Performance And Limitations

Question 1

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

Answer 1

Lift: the upward acting force
Gravity or wait: the downward acting force
Thrust: the forward acting force
Drag: the backward acting force

Question 2

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

Answer 2

In steady state, straight level, unaccelerated flight

Question 3

What is an air foil? State some examples.

Answer 3

An air foil is a device which gets its useful reaction from air moving over its surface, namely lift. Some examples are wings, horizontal tail services, vertical tail services and propellers.

Question 4

What is an angle of incidence

Answer 4

The angle of incidence is the angle formed by the longitudinal axis of the airplane and the cord of the wing

Question 5

What is relative wind?

Answer 5

Relative wind is the direction of the airflow with respect to the wing

Question 6

What is angle of attack?

Answer 6

Angle of attack is the angle between the wing cord line, and the direction of the relative wind

Question 7

What is bernoullis principle

Answer 7

As the velocity of a fluid (such as air) increases, its pressure decreases

Question 8

How will the wing area affect both lift and drag?

Answer 8

Lift and drag acting on a wing are roughly proportional to the wing area. A pilot can change wing area by using certain types of flaps.

Question 9

How does the shape of the air foil affect both lift and drag?

Answer 9

As the upper curvature of an air foil is increased, the lift produced increases. Lowering an aileron or flap device can accomplish this. Also ice or frost on a wing can disturb its normal airflow.

Question 10

How does angle of attack affect both lift and drag?

Answer 10

As angle of attack is increased, both lift and drag are increased up to a certain point

Question 11

How does velocity of the air affect both lift and drag?

Answer 11

An increase in velocity of air passing over the wing, increases lift and drag

Question 12

How does air density affect both lift and drag?

Answer 12

Lift and drag very directly with the density of air. As air density increases lift and drag in increase as air density decreases lift, and drag decrease air density is affected by these factors: pressure, temperature, and humidity.

Question 13

What is torque effect?

Answer 13

Torque effect involves newtons third law of physics: for every action there is an equal and opposite reaction. Applied to the airplane, this means that as the internal engine parts and the propeller are revolving in One Direction and equal force is trying to rotate the plane and the opposite reaction. It is greatest when at low air speeds with high power settings, and high angle of attack.

Question 14

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

Answer 14

In flight, torque reaction is acting around the longitudinal axis tending to make the airplane roll
On the ground during the takeoff roll and additional turning moment around the vertical axis is induced by a torque reaction

Question 15

What are the four factors that contribute to left turning tendencies

Answer 15

Torque reaction of the engine and propeller: newtons third law, the rotation of the propeller from the cockpit to the right tends to roll or bank the airplane to the left
Gyroscopic affect of the propeller: gyroscopic procession applies here if the axis of a propeller is tilted the resulting force will be exerted 90° ahead in the direction of rotation
Corkscrew effect of the propeller slipstream: high speed rotation of an airplane propeller results in a screwing rotation to the slipstream. The slipstream strikes the vertical tail surface on the left side, pushing the tail to the right and yawing the plane to the left.
P factor: when an airplane is flying with a high angle of attack, the bite of the downward moving propeller blade is greater than the bite of the upward moving blade. Consequently, there is greater thrust on the downward blade on the right side, and this forces the plane to yaw to the left .

Question 16

What is centrifugal force?

Answer 16

Centrifugal force is 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 17

What is load factor?

Answer 17

Load factor is the ratio of the total weight supported by the airplanes wing to the actual weight of the airplane and its contents. In other words, it is the actual load supported by the wings divided by the total weight of the plane.

Question 18

For what two reasons is load factor important to pilots

Answer 18

1. Because of the obviously dangerous overload that is possible for a pilot to impose on the aircraft structure.
2. Because it increased low factor increases the stalling speed, and makes stalls possible at seemingly safe flight speeds.

Question 19

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

Answer 19

Level turns, turbulence, speed

Question 20

What are the different operational categories for aircraft?

Answer 20

Normal, utility, aerobatic

Question 21

What effect does an increase in load factor have on stalling speed?

Answer 21

As load factor increases, stalling speed increases.

Question 22

Defined the term maneuvering speed

Answer 22

Maneuvering speed is the maximum speed at which the limit load can be imposed without causing structural damage. It is the speed below which you can, in smooth air, move a single flight control, one time, to its full deflection without risk of damage to the airplane.

Question 23

Discuss the effect on maneuvering speed of an increase or decrease in weight

Answer 23

Maneuvering speed increases with an increased weight and decreases with a decreased weight. An aircraft operating at a reduced weight is more vulnerable to rapid accelerations encountered during flight through turbulence or gusts.

Question 24

What causes an airplane to stall?

Answer 24

The direct cause of every stall is an excessive angle of attack. Each airplane has a particular angle of attack where the airflow separates from the upper surface of the wing and the stall occurs.

Question 25

What is a spin?

Answer 25

A maneuver, either recoverable, or possibly unrecoverable where an airplane descends in a helical path while flying at an angle of attack greater than the critical angle of attack. Spins result from aggravated stalls in either a slip or skid, if a stall does not occur a spin cannot occur.

Question 26

What causes a spin?

Answer 26

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

Question 27

When are spins most likely to occur

Answer 27

Engine failure on takeoff during climb out, crossed control turn from base to final, engine failure on approach to landing, go around with full nose up trim, go around with improper flap retraction

Question 28

What causes adverse yaw?

Answer 28

The added drag on the downward deflected aileron attempts to pull or veer the airplanes nose in the direction of the raised wing; that is, it tries to turn the plane in the direction opposite to that desired. This undesired veering is referred to as adverse yaw

Question 29

What is ground effect?

Answer 29

Ground effect is a condition of improved performance the airplane experiences when it’s operating near the ground.

Question 30

What major problems can be caused by ground effect

Answer 30

During landing, drag may be 40% less than when airplane is operating out of ground effect therefore, any excess speed during landing phase may result in significant float distance. The pilot may run out of runway and options at the same time.
During takeoff, due to the reduced drag in ground effect the aircraft may seem capable of takeoff well below recommended speed.

Question 31

Define empty weight

Answer 31

The weight of the airframe engines, all permanently installed equipment and unusable fuel, and depending on the aircraft either the undrainable oil or full reservoir oil is included

Question 32

Define gross weight

Answer 32

The maximum allowable weight of both the airplane and it’s contents

Question 33

Define useful load

Answer 33

The weight of the pilot, copilot passengers, baggage, usable fuel, and drainable oil

Question 34

Define arm

Answer 34

The horizontal distance in inches from the reference datum line to the center of gravity of the item

Question 35

Define moment

Answer 35

The product of the weight of an item multiplied by its arm. Moments are expressed in pound inches.

Question 36

Define center of gravity

Answer 36

The point about which an aircraft would balance if it were possible to suspend it at that point. Expressed in inches from datum.

Question 37

Define datum

Answer 37

An imaginary vertical plane or line from which all measurements of arm are taken. Established by the manufacturer.

Question 38

When shifting weight from one location to another on an airplane, what happens to the total moments?

Answer 38

When weight is shifted from one location to another, the total weight of an aircraft is unchanged. The total moments, however, do change in relation and proportion to the direction and distance the weight is moved.
When weight is moved forward the total moments decrease when weight is moved aft total moments increase .

Question 39

What performance characteristics will be adversely affected when an aircraft has been overloaded

Answer 39

Higher takeoff speed, longer takeoff run, reduced rate and angle of climb, lower maximum altitude, shorter range, reduced cruising speed, reduced maneuverability, higher stalling speed, higher landing speed, longer landing roll, excessive weight on the nose wheel

Question 40

What effect does a forward center of gravity have on an aircraft flight characteristics?

Answer 40

Higher stall speed: stalling angle of attack is reached at a higher speed due to increased wing loading
Slower cruise speed: increased drag; greater angle of attack is required to maintain altitude
More stable: the center of gravity is farther forward from the center of pressure which increases longitudinal stability
Greater back elevator pressure required: longer takeoff roll; higher approach speeds, and problems with landing flare

Question 41

What effect does a rearward center of gravity have on an aircraft flight characteristics?

Answer 41

Lower stall speed: less wing loading
Higher cruise speed: reduced drag; smaller angle of attack is required to maintain altitude
Less stable: stall and spin recovery more difficult; the center of gravity is closer to the center of pressure, causing longitudinal instability

Question 42

What are some of the main elements of aircraft performance?

Answer 42

Takeoff and landing distance, rate of climb, ceiling, payload, range, speed, fuel, economy, maneuverability, stability

Question 43

What factors affect the performance of an aircraft during takeoff and landings?

Answer 43

Air density, surface wind, runway surface, up slope or down slope of runway, weight

Question 44

What effect does wind have on aircraft performance?

Answer 44

Takeoff: the effect of a headwind is to allow the aircraft to reach the lift off speed at a lower ground speed which will increase airplane performance by shortening the takeoff and increasing the angle of climb. The effect of tailwind is the aircraft needs to achieve greater ground speed to get lift off.
Landing: the effect of wind on landing distance is identical to its effect on takeoff distance
Cruise flight: wins aloft have somewhat an opposite effect on airplane performance headwind will decrease performance by reducing ground speed which intern increases the fuel requirement for the flight. A tailwind will increase performance by increasing the ground speed, which will in turn reduce the fuel requirement for the flight.

Question 45

How does weight affect takeoff and landing performance?

Answer 45

Higher lift off speed, greater mass to accelerate, increased retarding force, and longer takeoff distance

Question 46

What effect does an increase in density altitude have on takeoff and landing performance?

Answer 46

An increase density altitude results in: increased takeoff distance, reduce rate of climb, increased true airspeed on approach in landing, and increased landing roll distance

Question 47

Defined the term density altitude

Answer 47

Density altitude is pressure altitude corrected for nonstandard temperature

Question 48

How does air density affect aircraft performance?

Answer 48

The density of the air has a direct effect on: lift produced by the wings, power output of the engine, propeller efficiency, and drag forces

Question 49

What factors affect air density?

Answer 49

Altitude: the higher the altitude, the less dense the air
Temperature: the warmer air, the less dense it is
Humidity: more humid air is less dense

Question 50

Define parasite drag

Answer 50

Parasite drag is caused by any aircraft surface that deflect or interferes with the smooth airflow around the airplane

Question 51

What are the three kinds of parasite drag?

Answer 51

Form drag - form drag results from the turbulent wake caused by the separation of airflow from the surface of the structure
Interference drag - interference drag occurs when the airflow around one part of the airplane interacts with the airflow around an adjacent part
Skin friction drag - skin friction drag is caused by the roughness of the airplane surfaces even though these surfaces may appear smooth under the microscope they can be quite rough

Question 52

What is induced drag?

Answer 52

Induced drag is generated by the airflow circulation around the wings as it creates lift

Question 53

What is total drag?

Answer 53

Total drag for an airplane is a sum of parasite and induced drag