Performance Limitations

Question 1

How is aircraft performance significantly affected as air becomes less dense? (FAA‑H‑8083‑25)

Answer 1

As air becomes less dense, it reduces

a. power because the engine takes in less air.

b. thrust because the propeller is less efficient in thin air.

c. lift because thin air exerts less force on airfoils.

Question 2

What is the standard atmosphere at sea level? (FAA‑H‑8083‑25)

Answer 2

Standard atmosphere at sea level includes a surface temperature of 59°F or 15°C, and a surface pressure of 29.92 in. Hg or 1013.2 millibars.

Question 3

What are standard atmosphere temperature and pressure lapse rates? (FAA‑H‑8083‑25)

Answer 3

A standard temperature lapse rate is one in which the temperature decreases at the rate of approximately 3.5°F or 2°C per 1,000 feet up to 36,000 feet. Above this point, the temperature is considered constant up to 80,000 feet. A standard pressure lapse rate is one in which pressure decreases at a rate of approximately 1 in. Hg per 1,000 feet of altitude gain to 10,000 feet.

Question 4

Define the term “pressure altitude.” (FAA‑H‑8083‑25)

Answer 4

Pressure altitude is the height above a standard datum plane. An altimeter is a sensitive barometer calibrated to indicate altitude in the standard atmosphere. If the altimeter is set for 29.92 in. Hg Standard Datum Plane (SDP), the altitude indicated is the pressure altitude—the altitude in the standard atmosphere corresponding to the sensed pressure.

Question 5

Why is pressure altitude important? (FAA‑H‑8083‑25)

Answer 5

Pressure altitude is important as a basis for determining airplane performance as well as for assigning flight levels to airplanes operating above 18,000 feet.

Question 6

What are three methods of determining pressure altitude? (FAA‑H‑8083‑25)

Answer 6

Pressure altitude can be determined by either of two methods:

a. By setting the barometric scale of the altimeter to 29.92 and reading the indicated altitude, or

b. By applying a correction factor to the indicated altitude according to the reported “altimeter setting.”

c. By using a flight computer.

Question 7

Define the term “density altitude.” (FAA‑H‑8083‑25)

Answer 7

Density altitude is pressure altitude corrected for nonstandard temperature. It is the altitude in the standard atmosphere corresponding to a particular value of air density.

Question 8

How does air density affect aircraft performance? (FAA‑H‑8083‑25)

Answer 8

As the density of the air increases (lower density altitude), airplane performance increases and conversely, as air density decreases (higher density altitude), airplane performance decreases. A decrease in air density means a high density altitude; an increase in air density means a lower density altitude.

Question 9

How is density altitude determined? (FAA‑H‑8083‑25)

Answer 9

First find pressure altitude and then correct it for nonstandard temperature variations. Because density varies directly with pressure, and inversely with temperature, a given pressure altitude may exist for a wide range of temperatures. However, a known density occurs for any one temperature and pressure altitude. Regardless of the actual altitude at which the airplane is operating, it will perform as though it were operating at an altitude equal to the existing density altitude.

Question 10

What factors affect air density? (FAA‑H‑8083‑25)

Answer 10

Air density is affected by changes in altitude, temperature, and humidity. High density altitude refers to thin air while low density altitude refers to dense air. The conditions that result in a high density altitude are high elevations, low atmospheric pressures, high temperatures, high humidity, or some combination of these factors. Lower elevations, high atmospheric pressure, low temperatures, and low humidity are more indicative of low density altitude.

Question 11

What effect does atmospheric pressure have on air density? (FAA‑H‑8083‑25)

Answer 11

Air density is directly proportional to pressure. If the pressure is doubled, the density is doubled, and if the pressure is lowered, so is the density. This statement is true only at a constant temperature.

Question 12

What effect does temperature have on air density? (FAA‑H‑8083‑25)

Answer 12

Increasing the temperature of a substance decreases its density. Conversely, decreasing the temperature increases the density. Thus, the density of air varies inversely with temperature. This statement is true only at a constant pressure.

Question 13

Since temperature and pressure decrease with altitude, how will air density be affected overall? (FAA‑H‑8083‑25)

Answer 13

The decrease in temperature and pressure have conflicting effects on density as you go up in altitude, but the fairly rapid drop in pressure with increasing altitude is usually the dominating factor. Hence, the density is likely to decrease with altitude gain.

Question 14

What effect does humidity have on air density? (FAA‑H‑8083‑25)

Answer 14

Water vapor is lighter than air, so moist air is lighter than dry air. As the water content of the air increases, the air becomes less dense, increasing density altitude and decreasing performance. It is lightest or least dense when it contains the maximum amount of water vapor. Humidity alone is usually not considered an important factor in calculating density altitude and airplane performance, but it does contribute.

Question 15

What is the definition of the term “relative humidity”? (FAA‑H‑8083‑25)

Answer 15

Relative humidity refers to the amount of water vapor in the atmosphere, and is expressed as a percentage of the maximum amount of water vapor the air can hold. This amount varies with the temperature—warm air can hold more water vapor and colder air can hold less.

Question 16

What effect does landing at high-elevation airports have on ground speed with comparable conditions relative to temperature, wind and airplane weight? (FAA‑H‑8083‑25)

Answer 16

Even if you use the same indicated airspeed appropriate for sea level operations, true airspeed is faster, resulting in a faster ground speed (with a given wind condition) throughout the approach, touchdown, and landing roll. This means greater distance to clear obstacles during the approach, a longer ground roll, and consequently the need for a longer runway. All of these factors should be taken into consideration when landing at high-elevation fields, particularly if the field is short.

Question 17

What are some of the main elements of aircraft performance? (FAA‑H‑8083‑25)

Answer 17

a. Takeoff and landing distance

b. Rate-of-climb

c. Ceiling

d. Payload

e. Range

f. Speed

g. Maneuverability

h. Stability

i. Fuel economy

Question 18

What is the relationship of lift, weight, thrust and drag in steady, unaccelerated, level flight? (FAA‑H‑8083‑25)

Answer 18

For the airplane to remain in steady, level flight, equilibrium must be obtained by a lift equal to the airplane weight and powerplant thrust equal to the airplane drag.

Question 19

What are the two types of drag? (FAA‑H‑8083‑25)

Answer 19

Total drag may be divided into two parts: the wing drag (induced), and drag from everything but the wings (parasite).

Question 20

Define induced drag. (FAA‑H‑8083‑25)

Answer 20

Induced drag is the part of total drag created by the production of lift. Induced drag increases with a decrease in airspeed. The lower the airspeed, the greater the angle of attack required to produce lift equal to the airplane’s weight, and therefore the greater the induced drag.

Question 21

Define parasite drag. (FAA‑H‑8083‑25)

Answer 21

Parasite drag is drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed. It is the drag that is not associated with the production of lift and 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. There are three types of parasite drag: form drag, interference drag, and skin friction drag.

Question 22

How much will drag increase as airplane speed increases? (FAA‑H‑8083‑25)

Answer 22

If an airplane in a steady flight condition at 100 knots is then accelerated to 200 knots, the parasite drag becomes four times as great, but the power required to overcome that drag is eight times the original value. Conversely, when the airplane is operated in steady, level flight at twice as great a speed, the induced drag is one-fourth the original value, and the power required to overcome that drag is only one-half the original value.

Question 23

Climb performance is a result of using the aircraft’s potential energy provided by one, or a combination of two, factors. What are those two factors? (FAA‑H‑8083‑25)

Answer 23

a. Use of excess power above that required for level flight. An aircraft equipped with an engine capable of 200 horsepower (at a given altitude) but using 130 horsepower to sustain level flight (at a given airspeed) has 70 excess horsepower available for climbing.

b. Use of the aircraft’s kinetic energy. An aircraft can trade off its kinetic energy and increase its potential energy by reducing its airspeed. The reduction in airspeed will increase the aircraft’s potential energy, making the aircraft climb.

Question 24

Define the term “service ceiling.” (FAA‑H‑8083‑25)

Answer 24

Service ceiling is the maximum density altitude where the best rate-of-climb airspeed will produce a 100 feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

Question 25

Will an aircraft always be capable of climbing to and maintaining its service ceiling? (FAA‑H‑8083‑25)

Answer 25

No. Depending on the density altitude, an airplane may not be able to reach it published service ceiling on any given day.

Question 26

What is the definition of “absolute ceiling”? (FAA‑H‑8083‑25)

Answer 26

Absolute ceiling is the altitude at which a climb is no longer possible.

Question 27

What is meant by the terms “power loading” and “wing loading”? (FAA‑H‑8083‑25)

Answer 27

Power loading is expressed in pounds per horsepower and is obtained by dividing the total weight of the airplane by the rated horsepower of the engine. It is a significant factor in the airplane’s takeoff and climb capabilities.

Wing loading is expressed in pounds per square foot and is obtained by dividing the total weight of the airplane in pounds by the wing area (including ailerons) in square feet. It is the airplane’s wing loading that determines the landing speed.

Question 28

Define the terms “maximum range” and “maximum endurance.” (FAA‑H‑8083‑25)

Answer 28

Maximum range is the maximum distance an airplane can fly for a given fuel supply and is obtained at the maximum lift/drag ratio (L/DMAX). For a given airplane configuration, the maximum lift/drag ratio occurs at a particular angle of attack and lift coefficient, and is unaffected by weight or altitude.

Maximum endurance is the maximum amount of time an airplane can fly for a given fuel supply and is obtained at the point of minimum power required since this would require the lowest fuel flow to keep the airplane in steady, level flight.

Question 29

In the event of an engine failure, what airspeed should you use to achieve the most distance forward for each foot of altitude lost? (FAA-H-8083-3)

Answer 29

The best glide speed is the one at which the airplane will travel the greatest forward distance for a given loss of altitude in still air. This speed corresponds to an angle of attack resulting in the least drag on the airplane and giving the best lift-to-drag ratio (L/DMAX).

Question 30

What is ground effect? (FAA‑H‑8083‑25)

Answer 30

Ground effect occurs due to the interference of the ground surface with the flow pattern about the airplane in flight, when the airplane is flown at approximately one wingspan above the surface. Especially with low-wing aircraft, it is most significant when the airplane is maintaining a constant attitude at low airspeed and low altitude. For example: during landing flare before touchdown, and during takeoff when the airplane lifts off and accelerates to climb speed. A wing in ground effect has a reduction in upwash, downwash, and tip vortices. With reduced tip vortices, induced drag is reduced. When the wing is at a height equal to one-fourth the span, the reduction in induced drag is about 25 percent, and when the wing is at a height equal to one-tenth the span, this reduction is about 50 percent.

Question 31

What major problems can be caused by ground effect? (FAA‑H‑8083‑25)

Answer 31

During landing—At a height of approximately one-tenth of a wing span above the surface, drag may be 50 percent less than when the airplane is operating out of ground effect. Therefore, any excess speed during the landing phase may result in a significant float distance. In such cases, if care is not exercised, 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 the recommended speed. However, as the airplane rises out of ground effect with a deficiency of speed, the greater induced drag may result in very marginal climb performance, or the inability of the airplane to fly at all. In extreme conditions such as high gross weight and high density altitude, the airplane may become airborne initially with a deficiency of speed and then settle back to the runway.

Question 32

What does “flight in the region of normal command” mean? (FAA‑H‑8083‑25)

Answer 32

It means that while holding a constant altitude, a higher airspeed requires a higher power setting, and a lower airspeed requires a lower power setting. The majority of all airplane flying (climb, cruise, and maneuvers) is conducted in the region of normal command.

Question 33

What does “flight in the region of reversed command” mean? (FAA‑H‑8083‑25)

Answer 33

It means that a higher airspeed requires a lower power setting, and a lower airspeed requires a higher power setting to hold altitude. It does not imply that a decrease in power will produce lower airspeed. The region of reversed command is encountered in the low-speed phases of flight. Flight speeds below the speed for maximum endurance (lowest point on the power curve) require higher power settings with a decrease in airspeed. Because the need to increase the required power setting with decreased speed is contrary to the “normal command” of flight, flight speeds between minimum required power setting (speed) and the stall speed (or minimum control speed) is termed the region of reversed command. In the region of reversed command, a decrease in airspeed must be accompanied by an increased power setting in order to maintain steady flight.

Question 34

What are examples of where an airplane would be operating in the region of reversed command? (FAA‑H‑8083‑25)

Answer 34

a. An airplane performing a low airspeed, high-pitch attitude, powered approach for a short-field landing.

b. A soft-field takeoff and climb where the pilot attempts to climb out of ground effect without first attaining normal climb pitch attitude and airspeed, is an example of inadvertently operating in the region of reversed command at a dangerously low altitude.

Question 35

Explain how runway surface and gradient affect performance. (FAA‑H‑8083‑25)

Answer 35

a. Runway surface—Any surface that is not hard and smooth will increase the ground roll during takeoff. This is due to the inability of the tires to smoothly roll along the runway. Although muddy and wet surface conditions can reduce friction between the runway and the tires, they can also act as obstructions and reduce the landing distance.

b. Braking effectiveness—The amount of power that is applied to the brakes without skidding the tires is referred to as braking effectiveness. Ensure that runways are adequate in length for takeoff acceleration and landing deceleration when less than ideal surface conditions are being reported, as it affects braking ability.

c. Runway gradient or slope—A positive gradient indicates that the runway height increases, and a negative gradient indicates that the runway decreases in height. An upsloping runway impedes acceleration and results in a longer ground run during takeoff. However, landing on an upsloping runway typically reduces the landing roll. A downsloping runway aids in acceleration on takeoff resulting in shorter takeoff distances. The opposite is true when landing, as landing on a downsloping runway increases landing distances.

Question 36

What factors affect the performance of an aircraft during takeoffs and landings? (FAA‑H‑8083‑25)

Answer 36

a. Air density (density altitude)

b. Surface wind

c. Runway surface

d. Upslope or downslope of runway

e. Weight

f. Powerplant thrust

Question 37

What effect does wind have on aircraft performance? (FAA‑H‑8083‑25)

Answer 37

Takeoff—The effect of a headwind is that it allows the aircraft to reach the lift-off speed at a lower ground speed, which will increase airplane performance by shortening the takeoff distance and increasing the angle of climb. The effect of a tailwind is that the aircraft will need to achieve greater ground speed to get to lift-off speed. This decreases aircraft performance by increasing takeoff distance and reducing the angle of climb.

Landing—The effect of wind on landing distance is identical to its effect on takeoff distance. A headwind will lower ground speed and increase airplane performance by steepening the approach angle and reducing the landing distance. A tailwind will increase ground speed and decrease performance by decreasing the approach angle and increasing the landing distance.

Cruise flight—Winds aloft have a somewhat opposite effect on airplane performance. A headwind will decrease performance by reducing ground speed, which in turn increases the fuel requirement for the flight. A tailwind will increase performance by increasing the ground speed, which in turn reduces the fuel requirement for the flight.

Question 38

How does weight affect takeoff and landing performance? (FAA‑H‑8083‑25)

Answer 38

Increased gross weight can produce these effects:

a. Higher liftoff and landing speed required;

b. Greater mass to accelerate or decelerate (slow acceleration/deceleration);

c. Increased retarding force (drag and ground friction); and

d. Longer takeoff and ground roll.

The effect of gross weight on landing distance is that the airplane will require a greater speed to support the airplane at the landing angle of attack and lift coefficient resulting in an increased landing distance.

Question 39

What effect does an increase in density altitude have on takeoff and landing performance? (FAA‑H‑8083‑25)

Answer 39

An increase in density altitude results in:

a. Increased takeoff distance (greater takeoff TAS required).

b. Reduced rate of climb (decreased thrust and reduced acceleration).

c. Increased true airspeed on approach and landing (same IAS).

d. Increased landing roll distance.

An increase in density altitude (decrease in air density) will increase the landing speed but will not alter the net retarding force. Thus, the airplane will land at the same indicated airspeed as normal but because of reduced air density the true airspeed will be greater. This will result in a longer minimum landing distance.

Question 40

Planning for a rejected takeoff is essential to the safety of every flight. What calculation must be made prior to every takeoff? (FAA-H-8083-3)

Answer 40

Prior to takeoff, the pilot should have in mind a point along the runway at which the airplane should be airborne. If that point is reached and the airplane is not airborne, immediate action should be taken to discontinue the takeoff. If properly planned and executed, the airplane can be stopped on the remaining runway without using extraordinary measures, such as excessive braking that may result in loss of directional control, airplane damage, and/or personal injury.

Question 41

Why does the manufacturer provide various manifold pressure/prop settings for a given power output?

Answer 41

The various power MAP/RPM combinations are provided so the pilot has a choice between operating the aircraft at best efficiency (minimum fuel flow) or operating at best power/speed condition. An aircraft engine operated at higher RPMs will produce more friction and, as a result, use more fuel. On the other hand, an aircraft operating at higher and higher altitudes will not be able to continue to produce the same constant power output due to a drop in manifold pressure. The only way to compensate for this is by operating the engine at a higher RPM.

Question 42

What does the term 75% brake horsepower mean? (FAA‑H‑8083‑25)

Answer 42

Brake horsepower (BHP) is the power delivered at the propeller shaft (main drive or main output) of an aircraft engine. 75% BHP means you are delivering 75 percent of the normally rated power or maximum continuous power available at sea level on a standard day to the propeller shaft.

Question 43

Explain how 75% BHP can be obtained from your engine. (FAA‑H‑8083‑25)

Answer 43

Set the throttle (manifold pressure) and propeller (RPM) to the recommended values found in the cruise performance chart of your POH.

Question 44

When would a pilot lean a normally-aspirated direct‑drive engine? (FAA-P-8740-13)

Answer 44

a. Lean anytime the power setting is 75 percent or less at any altitude.

b. At high-altitude airports, lean for taxi, takeoff, traffic pattern entry and landing.

c. When the density altitude is high (Hot, High, Humid).

d. For landings at airports below 5,000 feet density altitude, adjust the mixture for descent, but only as required.

e. Always consult the POH for proper leaning procedures.

Question 45

What are the different methods available for leaning aircraft engines? (FAA-P-8740-13)

Answer 45

Tachometer Method—For best economy operation, the mixture is first leaned from full rich to maximum power (peak RPM), then the leaning process is slowly continued until the engine starts to run rough. Then, enrich the mixture sufficiently to obtain a smoothly firing engine.

Fuel Flowmeter Method—Aircraft equipped with fuel flowmeters require that you lean the mixture to the published (POH) or marked fuel flow to achieve the correct mixture.

Exhaust Gas Temperature Method—Lean the mixture slowly to establish peak EGT then enrich the mixture by 50° rich (cooler) of peak EGT. This will provide the recommended lean condition for the established power setting.

Question 46

Define the following airplane performance speeds. (FAA‑H‑8083‑25)

Answer 46

VS0—The calibrated power-off stalling speed or the minimum steady flight speed at which the airplane is controllable in the landing configuration.

VS1—The calibrated power-off stalling speed or the minimum steady flight speed at which the airplane is controllable in a specified configuration.

VY—The calibrated airspeed at which the airplane will obtain the maximum increase in altitude per unit of time. This best rate-of-climb speed normally decreases slightly with altitude.

VX—The calibrated airspeed at which the airplane will obtain the highest altitude in a given horizontal distance. This best angle-of-climb speed normally increases slightly with altitude.

VLE—The maximum calibrated airspeed at which the airplane can be safely flown with the landing gear extended. This is a problem involving stability and controllability.

VLO—The maximum calibrated airspeed at which the landing gear can be safely extended or retracted. This is a problem involving the air loads imposed on the operating mechanism during extension or retraction of the gear.

VFE—The highest calibrated airspeed permissible with the wing flaps in a prescribed extended position. This is because of the air loads imposed on the structure of the flaps.

VA—The calibrated design maneuvering airspeed. This is the maximum speed at which the limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage. Operating at or below maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time.

VNO—The maximum calibrated airspeed for normal operation or the maximum structural cruising speed. This is the speed at which exceeding the limit load factor may cause permanent deformation of the airplane structure.

VNE—The calibrated airspeed which should never be exceeded. If flight is attempted above this speed, structural damage or structural failure may result.

Question 47

The following questions are designed to provide you with a review of some of the basic information you should know about your specific airplane before taking a flight check or review.

Answer 47

a. What is the normal climb-out speed?

b. What is the best rate-of-climb speed?

c. What is the best angle-of-climb speed?

d. What is the maximum flap extension speed?

e. What is the maximum gear extension speed?

f. What is the maximum gear retraction speed?

g. What is the stall speed in the normal landing configuration?

h. What is the stall speed in the clean configuration?

i. What is the normal approach-to-land speed?

j. What is the maneuvering speed?

k. What is the red-line speed?

l. What speed will give you the best glide ratio?

m. What is the maximum window-open speed?

n. What is the maximum allowable crosswind component for the aircraft?

o. What takeoff distance is required if a takeoff were made from a sea level pressure altitude?

Question 48

Takeoff and Landing Distance Charts

Answer 48

a. Given the following conditions:

Pressure Altitude = 4,000 feet

Temperature = 40°F

Runway = Hard Surfaced

Weight = Maximum Takeoff Weight

Wind = 10 Knot Headwind

What is the distance for a normal takeoff ground roll?

What is the distance to clear a 50-foot obstacle?

b. Given the following conditions:

Pressure altitude = 2,000 feet

Temperature = 25°C

Runway = Hard surfaced

Weight = Maximum Landing Weight

Wind = Calm

What is the normal landing distance?

What is the minimum landing distance over a 50-foot obstacle?

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 49

Time, Fuel, and Distance-to-Climb Chart

Answer 49

a. Given the following conditions:

Climb = 2,000 feet to 7,000 feet pressure altitude

Temperature = Standard

Airspeed = Best Rate-of-Climb

Wind speed = Calm

How much time is required for the climb?

How much fuel is required for the climb?

What distance will be covered during the climb?

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 50

Maximum Rate-of-Climb Chart

Answer 50

a. Given the following conditions:

Pressure Altitude = 4,000 feet

Outside Air Temperature = 0°C

What is the best rate-of-climb airspeed?

What is the best rate-of-climb, in feet per minute?

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 51

Cruise Performance Chart

Answer 51

a. Given the following conditions:

Pressure Altitude = 6,000 feet

Engine RPM = 2,400

MAP = 22 inches

Temperature = Standard

What will the true airspeed be?

What will the fuel consumption rate be?

What will the percent brake horsepower be?

b. Given the following conditions:

Density Altitude at cruising altitude = 4,000 feet

Temperature = Standard

What percentage of brake horsepower will be required to produce the maximum true airspeed?

What will the required power setting be?

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 52

Maximum Range/Endurance Chart

Answer 52

a. Given the following conditions:

Density Altitude = 8,000 feet

Temperature = Standard

Weight = Maximum Gross

Wind = Calm

Power = 75%

BHP Fuel = Full Tanks (Standard) 45 minute reserve

What true airspeed can be expected?

What maximum range will be achieved?

b. Using the data from the previous question, how long can the aircraft fly in hours?

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers

Question 53

Determine the approximate CAS you should use to obtain 180 knots TAS with a pressure altitude of 8,000 feet and a temperature of +4°C.

Answer 53

158 knots.

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 54

At speeds below 200 knots (where compressibility is not a factor), how is true airspeed computed?

Answer 54

True airspeed can be found by correcting calibrated airspeed for pressure altitude and temperature.

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 55

Compute the density altitude for the following conditions:

Answer 55

Temperature = 20°C

Field Elevation = 4,000 feet

Altimeter setting = 29.98

The density altitude is 5,424 feet.

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 56

Compute the standard temperature at 9,000 feet.

Answer 56

The standard temperature at sea level is 15°C. The average lapse rate is 2° per 1,000 feet. Compute standard temperature by multiplying the altitude by 2 and then subtracting that number from 15. Based on this information,

15° – (2° x 9 = 18°) = -3°C

The standard temperature at 9,000 feet is -3°C.

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 57

A descent is planned from 8,500 feet MSL when 20 NM from your destination airport. If ground speed is 150 knots and you desire to be at 4,500 feet MSL when over the airport, what should the rate of descent be?

Answer 57

• Change in altitude = 4,000 feet

• Calculate time to go 20 NM at 150 knots (8 minutes)

• 4,000 feet ÷ 8 minutes = 500 FPM

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 58

A descent is planned from 11,500 feet MSL to arrive at 7,000 feet MSL, 5 SM from a VORTAC. With a ground speed of 160 mph and a rate of descent of 600 FPM, at what distance from the VORTAC should the descent be started?

Answer 58

• Change in altitude = 4,500 feet

• Rate of Descent = 600 FPM

• Time to descend = 4,500 ÷ 600 = 7.5 minutes

• Ground speed in miles per minute = 160 ÷ 60 = 2.67 MPM

• 7.5 x 2.67 = 20 miles + 5 miles = 25 miles out

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 59

If fuel consumption is 15.3 GPH and ground speed is 167 knots, how much fuel is required for an aircraft to travel 620 NM?

Answer 59

• 620 nautical miles ÷ 167 knots = 221 minutes or 3 hours and 41 minutes

• 15.3 GPH x 3 hrs. 41 min. = 57 gallons of fuel used

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 60

If the ground speed is 215 knots, how far will the aircraft travel in 3 minutes?

Answer 60

• 215 knots ÷ 60 = 3.58 nautical miles per minute

• 3.58 NMPM x 3 minutes = 10.75 nautical miles

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 61

How accurate should you consider the predictions of performance charts to be?

Answer 61

Flight tests from which performance data was obtained were flown with a new, clean airplane, correctly rigged and loaded, and with an engine capable of delivering its full rated power. You can expect to do as well only if your airplane, too, is kept in peak condition.

This is a typical question concerning aircraft performance charts. Refer to your Pilot’s Operating Handbook (POH) for the answers.

Question 62

What performance characteristics will be adversely affected when an aircraft has been overloaded? (FAA-H‑8083‑25)

Answer 62

a. Higher takeoff speed.

b. Longer takeoff run.

c. Reduced rate and angle of climb.

d. Lower maximum altitude.

e. Shorter range.

f. Reduced cruising speed.

g. Reduced maneuverability.

h. Higher stalling speed.

i. Higher approach and landing speed.

j. Longer landing roll.

k. Excessive weight on the nosewheel.

Question 63

If the weight and balance of an aircraft has changed due to the addition or removal of fixed equipment in the aircraft, what responsibility does the owner or operator have?

Answer 63

The owner or operator of the aircraft should ensure that maintenance personnel make appropriate entries in the aircraft records when repairs or modifications have been accomplished. Weight changes must be accounted for and proper notations made in weight and balance records. The appropriate form for these changes is “Major Repairs and Alterations” (FAA Form 337).

Question 64

Define the term “center of gravity.” (FAA-H‑8083‑25)

Answer 64

The center of gravity (CG) is the point about which an aircraft would balance if it were possible to support the aircraft at that point. It is the mass center of the aircraft, or the theoretical point at which the entire weight of the aircraft is assumed to be concentrated. The CG must be within specific limits for safe flight.

Question 65

What effect does a forward center of gravity have on an aircraft’s flight characteristics? (FAA-H‑8083‑25)

Answer 65

Higher stall speed—Stalling angle of attack reached at a higher speed due to increased wing loading.

Slower cruise speed—Increased drag, greater angle of attack required to maintain altitude.

More stable—The center of gravity is further forward from the center of pressure, which increases longitudinal stability.

Greater back elevator pressure required—Longer takeoff roll, higher approach speeds and problems with the landing flare.

Question 66

What effect does an aft center of gravity have on an aircraft’s flight characteristics? (FAA-H‑8083‑25)

Answer 66

Lower stall speed—Less wing loading.

Higher cruise speed—Reduced drag, smaller angle of attack required to maintain altitude.

Less stable—Stall and spin recovery more difficult; when angle of attack is increased it tends to result in additional increased angle of attack.

Question 67

Define the following:

Arm • Basic empty weight (GAMA) • Center of gravity • Center of gravity limits • Center of gravity range • Datum • Floor load limit • Fuel load • Licensed empty weight • Maximum landing weight • Maximum ramp weight • Maximum takeoff weight • Maximum weight • Maximum zero fuel weight (GAMA) • Mean aerodynamic chord • Moment • Moment index • Payload (GAMA) • Standard empty weight (GAMA) • Station • Useful load (FAA-H‑8083‑25)

Answer 67

Arm—The horizontal distance in inches from the reference datum line to the center of gravity of an item.

Basic empty weight (GAMA)—The standard empty weight plus optional and special equipment that has been installed.

Center of gravity—The point about which an aircraft would balance if it were possible to suspend it at that point, expressed in inches from datum.

Center of gravity limits—The specified forward and aft or lateral points beyond which the CG must not be located during takeoff, flight or landing.

Center of gravity range—The distance between the forward and aft CG limits indicated on pertinent aircraft specifications.

Datum—An imaginary vertical plane or line from which all measurements of arm are taken. It is established by the manufacturer.

Floor load limit—The maximum weight the floor can sustain per square inch/foot as provided by the manufacturer.

Fuel load—The expendable part of the load of the aircraft. It includes only usable fuel, not fuel required to fill the lines or that which remains trapped in the tank sumps.

Licensed empty weight—The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization.

Maximum landing weight—The maximum weight at which the aircraft may normally be landed. The maximum landing weight may be limited to a lesser weight when runway length or atmospheric conditions are adverse.

Maximum ramp weight—The total weight of a loaded aircraft, and includes all fuel. It is greater than the takeoff weight due to the fuel that will be burned during the taxi and runup operations. Ramp weight may also be referred to as taxi weight.

Maximum takeoff weight—The maximum allowable weight at the start of the takeoff run. Some aircraft are approved for loading to a greater weight (ramp or taxi) only to allow for fuel burnoff during ground operation. The takeoff weight for a particular flight may be limited to a lesser weight when runway length, atmospheric conditions, or other variables are adverse.

Maximum weight—The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.

Maximum zero fuel weight (GAMA)—The maximum weight, exclusive of usable fuel.

Mean aerodynamic chord (MAC)—The average distance from the leading edge to the trailing edge of the wing. The MAC is specified for the aircraft by determining the average chord of an imaginary wing which has the same aerodynamic characteristics as the actual wing.

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

Moment index—A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of large aircraft where heavy items and long arms result in large, unmanageable numbers.

Payload (GAMA)—The weight of occupants, cargo, and baggage.

Standard empty weight (GAMA)—The airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed in the airplane; including fixed ballast, hydraulic fluid, unusable fuel, and full engine oil.

Station—A location in the aircraft which is identified by a number designating its distance in inches from the datum. The datum is, therefore, identified as station zero. The station and arm are usually identical. An item located at station +50 would have an arm of 50 inches.

Useful load—The weight of the pilot, copilot, passengers, baggage, usable fuel and drainable oil. It is the empty weight subtracted from the maximum allowable takeoff weight. The term applies to general aviation aircraft only.

Question 68

What basic equation is used in all weight and balance problems to find the center of gravity location of an airplane and/or its components? (FAA-H‑8083‑25)

Answer 68

Weight x Arm = Moment

By rearrangement of this equation to the forms,

Weight = Moment ÷ arm.

Arm = Moment ÷ weight.

CG = Moment ÷ weight.

With any two known values, the third value can be found.

Question 69

What basic equation is used to determine center of gravity? (FAA-H‑8083‑25)

Answer 69

Center of gravity is determined by dividing total moments by total weight.

Question 70

Explain the term percent of mean aerodynamic chord (MAC). (FAA-H-8083-1)

Answer 70

Expression of the CG relative to the MAC is a common practice in larger aircraft. The CG position is expressed as a percent MAC (percent of mean aerodynamic chord), and the CG limits are expressed in the same manner. Normally, an aircraft will have acceptable flight characteristics if the CG is located somewhere near the 25% average chord point. This means the CG is located one-fourth of the total distance back from the leading edge of the average wing section.

Question 71

If the weight of an aircraft is within takeoff limits but the CG limit has been exceeded, what actions can the pilot take to correct the situation? (FAA-H‑8083‑25)

Answer 71

The most satisfactory solution to this type of problem is to shift baggage, passengers, or both in an effort to make the aircraft CG fall within limits.

Question 72

When a shift in weight is required, what standardized and simple calculations can be made to determine the new CG? (FAA-H‑8083‑25)

Answer 72

A typical problem may involve calculation of a new CG for an aircraft which has shifted cargo due to the CG being out of limits.

Given:

Aircraft total weight - 6,680 pounds
CG - Station 80.0
CG limits - Station 70-78

Find: What is the location of the CG if 200 pounds is shifted from the aft compartment at station 150 to the forward at station 30?

Solution:
A. (Weight shifted x distance moved)/aircraft gross weight = CG change
B. (200 x 120)/6,680 = 3.6 in. Forward
C. Old CG minus new CG - 80.0 inches-3.6=76.4 inches
This same formula may be used to calculate how much weight must be shifted when you know how far you want to move the CG to come within limits.

Question 73

If the weight of an aircraft changes due to the addition or removal of cargo or passengers before flight, what formula may be used to calculate new CG? (FAA-H‑8083‑25)

Answer 73

A typical problem may involve the calculation of a new CG for an aircraft which, when loaded and ready for flight, receives some additional cargo or passengers just before departure time.

Given:

Aircraft total weight - 6,860 pounds
CG - Station 80.0

Find: What is the location of the CG if 140 lbs. of baggage is added to station 150?

Solution:

CG change = 1.4 inches aft

b. Add the CG change to the old CG:

New CG = 80.0 in. + 1.4 in. = 81.4 in.

By using “old total weight and new CG,” this same formula may be used to find out how much weight to add or remove, when it is known how far you want to move the CG to come within limits.

Question 74

What simple and fundamental weight check can be made by all pilots before flight? (FAA-H‑8083‑25)

Answer 74

A useful load check can be made to determine if the useful load limit has been exceeded. This check may be a mental calculation if the pilot is familiar with the aircraft’s limits and knows that unusually heavy loads are not aboard. The pilot needs to know the useful load limit of the particular aircraft. This information may be found in the latest weight and balance report, in a logbook, or on a Major Repair and Alteration Form located in the aircraft. If the useful load limit is not stated directly, simply subtract the empty weight from the maximum takeoff weight.

Question 75

What factors would contribute to a change in center of gravity location during flight?

Answer 75

The operator’s flight manual should show procedures which fully account for variations in CG travel during flight caused by variables such as the movement of passengers and the effect of the CG travel due to fuel used.

Question 76

If actual weights for weight and balance computations are unknown, what weights may be assumed for weight and balance computations? (FAA-H-8083-25, AC 120-27)

Answer 76

Crew and passengers - 190 lbs each
Gasoline - 6 lbs/U.S. gal
Oil - 7.5 lbs/U.S. gal
Water - 8.35 lbs/U.S. gal
Note: These weights are not to be used in lieu of actual weights, if available.

Question 77

How is the CG affected during flight as fuel is used? (FAA-H‑8083‑25)

Answer 77

As fuel is burned during flight, the weight of the fuel tanks will change and as a result the CG will change. Most aircraft, however, are designed with the fuel tanks positioned close to the CG; therefore, the consumption of fuel does not affect the CG to any great extent. Also, the lateral balance can be upset by uneven fuel loading or burn-off. The position of the lateral CG is not normally computed for an airplane, but the pilot must be aware of the adverse effects that will result from a laterally unbalanced condition.