You must give priority to flying the helicopter while
dividing your attention between navigation and
planning. When determining an altitude to use while
diverting, you should consider cloud heights, winds,
terrain, and radio reception.
LOST PROCEDURES
Getting lost in an aircraft is a potentially dangerous
situation especially when low on fuel. Helicopters have
an advantage over airplanes, as they can land almost
anywhere before they run out of fuel.
If you are lost, there are some good common sense
procedures to follow. If you are nowhere near or cannot
see a town or city, the first thing you should do is climb.
An increase in altitude increases radio and navigation
reception range, and also increases radar coverage. If
you are flying near a town or city, you may be able to
read the name of the town on a water tower or even land
to ask directions.
If your helicopter has a navigational radio, such as a
VOR or ADF receiver, you can possibly determine
your position by plotting your azimuth from two or
more navigational facilities. If GPS is installed, or you
have a portable aviation GPS on board, you can use it
to determine your position and the location of the
nearest airport.
Communicate with any available facility using
frequencies shown on the sectional chart. If you are
able to communicate with a controller, you may be
offered radar vectors. Other facilities may offer
direction finding (DF) assistance. To use this
procedure, the controller will request you to hold
down your transmit button for a few seconds and
then release it. The controller may ask you to change
directions a few times and repeat the transmit
procedure. This gives the controller enough infor-
mation to plot your position and then give you vec-
tors to a suitable landing sight. If your situation
becomes threatening, you can transmit your prob-
lems on the emergency frequency 121.5 MHZ and
set your transponder to 7700. Most facilities, and
even airliners, monitor the emergency frequency.
EMERGENCY EQUIPMENT AND
SURVIVAL GEAR
Both Canada and Alaska require pilots to carry survival
gear. However, it is good common sense that any time
you are flying over rugged and desolated terrain, con-
sider carrying survival gear. Depending on the size and
storage capacity of your helicopter, the following are
some suggested items:
• Food that is not subject to deterioration due to
heat or cold. There should be at least 10,000 calo-
ries for each person on board, and it should be
stored in a sealed waterproof container. It should
have been inspected by the pilot or his represen-
tative within the previous six months, and bear a
label verifying the amount and satisfactory con-
dition of the contents.
• A supply of water.
• Cooking utensils.
• Matches in a waterproof container.
• A portable compass.
• An ax at least 2.5 pounds with a handle not less
than 28 inches in length.
• A flexible saw blade or equivalent cutting tool.
• 30 feet of snare wire and instructions for use.
• Fishing equipment, including still-fishing bait
and gill net with not more than a two inch mesh.
• Mosquito nets or netting and insect repellent
sufficient to meet the needs of all persons aboard,
when operating in areas where insects are likely
to be hazardous.
• A signaling mirror.
• At least three pyrotechnic distress signals.
• A sharp, quality jackknife or hunting knife.
• A suitable survival instruction manual.
• Flashlight with spare bulbs and batteries.
• Portable ELT with spare batteries.
Additional items when there are no trees:
• Stove with fuel or a self-contained means of pro-
viding heat for cooking.
• Tent(s) to accommodate everyone on board.
Additional items for winter operations:
• Winter sleeping bags for all persons when the
temperature is expected to be below 7°C.
• Two pairs of snow shoes.
• Spare ax handle.
• Honing stone or file.
• Ice chisel.
• Snow knife or saw knife.
Attitude instrument flying in helicopters is essentially
visual flying with the flight instruments substituted for
the various reference points on the helicopter and the
natural horizon. Control changes, required to produce a
given attitude by reference to instruments, are identical
to those used in helicopter VFR flight, and your
thought processes are the same. Basic instrument train-
ing is intended as a building block towards attaining an
instrument rating. It will also enable you to do a 180°
turn in case of inadvertent incursion into instrument
meteorological conditions (IMC).
FLIGHT INSTRUMENTS
When flying a helicopter with reference to the flight
instruments, proper instrument interpretation is the
basis for aircraft control. Your skill, in part, depends on
your understanding of how a particular instrument or
system functions, including its indications and limita-
tions. With this knowledge, you can quickly determine
what an instrument is telling you and translate that
information into a control response.
PITOT-STATIC INSTRUMENTS
The pitot-static instruments, which include the airspeed
indicator, altimeter, and vertical speed indicator, oper-
ate on the principle of differential air pressure. Pitot
pressure, also called impact, ram, or dynamic pressure,
is directed only to the airspeed indicator, while static
pressure, or ambient pressure, is directed to all three
instruments. An alternate static source may be included
allowing you to select an alternate source of ambient
pressure in the event the main port becomes blocked.
[Figure 12-1]
AIRSPEED INDICATOR
The airspeed indicator displays the speed of the heli-
copter through the air by comparing ram air pressure
from the pitot tube with static air pressure from the
static port—the greater the differential, the greater the
speed. The instrument displays the result of this pres-
sure differential as indicated airspeed (IAS).
Manufacturers use this speed as the basis for determin-
ing helicopter performance, and it may be displayed in
knots, miles per hour, or both. [Figure 12-2] When an
indicated airspeed is given for a particular situation,
you normally use that speed without making a correc-
tion for altitude or temperature. The reason no correc-
tion is needed is that an airspeed indicator and aircraft
performance are affected equally by changes in air den-
sity. An indicated airspeed always yields the same
performance because the indicator has, in fact, com-
pensated for the change in the environment.
INSTRUMENT CHECK —During the preflight, ensure
that the pitot tube, drain hole, and static ports are unob-
structed. Before liftoff, make sure the airspeed indicator
is reading zero. If there is a strong wind blowing directly
at the helicopter, the airspeed indicator may read higher
Pitot□
Heater Switch
Pitot□
Tube
Airspeed□
Indicator
Vertical□
Speed□
Indicator□
(VSI) Altimeter
Drain□
Opening
Static Port
ON
OFF
Alternate Static Source
ALT□
STATIC AIR□
PULL ON
Figure 12-1. Ram air pressure is supplied only to the airspeed
indicator, while static pressure is used by all three instru-
ments. Electrical heating elements may be installed to pre-
vent ice from forming on the pitot tube. A drain opening to
remove moisture is normally included.
Diaphragm
Static Air Line
Ram Air
Pitot Tube
Figure 12-2. Ram air pressure from the pitot tube is directed
to a diaphragm inside the airspeed indicator. The airtight
case is vented to the static port. As the diaphragm expands
or contracts, a mechanical linkage moves the needle on the
face of the indicator.
than zero, depending on the wind speed and direction.
As you begin your takeoff, make sure the airspeed indi-
cator is increasing at an appropriate rate. Keep in mind,
however, that the airspeed indication might be unreli-
able below a certain airspeed due to rotor downwash.
ALTIMETER
The altimeter displays altitude in feet by sensing pres-
sure changes in the atmosphere. There is an adjustable
barometric scale to compensate for changes in atmos-
pheric pressure. [Figure 12-3]
The basis for altimeter calibration is the International
Standard Atmosphere (ISA), where pressure, tempera-
ture, and lapse rates have standard values. However,
actual atmospheric conditions seldom match the stan-
dard values. In addition, local pressure readings within
a given area normally change over a period of time, and
pressure frequently changes as you fly from one area to
another. As a result, altimeter indications are subject to
errors, the extent of which depends on how much the
pressure, temperature, and lapse rates deviate from stan-
dard, as well as how recently you have set the altimeter.
The best way to minimize altimeter errors is to update
the altimeter setting frequently. In most cases, use the
current altimeter setting of the nearest reporting station
along your route of flight per regulatory requirements.
INSTRUMENT CHECK —During the preflight, ensure
that the static ports are unobstructed. Before lift-off, set
the altimeter to the current setting. If the altimeter indi-
cates within 75 feet of the actual elevation, the altimeter
is generally considered acceptable for use.
VERTICAL SPEED INDICATOR
The vertical speed indicator (VSI) displays the rate of
climb or descent in feet per minute (f.p.m.) by measur-
ing how fast the ambient air pressure increases or
decreases as the helicopter changes altitude. Since the
VSI measures only the rate at which air pressure
changes, air temperature has no effect on this instru-
ment. [Figure 12-4]
There is a lag associated with the reading on the VSI,
and it may take a few seconds to stabilize when show-
ing rate of climb or descent. Rough control technique
and turbulence can further extend the lag period and
cause erratic and unstable rate indications. Some air-
craft are equipped with an instantaneous vertical speed
indicator (IVSI), which incorporates accelerometers to
compensate for the lag found in the typical VSI.
INSTRUMENT CHECK —During the preflight, ensure
that the static ports are unobstructed. Check to see that
the VSI is indicating zero before lift-off. During takeoff,
check for a positive rate of climb indication.
SYSTEM ERRORS
The pitot-static system and associated instruments are
usually very reliable. Errors are generally caused when
the pitot or static openings are blocked. This may be
caused by dirt, ice formation, or insects. Check the pitot
and static openings for obstructions during the preflight.
It is also advisable to place covers on the pitot and static
ports when the helicopter is parked on the ground.
The airspeed indicator is the only instrument affected by a
blocked pitot tube. The system can become clogged in two
Aneroid□
Wafers
Altimeter □
Setting Window
Altitude□
Indication□
Scale
10,000 ft□
Pointer
1,000 ft□
Pointer
100 ft Pointer
Altimeter Setting □
Adjustment Knob
Crosshatch□
Flag□
A crosshatched□
area appears□
on some altimeters□
when displaying□
an altitude below□
10,000 feet MSL.
Static Port
Figure 12-3. The main component of the altimeter is a stack of
sealed aneroid wafers. They expand and contract as atmos-
pheric pressure from the static source changes. The mechani-
cal linkage translates these changes into pointer movements on
the indicator.
Diaphragm
Direct Static□
PressureCalibrated□
Leak
Figure 12-4. Although the sealed case and diaphragm are
both connected to the static port, the air inside the case is
restricted through a calibrated leak. When the pressures are
equal, the needle reads zero. As you climb or descend, the
pressure inside the diaphragm instantly changes, and the
needle registers a change in vertical direction. When the
pressure differential stabilizes at a definite ratio, the needle
registers the rate of altitude change.
ways. If the ram air inlet is clogged, but the drain hole
remains open, the airspeed indicator registers zero, regard-
less of airspeed. If both the ram air inlet and the drain hole
become blocked, pressure in the line is trapped, and the
airspeed indicator reacts like an altimeter, showing an
increase in airspeed with an increase in altitude, and a
decrease in speed as altitude decreases. This occurs as
long as the static port remains unobstructed.
If the static port alone becomes blocked, the airspeed
indicator continues to function, but with incorrect read-
ings. When you are operating above the altitude where
the static port became clogged, the airspeed indicator
reads lower than it should. Conversely, when operating
below that altitude, the indicator reads higher than the
correct value. The amount of error is proportional to
the distance from the altitude where the static system
became blocked. The greater the difference, the greater
the error. With a blocked static system, the altimeter
freezes at the last altitude and the VSI freezes at zero.
Both instruments are then unusable.
Some helicopters are equipped with an alternate static
source, which may be selected in the event that the main
static system becomes blocked. The alternate source gen-
erally vents into the cabin, where air pressures are slightly
different than outside pressures, so the airspeed and
altimeter usually read higher than normal. Correction
charts may be supplied in the flight manual.
GYROSCOPIC INSTRUMENTS
The three gyroscopic instruments that are required for
instrument flight are the attitude indicator, heading
indicator, and turn indicator. When installed in helicop-
ters, these instruments are usually electrically powered.
Gyros are affected by two principles—rigidity in space and
precession. Rigidity in space means that once a gyro is
spinning, it tends to remain in a fixed position and resists
external forces applied to it. This principle allows a gyro to
be used to measure changes in attitude or direction.
Precession is the tilting or turning of a gyro in response to
pressure. The reaction to this pressure does not occur at
the point where it was applied; rather, it occurs at a point
that is 90° later in the direction of rotation from where the
pressure was applied. This principle allows the gyro to
determine a rate of turn by sensing the amount of pres-
sure created by a change in direction. Precession can also
create some minor errors in some instruments.
ATTITUDE INDICATOR
The attitude indicator provides a substitute for the nat-
ural horizon. It is the only instrument that provides an
immediate and direct indication of the helicopter’s
pitch and bank attitude. Since most attitude indicators
installed in helicopters are electrically powered, there
may be a separate power switch, as well as a warning
flag within the instrument, that indicates a loss of
power. A caging or “quick erect” knob may be
included, so you can stabilize the spin axis if the gyro
has tumbled. [Figure 12-5]
HEADING INDICATOR
The heading indicator, which is sometimes referred to
as a directional gyro (DG), senses movement around
the vertical axis and provides a more accurate heading
reference compared to a magnetic compass, which has
a number of turning errors. [Figure 12-6].
Bank Index
Gyro
Gimbal□
Rotation
Roll□
Gimbal
Pitch□
Gimbal
Horizon□
Reference□
Arm
Figure 12-5. The gyro in the attitude indicator spins in the
horizontal plane. Two mountings, or gimbals, are used so
that both pitch and roll can be sensed simultaneously. Due to
rigidity in space, the gyro remains in a fixed position relative
to the horizon as the case and helicopter rotate around it.
Adjustment Gears Adjustment□
Knob
Gimbal□
Rotation
Gimbal Gyro
Main□
Drive Gear
Compass□
Card Gear
Figure 12-6. A heading indicator displays headings based on
a 360° azimuth, with the final zero omitted. For example, a 6
represents 060°, while a 21 indicates 210°. The adjustment
knob is used to align the heading indicator with the magnetic
compass.
Due to internal friction within the gyroscope, preces-
sion is common in heading indicators. Precession
causes the selected heading to drift from the set value.
Some heading indicators receive a magnetic north ref-
erence from a remote source and generally need no
adjustment. Heading indicators that do not have this
automatic north-seeking capability are often called
“free” gyros, and require that you periodically adjust
them. You should align the heading indicator with the
magnetic compass before flight and check it at 15-
minute intervals during flight. When you do an in-flight
alignment, be certain you are in straight-and-level,
unaccelerated flight, with the magnetic compass show-
ing a steady indication.
TURN INDICATORS
Turn indicators show the direction and the rate of turn.
A standard rate turn is 3° per second, and at this rate
you will complete a 360° turn in two minutes. A half-
standard rate turn is 1.5° per second. Two types of
indicators are used to display this information. The
turn-and-slip indicator uses a needle to indicate direc-
tion and turn rate. When the needle is aligned with the
white markings, called the turn index, you are in a
standard rate turn. A half-standard rate turn is indi-
cated when the needle is halfway between the indexes.
The turn-and-slip indicator does not indicate roll rate.
The turn coordinator is similar to the turn-and-slip
indicator, but the gyro is canted, which allows it to
sense roll rate in addition to rate of turn. The turn coor-
dinator uses a miniature aircraft to indicate direction,
as well as the turn and roll rate. [Figure 12-7]
Another part of both the turn coordinator and the turn-
and-slip indicator is the inclinometer. The position of
the ball defines whether the turn is coordinated or not.
The helicopter is either slipping or skidding anytime
the ball is not centered, and usually requires an adjust-
ment of the antitorque pedals or angle of bank to cor-
rect it. [Figure 12-8]
INSTRUMENT CHECK —During your preflight, check
to see that the inclinometer is full of fluid and has no
air bubbles. The ball should also be resting at its lowest
point. Since almost all gyroscopic instruments installed
in a helicopter are electrically driven, check to see that
the power indicators are displaying off indications.
Turn the master switch on and listen to the gyros spool
up. There should be no abnormal sounds, such as a
grinding sound, and the power out indicator flags
should not be displayed. After engine start and before
liftoff, set the direction indicator to the magnetic com-
pass. During hover turns, check the heading indicator
for proper operation and ensure that it has not pre-
cessed significantly. The turn indicator should also
indicate a turn in the correct direction. During takeoff,
check the attitude indicator for proper indication and
recheck it during the first turn.
MAGNETIC COMPASS
In some helicopters, the magnetic compass is the only
direction seeking instrument. Although the compass
appears to move, it is actually mounted in such a way
that the helicopter turns about the compass card as the
card maintains its alignment with magnetic north.
COMPASS ERRORS
The magnetic compass can only give you reliable
directional information if you understand its limitations
and inherent errors. These include magnetic variation,
compass deviation, and magnetic dip.
MAGNETIC VARIATION
When you fly under visual flight rules, you ordinar-
ily navigate by referring to charts, which are oriented
Figure 12-7. The gyros in both the turn-and-slip indicator and
the turn coordinator are mounted so that they rotate in a verti-
cal plane. The gimbal in the turn coordinator is set at an angle,
or canted, which means precession allows the gyro to sense
both rate of roll and rate of turn. The gimbal in the turn-and-slip
indicator is horizontal. In this case, precession allows the gyro
to sense only rate of turn. When the needle or miniature aircraft
is aligned with the turn index, you are in a standard-rate turn.
Gyro□
Rotation
Gimbal□
Rotation
TURN-AND-SLIP□
INDICATOR
Gimbal
Gimbal□
Rotation
Gyro□
Rotation
Canted GyroTURN□
COORDINATOR
Horizontal□
Gyro
Inclinometer
Figure 12-8. In a coordinated turn (instrument 1), the ball is
centered. In a skid (instrument 2), the rate of turn is too great
for the angle of bank, and the ball moves to the outside of the
turn. Conversely, in a slip (instrument 3), the rate of turn is
too small for the angle of bank, and the ball moves to the
inside of the turn.
to true north. Because the aircraft compass is oriented
to magnetic north, you must make allowances for the
difference between these poles in order to navigate
properly. You do this by applying a correction called
variation to convert a true direction to a magnet direc-
tion. Variation at a given point is the angular differ-
ence between the true and magnetic poles. The amount
of variation depends on where you are located on the
earth’s surface. Isogonic lines connect points where
the variation is equal, while the agonic line defines the
points where the variation is zero. [Figure 12-9]
COMPASS DEVIATION
Besides the magnetic fields generated by the earth, other
magnetic fields are produced by metal and electrical
accessories within the helicopter. These magnetic fields
distort the earth’s magnet force and cause the compass
to swing away from the correct heading. Manufacturers
often install compensating magnets within the compass
housing to reduce the effects of deviation. These mag-
nets are usually adjusted while the engine is running and
all electrical equipment is operating. Deviation error,
however, cannot be completely eliminated; therefore, a
compass correction card is mounted near the compass.
The compass correction card corrects for deviation that
occurs from one heading to the next as the lines of force
interact at different angles.
MAGNETIC DIP
Magnetic dip is the result of the vertical component of
the earth’s magnetic field. This dip is virtually non-
existent at the magnetic equator, since the lines of force
are parallel to the earth’s surface and the vertical com-
ponent is minimal. As you move a compass toward the
poles, the vertical component increases, and magnetic
dip becomes more apparent at these higher latitudes.
Magnetic dip is responsible for compass errors during
acceleration, deceleration, and turns.
Acceleration and deceleration errors are fluctuations
in the compass during changes in speed. In the north-
ern hemisphere, the compass swings toward the north
during acceleration and toward the south during decel-
eration. When the speed stabilizes, the compass
returns to an accurate indication. This error is most
pronounced when you are flying on a heading of east
or west, and decreases gradually as you fly closer to a
north or south heading. The error does not occur when
you are flying directly north or south. The memory
aid, ANDS (Accelerate North, Decelerate South) may
help you recall this error. In the southern hemisphere,
this error occurs in the opposite direction.
Turning errors are most apparent when you are turning
to or from a heading of north or south. This error
increases as you near the poles as magnetic dip becomes
more apparent. There is no turning error when flying
near the magnetic equator. In the northern hemisphere,
when you make a turn from a northerly heading, the
compass gives an initial indication of a turn in the
opposite direction. It then begins to show the turn in
the proper direction, but lags behind the actual head-
ing. The amount of lag decreases as the turn continues,
then disappears as the helicopter reaches a heading of
east or west. When you make a turn from a southerly
heading, the compass gives an indication of a turn in
the correct direction, but leads the actual heading. This
error also disappears as the helicopter approaches an
east or west heading.
INSTRUMENT CHECK—Prior to flight, make sure that
the compass is full of fluid. During hover turns, the
compass should swing freely and indicate known head-
ings. Since that magnetic compass is required for all
flight operations, the aircraft should never be flown
with a faulty compass.
INSTRUMENT FLIGHT
To achieve smooth, positive control of the helicopter
during instrument flight, you need to develop three
fundamental skills. They are instrument cross-check,
instrument interpretation, and aircraft control.
INSTRUMENT CROSS-CHECK
Cross-checking, sometimes referred to as scanning, is
the continuous and logical observation of instruments
for attitude and performance information. In attitude
instrument flying, an attitude is maintained by reference
to the instruments, which produces the desired result in
performance. Due to human error, instrument error, and
helicopter performance differences in various atmos-
pheric and loading conditions, it is difficult to
establish an attitude and have performance remain
constant for a long period of time. These variables make
True□
North Pole
Magnetic□
North Pole
Agonic□
Line
20ϒ
20ϒ
15ϒ
15ϒ
10ϒ 5ϒ
5ϒ
0ϒ
Isogonic Lines
17ϒ
10ϒ
Figure 12-9. Variation at point A in the western United States
is 17°. Since the magnetic north pole is located to the east of
the true north pole in relation to this point, the variation is
easterly. When the magnetic pole falls to the west of the true
north pole, variation is westerly.
it necessary for you to constantly check the instruments
and make appropriate changes in the helicopter’s atti-
tude. The actual technique may vary depending on what
instruments are installed and where they are installed,
as well as your experience and proficiency level. For
this discussion, we will concentrate on the six basic
flight instruments discussed earlier. [Figure 12-10]
At first, you may have a tendency to cross-check
rapidly, looking directly at the instruments without
knowing exactly what information you are seeking.
However, with familiarity and practice, the instrument
cross-check reveals definite trends during specific
flight conditions. These trends help you control the
helicopter as it makes a transition from one flight
condition to another.
If you apply your full concentration to a single instrument,
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 usu-
ally results in poor control. For example, while performing
a turn, you may have a tendency to watch only the turn-and-
slip 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 con-
tinue 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 dif-
fers 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 fol-
lowing attitude changes. For example, during leveloff
from a climb or descent, you may concentrate on pitch
control, while forgetting about heading or roll informa-
tion. 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 hel-
icopter 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 condi-
tions, 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 instru-
ment that provides instant and direct aircraft attitude
information, it should be considered primary during
any change in pitch or bank attitude. After the new atti-
tude is established, other instruments become primary,
and the attitude indicator usually becomes the support-
ing 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.