直升机飞行手册Rotorcraft flying handbook

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you will encounter a problem called “fixation.” This results

from a natural human inclination to observe a specific

instrument carefully and accurately, often to the exclusion

of other instruments. Fixation on a single instrument usually results in poor control. For example, while performing

a turn, you may have a tendency to watch only the turn-andslip indicator instead of including other instruments in your

cross-check. This fixation on the turn-and-slip indicator

often leads to a loss of altitude through poor pitch and bank

control. You should look at each instrument only long

enough to understand the information it presents, then continue on to the next one. Similarly, you may find yourself

placing too much “emphasis” on a single instrument,

instead of relying on a combination of instruments nec-

essary for helicopter performance information. This differs from fixation in that you are using other instruments,

but are giving too much attention to a particular one.

During performance of a maneuver, you may sometimes

fail to anticipate significant instrument indications following attitude changes. For example, during leveloff

from a climb or descent, you may concentrate on pitch

control, while forgetting about heading or roll information. This error, called “omission,” results in erratic

control of heading and bank.

In spite of these common errors, most pilots can adapt

well to flight by instrument reference after instruction

and practice. You may find that you can control the helicopter more easily and precisely by instruments.

INSTRUMENT INTERPRETATION

The flight instruments together give a picture of what

is going on. No one instrument is more important than

the next; however, during certain maneuvers or conditions, those instruments that provide the most pertinent

and useful information are termed primary instruments.

Those which back up and supplement the primary

instruments are termed supporting instruments. For

example, since the attitude indicator is the only instrument that provides instant and direct aircraft attitude

information, it should be considered primary during

any change in pitch or bank attitude. After the new attitude is established, other instruments become primary,

and the attitude indicator usually becomes the supporting instrument.

Figure 12-10. In most situations, the cross-check pattern includes the attitude indicator between the cross-check of each of the

other instruments. A typical cross-check might progress as follows: attitude indicator, altimeter, attitude indicator, VSI, attitude

indicator, heading indicator, attitude indicator, and so on.

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AIRCRAFT CONTROL

Controlling the helicopter is the result of accurately

interpreting the flight instruments and translating these

readings into correct control responses. Aircraft control

involves adjustment to pitch, bank, power, and trim in

order to achieve a desired flight path.

Pitch attitude control is controlling the movement of

the helicopter about its lateral axis. After interpreting

the helicopter’s pitch attitude by reference to the pitch

instruments (attitude indicator, altimeter, airspeed indicator, and vertical speed indicator), cyclic control

adjustments are made to affect the desired pitch attitude. In this chapter, the pitch attitudes illustrated are

approximate and will vary with different helicopters.

Bank attitude control is controlling the angle made by

the lateral tilt of the rotor and the natural horizon, or,

the movement of the helicopter about its longitudinal

axis. After interpreting the helicopter’s bank instruments (attitude indicator, heading indicator, and turn

indicator), cyclic control adjustments are made to attain

the desired bank attitude.

Power control is the application of collective pitch with

corresponding throttle control, where applicable. In

straight-and-level flight, changes of collective pitch are

made to correct for altitude deviations if the error is

more than 100 feet, or the airspeed is off by more than

10 knots. If the error is less than that amount, use a

slight cyclic climb or descent.

In order to fly a helicopter by reference to the

instruments, you should know the approximate

power settings required for your particular helicopter

in various load configurations and flight conditions.

Trim, in helicopters, refers to the use of the cyclic centering button, if the helicopter is so equipped, to relieve all

possible cyclic pressures. Trim also refers to the use of

pedal adjustment to center the ball of the turn indicator.

Pedal trim is required during all power changes.

The proper adjustment of collective pitch and cyclic

friction helps you relax during instrument flight.

Friction should be adjusted to minimize overcontrolling and to prevent creeping, but not applied to such a

degree that control movement is limited. In addition,

many helicopters equipped for instrument flight contain stability augmentation systems or an autopilot to

help relieve pilot workload.

STRAIGHT-AND-LEVEL FLIGHT

Straight-and-level unaccelerated flight consists of

maintaining the desired altitude, heading, airspeed, and

pedal trim.

PITCH CONTROL

The pitch attitude of a helicopter is the angular relation

of its longitudinal axis and the natural horizon. If available, the attitude indicator is used to establish the

desired pitch attitude. In level flight, pitch attitude

varies with airspeed and center of gravity. At a constant

altitude and a stabilized airspeed, the pitch attitude is

approximately level. [Figure 12-11]

PITCH CONTR CONTROL OL

PITCH CONTROL

Figure 12-11. The flight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and vertical

speed indicator.

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ATTITUDE INDICATOR

The attitude indicator gives a direct indication of the

pitch attitude of the helicopter. In visual flight, you

attain the desired pitch attitude by using the cyclic to

raise and lower the nose of the helicopter in relation to

the natural horizon. During instrument flight, you follow exactly the same procedure in raising or lowering

the miniature aircraft in relation to the horizon bar.

You may note some delay between control application

and resultant instrument change. This is the normal

control lag in the helicopter and should not be confused

with instrument lag. The attitude indicator may show

small misrepresentations of pitch attitude during

maneuvers involving acceleration, deceleration, or

turns. This precession error can be detected quickly by

cross-checking the other pitch instruments.

If the miniature aircraft is properly adjusted on the

ground, it may not require readjustment in flight. If the

miniature aircraft is not on the horizon bar after leveloff at normal cruising airspeed, adjust it as necessary

while maintaining level flight with the other pitch

instruments. Once the miniature aircraft has been

adjusted in level flight at normal cruising airspeed,

leave it unchanged so it will give an accurate picture of

pitch attitude at all times.

When making initial pitch attitude corrections to maintain altitude, the changes of attitude should be small

and smoothly applied. The initial movement of the

horizon bar should not exceed one bar width high or

low. [Figure 12-12] If a further change is required, an

additional correction of one-half bar normally corrects

any deviation from the desired altitude. This one and

one-half bar correction is normally the maximum pitch

attitude correction from level flight attitude. After you

have made the correction, cross-check the other pitch

instruments to determine whether the pitch attitude

change is sufficient. If more correction is needed to

return to altitude, or if the airspeed varies more than 10

knots from that desired, adjust the power.

ALTIMETER

The altimeter gives an indirect indication of the pitch

attitude of the helicopter in straight-and-level flight.

Since the altitude should remain constant in level

flight, deviation from the desired altitude shows a need

for a change in pitch attitude, and if necessary, power.

When losing altitude, raise the pitch attitude and, if

necessary, add power. When gaining altitude, lower the

pitch attitude and, if necessary, reduce power.

The rate at which the altimeter moves helps in determining pitch attitude. A very slow movement of the

altimeter indicates a small deviation from the desired

pitch attitude, while a fast movement of the altimeter

indicates a large deviation from the desired pitch attitude. Make any corrective action promptly, with small

control changes. Also, remember that movement of the

altimeter should always be corrected by two distinct

changes. The first is a change of attitude to stop the

altimeter; and the second, a change of attitude to

return smoothly to the desired altitude. If the altitude

and airspeed are more than 100 feet and 10 knots low,

respectively, apply power along with an increase of

pitch attitude. If the altitude and airspeed are high by

more than 100 feet and 10 knots, reduce power and

lower the pitch attitude.

There is a small lag in the movement of the altimeter;

however, for all practical purposes, consider that the

altimeter gives an immediate indication of a change, or

a need for change in pitch attitude.

Since the altimeter provides the most pertinent information regarding pitch in level flight, it is considered

primary for pitch.

VERTICAL SPEED INDICATOR

The vertical speed indicator gives an indirect indication

of the pitch attitude of the helicopter and should be used

in conjunction with the other pitch instruments to attain

a high degree of accuracy and precision. The instrument

indicates zero when in level flight. Any movement of

the needle from the zero position shows a need for an

immediate change in pitch attitude to return it to zero.

Always use the vertical speed indicator in conjunction

with the altimeter in level flight. If a movement of the

vertical speed indicator is detected, immediately use the

proper corrective measures to return it to zero. If the

correction is made promptly, there is usually little or no

change in altitude. If you do not zero the needle of the

Figure 12-12. The initial pitch correction at normal cruise is

one bar width.

12-9

vertical speed indicator immediately, the results will

show on the altimeter as a gain or loss of altitude.

The initial movement of the vertical speed needle is

instantaneous and indicates the trend of the vertical

movement of the helicopter. It must be realized that

a period of time is necessary for the vertical speed

indicator to reach its maximum point of deflection

after a correction has been made. This time element

is commonly referred to as “lag.” The lag is directly

proportional to the speed and magnitude of the pitch

change. If you employ smooth control techniques

and make small adjustments in pitch attitude, lag is

minimized, and the vertical speed indicator is easy

to interpret. Overcontrolling can be minimized by

first neutralizing the controls and allowing the pitch

attitude to stabilize; then readjusting the pitch attitude by noting the indications of the other pitch

instruments.

Occasionally, the vertical speed indicator may be

slightly out of calibration. This could result in the

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instrument indicating a slight climb or descent even

when the helicopter is in level flight. If it cannot be

readjusted properly, this error must be taken into consideration when using the vertical speed indicator for

pitch control. For example, if the vertical speed indicator showed a descent of 100 f.p.m. when the helicopter

was in level flight, you would have to use that indication as level flight. Any deviation from that reading

would indicate a change in attitude.

AIRSPEED INDICATOR

The airspeed indicator gives an indirect indication of

helicopter pitch attitude. With a given power setting

and pitch attitude, the airspeed remains constant. If the

airspeed increases, the nose is too low and should be

raised. If the airspeed decreases, the nose is too high

and should be lowered. A rapid change in airspeed indicates a large change in pitch attitude, and a slow change

in airspeed indicates a small change in pitch attitude.

There is very little lag in the indications of the airspeed

indicator. If, while making attitude changes, you notice

some lag between control application and change of

airspeed, it is most likely due to cyclic control lag.

Generally, a departure from the desired airspeed, due to

an inadvertent pitch attitude change, also results in a

change in altitude. For example, an increase in airspeed

due to a low pitch attitude results in a decrease in altitude. A correction in the pitch attitude regains both airspeed and altitude.

BANK CONTROL

The bank attitude of a helicopter is the angular relation

of its lateral axis and the natural horizon. To maintain a

straight course in visual flight, you must keep the

lateral axis of the helicopter level with the natural horizon. Assuming the helicopter is in coordinated flight,

any deviation from a laterally level attitude produces a

turn. [Figure 12-13]

ATTITUDE INDICATOR

The attitude indicator gives a direct indication of the

bank attitude of the helicopter. For instrument flight,

BANK CONTR CONTROL OL

BANK CONTROL

Figure 12-13. The flight instruments used for bank control are the attitude, heading, and turn indicators.

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the miniature aircraft and the horizon bar of the attitude

indicator are substituted for the actual helicopter and

the natural horizon. Any change in bank attitude of the

helicopter is indicated instantly by the miniature aircraft. For proper interpretations of this instrument, you

should imagine being in the miniature aircraft. If the

helicopter is properly trimmed and the rotor tilts, a turn

begins. The turn can be stopped by leveling the miniature

aircraft with the horizon bar. The ball in the turn-and-slip

indicator should always be kept centered through proper

pedal trim.

The angle of bank is indicated by the pointer on the

banking scale at the top of the instrument. [Figure 12-

14] Small bank angles, which may not be seen by

observing the miniature aircraft, can easily be determined by referring to the banking scale pointer.

Pitch and bank attitudes can be determined simultaneously on the attitude indicator. Even though the miniature

aircraft is not level with the horizon bar, pitch attitude can

be established by observing the relative position of the

miniature aircraft and the horizon bar.

The attitude indicator may show small misrepresentations of bank attitude during maneuvers that involve

turns. This precession error can be immediately

detected by closely cross-checking the other bank

instruments during these maneuvers. Precession normally is noticed when rolling out of a turn. If, on the

completion of a turn, the miniature aircraft is level and

the helicopter is still turning, make a small change of

bank attitude to center the turn needle and stop the

movement of the heading indicator.

HEADING INDICATOR

In coordinated flight, the heading indicator gives an

indirect indication of the helicopter’s bank attitude.

When a helicopter is banked, it turns. When the lateral

axis of the helicopter is level, it flies straight.

Therefore, in coordinated flight, when the heading indicator shows a constant heading, the helicopter is level

laterally. A deviation from the desired heading indicates a bank in the direction the helicopter is turning.

A small angle of bank is indicated by a slow change of

heading; a large angle of bank is indicated by a rapid

change of heading. If a turn is noticed, apply opposite

cyclic until the heading indicator indicates the desired

heading, simultaneously checking that the ball is centered. When making the correction to the desired heading, you should not use a bank angle greater than that

required to achieve a standard rate turn. In addition, if

the number of degrees of change is small, limit the

bank angle to the number of degrees to be turned. Bank

angles greater than these require more skill and precision in attaining the desired results. During straightand-level flight, the heading indicator is the primary

reference for bank control.

TURN INDICATOR

During coordinated flight, the needle of the turn-andslip indicator gives an indirect indication of the bank

attitude of the helicopter. When the needle is displaced from the vertical position, the helicopter is

turning in the direction of the displacement. Thus, if

the needle is displaced to the left, the helicopter is

turning left. Bringing the needle back to the vertical

position with the cyclic produces straight flight. A

close observation of the needle is necessary to accurately interpret small deviations from the desired

position.

Cross-check the ball of the turn-and-slip indicator to

determine that the helicopter is in coordinated flight. If

the rotor is laterally level and torque is properly compensated for by pedal pressure, the ball remains in the

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center. To center the ball, level the helicopter laterally

by reference to the other bank instruments, then center

the ball with pedal trim. Torque correction pressures

vary as you make power changes. Always check the

ball following such changes.

COMMON ERRORS DURING STRAIGHT-AND-

LEVEL FLIGHT

1. Failure to maintain altitude.

2. Failure to maintain heading.

3. Overcontrolling pitch and bank during corrections.

4. Failure to maintain proper pedal trim.

5. Failure to cross-check all available instruments.

30°

0°

60°

90°

Figure 12-14. The banking scale at the top of the attitude indicator indicates varying degrees of bank. In this example, the

helicopter is banked a little over 10° to the right.

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POWER CONTROL DURING STRAIGHT-AND-

LEVEL FLIGHT

Establishing specific power settings is accomplished

through collective pitch adjustments and throttle

control, where necessary. For reciprocating powered

helicopters, power indications are observed on the

manifold pressure gauge. For turbine powered helicopters, power is observed on the torque gauge. (Since most

IFR certified helicopters are turbine powered, this

discussion concentrates on this type of helicopter.)

At any given airspeed, a specific power setting determines whether the helicopter is in level flight, in a

climb, or in a descent. For example, cruising airspeed

maintained with cruising power results in level flight.

If you increase the power setting and hold the airspeed

constant, the helicopter climbs. Conversely, if you

decrease power and hold the airspeed constant, the helicopter descends. As a rule of thumb, in a turbine-engine

powered helicopter, a 10 to 15 percent change in the

torque value required to maintain level flight results in a

climb or descent of approximately 500 f.p.m., if the airspeed remains the same.

If the altitude is held constant, power determines the

airspeed. For example, at a constant altitude, cruising

power results in cruising airspeed. Any deviation from

the cruising power setting results in a change of airspeed. When power is added to increase airspeed, the

nose of the helicopter pitches up and yaws to the right

in a helicopter with a counterclockwise main rotor

blade rotation. When power is reduced to decrease airspeed, the nose pitches down and yaws to the left. The

yawing effect is most pronounced in single-rotor helicopters, and is absent in helicopters with counter-rotating

rotors. To counteract the yawing tendency of the helicopter, apply pedal trim during power changes.

To maintain a constant altitude and airspeed in level

flight, coordinate pitch attitude and power control. The

relationship between altitude and airspeed determines

the need for a change in power and/or pitch attitude. If

the altitude is constant and the airspeed is high or low,

change the power to obtain the desired airspeed.

During the change in power, make an accurate interpretation of the altimeter; then counteract any deviation from the desired altitude by an appropriate change

of pitch attitude. If the altitude is low and the airspeed

is high, or vice versa, a change in pitch attitude alone

may return the helicopter to the proper altitude and airspeed. If both airspeed and altitude are low, or if both

are high, a change in both power and pitch attitude is

necessary.

To make power control easy when changing airspeed, it

is necessary to know the approximate power settings for

the various airspeeds that will be flown. When the air-

speed is to be changed any appreciable amount, adjust

the torque so that it is approximately five percent over or

under that setting necessary to maintain the new airspeed.

As the power approaches the desired setting, include the

torque meter in the cross-check to determine when the

proper adjustment has been accomplished. As the airspeed is changing, adjust the pitch attitude to maintain a

constant altitude. A constant heading should be maintained throughout the change. As the desired airspeed is

approached, adjust power to the new cruising power setting and further adjust pitch attitude to maintain altitude.

Overpowering and underpowering torque approximately

five percent results in a change of airspeed at a moderate

rate, which allows ample time to adjust pitch and bank

smoothly. The instrument indications for straight-andlevel flight at normal cruise, and during the transition

from normal cruise to slow cruise are illustrated in figures 12-15 and 12-16 on the next page. After the airspeed

has stabilized at slow cruise, the attitude indicator shows

an approximate level pitch attitude.

The altimeter is the primary pitch instrument during

level flight, whether flying at a constant airspeed, or

during a change in airspeed. Altitude should not change

during airspeed transitions. The heading indicator

remains the primary bank instrument. Whenever the

airspeed is changed any appreciable amount, the torque

meter is momentarily the primary instrument for power

control. When the airspeed approaches that desired, the

airspeed indicator again becomes the primary instrument for power control.

The cross-check of the pitch and bank instruments to

produce straight-and-level flight should be combined

with the power control instruments. With a constant

power setting, a normal cross-check should be

satisfactory. When changing power, the speed of the

cross-check must be increased to cover the pitch and

bank instruments adequately. This is necessary to

counteract any deviations immediately.

COMMON ERRORS DURING AIRSPEED CHANGES

1. Improper use of power.

2. Overcontrolling pitch attitude.

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3. Failure to maintain heading.

4. Failure to maintain altitude.

5. Improper pedal trim.

STRAIGHT CLIMBS (CONSTANT AIRSPEED

AND CONSTANT RATE)

For any power setting and load condition, there is only

one airspeed that will give the most efficient rate of

climb. To determine this, you should consult the climb

data for the type of helicopter being flown. The technique varies according to the airspeed on entry and

whether you want to make a constant airspeed or constant rate climb.

12-12

ENTRY

To enter a constant airspeed climb from cruise airspeed,

when the climb speed is lower than cruise speed, simultaneously increase power to the climb power setting

and adjust pitch attitude to the approximate climb attitude. The increase in power causes the helicopter to

start climbing and only very slight back cyclic pressure

is needed to complete the change from level to climb

attitude. The attitude indicator should be used to

accomplish the pitch change. If the transition from

level flight to a climb is smooth, the vertical speed indicator shows an immediate upward trend and then stops

at a rate appropriate to the stabilized airspeed and attitude. Primary and supporting instruments for climb

entry are illustrated in figure 12-17.

When the helicopter stabilizes on a constant airspeed

and attitude, the airspeed indicator becomes primary

Figure 12-16. Flight instrument indications in straight-and-level flight with airspeed decreasing.

Figure 12-15. Flight instrument indications in straight-and-level flight at normal cruise speed.

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0

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TORQUE

PERCENT

Supporting Pitch

and Bank

Primary Power Primary Pitch

Supporting Pitch Primary Bank Supporting Bank

Supporting

Power

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110

120

0

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PERCENT

Primary Bank

Primary

Power

Initially

Primary Pitch Supporting Pitch

and Bank

Primary Power as Airspeed

Approaches Desired Value

Supporting Pitch Supporting Bank

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for pitch. The torque meter continues to be primary for

power and should be monitored closely to determine if

the proper climb power setting is being maintained.

Primary and supporting instruments for a stabilized

constant airspeed climb are shown in figure 12-18.

The technique and procedures for entering a constant

rate climb are very similar to those previously

described for a constant airspeed climb. For training

purposes, a constant rate climb is entered from climb

airspeed. The rate used is the one that is appropriate for

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0

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TORQUE

PERCENT

Primary Pitch

Supporting Bank

Primary

Power

Supporting Pitch Primary Bank Supporting Bank

Figure 12-17. Flight instrument indications during climb entry for a constant airspeed climb.

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110

120

0

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TORQUE

PERCENT

Primary Pitch Supporting Pitch

and Bank

Primary

Power

Supporting Pitch Primary Bank Supporting Bank

Figure 12-18. Flight instrument indications in a stabilized, constant airspeed climb.

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the particular helicopter being flown. Normally, in helicopters with low climb rates, 500 f.p.m. is appropriate,

in helicopters capable of high climb rates, use a rate of

1,000 f.p.m.

To enter a constant rate climb, increase power to the

approximate setting for the desired rate. As power is

applied, the airspeed indicator is primary for pitch until

the vertical speed approaches the desired rate. At this

time, the vertical speed indicator becomes primary for

pitch. Change pitch attitude by reference to the attitude

indicator to maintain the desired vertical speed. When

the VSI becomes primary for pitch, the airspeed indicator becomes primary for power. Primary and supporting

instruments for a stabilized constant rate climb are illustrated in figure 12-19. Adjust power to maintain desired

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airspeed. Pitch attitude and power corrections should be

closely coordinated. To illustrate this, if the vertical

speed is correct but the airspeed is low, add power. As

power is increased, it may be necessary to lower the

pitch attitude slightly to avoid increasing the vertical

rate. Adjust the pitch attitude smoothly to avoid overcontrolling. Small power corrections usually will be

sufficient to bring the airspeed back to the desired indication.

LEVELOFF

The leveloff from a constant airspeed climb must be

started before reaching the desired altitude. Although the

amount of lead varies with the helicopter being flown

and your piloting technique, the most important factor is

vertical speed. As a rule of thumb, use 10 percent of the

vertical velocity as your lead point. For example, if the

rate of climb is 500 f.p.m., initiate the leveloff approximately 50 feet before the desired altitude. When the

proper lead altitude is reached, the altimeter becomes

primary for pitch. Adjust the pitch attitude to the level

flight attitude for that airspeed. Cross-check the altimeter and VSI to determine when level flight has been

attained at the desired altitude. To level off at cruise airspeed, if this speed is higher than climb airspeed, leave

the power at the climb power setting until the airspeed

approaches cruise airspeed, then reduce it to the cruise

power setting.

The leveloff from a constant rate climb is accomplished

in the same manner as the leveloff from a constant airspeed climb.

STRAIGHT DESCENTS (CONSTANT

AIRSPEED AND CONSTANT RATE)

A descent may be performed at any normal airspeed the

helicopter is capable of, but the airspeed must be determined prior to entry. The technique is determined by

whether you want to perform a constant airspeed or a

constant rate descent.

ENTRY

If your airspeed is higher than descending airspeed, and

you wish to make a constant airspeed descent at the

descending airspeed, reduce power to the descending

power setting and maintain a constant altitude using

cyclic pitch control. When you approach the descending airspeed, the airspeed indicator becomes primary

for pitch, and the torque meter is primary for power. As

you hold the airspeed constant, the helicopter begins to

descend. For a constant rate descent, reduce the power

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TORQUE

PERCENT

Supporting

Power

Supporting Pitch

and Bank

Primary Bank

Primary Power

Primary Pitch Supporting Bank

Figure 12-19. Flight instrument indications in a stabilized constant rate climb.

12-15

to the approximate setting for the desired rate. If the

descent is started at the descending airspeed, the airspeed indicator is primary for pitch until the VSI

approaches the desired rate. At this time, the vertical

speed indicator becomes primary for pitch, and the

airspeed indicator becomes primary for power.

Coordinate power and pitch attitude control as was

described earlier for constant rate climbs.

LEVELOFF

The leveloff from a constant airspeed descent may be

made at descending airspeed or at cruise airspeed, if

this is higher than descending airspeed. As in a climb

leveloff, the amount of lead depends on the rate of

descent and control technique. For a leveloff at

descending airspeed, the lead should be approximately

10 percent of the vertical speed. At the lead altitude,

simultaneously increase power to the setting necessary

to maintain descending airspeed in level flight. At this

point, the altimeter becomes primary for pitch, and the

airspeed indicator becomes primary for power.

To level off at a higher airspeed than descending airspeed, increase the power approximately 100 to 150 feet

prior to reaching the desired altitude. The power setting

should be that which is necessary to maintain the

desired airspeed in level flight. Hold the vertical speed

constant until approximately 50 feet above the desired

altitude. At this point, the altimeter becomes primary

for pitch, and the airspeed indicator becomes primary

for power. The leveloff from a constant rate descent

should be accomplished in the same manner as the leveloff from a constant airspeed descent.

COMMON ERRORS DURING STRAIGHT CLIMBS

AND DESCENTS

1. Failure to maintain heading.

2. Improper use of power.

3. Poor control of pitch attitude.

4. Failure to maintain proper pedal trim.

5. Failure to level off on desired altitude.

TURNS

When making turns by reference to the flight instruments, they should be made at a definite rate. Turns

described in this chapter are those that do not exceed a

standard rate of 3° per second as indicated on the turnand-slip indicator. True airspeed determines the angle

of bank necessary to maintain a standard rate turn. A

rule of thumb to determine the approximate angle of

bank required for a standard rate turn is to divide your

airspeed by 10 and add one-half the result. For example, at 60 knots, approximately 9° of bank is required

(60 ÷ 10 = 6 + 3 = 9); at 80 knots, approximately 12° of

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bank is needed for a standard rate turn.

To enter a turn, apply lateral cyclic in the direction of the

desired turn. The entry should be accomplished

smoothly, using the attitude indicator to establish the

approximate bank angle. When the turn indicator indicates a standard rate turn, it becomes primary for bank.

The attitude indicator now becomes a supporting instrument. During level turns, the altimeter is primary for

pitch, and the airspeed indicator is primary for power.

Primary and supporting instruments for a stabilized standard rate turn are illustrated in figure 12-20. If an

Figure 12-20. Flight instrument indications for a standard rate turn to the left.

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PERCENT

Primary Bank Initially

Supporting Pitch

Primary Power Primary Pitch

Supporting Pitch Primary Bank as

Turn is Established

Supporting

Power

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increase in power is required to maintain airspeed, slight

forward cyclic pressure may be required since the helicopter tends to pitch up as collective pitch angle is

increased. Apply pedal trim, as required, to keep the ball

centered.

To recover to straight-and-level flight, apply cyclic in

the direction opposite the turn. The rate of roll-out

should be the same as the rate used when rolling into

the turn. As you initiate the turn recover, the attitude

indicator becomes primary for bank. When the helicopter is approximately level, the heading indicator

becomes primary for bank as in straight-and-level

flight. Cross-check the airspeed indicator and ball

closely to maintain the desired airspeed and pedal trim.

TURNS TO A PREDETERMINED HEADING

A helicopter turns as long as its lateral axis is tilted; therefore, the recovery must start before the desired heading is

reached. The amount of lead varies with the rate of turn

and your piloting technique.

As a guide, when making a 3° per second rate of turn,

use a lead of one-half the bank angle. For example, if

you are using a 12° bank angle, use half of that, or 6°,

as the lead point prior to your desired heading. Use this

lead until you are able to determine the exact amount

required by your particular technique. The bank angle

should never exceed the number of degrees to be

turned. As in any standard rate turn, the rate of recovery should be the same as the rate for entry. During

turns to predetermined headings, cross-check the primary and supporting pitch, bank, and power instruments closely.

TIMED TURNS

A timed turn is a turn in which the clock and turn-andslip indicator are used to change heading a definite

number of degrees in a given time. For example, using

a standard rate turn, a helicopter turns 45° in 15 seconds. Using a half-standard rate turn, the helicopter

turns 45° in 30 seconds. Timed turns can be used if

your heading indicator becomes inoperative.

Prior to performing timed turns, the turn coordinator

should be calibrated to determine the accuracy of its

indications. To do this, establish a standard rate turn by

referring to the turn-and-slip indicator. Then as the

sweep second hand of the clock passes a cardinal point

(12, 3, 6, or 9), check the heading on the heading indicator. While holding the indicated rate of turn constant,

note the heading changes at 10-second intervals. If the

helicopter turns more or less than 30° in that interval, a

smaller or larger deflection of the needle is necessary

to produce a standard rate turn. When you have calibrated the turn-and-slip indicator during turns in each

direction, note the corrected deflections, if any, and

apply them during all timed turns.

You use the same cross-check and control technique in

making timed turns that you use to make turns to a predetermined heading, except that you substitute the

clock for the heading indicator. The needle of the turnand-slip indicator is primary for bank control, the

altimeter is primary for pitch control, and the airspeed

indicator is primary for power control. Begin the roll-in

when the clock’s second hand passes a cardinal point,

hold the turn at the calibrated standard-rate indication,

or half-standard-rate for small changes in heading, and

begin the roll-out when the computed number of seconds has elapsed. If the roll-in and roll-out rates are the

same, the time taken during entry and recovery need

not be considered in the time computation.

If you practice timed turns with a full instrument panel,

check the heading indicator for the accuracy of your

turns. If you execute the turns without the heading indicator, use the magnetic compass at the completion of

the turn to check turn accuracy, taking compass deviation errors into consideration.

CHANGE OF AIRSPEED IN TURNS

Changing airspeed in turns is an effective maneuver for

increasing your proficiency in all three basic instrument skills. Since the maneuver involves simultaneous

changes in all components of control, proper execution

requires a rapid cross-check and interpretation, as well

as smooth control. Proficiency in the maneuver also

contributes to your confidence in the instruments during attitude and power changes involved in more complex maneuvers.

Pitch and power control techniques are the same as

those used during airspeed changes in straight-andlevel flight. As discussed previously, the angle of

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bank

necessary for a given rate of turn is proportional to the

true airspeed. Since the turns are executed at standard

rate, the angle of bank must be varied in direct proportion to the airspeed change in order to maintain a

constant rate of turn. During a reduction of airspeed,

you must decrease the angle of bank and increase the

pitch attitude to maintain altitude and a standard rate

turn.

The altimeter and the needle on the turn indicator

should remain constant throughout the turn. The

altimeter is primary for pitch control, and the turn needle is primary for bank control. The torque meter is

primary for power control while the airspeed is changing. As the airspeed approaches the new indication, the

airspeed indicator becomes primary for power control.

Two methods of changing airspeed in turns may be

used. In the first method, airspeed is changed after the

turn is established. In the second method, the airspeed

change is initiated simultaneously with the turn entry.

The first method is easier, but regardless of the method

12-17

used, the rate of cross-check must be increased as you

reduce power. As the helicopter decelerates, check the

altimeter and VSI for needed pitch changes, and the

bank instruments for needed bank changes. If the needle

of the turn-and-slip indicator shows a deviation from

the desired deflection, change the bank. Adjust pitch

attitude to maintain altitude. When the airspeed

approaches that desired, the airspeed indicator becomes

primary for power control. Adjust the torque meter to

maintain the desired airspeed. Use pedal trim to ensure

the maneuver is coordinated.

Until your control technique is very smooth, frequently

cross-check the attitude indicator to keep from overcontrolling and to provide approximate bank angles

appropriate for the changing airspeeds.

30° BANK TURN

A turn using 30° of bank is seldom necessary, or advisable, in IMC, but it is an excellent maneuver to increase

your ability to react quickly and smoothly to rapid

changes of attitude. Even though the entry and recovery technique are the same as for any other turn, you

will probably find it more difficult to control pitch

because of the decrease in vertical lift as the bank

increases. Also, because of the decrease in vertical lift,

there is a tendency to lose altitude and/or airspeed.

Therefore, to maintain a constant altitude and airspeed,

additional power is required. You should not initiate a

correction, however, until the instruments indicate the

need for a correction. During the maneuver, note the

need for a correction on the altimeter and vertical speed

indicator, then check the indications on the attitude

indicator, and make the necessary adjustments. After

you have made this change, again check the altimeter

and vertical speed indicator to determine whether or

not the correction was adequate.

CLIMBING AND DESCENDING TURNS

For climbing and descending turns, the techniques

described earlier for straight climbs and descents and

those for standard rate turns are combined. For practice,

start the climb or descent and turn simultaneously. The

primary and supporting instruments for a stabilized constant airspeed left climbing turn are illustrated in figure

12-21. The leveloff from a climbing or descending turn

is the same as the leveloff from a straight climb or

descent. To recover to straight-and-level flight, you may

stop the turn and then level off, level off and then stop

the turn, or simultaneously level off and stop the turn.

During climbing and descending turns, keep the ball of

the turn indicator centered with pedal trim.

COMPASS TURNS

The use of gyroscopic heading indicators make heading control very easy. However, if the heading indicator fails or your helicopter does not have one installed,

you must use the magnetic compass for heading reference. When making compass-only turns, you need to

adjust for the lead or lag created by acceleration and

deceleration errors so that you roll out on the desired

heading. When turning to a heading of north, the lead

for the roll-out must include the number of degrees of

your latitude plus the lead you normally use in recovery from turns. During a turn to a south heading, maintain the turn until the compass passes south the number

40

50

60 70

80

90

100

110

120

0

10

20

30

TORQUE

PERCENT

Primary

Power

Supporting Pitch

and Bank

Primary Bank

Primary Pitch

Supporting Pitch

Figure 12-21. Flight instrument indications for a stabilized left climbing turn at a constant airspeed.

12-18

COMMON ERRORS DURING

UNUSUAL ATTITUDE RECOVERIES

1. Failure to make proper pitch correction.

2. Failure to make proper bank correction.

3. Failure to make proper power correction.

4. Overcontrol of pitch and/or bank attitude.

5. Overcontrol of power.

6. Excessive loss of altitude.

EMERGENCIES

Emergencies under instrument flight are handled similarly to those occurring during VFR flight. A thorough

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knowledge of the helicopter and its systems, as well as

good aeronautical knowledge and judgment, prepares

you to better handle emergency situations. Safe operations begin with preflight planning and a thorough preflight. Plan your route of flight so that there are adequate

landing sites in the event you have to make an emergency landing. Make sure you have all your resources,

such as maps, publications, flashlights, and fire extinguishers readily available for use in an emergency.

During any emergency, you should first fly the aircraft.

This means that you should make sure the helicopter is

under control, including the determination of emergency

landing sites. Then perform the emergency checklist

memory items, followed by written items in the RFM.

Once all these items are under control, you should notify

ATC. Declare any emergency on the last assigned ATC

frequency, or if one was not issued, transmit on the emergency frequency 121.5. Set the transponder to the emergency squawk code 7700. This code triggers an alarm or

a special indicator in radar facilities.

Most in-flight emergencies, including low fuel and a

complete electrical failure, require you to land as soon

as possible. In the event of an electrical fire, turn all nonessential equipment off and land immediately. Some

essential electrical instruments, such as the attitude indicator, may be required for a safe landing. A navigation

radio failure may not require an immediate landing as

long as the flight can continue safely. In this case, you

should land as soon as practical. ATC may be able to

provide vectors to a safe landing area. For the specific

details on what to do during an emergency, you should

refer to the RFM for the helicopter you are flying.

of degrees of your latitude, minus your normal roll-out

lead. For example, when turning from an easterly

direction to north, where the latitude is 30°, start the

roll-out when the compass reads 037° (30° plus onehalf the 15° angle of bank, or whatever amount is

appropriate for your rate of roll-out). When turning

from an easterly direction to south, start the roll-out

when the magnetic compass reads 203° (180° plus 30°

minus one-half the angle of bank). When making similar turns from a westerly direction, the appropriate

points at which to begin your roll-out would be 323°

for a turn to north, and 157° for a turn to south.

COMMON ERRORS DURING TURNS

1. Failure to maintain desired turn rate.

2. Failure to maintain altitude in level turns.

3. Failure to maintain desired airspeed.

4. Variation in the rate of entry and recovery.

5. Failure to use proper lead in turns to a heading.

6. Failure to properly compute time during timed turns.

7. Failure to use proper leads and lags during the

compass turns.

8. Improper use of power.

9. Failure to use proper pedal trim.

UNUSUAL ATTITUDES

Any maneuver not required for normal helicopter instrument flight is an unusual attitude and may be caused by

any one or a combination of factors, such as turbulence,

disorientation, instrument failure, confusion, preoccupation with cockpit duties, carelessness in cross-checking,

errors in instrument interpretation, or lack of proficiency

in aircraft control. Due to the instability characteristics

of the helicopter, unusual attitudes can be extremely critical. As soon as you detect an unusual attitude, make a

recovery to straight-and-level flight as soon as possible

with a minimum loss of altitude.

To recover from an unusual attitude, correct bank and

pitch attitude, and adjust power as necessary. All components are changed almost simultaneously, with little

lead of one over the other. You must be able to perform

this task with and without the attitude indicator. If the

helicopter is in a climbing or descending turn, correct

bank, pitch, and power. The bank attitude should be

corrected by referring to the turn-and-slip indicator and

attitude indicator. Pitch attitude should be corrected by

reference to the altimeter, airspeed indicator, VSI, and

attitude indicator. Adjust power by referring to the airspeed indicator and torque meter.

Since the displacement of the controls used in recoveries from unusual attitudes may be greater than those for

normal flight, take care in making adjustments as

straight-and-level flight is approached. Cross-check the

other instruments closely to avoid overcontrolling.

Land as soon as possible—Land without delay at the nearest suitable

area, such as an open field, at which a safe approach and landing is

assured.

Land immediately—The urgency of the landing is paramount. The primary consideration is to assure the survival of the occupants. Landing in

trees, water, or other unsafe areas should be considered only as a last

resort.

Land as soon as practical—The landing site and duration of flight are

at the discretion of the pilot. Extended flight beyond the nearest

approved landing area is not recommended.

12-19

AUTOROTATIONS

Both straight-ahead and turning autorotations should

be practiced by reference to instruments. This training

will ensure that you can take prompt corrective action

to maintain positive aircraft control in the event of an

engine failure.

To enter autorotation, reduce collective pitch smoothly

to maintain a safe rotor r.p.m. and apply pedal trim to

keep the ball of the turn-and-slip indicator centered.

The pitch attitude of the helicopter should be approximately level as shown by the attitude indicator. The

airspeed indicator is the primary pitch instrument and

should be adjusted to the recommended autorotation

speed. The heading indicator is primary for bank in a

straight-ahead autorotation. In a turning autorotation, a

standard rate turn should be maintained by reference to

the needle of the turn-and-slip indicator.

COMMON ERRORS DURING AUTOROTATIONS

1. Uncoordinated entry due to improper pedal trim.

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2. Poor airspeed control due to improper pitch attitude.

3. Poor heading control in straight-ahead autorotations.

4. Failure to maintain proper rotor r.p.m.

5. Failure to maintain a standard rate turn during turning autorotations.

SERVO FAILURE

Most helicopters certified for single-pilot IFR flight are

required to have autopilots, which greatly reduces pilot

workload. If an autopilot servo fails, however, you

have to resume manual control of the helicopter. How

much your workload increases, depends on which

servo fails. If a cyclic servo fails, you may want to land

immediately as the workload increases tremendously.

If an antitorque or collective servo fails, you might be

able to continue to the next suitable landing site.

INSTRUMENT TAKEOFF

This maneuver should only be performed as part of

your training for an instrument rating. The procedures

and techniques described here should be modified, as

necessary, to conform with those set forth in the operating instructions for the particular helicopter being

flown.

Adjust the miniature aircraft in the attitude indicator,

as appropriate, for the aircraft being flown. After the

helicopter is aligned with the runway or takeoff pad, to

prevent forward movement of a helicopter equipped

with a wheel-type landing gear, set the parking brake

or apply the toe brakes. If the parking brake is used, it

must be unlocked after the takeoff has been completed.

Apply sufficient friction to the collective pitch control to

minimize overcontrolling and to prevent creeping.

Excessive friction should be avoided since this limits

collective pitch movement.

After checking all instruments for proper indications,

start the takeoff by applying collective pitch and a predetermined power setting. Add power smoothly and

steadily to gain airspeed and altitude simultaneously and

to prevent settling to the ground. As power is applied and

the helicopter becomes airborne, use the antitorque pedals initially to maintain the desired heading. At the same

time, apply forward cyclic to begin accelerating to

climbing airspeed. During the initial acceleration, the

pitch attitude of the helicopter, as read on the attitude

indicator, should be one to two bar widths low. The primary and supporting instruments after becoming airborne

are illustrated in figure 12-22. As the airspeed increases

40

50

60 70

80

90

100

110

120

0

10

20

30

TORQUE

PERCENT

Primary

Power

Primary Pitch

Supporting Bank

Supporting Pitch

Supporting Bank

Supporting Pitch

Supporting Pitch Primary Bank

Figure 12-22. Flight instrument indications during an instrument takeoff.

12-20

to the appropriate climb airspeed, adjust pitch gradually

to climb attitude. As climb airspeed is reached, reduce

power to the climb power setting and transition to a fully

coordinated straight climb.

During the initial climbout, minor heading corrections should be made with pedals only until sufficient airspeed is attained to transition to fully

coordinated flight. Throughout the instrument takeoff, instrument cross-check and interpretations must

be rapid and accurate, and aircraft control positive

and smooth.

COMMON ERRORS DURING INSTRUMENT

TAKEOFFS

1. Failure to maintain heading.

2. Overcontrolling pedals.

3. Failure to use required power.

4. Failure to adjust pitch attitude as climbing airspeed is reached.

13-1

Flying at night can be a very pleasant experience. The

air is generally cooler and smoother, resulting in better

helicopter performance and a more comfortable flight.

You generally also experience less traffic and less radio

congestion.

NIGHT FLIGHT PHYSIOLOGY

Before discussing night operations, it is important you

understand how your vision is affected at night and

how to counteract the visual illusions, which you might

encounter.

VISION IN FLIGHT

Vision is by far the most important sense that you

have, and flying is obviously impossible without it.

Most of the things you perceive while flying are

visual or heavily supplemented by vision. The visual

sense is especially important in collision avoidance

and depth perception. Your vision sensors are your

eyes, even though they are not perfect in the way they

function or see objects. Since your eyes are not

always able to see all things at all times, illusions and

blindspots occur. The more you understand the eye

and how it functions, the easier it is to compensate for

these illusions and blindspots.

THE EYE

The eye works in much the same way as a camera. Both

have an aperture, lens, method of focusing, and a surface for registering images. [Figure 13-1].

Vision is primarily the result of light striking a photosensitive layer, called the retina, at the back of the eye.

The retina is composed of light-sensitive cones and

rods. The cones in your eye perceive an image best

when the light is bright, while the rods work best in low