Aerodynamics of Flight

Aerodynamics of Flight
Ground School Chapter 3 Aerodynamics of Flight

The four forces acting on an airplane in flight are:
a. lift, weight, thrust, and drag. b. lift, weight, gravity, and thrust. lift, gravity, power, and friction. When are the four forces that act on an airplane in equilibrium? During unaccelerated flight. When the aircraft is at rest on the ground. When the aircraft is accelerating. (Refer to figure 1.) The acute angle A is the angle of a. Dihedral. b. Incidence. c. Attack. A. C.

4. The term "angle of attack" is defined as the angle
formed by the longitudinal axis of the airplane and the chord line of the wing. between the wing chord line and the relative wind. between the airplane's climb angle and the horizon. 5. What is the relationship of lift, drag, thrust, and weight when the airplane is in straight-and-level flight? a. Lift, drag, and weight equal thrust. b. Lift equals weight and thrust equals drag. c. Lift and weight equal thrust and drag. 6. How will frost on the wings of an airplane affect takeoff performance? a. Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability. b. Frost will change the camber of the wing, increasing its lifting capability. c. Frost will cause the airplane to become airborne with a higher angle of attack, decreasing the stall speed B A.

Low airspeed, high power, high angle of attack.
7. In what flight condition is torque effect the greatest in a single-engine airplane? Low airspeed, high power, high angle of attack. High airspeed, high power, high angle of attack. Low airspeed, low power, low angle of attack. The left turning tendency of an airplane caused by P-factor is the result of the gyroscopic forces applied to the rotating propeller blades acting 90° in advance of the point the force was applied. b. clockwise rotation of the engine and the propeller turning the airplane counter-clockwise. c. propeller blade descending on the right, producing more thrust than the ascending blade on the left. When does P-factor cause the airplane to yaw to the left? When at high angles of attack. When at high airspeeds. When at low angles of attack. A. C.

10. An airplane said to be inherently stable will
require less effort to control. be difficult to stall. not spin. 11. What determines the longitudinal stability of an airplane? a. The relationship of thrust and lift to weight and drag. b. The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab. c. The location of the CG with respect to the center of lift. 12. What causes an airplane (except a T-tail) to pitch nosedown when power is reduced and controls are not adjusted? a. The downwash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced. b. The CG shifts forward when thrust and drag are reduced. c. When thrust is reduced to less than weight, lift is also reduced and the wings can no longer support the weight A. C.

13. What is the purpose of the rudder on an airplane? To control yaw.
To control overbanking tendency. To control roll. 14. (Refer to figure 2.) If an airplane weighs 2,300 pounds, what approximate weight would the airplane structure be required to support during a 60° banked turn while maintaining altitude? a. 4,600 pounds. b. 2,300 pounds. c. 3,400 pounds. 15. (Refer to figure 2.) If an airplane weighs 4,500 pounds, what approximate weight would the airplane structure be required to support during a 45° banked turn while maintaining altitude? a. 4,500 pounds. b. 7,200 pounds. c. 6,750 pounds. A. C.

abruptness at which the load is applied. b. speed of the airplane.
The amount of excess load that can be imposed on the wing of an airplane depends upon the abruptness at which the load is applied. b. speed of the airplane. position of the CG. 17. Which basic flight maneuver increases the load factor on an airplane as compared to straight-and-level flight? a. Stalls. b. Climbs. c. Turns. 18. The angle of attack at which an airplane wing stalls will a. increase if the CG is moved forward. b. remain the same regardless of gross weight. c. change with an increase in gross weight. B. C.

Stall at a higher airspeed. Be more difficult to control.
19. During an approach to a stall, an increased load factor will cause the airplane to Have a tendency to spin. Stall at a higher airspeed. Be more difficult to control. 20. One of the main functions of flaps during approach and landing is to a. increase the angle of descent without increasing the airspeed. b. decrease the angle of descent without increasing the airspeed. c. permit a touchdown at a higher indicated airspeed. 21. What is one purpose of wing flaps? a. To relieve the pilot of maintaining continuous pressure on the controls. b. To decrease wing area to vary the lift. c. To enable the pilot to make steeper approaches to a landing without increasing the airspeed. B. A. C.

An airplane said to be inherently stable will
Question: An airplane said to be inherently stable will Be difficult to stall Require less effort to control Not spin A stable airplane will tend to return to the original condition of flight if disturbed by a force such as turbulent air. This means that a stable airplane is easy to fly. Answer (A) is incorrect because stability of an airplane has an effect on its stall recovery, not the difficulty of stall entry. Answer (C) is incorrect because an inherently stable aircraft can still spin.

Changes in the center of pressure of a wing affect the aircraft`s
Question: Changes in the center of pressure of a wing affect the aircraft`s lift/drag ratio Lifting capacity Aerodynamic balance and controllability The center of pressure of an asymmetrical airfoil moves forward as the angle of attack is increased, and backward as the angle of attack is decreased. This backward and forward movement of the point at which lift acts, affects the aerodynamic balance and the controllability of the aircraft. Answer (A) is incorrect because the lift/drag ratio is determined by the angle of attack. Answer (B) is incorrect because lifting capacity is determined by angle of attack and airspeed.

What determines the longitudinal stability of an airplane?
Question: What determines the longitudinal stability of an airplane? The location of the CG with respect to the center of lift The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab The relationship of thrust and lift to weight and drag The location of the center of gravity with respect to the center of lift determines to a great extent the longitudinal stability of an airplane. Center of gravity aft of the center of lift will result in an undesirable pitch-up moment during flight. An airplane with the center of gravity forward of the center of lift will pitch down when power is reduced. This will increase the airspeed and the downward force on the elevators. This increased downward force on the elevators will bring the nose up, providing positive stability. The farther forward the CG is, the more stable the airplane. Answer (B) is incorrect because the rudder and rudder trim tab control the yaw. Answer (C) is incorrect because the relationship of thrust and lift to weight and drag affects speed and altitude.

The CG shifts forward when thrust and drag are reduced
Question: What causes an airplane (except a T-tail) to pitch nosedown when power is reduced and controls are not adjusted? The CG shifts forward when thrust and drag are reduced The downwash on the elevator from the propeller slipstream is reduced and elevator effectiveness is reduced When thrust is reduced to less than weight, lift is also reduced and the wings can no longer support the weight. The location of the center of gravity with respect to the center of lift determines to a great extent the longitudinal stability of an airplane. Center of gravity aft of the center of lift will result in an undesirable pitch-up moment during flight. An airplane with the center of gravity forward of the center of lift will pitch down when power is reduced. This will increase the airspeed and the downward force on the elevators. This increased downward force on the elevators will bring the nose up, providing positive stability. The farther forward the CG is, the more stable the airplane. Answer (A) is incorrect because the CG is not affected by changes in thrust or drag. Answer (C) is incorrect because thrust and weight have a small relationship to each other, unless thrust is opposite weight, as in the case of jet fighters and space shuttles.

Difficulty in recovering from a stalled condition
Question: An airplane has been loaded in such a manner that the CG is located aft of the aft CG limit. One undesirable flight characteristic a pilot might experience with this airplane would be A longer takeoff run Difficulty in recovering from a stalled condition Stalling at higher-than-normal airspeed Loading in a tail-heavy condition can reduce the airplane's ability to recover from stalls and spins. Tail-heavy loading also produces very light stick forces, making it easy for the pilot to inadvertently overstress the airplane. Answer (A) is incorrect because an airplane with an aft CG has less drag from a reduction in horizontal stabilizer lift, resulting in a short takeoff run. Answer (C) is incorrect because an airplane with an aft CG flies at a lower angle of attack, resulting in a lower stall speed.

Loading an airplane to the most aft CG will cause the airplane to be
Question: Loading an airplane to the most aft CG will cause the airplane to be Less stable at all speeds Less stable at slow speeds, but more stable at high speeds Less stable at high speeds, but more stable at low speeds Loading in a tail-heavy condition can reduce the airplane's ability to recover from stalls and spins. Tail-heavy loading also produces very light stick forces at all speeds, making it easy for the pilot to inadvertently overstress the airplane. Answer (B) is incorrect because an aft CG location causes an aircraft to be less stable at all airspeeds, due to less elevator effectiveness. Answer (C) is incorrect because an aft CG location causes an aircraft to be less stable at all airspeeds, due to less elevator effectiveness.

In what flight condition must an aircraft be placed in order to spin?
Question: In what flight condition must an aircraft be placed in order to spin? Partially stalled with one wing low In a steep diving spiral stalled A spin results when a sufficient degree of rolling or yawing control input is imposed on an airplane in the stalled condition. If the wing is not stalled, a spin cannot occur. Answer (A) is incorrect because the aircraft must be at a full stall in order to spin. Answer (B) is incorrect because an airplane is not necessarily stalled when in a steep diving spiral.

During a spin to the left, which wing(s) is/are stalled?
Question: During a spin to the left, which wing(s) is/are stalled? Both wings are stalled Neither wing is stalled Only the left wing is stalled One wing is less stalled than the other, but both wings are stalled in a spin. Answer (B) is incorrect because both wings must be stalled through the spin. Answer (C) is incorrect because both wings are stalled; but the right wing is less fully stalled than the left.

Left-Turning Tendencies
Torque Gyroscopic Precession Asymmetrical Thrust Spiraling Slipstream

Left-Turning Tendencies Torque
Torque Effect is greatest at low airspeeds, high power settings, and high angles of attack Newton’s Third Law: “For every action, there is an equal and opposite reaction” prop rotates clockwise, fuselage reacts counterclockwise

Left-Turning Tendencies Gyroscopic Precession
Turning prop exhibits rigidity in space and gyroscopic precession, like a gyroscope Gyroscopic precession is the resultant reaction when a force is applied to the rim of a rotating disc Reaction to a force occurs 90º later in the plane of rotation; only experienced when there is a change of aircraft attitude

Left-Turning Tendencies Gyroscopic Precession

Left-Turning Tendencies Asymmetrical Thrust
P-Factor causes an airplane to yaw to the left when it is at high angles of attack. P-Factor results from the descending prop blade on the right producing more thrust than the ascending blade on the left

Left-Turning Tendencies Spiraling Slipstream
As prop rotates, it creates a backward flow of air, or slipstream, which wraps around the airplane The slipstream can cause a change in airflow around the vertical stabilizer; it strikes the lower left side of the vertical fin, resulting in a yaw to the left

Questions Under what speed and power circumstances are the left turning tendencies most pronounced? In what phases of flight do you encounter these speed and power circumstances? High power (more torque) High pitch (more gyroscopic precession)

Left-Turning Tendencies Aircraft Design Considerations
In small aircraft, often a metal tab on the trailing edge of the rudder that is bent to the left so pressure from the passing airflow will push on the tab and force the rudder slightly to the right This slight right-hand rudder displacement creates a yawing moment that opposes the left-turning tendency caused by spiraling slipstream

Lift-to-Drag Ratio Lift-to-drag ratio (L/D) can be used to measure the gliding efficiency of your airplane The angle of attack resulting in the least drag on your airplane will give you the maximum lift-to-drag ratio (L/Dmax), the best glide angle, and the maximum gliding distance

Glide Speed At a given weight, L/Dmax will correspond to a certain airspeed This speed correlates to your best glide speed (maximum horizontal distance for altitude lost) If power failure occurs after takeoff, immediately establish the proper gliding attitude and airspeed

Glide Ratio and Angle Glide Ratio represents the distance an airplane will travel forward, without power, in relation to altitude loss Example, 10:1 means aircraft will travel 10,000 feet of horizontal distance for every 1,000 feet loss of altitude Glide Angle is the angle between the actual glide path of your airplane and the horizontal; glide angle increases as drag increases

Factors Affecting the Glide
Weight Configuration Wind

Factors Affecting the Glide Weight
Variations in weight do not affect the glide ratio, however there is a specific airspeed that is optimum for a given weight Two aerodynamically identical aircraft with different weights can glide the same distance from the same altitude; can only be done if the heavier aircraft flies at a higher airspeed than the lighter

Factors Affecting the Glide Configuration
If you increase drag, such as by lowering landing gear, the maximum lift-to-drag ratio and glide ratio are both reduced

Factors Affecting the Glide Wind
A headwind will always reduce your glide range while a tailwind will always increase your glide range In a strong headwind or tailwind (winds > 25% of glide speed), best glide may not be found at L/Dmax, and you may have to make adjustments to maximize your travel over the ground

Turning Flight For an airplane to turn, must overcome inertia, or tendency to continue in a straight line We create the necessary force by using the ailerons to bank the airplane so that the direction of total lift is inclined The horizontal component of lift causes an airplane to turn

Turning Flight To maintain altitude in a turn, you will need to apply backpressure and pitch up, until your vertical component of lift = weight Horizontal component of lift creates force toward center of rotation; centripetal force Opposite force, centrifugal force; not a true force; apparent force resulting from effect of inertia during turn

Turning Flight Adverse Yaw
Adverse yaw is the yawing tendency toward the outside of a turn It is caused by higher induced drag on the outside wing, which is producing more lift Need to apply rudder into the turn to control adverse yaw Adverse yaw is greatest at high angles of attack and with large aileron deflection

Turning Flight Overbanking Tendency
As you enter a turn and increase the angle of bank, you may notice the tendency of the airplane to continue rolling into a steeper bank Overbanking tendency is caused by the additional lift on the outside, or raised wing Counteract overbanking tendency with small amount of opposite aileron

Turning Flight Rate and Radius of Turn
Rate of turn refers to the amount of time it takes for an airplane to turn a specific number of degrees Radius of turn refers to the amount of horizontal distance an aircraft uses to complete a turn If airspeed increases and angle of bank remains same -- rate of turn decreases, and radius of turn increases

Load Factor (G) Load factor is the ratio of the load supported by the airplane’s wings to the actual weight of the aircraft and its contents Aircraft in cruising flight, while not accelerating in any direction, has a load factor of one. The wings only supporting its own weight and contents If wings are supporting twice as much weight as the weight of the airplane and its contents, the load factor is two

Load Factor in Turns During constant altitude turns, the relationship between load factor, or G’s, and bank angle is the same for all airplanes In a 60º bank, 2 G’s are required to maintain level flight

Load Factor and Stall Speed
Additional load factor incurred during constant altitude turns will also increase stall speed Stalls that occur with G forces are called accelerated stalls

Limit Load Factor Limit load factor is the amount of stress or load factor that an airplane can withstand before structural damage or failure occurs Usually expressed in terms of G’s

Maneuvering Speed Design Maneuvering Speed, or VA, represents the max speed at which you can use full, abrupt control movement without overstressing the airframe

A low airspeed, high power, high aoa
The downward-moving blade on the right side of the propeller has a higher angle of attack and greater action and reaction than the upward moving blade on the left. This results in a tendency for the airplane to yaw around the vertical axis to the left. Answer (A) is incorrect because it describes the characteristics involved with torque effect. Answer (C) is incorrect because it describes gyroscopic precession.

Question: If an airplane weighs 2,300 pounds, what approximate weight would the airplane structure be required to support during a 60° banked turn while maintaining altitude? 2,300 pounds 3,400 pounds 4,600 pounds Referencing FAA Figure 2, use the following steps: 1. Enter the chart at a 60° angle of bank and proceed upward to the curved reference line. From the point of intersection, move to the left side of the chart and read a load factor of 2 Gs. 2. Multiply the aircraft weight by the load factor: 2,300 x 2 = 4,600 lbs Or, working from the table: 2,300 x 2.0 (load factor) = 4,600 lbs

Question: If an airplane weighs 3,300 pounds, what approximate weight would the airplane structure be required to support during a 30° banked turn while maintaining altitude? 1,200 pounds 3,100 pounds 3,960 pounds Referencing FAA Figure 2, use the following steps: 1. Enter the chart at a 30° angle of bank and proceed upward to the curved reference line. From the point of intersection, move to the left side of the chart and read an approximate load factor of 1.2 Gs. 2. Multiply the aircraft weight by the load factor: 3,300 x 1.2 = 3,960 lbs Or, working from the table: 3,300 x (load factor) = 3,808 lbs Answer C is the closest. Answer (A) is incorrect because they are less than 3,300 pounds; load factor increases with bank for level flight. Answer (B) is incorrect because they are less than 3,300 pounds; load factor increases with bank for level flight.

Question: If an airplane weighs 4,500 pounds, what approximate weight would the airplane structure be required to support during a 45° banked turn while maintaining altitude? 4,500 pounds 6,750 pounds 7,200 pounds Referencing FAA Figure 2, use the following steps: 1. Enter the chart at a 45° angle of bank and proceed upward to the curved reference line. From the point of intersection, move to the left side of the chart and read a load factor of 1.5 Gs. 2. Multiply the aircraft weight by the load factor. 4,500 x 1.5 = 6,750 lbs Or, working from the table: 4,500 x (load factor) = 6,363 lbs Answer B is the closest.

Question: Which basic flight maneuver increases the load factor on an airplane as compared to straight-and-level flight? Climbs Turns Stalls A change in speed during straight flight will not produce any appreciable change in load, but when a change is made in the airplane's flight path, an additional load is imposed upon the airplane structure. This is particularly true if a change in direction is made at high speeds with rapid, forceful control movements. Answer (A) is incorrect because the load increases only as the angle of attack is changed, momentarily. Once the climb attitude has been set, the wings only carry the load produced by the weight of the aircraft. Answer (C) is incorrect because in a stall, the wings are not producing lift.

What force makes an airplane turn?
Question: What force makes an airplane turn? The horizontal component of lift The vertical component of lift Centrifugal force As the airplane is banked, lift acts horizontally as well as vertically and the airplane is pulled around the turn. Answer (B) is incorrect because the vertical component of lift has no horizontal force to make the airplane turn. Answer (C) is incorrect because the centrifugal force acts against the horizontal component of lift.

The angle of attack at which an airplane wing stalls will
Question: The angle of attack at which an airplane wing stalls will Increase if the CG is moved forward Change with an increase in gross weight Remain the same regardless of gross weight When the angle of attack is increased to between 18° and 20° (critical angle of attack) on most airfoils, the airstream can no longer follow the upper curvature of the wing because of the excessive change in direction. The airplane will stall if the critical angle of attack is exceeded. The indicated airspeed at which stall occurs will be determined by weight and load factor, but the stall angle of attack is the same. Answer (A) is incorrect because an airplane will always stall at the same angle of attack, regardless of the CG position or gross weight. Answer (B) is incorrect because an airplane will always stall at the same angle of attack, regardless of the CG position or gross weight.

Stall at higher airspeed Have a tendency to spin
Question: During an approach to a stall, an increased load factor will cause the aircraft to Stall at higher airspeed Have a tendency to spin Be more difficult to control Stall speed increases in proportion to the square root of the load factor. Thus, with a load factor of 4, an aircraft will stall at a speed which is double the normal stall speed. Answer (B) is incorrect because an airplane's tendency to spin does not relate to an increase in load factors. Answer (C) is incorrect because an airplane's stability determines its controllability.

Aircraft power, pitch, bank, and trim
Question: Select the four flight fundamentals involved in maneuvering an aircraft. Aircraft power, pitch, bank, and trim Starting, taxing, takeoff, and landing Straight-and-level flight, turns, climbs, and descents The four flight fundamentals involved in maneuvering an aircraft are: straight-and-level flight, turns, climbs, and descents.

Wingtip vortices are created only when an aircraft is
Question: Wingtip vortices are created only when an aircraft is Operating at high airspeeds Heavily loaded Developing lift Lift is generated by the creation of a pressure differential over the wing surface. The lowest pressure occurs over the wing surface and the highest pressure occurs under the wing. This pressure differential triggers the roll up of the airflow aft of the wing, resulting in wing-tip vortices. Vortices are generated from the moment an aircraft leaves the ground, since trailing vortices are a by-product of wing lift. Answer (A) is incorrect because the greatest turbulence is produced from an airplane developing lift at a slow airspeed. Answer (B) is incorrect because even though a heavily loaded airplane may produce greater turbulence, an airplane does not have to be heavily loaded in order to produce wing-tip vortices.

The greatest vortex strength occurs when the generating aircraft is
Question: The greatest vortex strength occurs when the generating aircraft is light, dirty, and fast Heavy, dirty, and fast Heavy, clean, and slow The strength of the vortex is governed by the weight, speed, and shape of the wing of the generating aircraft. The greatest vortex strength occurs when the generating aircraft is heavy, clean and slow. Answer (A) is incorrect because light aircraft produce less vortex turbulence than heavy aircraft. Answer (B) is incorrect because in order to be fast, the wing tip must be at a lower angle of attack, thus producing less lift than during climbout. Also, being dirty presents less of a danger than when clean and/or slow.

Wingtip vortices created by large aircraft tend to
Question: Wingtip vortices created by large aircraft tend to Sink below the aircraft generating turbulence Rise into the traffic pattern Rise into the takeoff or landing path of a crossing runway Flight tests have shown that the vortices from large aircraft sink at a rate of about 400 to 500 feet per minute. They tend to level off at a distance about 900 feet below the path of the generating aircraft. Answer (B) is incorrect because wing-tip vortices sink toward the ground; however, they may move horizontally depending on crosswind conditions. Answer (C) is incorrect because wing-tip vortices sink toward the ground; however, they may move horizontally depending on crosswind conditions.

Wingtip vortices created by large aircraft tend to
Question: Wingtip vortices created by large aircraft tend to Sink below the aircsaft generating turbulence Rise into the traffic pattern Rise into the takeoff or landing path of a crossing runway Flight tests have shown that the vortices from large aircraft sink at a rate of about 400 to 500 feet per minute. They tend to level off at a distance about 900 feet below the path of the generating aircraft. Answer (B) is incorrect because wing-tip vortices sink toward the ground; however, they may move horizontally depending on crosswind conditions. Answer (C) is incorrect because wing-tip vortices sink toward the ground; however, they may move horizontally depending on crosswind conditions.

light, quartering headwind Light, quartering tailwind Strong headwind
Question: The wind condition that requires maximum caution when avoiding wake turbulence on landing is a light, quartering headwind Light, quartering tailwind Strong headwind A tailwind condition can move the vortices of a preceding aircraft forward into the touchdown zone. A light quartering tailwind requires maximum caution. Pilots should be alert to large aircraft upwind from their approach and takeoff flight paths. Answer (A) is incorrect because headwinds push the vortices out of the touchdown zone when landing beyond the touchdown point of the preceding aircraft. Answer (C) is incorrect because strong winds help diffuse wake turbulence vortices.

Question: When landing behind a large aircraft, the pilot should avoid wake turbulence by staying Above the large aircraft’s final approach path and landing beyond the large aircraft’s touchdown point Below the large aircraft’s final approach path and landing before the large aircraft’s touchdown point Above the large aircraft’s final approach path and landing before the large aircraft’s touchdown point When landing behind a large aircraft stay at or above the large aircraft's final approach path. Note its touchdown point and land beyond it. Answer (B) is incorrect because below the flight path, you will fly into the sinking vortices generated by the large aircraft. Answer (C) is incorrect because by landing before the large aircraft's touchdown point, you will have to fly below the preceding aircraft's flight path, and into the vortices.

Below and downwind from the heavy aircraft
Question: When departing behind a heavy aircraft, the pilot should avoid wake turbulence by maneuvering the aircraft Below and downwind from the heavy aircraft Above and upwind from the heavy aircraft Below and upwind from the heavy aircraft When departing behind a large aircraft, note the large aircraft's rotation point, rotate prior to it, continue to climb above it, and request permission to deviate upwind of the large aircraft's climb path until turning clear of the aircraft's wake.

Aerodynamics of Flight

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