直升机飞行手册Rotorcraft flying handbook

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most airplanes, where discharging a passenger is

unlikely to adversely affect the CG, off-loading a passenger from a helicopter could make the aircraft unsafe

to fly. Another difference between helicopter and airplane loading is that most small airplanes carry fuel in

the wings very near the center of gravity. Burning off

fuel has little effect on the loaded CG. However, helicopter fuel tanks are often significantly behind the center

of gravity. Consuming fuel from a tank aft of the rotor

mast causes the loaded helicopter CG to move forward.

As standard practice, you should compute the weight

and balance with zero fuel to verify that your helicopter

remains within the acceptable limits as fuel is used.

A B

C

D

F

1,600

1,500

1,400

1,300

1,200

1,100

104 105 106 107 108 109

Baggage Compartment

Loading Lines

Fuel Loading

Lines

E

Figure 7-6. Loading chart illustrating the solution to sample

problems 1 and 2.

7-6

SAMPLE PROBLEM 3

The loading chart used in the sample problems 1 and 2

is designed to graphically calculate the loaded center of

gravity and show whether it is within limits, all on a

single chart. Another type of loading chart calculates

moments for each station. You must then add up these

moments and consult another graph to determine

whether the total is within limits. Although this method

has more steps, the charts are sometimes easier to use.

To begin, record the basic empty weight of the helicopter, along with its total moment. Remember to use the

actual weight and moment of the helicopter you are flying. Next, record the weights of the pilot, passengers,

fuel, and baggage on a weight and balance worksheet.

Then, determine the total weight of the helicopter.

Once you have determined the weight to be within prescribed limits, compute the moment for each weight

and for the loaded helicopter. Do this with a loading

graph provided by the manufacturer. Use figure 7-7 to

determine the moments for a pilot and passenger

weighing 340 pounds and for 211 pounds of fuel.

Start at the bottom scale labeled LOAD WEIGHT.

Draw a line from 211 pounds up to the line labeled

“FUEL @ STA108.5.” Draw your line to the left to

intersect the MOMENT scale and read the fuel moment

(22.9 thousand lb.-inches). Do the same for the pilot/passenger moment. Draw a line from a weight of

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340

pounds up to the line labeled “PILOT & PASSENGER

@STA. 83.2.” Go left and read the pilot/passenger

moment (28.3 thousand lb.-inches).

Reduction factors are often used to reduce the size of

large numbers to manageable levels. In figure 7-7, the

scale on the loading graph gives you moments in thousands of pound-inches. In most cases, when using this

type of chart, you need not be concerned with reduction factors because the CG/moment envelope chart

normally uses the same reduction factor. [Figure 7-8]

After recording the basic empty weight and moment of

the helicopter, and the weight and moment for each

item, total and record all weights and moments. Next,

plot the calculated takeoff weight and moment on the

sample moment envelope graph. Based on a weight of

1,653 pounds and a moment/1,000 of 162 pound-inches,

the helicopter is within the prescribed CG limits.

COMBINATION METHOD

The combination method usually uses the computation method to determine the moments and center of

gravity. Then, these figures are plotted on a graph to

determine if they intersect within the acceptable envelope. Figure 7-9 illustrates that with a total weight of

2,399 pounds and a total moment of 225,022 pound-

FUEL@ STA. 108.5

PILOT& PASSENGER@ STA. 83.2

0

100 200 300 400 500

4

8

12

16

20

24

28

32

36

MOMENT (THOUSANDS OF LBS.-IN.)

LOAD WEIGHT (LBS)

Figure 7-7. Moments for fuel, pilot, and passenger.

190

180

170

160

150

140

130

120

110

100

1,100 1,200 1,300 1,400 1,500 1,600 1,700

LOADED WEIGHT (POUND)

LOAD MOMENT/1000

(POUNDS - INCHES)

1. Basic Empty Weight..................

2. Pilot and Front Passenger........

3. Fuel...........................................

5. Baggage...................................

TOTALS

Weight

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(lbs.)

Moment

(lb.-ins.

/1,000)

1,102 110.8

28.3 340

22.9 211

162.0 1,653

Aft CG Limit

Station 101.0

Forward CG Limit

Station 95.0

Figure 7-8. CG/Moment Chart.

7-7

inches, the CG is 93.8. Plotting this CG against the

weight indicates that the helicopter is loaded within

the longitudinal limits (point A).

CALCULATING LATERAL CG

Some helicopter manufacturers require that you also

determine the lateral CG limits. These calculations are

similar to longitudinal calculations. However, since the

lateral CG datum line is almost always defined as the

center of the helicopter, you are likely to encounter

negative CGs and moments in your calculations.

Negative values are located on the left side while positive stations are located on the right.

Refer to figure 7-10. When computing moment for the

pilot, 170 pounds is multiplied by the arm of 12.2 inches

resulting in a moment of 2,074 pound-inches. As with

any weight placed right of the aircraft centerline, the

moment is expressed as a positive value. The forward

passenger sits left of the aircraft centerline. To compute

this moment, multiply 250 pounds by –10.4 inches. The

result is in a moment of –2,600 pound-inches. Once the

aircraft is completely loaded, the weights and moments

are totaled and the CG is computed. Since more weight

is located left of the aircraft centerline, the resulting

total moment is –3,837 pound-inches. To calculate CG,

divide –3,837 pound-inches by the total weight of 2,399

pounds. The result is –1.6 inches, or a CG that is 1.6

inches left of the aircraft centerline.

Weight Arm Moment

(pounds) (inches) (lb/inches)

Basic Empty Weight

Pilot

Fwd Passenger

Right Fwd Baggage

Left Fwd Baggage

Right Aft Passenger

Left Aft Passenger

Right Aft Baggage

Left Aft Baggage

Totals with Zero Fuel

Main Fuel Tank

Aux Fuel Tank

Totals with Fuel

CG

1,400

170

250

185

50

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50

2,105

184

110

2,399

107.75

49.5

49.5

44

44

79.5

79.5

79.5

79.5

106

102

93.8

150,850

8,415

12,375

0

0

0

14,708

3,975

3,975

194,298

19,504

11,220

225,022

Longitudinal

2,500

2,300

2,100

1,900

1,700

1,500

C

L

91 93 95 97 99 101 103

260

256

252

248

244

240

236

232

1,100

1,050

1,000

950

900

850

800

750

700

Fuselage Station (CM from Datum)

Gross Weight - lb.

Gross Weight - KG

Fuselage Station (in. from Datum)

Main

Rotor

Most Fwd

CG with

Full Fuel

Longitudinal

(Point A)

Figure 7-9. Use the longitudinal CG envelope along with the computed CGs to determine if the helicopter is loaded properly.

Figure 7-10. Computed Lateral CG.

Weight Arm Moment

(pounds) (inches) (lb/inches)

Basic Empty Weight

Pilot

Fwd Passenger

Right Fwd Baggage

Left Fwd Baggage

Right Aft Passenger

Left Aft Passenger

Right Aft Baggage

Left Aft Baggage

Totals with Zero Fuel

Main Fuel Tank

Aux Fuel Tank

Totals with Fuel

CG

1,400

170

250

185

50

50

2,105

184

110

2,399

0

12.2

–10.4

11.5

–11.5

12.2

–12.2

12.2

–12.2

–13.5

13

–1.6

0

2,074

–2,600

0

0

0

–2,257

610

–610

–2,783

–2,484

1,430

–3,837

Lateral

7-8

Lateral CG is often plotted against the longitudinal CG.

[Figure 7-11] In this case, –1.6 is plotted against 93.8,

which was the longitudinal CG determined in the previous problem. The intersection of the two lines falls well

within the lateral CG envelope.

C

L

260

256

252

248

244

240

236

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232

8R

6R

4R

2R

0

2L

4L

6L

8L

Fuselage Station (CM from Datum)

Lateral - in.

Lateral CG - CM

Fuselage Station (in. from Datum)

Lateral

3R

1R

1L

3L

C

L

Main

Rotor

(Point A)

91 93 95 97 99 101 103

Figure 7-11. Use the lateral CG envelope to determine if the

helicopter is properly loaded.

8-1

Your ability to predict the performance of a helicopter

is extremely important. It allows you to determine

how much weight the helicopter can carry before

takeoff, if your helicopter can safely hover at a specific altitude and temperature, how far it will take to

climb above obstacles, and what your maximum

climb rate will be.

FACTORS AFFECTING PERFORMANCE

A helicopter’s performance is dependent on the power

output of the engine and the lift production of the

rotors, whether it is the main rotor(s) or tail rotor. Any

factor that affects engine and rotor efficiency affects

performance. The three major factors that affect performance are density altitude, weight, and wind.

DENSITY ALTITUDE

The density of the air directly affects the performance

of the helicopter. As the density of the air increases,

engine power output, rotor efficiency, and aerodynamic

lift all increase. Density altitude is the altitude above

mean sea level at which a given atmospheric density

occurs in the standard atmosphere. It can also be

interpreted as pressure altitude corrected for nonstandard temperature differences.

Pressure altitude is displayed as the height above a

standard datum plane, which, in this case, is a theoretical plane where air pressure is equal to 29.92 in. Hg.

Pressure altitude is the indicated height value on the

altimeter when the altimeter setting is adjusted to

29.92 in. Hg. Pressure altitude, as opposed to true altitude, is an important value for calculating performance as it more accurately represents the air content at

a particular level. The difference between true altitude

and pressure altitude must be clearly understood. True

altitude means the vertical height above mean sea level

and is displayed on the altimeter when the altimeter is

correctly adjusted to the local setting.

For example, if the local altimeter setting is 30.12 in.

Hg., and the altimeter is adjusted to this value, the

altimeter indicates exact height above sea level.

However, this does not reflect conditions found at this

height under standard conditions. Since the altimeter

setting is more than 29.92 in. Hg., the air in this example has a higher pressure, and is more compressed,

indicative of the air found at a lower altitude.

Therefore, the pressure altitude is lower than the actual

height above mean sea level.

To calculate pressure altitude without the use of an

altimeter, remember that the pressure decreases

approximately 1 inch of mercury for every 1,000-foot

increase in altitude. For example, if the current local

altimeter setting at a 4,000-foot elevation is 30.42, the

pressure altitude would be 3,500 feet. (30.42 – 29.92 =

.50 in. Hg. 31,000 feet = 500 feet. Subtracting 500 feet

from 4,000 equals 3,500 feet).

The four factors that most affect density altitude are:

atmospheric pressure, altitude, temperature, and the

moisture content of the air.

ATMOSPHERIC PRESSURE

Due to changing weather conditions, atmospheric pressure at a given location changes from day to day. If the

pressure is lower, the air is less dense. This means a

higher density altitude and less helicopter performance.

Density Altitude—Pressure altitude corrected for nonstandard temperature variations. Performance charts for many older aircraft are based

on this value.

Standard Atmosphere—At sea level, the standard atmosphere consists

of a barometric pressure of 29.92 inches of mercury (in. Hg.) or 1013.2

millibars, and a temperature of 15°C (59°F). Pressure and temperature

normally decrease as altitude increases. The standard lapse rate in the

lower atmosphere for each 1,000 feet of altitude is approximately 1 in.

Hg. and 2°C (3.5°F). For example, the standard pressure and temperature at 3,000 feet mean sea level (MSL) is 26.92 in. Hg. (29.92 – 3) and

9°C (15°C – 6°C).

Pressure Altitude—The height above the standard pressure level of

29.92 in. Hg. It is obtained by setting 29.92 in the barometric pressure

window and reading the altimeter.

True Altitude—The actual height of an object above mean sea level.

8-2

ALTITUDE

As altitude increases, the air becomes thinner or less

dense. This is because the atmospheric pressure acting

on a given volume of air is less, allowing the air molecules to move further apart. Dense air contains more air

molecules spaced closely together, while thin air contains less air molecules because they are spaced further

apart. As altitude increases, density altitude increases.

TEMPERATURE

Temperature changes have a large affect on density altitude. As warm air expands, the air molecules move further apart, creating less dense air. Since cool air

contracts, the air molecules move closer together, creating denser air. High temperatures cause even low elevations to have high density altitudes.

MOISTURE (HUMIDITY)

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The water content of the air also changes air density

because water vapor weighs less than dry air.

Therefore, as the water content of the air increases, the

air becomes less dense, increasing density altitude and

decreasing performance.

Humidity, also called “relative humidity,” refers to the

amount of water vapor contained in the atmosphere,

and is expressed as a percentage of the maximum

amount of water vapor the air can hold. This amount

varies with temperature; warm air can hold more water

vapor, while colder air can hold less. Perfectly dry air

that contains no water vapor has a relative humidity of

0 percent, while saturated air that cannot hold any more

water vapor, has a relative humidity of 100 percent.

Humidity alone is usually not considered an important

factor in calculating density altitude and helicopter performance; however, it does contribute. There are no

rules-of-thumb or charts used to compute the effects of

humidity on density altitude, so you need to take this

into consideration by expecting a decrease in hovering

and takeoff performance in high humidity conditions.

HIGH AND LOW

DENSITY ALTITUDE CONDITIONS

You need to thoroughly understand the terms “high

density altitude” and “low density altitude.” In general,

high density altitude refers to thin air, while low density altitude refers to dense air. Those conditions that

result in a high density altitude (thin air) are high elevations, low atmospheric pressure, high temperatures,

high humidity, or some combination thereof. Lower

elevations, high atmospheric pressure, low temperatures, and low humidity are more indicative of low

density altitude (dense air). However, high density

altitudes may be present at lower elevations on hot

days, so it is important to calculate the density altitude

and determine performance before a flight.

One of the ways you can determine density altitude is

through the use of charts designed for that purpose.

[Figure 8-1]. For example, assume you are planning to

depart an airport where the field elevation is 1,165 feet

MSL, the altimeter setting is 30.10, and the temperature is 70°F. What is the density altitude? First, correct

for nonstandard pressure (30.10) by referring to the

right side of the chart, and subtracting 165 feet from

the field elevation. The result is a pressure altitude of

1,000 feet. Then, enter the chart at the bottom, just

above the temperature of 70°F (21°C). Proceed up the

chart vertically until you intercept the diagonal 1,000-

foot pressure altitude line, then move horizontally to

the left and read the density altitude of approximately

2,000 feet. This means your helicopter will perform as

if it were at 2,000 feet MSL on a standard day.

Most performance charts do not require you to compute density altitude. Instead, the computation is built

into the performance chart itself. All you have to do is

enter the chart with the correct pressure altitude and the

temperature.

WEIGHT

Lift is the force that opposes weight. As weight

increases, the power required to produce the lift needed

to compensate for the added weight must also increase.

Most performance charts include weight as one of the

variables. By reducing the weight of the helicopter, you

may find that you are able to safely take off or land at a

location that otherwise would be impossible. However,

if you are ever in doubt about whether you can safely

perform a takeoff or landing, you should delay your

takeoff until more favorable density altitude conditions

exist. If airborne, try to land at a location that has more

favorable conditions, or one where you can make a

landing that does not require a hover.

In addition, at higher gross weights, the increased

power required to hover produces more torque, which

means more antitorque thrust is required. In some helicopters, during high altitude operations, the maximum

antitorque produced by the tail rotor during a hover

may not be sufficient to overcome torque even if the

gross weight is within limits.

WINDS

Wind direction and velocity also affect hovering, takeoff, and climb performance. Translational lift occurs

anytime there is relative airflow over the rotor disc.

This occurs whether the relative airflow is caused by

helicopter movement or by the wind. As wind speed

increases, translational lift increases, resulting in less

power required to hover.

The wind direction is also an important consideration.

Headwinds are the most desirable as they contribute to

the most increase in performance. Strong crosswinds

8-3

and tailwinds may require the use of more tail rotor

thrust to maintain directional control. This increased

tail rotor thrust absorbs power from the engine, which

means there is less power available to the main rotor

for the production of lift. Some helicopters even have a

critical wind azimuth or maximum safe relative wind

chart. Operating the helicopter beyond these limits

could cause loss of tail rotor effectiveness.

Takeoff and climb performance is greatly affected by

wind. When taking off into a headwind, effective translational lift is achieved earlier, resulting in more lift and

a steeper climb angle. When taking off with a tailwind,

more distance is required to accelerate through translation lift.

PERFORMANCE CHARTS

In developing performance charts, aircraft manufacturers make certain assumptions about the condition of the

helicopter and the ability of the pilot. It is assumed that

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the helicopter is in good operating condition and the

engine is developing its rated power. The pilot is

assumed to be following normal operating procedures

and to have average flying abilities. Average means a

pilot capable of doing each of the required tasks correctly and at the appropriate times.

Using these assumptions, the manufacturer develops performance data for the helicopter based on

actual flight tests. However, they do not test the helicopter under each and every condition shown on a

performance chart. Instead, they evaluate specific

data and mathematically derive the remaining data.

HOVERING PERFORMANCE

Helicopter performance revolves around whether or

not the helicopter can be hovered. More power is

required during the hover than in any other flight

regime. Obstructions aside, if a hover can be maintained,

a takeoff can be made, especially with the additional

benefit of translational lift. Hover charts are provided for

in ground effect (IGE) hover and out of ground effect

(OGE) hoverunder various conditions of gross weight,

altitude, temperature, and power. The “in ground effect”

hover ceiling is usually higher than the “out of ground

effect” hover ceiling because of the added lift benefit

produced by ground effect.

28.0

28.1

28.2

28.3

28.4

28.5

28.6

28.7

28.8

28.9

29.0

29.1

29.2

29.3

29.4

29.5

29.6

29.7

29.8

29.9

29.92

30.0

30.1

30.2

30.3

30.4

30.5

30.6

30.7

30.8

30.9

31.0

1,824

1,727

1,630

1,533

1,436

1,340

1,244

1,148

1,053

957

863

768

673

579

485

392

298

205

112

20

0

-73

-165

-257

-348

-440

-531

-622

-712

-803

-893

-983

Altimeter

Setting

Pressure

Altitude

Conversion

Factor

0

-18

°F

°C -12

10

-7

20

-1

30

4

40

10

50

16

60

21

70

27

80

32

90

Outside Air Temperature

Approximate Density Altitude – Thousands of Feet

13

12

11

10

9

8

7

6

5

4

3

2

1

SL

12,000

11,000

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

-1,000

PressureAltitude– Feet

StandardTemperature

SeaLevel

Figure 8-1. Density Altitude Chart.

In Ground Effect (IGE) Hover—Hovering close to the surface (usually

less than one rotor diameter above the surface) under the influence of

ground effect.

Out of Ground Effect (OGE) Hover—Hovering greater than one rotor

diameter distance above the surface. Because induced drag is greater

while hovering out of ground effect, it takes more power to achieve a

hover. See Chapter 3—Aerodynamics of Flight for more details on IGE

and OGE hover.

8-4

Since the gross weight of your helicopter is less than

this, you can safely hover with these conditions.

SAMPLE PROBLEM 2

Once you reach the remote location in the previous

problem, you will need to hover out of ground effect

for some of the pictures. The pressure altitude at the

remote site is 9,000 feet, and you will use 50 pounds

of fuel getting there. (The new gross weight is now

1,200 pounds.) The temperature will remain at +15°C.

Using figure 8-3, can you accomplish the mission?

Enter the chart at 9,000 feet (point A) and proceed to

point B (+15°C). From there determine that the maximum gross weight to hover out of ground effect is

approximately 1,130 pounds (point C). Since your

gross weight is higher than this value, you will not be

able to hover with these conditions. To accomplish the

mission, you will have to remove approximately 70

pounds before you begin the flight.

These two sample problems emphasize the importance of

determining the gross weight and hover ceiling throughout

DENSITY ALTITUDE

12,600 FT

STANDARD DAY

(Point A)

900 1,000 1,100 1,200 1,300 1,400

GROSS WEIGHT - LBS.

425 450 475 500 525 550 575

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PRESSURE ALTITUDE - HpX 1,000 FT.

OAT

°C °F

– 20 – 4

+ 14

+ 32

+ 50

+ 68

+ 86

+ 104

– 10

+ 10

+ 20

+ 30

+ 40

0

OUT OF GROUND EFFECT

FULL THROTTLE ( OR LIMIT MANIFOLD

PRESSURE) AND 104% RPM

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GROSS WEIGHT - KGS.

MAX CONT. OR FULL THROTTLE

OGE HOVER CEILING VS. GROSS WEIGHT

600 625

–20

–10

+10

+20

+30

+40

0

OAT

°C

(Point B)

(Point C)

Figure 8-3. Out of Ground Effect Hover Ceiling versus Gross

Weight Chart.

As density altitude increases, more power is required to

hover. At some point, the power required is equal to the

power available. This establishes the hovering ceiling

under the existing conditions. Any adjustment to the

gross weight by varying fuel, payload, or both, affects

the hovering ceiling. The heavier the gross weight, the

lower the hovering ceiling. As gross weight is

decreased, the hover ceiling increases.

SAMPLE PROBLEM 1

You are to fly a photographer to a remote location to

take pictures of the local wildlife. Using figure 8-2, can

you safely hover in ground effect at your departure

point with the following conditions?

Pressure Altitude..................................8,000 feet

Temperature...............................................+15°C

Takeoff Gross Weight.....................1,250 pounds

R.P.M..........................................................104%

First enter the chart at 8,000 feet pressure altitude

(point A), then move right until reaching a point midway between the +10°C and +20°C lines (point B).

From that point, proceed down to find the maximum

gross weight where a 2 foot hover can be achieved. In

this case, it is approximately 1,280 pounds (point C).

DENSITY ALTITUDE

12,600 FT

STANDARD DAY

1,370

(Point A)

(Point B)

900 1,000 1,100 1,200 1,300 1,400

GROSS WEIGHT - LBS.

425 450 475 500 525 550 575

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OAT

°C

PRESSURE ALTITUDE - HpX 1,000 FT.

OAT

°C °F

– 20 – 4

+ 14

+ 32

+ 50

+ 68

+ 86

+ 104

– 10

+ 10

+ 20

+ 30

+ 40

0

IN GROUND EFFECT AT 2 FOOT SKID CLEARANCE

FULL THROTTLE AND 104% RPM

GROSS WEIGHT - KGS.

–20

–10

+10

+20

+30

+40

0

IGE HOVER CEILING VS. GROSS WEIGHT

(Point C)

Figure 8-2. In Ground Effect Hover Ceiling versus Gross

Weight Chart.

8-5

the entire flight operation. Being able to hover at the takeoff location with a certain gross weight does not ensure the

same performance at the landing point. If the destination

point is at a higher density altitude because of higher elevation, temperature, and/or relative humidity, more power

is required to hover. You should be able to predict whether

hovering power will be available at the destination by

knowing the temperature and wind conditions, using the

performance charts in the helicopter flight manual, and

making certain power checks during hover and in flight

prior to commencing the approach and landing.

TAKEOFF PERFORMANCE

If takeoff charts are included in the rotorcraft flight manual, they usually indicate the distance it takes to clear a 50-

foot obstacle based on various conditions of weight,

pressure altitude, and temperature. In addition, the values

computed in the takeoff charts usually assume that the

flight profile is per the applicable height-velocity diagram.

SAMPLE PROBLEM 3

In this example, determine the distance to clear a 50-

foot obstacle with the following conditions:

Pressure Altitude..................................5,000 feet

Takeoff Gross Weight.....................2,850 pounds

Temperature .................................................95°F

Using figure 8-4, locate 2,850 pounds in the first column. Since the pressure altitude of 5,000 feet is not one

of the choices in column two, you have to interpolate

between the values from the 4,000- and 6,000-foot

lines. Follow each of these rows out to the column

headed by 95°F. The values are 1,102 feet and 1,538

feet. Since 5,000 is halfway between 4,000 and 6,000,

the interpolated value should be halfway between these

two values or 1,320 feet ([1,102 + 1,538] 42 = 1,320).

CLIMB PERFORMANCE

Most of the factors affecting hover and takeoff performance also affect climb performance. In addition,

turbulent air, pilot techniques, and overall condition of

the helicopter can cause climb performance to vary.

A helicopter flown at the “best rate-of-climb” speed

will obtain the greatest gain in altitude over a given

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period of time. This speed is normally used during the

climb after all obstacles have been cleared and is usually maintained until reaching cruise altitude. Rate of

climb must not be confused with angle of climb.

Angle of climb is a function of altitude gained over a

given distance. The best rate-of-climb speed results in

the highest climb rate, but not the steepest climb angle

and may not be sufficient to clear obstructions. The

“best angle-of-climb” speed depends upon the power

available. If there is a surplus of power available, the

helicopter can climb vertically, so the best angle-ofclimb speed is zero.

Wind direction and speed have an effect on climb performance, but it is often misunderstood. Airspeed is

the speed at which the helicopter is moving through

the atmosphere and is unaffected by wind.

Atmospheric wind affects only the groundspeed, or

speed at which the helicopter is moving over the

earth’s surface. Thus, the only climb performance

Gross

Weight

Pounds

Pressure

Altitude

Feet

At

–13°F

–25°C

At

23°F

–5°C

At

59°F

15°C

At

95°F

35°C

TAKE-OFF DISTANCE (FEET TO CLEAR 50 FOOT OBSTACLE)

373

400

428

461

567

531

568

611

654

811

743

770

861

939

1,201

401

434

462

510

674

569

614

660

727

975

806

876

940

1,064

1,527

430

461

494

585

779

613

660

709

848

1,144

864

929

1,017

1,255

– –

2,150

2,500

2,850

458

491

527

677

896

652

701

759

986

1,355

929

1,011

1,102

1,538

1,320

SL

2,000

4,000

6,000

8,000

SL

2,000

4,000

6,000

8,000

SL

2,000

4,000

6,000

8,000

Figure 8-4. Takeoff Distance Chart.

8-6

affected by atmospheric wind is the angle of climb and

not the rate of climb.

SAMPLE PROBLEM 4

Determine the best rate of climb using figure 8-5. Use

the following conditions:

Pressure Altitude................................12,000 feet

Outside Air Temperature ...........................+10°C

Gross Weight..................................3,000 pounds

Power ...........................................Takeoff Power

Anti-ice ..........................................................ON

Indicated Airspeed .................................52 knots

With this chart, first locate the temperature of +10°C

帅哥

(point A). Then proceed up the chart to the 12,000-foot

pressure altitude line (point B). From there, move horizontally to the right until you intersect the 3,000-foot

line (point C). With this performance chart, you must

now determine the rate of climb with anti-ice off and

then subtract the rate of climb change with it on. From

point C, go to the bottom of the chart and find that the

maximum rate of climb with anti-ice off is approximately 890 feet per minute. Then, go back to point C

and up to the anti-ice-on line (point D). Proceed horizontally to the right and read approximately 240 feet

per minute change (point E). Now subtract 240 from

890 to get a maximum rate of climb, with anti-ice on,

of 650 feet per minute.

Other rate-of-climb charts use density altitude as a

starting point. [Figure 8-6] While it cleans up the chart

somewhat, you must first determine density altitude.

Notice also that this chart requires a change in the indicated airspeed with a change in altitude.

RATE OF CLIMB — MAXIMUM

TAKEOFF POWER

–40–20 0 20 40 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

OAT — ° C ANTI-ICE OFF RATE OF CLIMB — FT./MIN. (X 100)

0

100

200

300

400

500

R/Correction — FT./MIN.

This Chart is Based on:

Indicated Airspeed 60 MPH 52 KNOTS

N2 ENGINE RPM 100%

PRESSURE

ALTITUDE— FT.

20,000

18,000

16,000

14,000

12,000

10,000

6,000

4,000

2,000

S.L.

GROSSWEIGHT

POUNDS

2,000

2,200

2,400

2,600

2,800

3,000

3,200

8,000

(Point A)

(Point B) (Point C)

(Point D)

(Point E)

890 ft/min.

– 240 ft/min.

650 ft/min.

HOT

DAY

ANTI-ICE ON

Figure 8-5. Maximum Rate-of-Climb Chart.

400 600 800 1,000 1,200 1,400

12,000

10,000

8,000

6,000

4,000

2,000

0

Rate of Climb, Feet Per Minute

Density Altitude — Feet

RATE OF CLIMB/DENSITY ALTITUDE

2,350 LBS. GROSS WEIGHT

BEST RATE OF CLIMB SPEED VARIES WITH

ALTITUDE; 57 MPH AT S.L. DECREASING TO 49

MPH, IAS AT 12,000 FT.

Figure 8-6. This chart uses density altitude in determining

maximum rate of climb.

9-1

From the previous chapters, it should be apparent that

no two helicopters perform the same way. Even when

flying the same model of helicopter, wind, temperature,

humidity, weight, and equipment make it difficult to

predict just how the helicopter will perform. Therefore,

this chapter presents the basic flight maneuvers in a

way that would apply to a majority of the helicopters.

In most cases, the techniques described apply to small

training helicopters with:

• A single, main rotor rotating in a counterclockwise direction (looking downward on the rotor).

• An antitorque system.

Where a technique differs, it will be noted. For example,

a power increase on a helicopter with a clockwise rotor

system requires right antitorque pedal pressure instead

of left pedal pressure. In many cases, the terminology

“apply proper pedal pressure” is used to indicate both

types of rotor systems. However, when discussing throttle coordination to maintain proper r.p.m., there will be

no differentiation between those helicopters with a governor and those without. In a sense, the governor is doing

the work for you. In addition, instead of using the terms

collective pitch control and the cyclic pitch control

throughout the chapter, these controls are referred to as

just collective and cyclic.

Because helicopter performance varies with different

weather conditions and aircraft loading, specific nose

attitudes and power settings will not be discussed. In

addition, this chapter does not detail each and every

attitude of a helicopter in the various flight maneuvers,

nor each and every move you must make in order to

perform a given maneuver.

When a maneuver is presented, there will be a brief

description, followed by the technique to accomplish

the maneuver. In most cases, there is a list of common

errors at the end of the discussion.

PREFLIGHT

Before any flight, you must ensure the helicopter is

airworthy by inspecting it according to the rotorcraft

flight manual, pilot’s operating handbook, or other

information supplied either by the operator or the manufacturer. Remember that as pilot in command, it is