer 18

The primary cause of an inadvertent spin is exceeding the critical AOA while applying excessive or insufficient rudder, and to a lesser extent, aileron.

Question 19

When are spins most likely to occur?

Answer 19

a. Engine failure on takeoff during climb out - pilot tries to stretch glide to landing area by increasing back pressure or makes an uncoordinated turn back to departure runway at relatively low airspeed
b. Crossed-control turn from base to final (slipping or skidding turn) - pilot overshoots final and makes uncoordinated turn at low airspeed
c. Engine failure on approach to landing - pilot tries to stretch glide to runway by increasing back pressure
d. Go-around with full nose up trim - pilot applies power with full flaps and nose up trim combined with uncoordinated rudder
e. Go-around with improper flap retraction - pilot applies power and retracts flaps rapidly resulting in rapid sink rate followed by instinctive increase in back pressure

Question 20

What procedure should be used to recover from an inadvertent spin?

Answer 20

a. Close the throttle
b. Neutralize the ailerons
c. apply full opposite rudder
d. briskly move elevator control forward to approx. the neutral position (different a/c require different pressure)
e. once stall is broken spinning will stop. neutralize rudder at this point.
f. when rudder is neutralized, gradually apply enough aft elevator pressure to return to level flight.”

Question 21

What is adverse yaw?

Answer 21

while turning left for example, the downward right aileron produces more lift and more drag and the left on produces less lift and less drag. the added lift and drag on right tries to turn airplane that direction which is no desired and is referred to as adverse yaw.

Question 22

What is “ground effect?

Answer 22

A condition of improved performance the airplane experiences when it is operating near the ground. A change occurs in the three-dimensional flow pattern around the airplane because the airflow around the wing is restricted by the ground surface.

Question 23

Major problems that can be caused by ground effect?

Answer 23

“During landing - at a height of approx, one-tenth of a wing span above the surface, drag may be 40 percent less than when the airplane is out of ground effect. May result in excess speed during landing increasing float time causing you to run out of runway.

During takeoff - Airplane seems to be capable of takeoff well below the recommended airspeed. could settle back to ground especially in extreme conditions”

Question 24

What effect does wind have on aircraft performance?

Answer 24

Takeoff - headwind will increase performance by shortening takeoff distance and increasing the angle of climb. A tailwind will decrease aircraft performance.

Landing- head wind will increase airplane performance by steepening the approach angle and reducing the landing distance. Tailwind will decrease performance by decreasing the approach angle and increasing the landing distance.

Cruise flight - winds aloft have opposite of previous two on aircraft performance. Tailwind increases performance by increasing ground speed which reduces the fuel required. Headwind decreases performance by reducing ground speed and increases fuel requirement for the flight.