Operation Principle of Vertical Speed Indicator

Vertical Speed Indicator (VSI) is an instrument that uses static pressure to display a rate of climb or descent in feet per minute. The VSI can also sometimes be called a vertical velocity indicator (VVI).

The vertical speed indicator (VSI), which is sometimes called a vertical velocity indicator (VVI), indicates whether the airplane is climbing, descending, or in level flight. The rate of climb or descent is indicated in feet per minute. If properly calibrated, the VSI indicates zero in level flight.

Although the vertical speed indicator operates solely from static pressure, it is a differential pressure instrument. It contains a diaphragm with connecting linkage and gearing to the indicator pointer inside an airtight case. The inside of the diaphragm is connected directly to the static line of the pitot-static system.

The vertical speed indicator is capable of displaying two different types of information:
Trend information shows an immediate indication of an increase or decrease in the airplane's rate of climb or descent.
Rate information shows a stabilized rate of change in altitude.

For example, if maintaining a steady 500-foot per minute (f.p.m.) climb, and the nose is lowered slightly, the VSI immediately senses this change and indicates a decrease in the rate of climb. This first indication is called the trend. After a short time, the VSI needle stabilizes on the new rate of climb, which in this example, is something less than 500 f.p.m. The time from the initial change in the rate of climb, until the VSI displays an accurate indication of the new rate, is called the lag. Rough control technique and turbulence can extend the lag period and cause erratic and unstable rate indications. Some airplanes are equipped with an instantaneous vertical speed indicator (IVSI), which incorporates accelerometers to compensate for the lag in the typical VSI.

Instrument Meteorological Conditions (IMC)

Flying in instrument meteorological conditions (IMC) can result in sensations that are misleading to the body’s sensory system. A safe pilot needs to understand these sensations and effectively counteract them. Instrument flying requires a pilot to make decisions using all available resources.

Aircraft that are flown in instrument meteorological conditions (IMC) are equipped with instruments that provide attitude and direction reference, as well as radio navigation instruments that allow precision flight from takeoff to landing with limited or no outside visual reference.

A turn using 30° of bank is seldom necessary, or advisable, in instrument meteorological conditions (IMC) and is considered an unusual attitude in a helicopter.

Tag: Flying instrument, instrument flight, aviation, piloting, instrument rating, instrument flying training, instrument flight rating, instrument rating requirement, instrument rating regulation, aircraft, aero plane, airplane, and aeronautical knowledge.


Pilots should have a basic understanding of GPS approach procedures and practice GPS IAPs under visual meteorological conditions (VMC) until thoroughly proficient with all aspects of their equipment (receiver and installation) prior to attempting flight in instrument meteorological conditions (IMC).

Pilots who fly in familiar uncongested areas, stay continually alert to weather developments, and accept an alternative to their original plan, may not need an Instrument Rating. However, some cross-country destinations may take a pilot to unfamiliar airports and/or through high activity areas in marginal visual or instrument meteorological conditions (IMC). Under these conditions, an Instrument Flying Rating may be an alternative to rerouting, rescheduling, or canceling a flight. Many accidents are the result of pilots who lack the necessary skills or equipment to fly in marginal visual meteorological conditions (VMC) or IMC conditions and attempt flight without outside references.

Aircraft Major Components Structure

Aircraft—A device that is used for flight in the air.

Airplane—An engine-driven, fixed-wing aircraft heavier than air that is supported in flight by the dynamic reaction of air against its wings.

FUSELAGE—The section of the airplane that consists of the cabin and/or cockpit, containing seats for the occupants and the controls for the airplane.

WINGS—Airfoils attached to each side of the fuselage and are the main lifting surfaces that support the airplane in flight.

EMPENNAGE—The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces.

CONVENTIONAL LANDING GEAR—Landing gear employing a third rear-mounted wheel. These airplanes are also sometimes referred to as tailwheel airplanes.

Nacelle—A streamlined enclosure on an aircraft in which an engine is mounted. On multiengine propeller-driven airplanes, the nacelle is normally mounted on the leading edge of the wing.

Biplane—An airplane that has two main airfoil surfaces or wings on each side of the fuselage, one placed above the other.

Airfoil—An airfoil is any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air.

Monoplane—An airplane that has only one main lifting surface or wing, usually divided into two parts by the fuselage.

Truss—A fuselage design made up of supporting structural members that resist deformation by applied loads.

Monocoque—A shell-like fuselage design in which the stressed outer skin is used to support the majority of imposed stresses. Monocoque fuselage design may include bulkheads but not stringers.

Semi-Monocoque—A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, to support flight loads and stresses imposed on the fuselage.

HUNG START AND HOT START

HUNG START - In gas turbine engines, a condition of normal light off but with rpm remaining at some low value rather than increasing to the normal idle rpm. This is often the result of insufficient power to the engine from the starter. In the event of a hung start, the engine should be shut down.

HOT START - In gas turbine engines, a start which occurs with normal engine rotation, but exhaust temperature exceeds prescribed limits. This is usually caused by an excessively rich mixture in the combustor. The fuel to the engine must be terminated immediately to prevent engine damage.

TURBINE ENGINE HOT/HUNG START
A hot start is when the EGT exceeds the safe limit. Too much fuel entering the combustion chamber or insufficient turbine rpm causes hot starts. Any time an engine has a hot start, refer to the AFM, POH, or an appropriate maintenance manual for inspection requirements.

If the engine fails to accelerate to the proper speed after ignition or does not accelerate to idle rpm, a hung start has occurred. A hung start may also be called a false start. A hung start may be caused by an insufficient starting power source or fuel control malfunction.

Common Errors in Straight-and-Level Flight

Pitch
Pitch errors usually result from the following faults:

Improper adjustment of the attitude indicator's miniature aircraft to
the wings-level attitude. Following your initial level-off from a climb,
check the attitude indicator and make any necessary adjustment in the
miniature aircraft for level flight indication at normal cruise
airspeed.
Insufficient cross-check and interpretation of pitch instruments. For
example, the airspeed indication is low. Believing you are in a
nose-high attitude, you react with forward pressure without noting that
a low power setting is the cause of the airspeed discrepancy. Increase
your cross-check speed to include all relevant instrument indications
before you make a control response.
Uncaging the attitude indicator (if it has a caging feature) when the
airplane is not in level flight. The altimeter and heading indicator
must be stabilized with airspeed indication at normal cruise when you
pull out the caging knob, if you expect the instrument to read
straight-and-level at normal cruise airspeed.
Failure to interpret the attitude indicator in terms of the existing
airspeed.
Late pitch corrections. Pilots commonly like to leave well enough alone.
When the altimeter shows a 20-foot error, there is a reluctance to
correct it, perhaps because of fear of overcontrolling. If
overcontrolling is the error, the more you practice small corrections
and find out the cause of overcontrolling, the closer you will be able
to hold your altitude. If you tolerate a deviation, your errors will
increase.
Chasing the vertical-speed indications. This tendency can be corrected
by proper cross-check of other pitch instruments, as well as by
increasing your understanding of the instrument characteristics.
Using excessive pitch corrections for the altimeter evaluation. Rushing
a pitch correction by making a large pitch change usually aggravates the
existing error and saves neither time nor effort.
Failure to maintain established pitch corrections. This is a common
error associated with cross-check and trim errors. For example, having
established a pitch change to correct an altitude error, you tend to
slow down your crosscheck, waiting for the airplane to stabilize in the
new pitch attitude. To maintain the attitude, you must continue to
cross-check and trim off the pressures you are holding.
Fixations during cross-check. After initiating a heading correction, for
example, you become preoccupied with bank control and neglect to notice
a pitch error. Likewise, during an airspeed change, unnecessary gazing
at the power instrument is common. Bear in mind that a small error in
power setting is of less consequence than large altitude and heading
errors. The airplane will not decelerate any faster if you stare at the
manifold pressure gauge than if you continue your cross-check.

Trim: Adjusting the aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.

Uncaging: Unlocking the gimbals of a gyroscopic instrument, making it
susceptible to damage by abrupt flight maneuvers or rough handling.

Heading
Heading errors usually result from the following faults:

Failure to cross-check the heading indicator, especially during changes
in power or pitch attitude.
Misinterpretation of changes in heading, with resulting corrections in
the wrong direction.
Failure to note, and remember, a preselected heading.
Failure to observe the rate of heading change and its relation to bank
attitude.
Overcontrolling in response to heading changes, especially during
changes in power settings.
Anticipating heading changes with premature application of rudder
control.
Failure to correct small heading deviations. Unless zero error in
heading is your goal, you will find yourself tolerating larger and
larger deviations. Correction of a 1° error takes a lot less time and
concentration than correction of a 20° error.
Correcting with improper bank attitude. If you correct a 10° heading
error with a 20° bank correction, you can roll past the desired heading
before you have the bank established, requiring another correction in
the opposite direction. Do not multiply existing errors with errors in
corrective technique.
Failure to note the cause of a previous heading error and thus repeating
the same error. For example, your airplane is out of trim, with a left
wing low tendency. You repeatedly correct for a slight left turn, yet do
nothing about trim.
Failure to set the heading indicator properly, or failure to uncage it.

Power
Power errors usually result from the following faults:

Failure to know the power settings and pitch attitudes appropriate to
various airspeeds and airplane configurations.
Abrupt use of throttle.
Failure to lead the airspeed when making power changes. For example,
during an airspeed reduction in level flight, especially with gear and
flaps extended, adjust the throttle to maintain the slower speed before
the airspeed reaches the desired speed. Otherwise, the airplane will
decelerate to a speed lower than that desired, resulting in further
power adjustments. How much you lead the airspeed depends upon how fast
the airplane responds to power changes.
Fixation on airspeed or manifold pressure instruments during airspeed
changes, resulting in erratic control of both airspeed and power.

Trim
Trim errors usually result from the following faults:

Improper adjustment of seat or rudder pedals for comfortable position of
legs and feet. Tension in the ankles makes it difficult to relax rudder
pressures.
Confusion as to the operation of trim devices, which differ among
various airplane types. Some trim wheels are aligned appropriately with
the airplane's axes; others are not. Some rotate in a direction contrary
to what you expect.
Faulty sequence in trim technique. Trim should be used, not as a
substitute for control with the wheel (stick) and rudders, but to
relieve pressures already held to stabilize attitude. As you gain
proficiency, you become familiar with trim settings, just as you do with
power settings. With little conscious effort, you trim off pressures
continually as they occur.
Excessive trim control. This induces control pressures that must be held
until you retrim properly. Use trim frequently and in small amounts.
Failure to understand the cause of trim changes. If you do not
understand the basic aerodynamics related to the basic instrument
skills, you will continually lag behind the airplane.

Straight Climbs and Descents

Climbs
For a given power setting and load condition, there is only one attitude
that will give the most efficient rate of climb. The airspeed and the climb
power setting that will determine this climb attitude are given in the
performance data found in your POH/AFM. Details of the technique for
entering a climb vary according to airspeed on entry and the type of climb
(constant airspeed or constant rate) desired. (Heading and trim control are
maintained as discussed under straight-and-level flight.)

Entry
To enter a constant-airspeed climb from cruising airspeed, raise the
miniature aircraft to the approximate nose-high indication for the
predetermined climb speed. The attitude will vary according to the type of
airplane you are flying. Apply light back-elevator pressure to initiate and
maintain the climb attitude. The pressures will vary as the airplane
decelerates. Power may be advanced to the climb power setting
simultaneously with the pitch change, or after the pitch change is
established and the airspeed approaches climb speed. If the transition from
level flight to climb is smooth, the vertical speed indicator will show an
immediate trend upward, continue to move slowly, then stop at a rate
appropriate to the stabilized airspeed and attitude. (Primary and
supporting instruments for the climb entry are shown in figure 5-25.)

(See attached file: 5-25 Climb entry for constant-airspeed climb.jpg)

Once the airplane stabilizes at a constant airspeed and attitude, the
airspeed indicator is primary for pitch and the heading indicator remains
primary for bank. [Figure 5-26] You will monitor the tachometer or manifold
pressure gauge as the primary power instrument to ensure the proper climb
power setting is being maintained. If the climb attitude is correct for the
power setting selected, the airspeed will stabilize at the desired speed.
If the airspeed is low or high, make an appropriate small pitch correction.

(See attached file: 5-26 Stabilized climb at constant airspeed.jpg)

To enter a constant-airspeed climb, first complete the airspeed reduction
from cruise airspeed to climb speed in straight-and-level flight. The climb
entry is then identical to entry from cruising airspeed, except that power
must be increased simultaneously to the climb setting as the pitch attitude
is increased. Climb entries on partial panel are more easily and accurately
controlled if you enter the maneuver from climbing speed.

The technique for entering a constant-rate climb is very similar to that
used for entry to a constant-airspeed climb from climb airspeed. As the
power is increased to the approximate setting for the desired rate,
simultaneously raise the miniature aircraft to the climbing attitude for
the desired airspeed and rate of climb. As the power is increased, the
airspeed indicator is primary for pitch control until the vertical speed
approaches the desired value. As the vertical-speed needle stabilizes, it
becomes primary for pitch control and the airspeed indicator becomes
primary for power control. [Figure 5-27]

(See attached file: 5-27 Stabilized climb at constant rate.jpg)

Pitch and power corrections must be promptly and closely coordinated. For
example, if the vertical speed is correct, but the airspeed is low, add
power. As the power is increased, the miniature aircraft must be lowered
slightly to maintain constant vertical speed. If the vertical speed is high
and the airspeed is low, lower the miniature aircraft slightly and note the
increase in airspeed to determine whether or not a power change is also
necessary. [Figure 5-28] Familiarity with the approximate power settings
helps to keep your pitch and power corrections at a minimum.

(See attached file: 5-28 Airspeed low and vertical high-reduce pitch.jpg)

Leveling Off
To level off from a climb and maintain an altitude, it is necessary to
start the level off before reaching the desired altitude. The amount of
lead varies with rate of climb and pilot technique. If your airplane is
climbing at 1,000 fpm, it will continue to climb at a decreasing rate
throughout the transition to level flight. An effective practice is to lead
the altitude by 10 percent of the vertical speed shown (500-fpm/ 50-foot
lead, 1,000 fpm/100-foot lead).

To level off at cruising airspeed, apply smooth, steady forward-elevator
pressure toward level-flight attitude for the speed desired. As the
attitude indicator shows the pitch change, the vertical-speed needle will
move slowly toward zero, the altimeter needle will move more slowly, and
the airspeed will show acceleration. [Figure 5-29] Once the altimeter,
attitude indicator, and vertical speed indicator show level flight,
constant changes in pitch and torque control will have to be made as the
airspeed increases. As the airspeed approaches cruising speed, reduce power
to the cruise setting. The amount of lead depends upon the rate of
acceleration of your airplane.

(See attached file: 5-29 Level-off at cruising speed.jpg)

To level off at climbing airspeed, lower the nose to the pitch attitude
appropriate to that airspeed in level flight. Power is simultaneously
reduced to the setting for that airspeed as the pitch attitude is lowered.
If your power reduction is at a rate proportionate to the pitch change, the
airspeed will remain constant.

Descents
A descent can be made at a variety of airspeeds and attitudes by reducing
power, adding drag, and lowering the nose to a predetermined attitude.
Sooner or later the airspeed will stabilize at a constant value. Meanwhile,
the only flight instrument providing a positive attitude reference, by
itself, is the attitude indicator. Without the attitude indicator (such as
during a partial-panel descent) the airspeed indicator, the altimeter, and
the vertical speed indicator will be showing varying rates of change until
the airplane decelerates to a constant airspeed at a constant attitude.
During the transition, changes in control pressure and trim, as well as
cross-check and interpretation, must be very accurate if you expect to
maintain positive control.

Entry
The following method for entering descents is effective either with or
without an attitude indicator. First, reduce airspeed to your selected
descent airspeed while maintaining straight-and-level flight, then make a
further reduction in power (to a predetermined setting). As the power is
adjusted, simultaneously lower the nose to maintain constant airspeed, and
trim off control pressures.

During a constant-airspeed descent, any deviation from the desired airspeed
calls for a pitch adjustment. For a constant rate descent, the entry is the
same, but the vertical-speed indicator is primary for pitch control (after
it stabilizes near the desired rate), and the airspeed indicator is primary
for power control. Pitch and power must be closely coordinated when
corrections are made, as they are in climbs. [Figure 5-30]

(See attached file: 5-30 Constant airspeed descent.jpg)

Leveling Off
The level off from a descent must be started before you reach the desired
altitude. The amount of lead depends upon the rate of descent and control
technique. With too little lead, you will tend to overshoot the selected
altitude unless your technique is rapid. Assuming a 500-fpm rate of
descent, lead the altitude by 100–150 feet for a level off at airspeed
higher than descending speed. At the lead point, add power to the
appropriate level-flight cruise setting. [Figure 5-31] Since the nose will
tend to rise as the airspeed increases, hold forward-elevator pressure to
maintain the vertical speed at the descending rate until approximately 50
feet above the altitude, then smoothly adjust the pitch attitude to the
level flight attitude for the airspeed selected.

(See attached file: 5-31 Level-off airspeed higher than descent
airspeed.jpg)

To level-off from a descent at descent airspeed, lead the desired altitude
by approximately 50 feet, simultaneously adjusting the pitch attitude to
level flight and adding power to a setting that will hold the airspeed
constant. [Figure 5-32] Trim off the control pressures and continue with
the normal straight-and-level flight cross-check.

(See attached file: 5-32 Level-off at descent airspeed.jpg)

Airplane Attitude Instrument Flying

Introduction
Attitude instrument flying may be defined as the control of an aircraft's
spatial position by using instruments rather than outside visual
references.

Any flight, regardless of the aircraft used or route flown, consists of
basic maneuvers. In visual flight, you control aircraft attitude with
relation to the natural horizon by using certain reference points on the
aircraft. In instrument flight, you control aircraft attitude by reference
to the flight instruments. A proper interpretation of the flight
instruments will give you essentially the same information that outside
references do in visual flight. Once you learn the role of all the
instruments in establishing and maintaining a desired aircraft attitude,
you will be better equipped to control the aircraft in emergency situations
involving failure of one or more key instruments.

Two basic methods used for learning attitude instrument flying are "control
and performance" and "primary and supporting." Both methods involve the use
of the same instruments, and both use the same responses for attitude
control. They differ in their reliance on the attitude indicator and
interpretation of other instruments.

Attitude instrument flying: Controlling the aircraft by reference to the
instruments rather than outside visual cues.


Control and Performance Method
Aircraft performance is achieved by controlling the aircraft attitude and
power (angle of attack and thrust to drag relationship). Aircraft attitude
is the relationship of its longitudinal and lateral axes to the Earth's
horizon. An aircraft is flown in instrument flight by controlling the
attitude and power, as necessary, to produce the desired performance. This
is known as the control and performance method of attitude instrument
flying and can be applied to any basic instrument maneuver. [Figure 4-1]
(See attached file: 4-1 Control-Performance cross-check method.jpg) The
three general categories of instruments are control, performance, and
navigation instruments.

Control Instruments
The control instruments display immediate attitude and power indications
and are calibrated to permit attitude and power adjustments in precise
amounts. In this discussion, the term "power" is used in place of the more
technically correct term "thrust or drag relationship." Control is
determined by reference to the attitude indicator and power indicators.
These power indicators vary with aircraft and may include tachometers,
manifold pressure, engine pressure ratio, fuel flow, etc.

Instrument flight fundamental: Attitude + Power = Performance


Performance Instruments
The performance instruments indicate the aircraft's actual performance.
Performance is determined by reference to the altimeter, airspeed or Mach
indicator, vertical speed indicator, heading indicator, angle-of-attack
indicator, and turn-and-slip indicator.

Navigation Instruments
The navigation instruments indicate the position of the aircraft in
relation to a selected navigation facility or fix. This group of
instruments includes various types of course indicators, range indicators,
glide-slope indicators, and bearing pointers.

Procedural Steps
1. Establish—Establish an attitude and power setting on the control
instruments that will result in the desired performance. Known or computed
attitude changes and approximate power settings will help to reduce the
pilot's workload.
2. Trim—Trim until control pressures are neutralized. Trimming for
hands-off flight is essential for smooth, precise aircraft control. It
allows pilots to divert their attention to other cockpit duties with
minimum deviation from the desired attitude.
3. Cross-check—Cross-check the performance instruments to determine if the
established attitude or power setting is providing the desired performance.
The crosscheck involves both seeing and interpreting. If a deviation is
noted, determine the magnitude and direction of adjustment required to
achieve the desired performance.
4. Adjust—Adjust the attitude or power setting on the control instruments
as necessary.


Trim: Adjusting the aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.

Attitude Control
Proper control of aircraft attitude is the result of maintaining a constant
attitude, knowing when and how much to change the attitude, and smoothly
changing the attitude a precise amount. Aircraft attitude control is
accomplished by properly using the attitude indicator. The attitude
reference provides an immediate, direct, and corresponding indication of
any change in aircraft pitch or bank attitude.

Pitch Control
Pitch changes are made by changing the "pitch attitude" of the miniature
aircraft or fuselage dot by precise amounts in relation to the horizon.
These changes are measured in degrees or fractions thereof, or bar widths
depending upon the type of attitude reference. The amount of deviation from
the desired performance will determine the magnitude of the correction.

Bank Control
Bank changes are made by changing the "bank attitude" or bank pointers by
precise amounts in relation to the bank scale. The bank scale is normally
graduated at 0°, 10°, 20°, 30°, 60°, and 90° and may be located at the top
or bottom of the attitude reference. Normally, use a bank angle that
approximates the degrees to turn, not to exceed 30°.

Power Control
Proper power control results from the ability to smoothly establish or
maintain desired airspeeds in coordination with attitude changes. Power
changes are made by throttle adjustments and reference to the power
indicators. Power indicators are not affected by such factors as
turbulence, improper trim, or inadvertent control pressures. Therefore, in
most aircraft little attention is required to ensure the power setting
remains constant.

From experience in an aircraft, you know approximately how far to move the
throttles to change the power a given amount. Therefore, you can make power
changes primarily by throttle movement and then crosscheck the indicators
to establish a more precise setting. The key is to avoid fixating on the
indicators while setting the power. Knowledge of approximate power settings
for various flight configurations will help you avoid over-controlling
power.


Primary and Supporting Method
Another basic method for presenting attitude instrument flying classifies
the instruments as they relate to control function as well as aircraft
performance. All maneuvers involve some degree of motion about the lateral
(pitch), longitudinal (bank/roll), and vertical (yaw) axes. Attitude
control is stressed in this handbook in terms of pitch control, bank
control, power control, and trim control. [Figure 4-2] (See attached file:
4-2 Primary - Supporting crosscheck method.jpg) Instruments are grouped as
they relate to control function and aircraft performance as follows:

Pitch Instruments
Attitude Indicator
Altimeter
Airspeed Indicator
Vertical Speed Indicator

Bank Instruments
Attitude Indicator
Heading Indicator
Magnetic Compass
Turn Coordinator

Power Instruments
Airspeed Indicator
Engine Instruments
Manifold Pressure Gauge (MP)
Tachometer/RPM
Engine Pressure Ratio (EPR)—Jet

For any maneuver or condition of flight, the pitch, bank, and power control
requirements are most clearly indicated by certain key instruments. The
instruments that provide the most pertinent and essential information will
be referred to as primary instruments. Supporting instruments back up and
supplement the information shown on the primary

Fixating: Staring at a single instrument, thereby interrupting the
crosscheck process.

Flight configurations: Adjusting the aircraft controls surfaces (including
flaps and landing gear) in a manner that will achieve a specified attitude.

instruments. Straight-and-level flight at a constant airspeed, for example,
means that an exact altitude is to be maintained with zero bank (constant
heading) at a constant airspeed. The pitch, bank, and power instruments
that tell you whether you are maintaining this flight condition are the:

1. Altimeter—supplies the most pertinent altitude information and is
therefore primary for pitch.
2. Heading Indicator—supplies the most pertinent bank or heading
information, and is primary for bank.
3. Airspeed Indicator—supplies the most pertinent information concerning
performance in level flight in terms of power output, and is primary for
power.

Although the attitude indicator is the basic attitude reference, this
concept of primary and supporting instruments does not devalue any
particular flight instrument. It is the only instrument that portrays
instantly and directly to the actual flight attitude. It should always be
used, when available, in establishing and maintaining pitch-and-bank
attitudes. You will better understand the specific use of primary and
supporting instruments when the basic instrument maneuvers are presented in
detail in Chapter 5, "Airplane Basic Flight Maneuvers."

You will find the terms "direct indicating instrument" and "indirect
indicating instrument" used in the following pages. A "direct" indication
is the true and instantaneous reflection of airplane pitch-and-bank
attitude by the miniature aircraft relative to the horizon bar of the
attitude indicator. The altimeter, airspeed indicator, and vertical speed
indicator give supporting ("indirect") indications of pitch attitude at a
given power setting. The heading indicator and turn needle give supporting
indications for bank attitude.

Fundamental Skills
During attitude instrument training, you must develop three fundamental
skills involved in all instrument flight maneuvers: instrument cross-check,
instrument interpretation, and aircraft control. Although you learn these
skills separately and in deliberate sequence, a measure of your proficiency
in precision flying will be your ability to integrate these skills into
unified, smooth, positive control responses to maintain any prescribed
flight path.

Cross-Check
The first fundamental skill is cross-checking (also called "scanning" or
"instrument coverage"). Cross-checking is the continuous and logical
observation of instruments for attitude and performance information. In
attitude instrument flying, the pilot maintains an attitude by reference to
instruments that will produce the desired result in performance. Due to
human error, instrument error, and airplane performance differences in
various atmospheric and loading conditions, it is impossible to establish
an attitude and have performance remain constant for a long period of time.
These variables make it necessary for the pilot to constantly check the
instruments and make appropriate changes in airplane attitude.

Selected Radial Cross-Check
When you use the selected radial cross-check, your eyes spend 80 to 90
percent of the time looking at the attitude indicator, leaving it only to
take a quick glance at one of the flight instruments (for this discussion,
the five instruments surrounding the attitude indicator will be called the
flight instruments). With this method, your eyes never travel directly
between the flight instruments but move by way of the attitude indicator.
The maneuver being performed determines which instruments to look at in the
pattern. [Figure 4-3] (See attached file: 4-3 Selected radial crosscheck
pattern.jpg)

Inverted-V Cross-Check
Moving your eyes from the attitude indicator down to the turn instrument,
up to the attitude indicator, down to the vertical speed indicator, and
back up to the attitude indicator is called the inverted-V cross-check.
[Figure 4-4] (See attached file: 4-4 Inverted- V cross-check.jpg)

The Rectangular Cross-Check
If you move your eyes across the top three instruments (airspeed indicator,
attitude indicator, and altimeter) and drop them down to scan the bottom
three instruments (vertical speed indicator, heading indicator, and turn
instrument), their path will describe a rectangle (clockwise or
counterclockwise rotation is a personal choice). [Figure 4-5] (See attached
file: 4-5 Rectangular interchange format.jpg)

This cross-checking method gives equal weight to the information from each
instrument, regardless of its importance to the maneuver being performed.
However, this method lengthens the time it takes for your eyes to return to
an instrument critical to the successful completion of the maneuver.

Common Cross-Check Errors
As a beginner, you might cross-check rapidly, looking at the instruments
without knowing exactly what you are looking for. With increasing
experience in basic instrument maneuvers and familiarity with the
instrument indications associated with them, you will learn what to look
for, when to look for it, and what response to make. As proficiency
increases, you cross-check primarily from habit, suiting your scanning rate
and sequence to the demands of the flight situation.

You can expect to make many of the following common scanning errors, both
during training and at any subsequent time, if you fail to maintain basic
instrument proficiency through practice:

1. Fixation, or staring at a single instrument, usually occurs for a good
reason, but has poor results. For instance, you may find yourself staring
at your altimeter, which reads 200 feet below the assigned altitude,
wondering how the needle got there. While you gaze at the instrument,
perhaps with increasing tension on the controls, a heading change occurs
unnoticed, and more errors accumulate. Another common fixation is likely
when you initiate an attitude change. For example, you establish a shallow
bank for a 90° turn and stare at the heading indicator throughout the turn,
instead of maintaining your cross-check of other pertinent instruments. You
know the aircraft is turning and you do not need to recheck the heading
indicator for approximately 25 seconds after turn entry, yet you cannot
take your eyes off the instrument. The problem here may not be entirely due
to cross-check error. It may be related to difficulties with one or both of
the other fundamental skills. You may be fixating because of uncertainty
about reading the heading indicator (interpretation), or because of
inconsistency in rolling out of turns (control).
2. Omission of an instrument from your cross-check is another likely fault.
It may be caused by failure to anticipate significant instrument
indications following attitude changes. For example, on your roll-out from
a 180° steep turn, you establish straight-and-level flight with reference
to the attitude indicator alone, neglecting to check the heading indicator
for constant heading information. Because of precession error, the attitude
indicator will temporarily show a slight error, correctable by quick
reference to the other flight instruments.
3. Emphasis on a single instrument, instead of on the combination of
instruments necessary for attitude information, is an understandable fault
during the initial stages of training. You naturally tend to rely on the
instrument that you understand most readily, even when it provides
erroneous or inadequate information. Reliance on a single instrument is
poor technique. For example, you can maintain reasonably close altitude
control with the attitude indicator, but you cannot hold altitude with
precision without including the altimeter in your crosscheck.

Instrument Interpretation
The second fundamental skill, instrument interpretation, requires the most
thorough study and analysis. It begins as you understand each instrument's
construction and operating principles. Then you must apply this knowledge
to the performance of the aircraft that you are flying, the particular
maneuvers to be executed, the cross-check and control techniques applicable
to that aircraft, and the flight conditions in which you are operating.

Tension: Maintaining an excessively strong grip on the control column;
usually results in an over controlled situation.

For example, a pilot uses full power in a small airplane for a 5-minute
climb from near sea level, and the attitude indicator shows the miniature
aircraft two bar widths (twice the thickness of the miniature aircraft
wings) above the artificial horizon. [Figure 4-6] (See attached file: 4-6
Power and attitude equal performance.jpg) The airplane is climbing at 500
feet per minute (fpm) as shown on the vertical speed indicator, and at
airspeed of 90 knots, as shown on the airspeed indicator. With the power
available in this particular airplane and the attitude selected by the
pilot, the performance is shown on the instruments.

Now set up the identical picture on the attitude indicator in a jet
airplane. With the same airplane attitude as shown in the first example,
the vertical speed indicator in the jet reads 2,000 fpm, and the airspeed
indicates 300 knots. As you learn the performance capabilities of the
aircraft in which you are training, you will interpret the instrument
indications appropriately in terms of the attitude of the aircraft. If the
pitch attitude is to be determined, the airspeed indicator, altimeter,
vertical speed indicator, and attitude indicator provide the necessary
information. If the bank attitude is to be determined, the heading
indicator, turn coordinator, and attitude indicator must be interpreted.

For each maneuver, you will learn what performance to expect and the
combination of instruments you must interpret in order to control aircraft
attitude during the maneuver.

Aircraft Control
The third fundamental instrument flying skill is aircraft control. When you
use instruments as substitutes for outside references the necessary control
responses and thought processes are the same as those for controlling
aircraft performance by means of outside references. Knowing the desired
attitude of the aircraft with respect to the natural and artificial
horizon, you maintain the attitude or change it by moving the appropriate
controls.

Aircraft control is composed of four components: pitch control, bank
control, power control, and trim.

1. Pitch control is controlling the rotation of the aircraft about the
lateral axis by movement of the elevators. After interpreting the pitch
attitude from the proper flight instruments, you exert control pressures to
effect the desired pitch attitude with reference to the horizon.
2. Bank control is controlling the angle made by the wing and the horizon.
After interpreting the bank attitude from the appropriate instruments, you
exert the necessary pressures to move the ailerons and roll the aircraft
about the longitudinal axis.
3. Power control is used when interpretation of the flight instruments
indicates a need for a change in thrust.
4. Trim is used to relieve all control pressures held after a desired
attitude has been attained. An improperly trimmed aircraft requires
constant control pressures, produces tension, distracts your attention from
cross-checking, and contributes to abrupt and erratic attitude control. The
pressures you feel on the controls must be those you apply while
controlling a planned change in aircraft attitude, not pressures held
because you let the aircraft control you.

Airplane Attitude Instrument Flying

Introduction
Attitude instrument flying may be defined as the control of an aircraft's
spatial position by using instruments rather than outside visual
references.

Any flight, regardless of the aircraft used or route flown, consists of
basic maneuvers. In visual flight, you control aircraft attitude with
relation to the natural horizon by using certain reference points on the
aircraft. In instrument flight, you control aircraft attitude by reference
to the flight instruments. A proper interpretation of the flight
instruments will give you essentially the same information that outside
references do in visual flight. Once you learn the role of all the
instruments in establishing and maintaining a desired aircraft attitude,
you will be better equipped to control the aircraft in emergency situations
involving failure of one or more key instruments.

Two basic methods used for learning attitude instrument flying are "control
and performance" and "primary and supporting." Both methods involve the use
of the same instruments, and both use the same responses for attitude
control. They differ in their reliance on the attitude indicator and
interpretation of other instruments.

Attitude instrument flying: Controlling the aircraft by reference to the
instruments rather than outside visual cues.


Control and Performance Method
Aircraft performance is achieved by controlling the aircraft attitude and
power (angle of attack and thrust to drag relationship). Aircraft attitude
is the relationship of its longitudinal and lateral axes to the Earth's
horizon. An aircraft is flown in instrument flight by controlling the
attitude and power, as necessary, to produce the desired performance. This
is known as the control and performance method of attitude instrument
flying and can be applied to any basic instrument maneuver. [Figure 4-1]
(See attached file: 4-1 Control-Performance cross-check method.jpg) The
three general categories of instruments are control, performance, and
navigation instruments.

Control Instruments
The control instruments display immediate attitude and power indications
and are calibrated to permit attitude and power adjustments in precise
amounts. In this discussion, the term "power" is used in place of the more
technically correct term "thrust or drag relationship." Control is
determined by reference to the attitude indicator and power indicators.
These power indicators vary with aircraft and may include tachometers,
manifold pressure, engine pressure ratio, fuel flow, etc.

Instrument flight fundamental: Attitude + Power = Performance


Performance Instruments
The performance instruments indicate the aircraft's actual performance.
Performance is determined by reference to the altimeter, airspeed or Mach
indicator, vertical speed indicator, heading indicator, angle-of-attack
indicator, and turn-and-slip indicator.

Navigation Instruments
The navigation instruments indicate the position of the aircraft in
relation to a selected navigation facility or fix. This group of
instruments includes various types of course indicators, range indicators,
glide-slope indicators, and bearing pointers.

Procedural Steps
1. Establish—Establish an attitude and power setting on the control
instruments that will result in the desired performance. Known or computed
attitude changes and approximate power settings will help to reduce the
pilot's workload.
2. Trim—Trim until control pressures are neutralized. Trimming for
hands-off flight is essential for smooth, precise aircraft control. It
allows pilots to divert their attention to other cockpit duties with
minimum deviation from the desired attitude.
3. Cross-check—Cross-check the performance instruments to determine if the
established attitude or power setting is providing the desired performance.
The crosscheck involves both seeing and interpreting. If a deviation is
noted, determine the magnitude and direction of adjustment required to
achieve the desired performance.
4. Adjust—Adjust the attitude or power setting on the control instruments
as necessary.


Trim: Adjusting the aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.

Attitude Control
Proper control of aircraft attitude is the result of maintaining a constant
attitude, knowing when and how much to change the attitude, and smoothly
changing the attitude a precise amount. Aircraft attitude control is
accomplished by properly using the attitude indicator. The attitude
reference provides an immediate, direct, and corresponding indication of
any change in aircraft pitch or bank attitude.

Pitch Control
Pitch changes are made by changing the "pitch attitude" of the miniature
aircraft or fuselage dot by precise amounts in relation to the horizon.
These changes are measured in degrees or fractions thereof, or bar widths
depending upon the type of attitude reference. The amount of deviation from
the desired performance will determine the magnitude of the correction.

Bank Control
Bank changes are made by changing the "bank attitude" or bank pointers by
precise amounts in relation to the bank scale. The bank scale is normally
graduated at 0°, 10°, 20°, 30°, 60°, and 90° and may be located at the top
or bottom of the attitude reference. Normally, use a bank angle that
approximates the degrees to turn, not to exceed 30°.

Power Control
Proper power control results from the ability to smoothly establish or
maintain desired airspeeds in coordination with attitude changes. Power
changes are made by throttle adjustments and reference to the power
indicators. Power indicators are not affected by such factors as
turbulence, improper trim, or inadvertent control pressures. Therefore, in
most aircraft little attention is required to ensure the power setting
remains constant.

From experience in an aircraft, you know approximately how far to move the
throttles to change the power a given amount. Therefore, you can make power
changes primarily by throttle movement and then crosscheck the indicators
to establish a more precise setting. The key is to avoid fixating on the
indicators while setting the power. Knowledge of approximate power settings
for various flight configurations will help you avoid over-controlling
power.


Primary and Supporting Method
Another basic method for presenting attitude instrument flying classifies
the instruments as they relate to control function as well as aircraft
performance. All maneuvers involve some degree of motion about the lateral
(pitch), longitudinal (bank/roll), and vertical (yaw) axes. Attitude
control is stressed in this handbook in terms of pitch control, bank
control, power control, and trim control. [Figure 4-2] (See attached file:
4-2 Primary - Supporting crosscheck method.jpg) Instruments are grouped as
they relate to control function and aircraft performance as follows:

Pitch Instruments
Attitude Indicator
Altimeter
Airspeed Indicator
Vertical Speed Indicator

Bank Instruments
Attitude Indicator
Heading Indicator
Magnetic Compass
Turn Coordinator

Power Instruments
Airspeed Indicator
Engine Instruments
Manifold Pressure Gauge (MP)
Tachometer/RPM
Engine Pressure Ratio (EPR)—Jet

For any maneuver or condition of flight, the pitch, bank, and power control
requirements are most clearly indicated by certain key instruments. The
instruments that provide the most pertinent and essential information will
be referred to as primary instruments. Supporting instruments back up and
supplement the information shown on the primary

Fixating: Staring at a single instrument, thereby interrupting the
crosscheck process.

Flight configurations: Adjusting the aircraft controls surfaces (including
flaps and landing gear) in a manner that will achieve a specified attitude.

instruments. Straight-and-level flight at a constant airspeed, for example,
means that an exact altitude is to be maintained with zero bank (constant
heading) at a constant airspeed. The pitch, bank, and power instruments
that tell you whether you are maintaining this flight condition are the:

1. Altimeter—supplies the most pertinent altitude information and is
therefore primary for pitch.
2. Heading Indicator—supplies the most pertinent bank or heading
information, and is primary for bank.
3. Airspeed Indicator—supplies the most pertinent information concerning
performance in level flight in terms of power output, and is primary for
power.

Although the attitude indicator is the basic attitude reference, this
concept of primary and supporting instruments does not devalue any
particular flight instrument. It is the only instrument that portrays
instantly and directly to the actual flight attitude. It should always be
used, when available, in establishing and maintaining pitch-and-bank
attitudes. You will better understand the specific use of primary and
supporting instruments when the basic instrument maneuvers are presented in
detail in Chapter 5, "Airplane Basic Flight Maneuvers."

You will find the terms "direct indicating instrument" and "indirect
indicating instrument" used in the following pages. A "direct" indication
is the true and instantaneous reflection of airplane pitch-and-bank
attitude by the miniature aircraft relative to the horizon bar of the
attitude indicator. The altimeter, airspeed indicator, and vertical speed
indicator give supporting ("indirect") indications of pitch attitude at a
given power setting. The heading indicator and turn needle give supporting
indications for bank attitude.

Fundamental Skills
During attitude instrument training, you must develop three fundamental
skills involved in all instrument flight maneuvers: instrument cross-check,
instrument interpretation, and aircraft control. Although you learn these
skills separately and in deliberate sequence, a measure of your proficiency
in precision flying will be your ability to integrate these skills into
unified, smooth, positive control responses to maintain any prescribed
flight path.

Cross-Check
The first fundamental skill is cross-checking (also called "scanning" or
"instrument coverage"). Cross-checking is the continuous and logical
observation of instruments for attitude and performance information. In
attitude instrument flying, the pilot maintains an attitude by reference to
instruments that will produce the desired result in performance. Due to
human error, instrument error, and airplane performance differences in
various atmospheric and loading conditions, it is impossible to establish
an attitude and have performance remain constant for a long period of time.
These variables make it necessary for the pilot to constantly check the
instruments and make appropriate changes in airplane attitude.

Selected Radial Cross-Check
When you use the selected radial cross-check, your eyes spend 80 to 90
percent of the time looking at the attitude indicator, leaving it only to
take a quick glance at one of the flight instruments (for this discussion,
the five instruments surrounding the attitude indicator will be called the
flight instruments). With this method, your eyes never travel directly
between the flight instruments but move by way of the attitude indicator.
The maneuver being performed determines which instruments to look at in the
pattern. [Figure 4-3] (See attached file: 4-3 Selected radial crosscheck
pattern.jpg)

Inverted-V Cross-Check
Moving your eyes from the attitude indicator down to the turn instrument,
up to the attitude indicator, down to the vertical speed indicator, and
back up to the attitude indicator is called the inverted-V cross-check.
[Figure 4-4] (See attached file: 4-4 Inverted- V cross-check.jpg)

The Rectangular Cross-Check
If you move your eyes across the top three instruments (airspeed indicator,
attitude indicator, and altimeter) and drop them down to scan the bottom
three instruments (vertical speed indicator, heading indicator, and turn
instrument), their path will describe a rectangle (clockwise or
counterclockwise rotation is a personal choice). [Figure 4-5] (See attached
file: 4-5 Rectangular interchange format.jpg)

This cross-checking method gives equal weight to the information from each
instrument, regardless of its importance to the maneuver being performed.
However, this method lengthens the time it takes for your eyes to return to
an instrument critical to the successful completion of the maneuver.

Common Cross-Check Errors
As a beginner, you might cross-check rapidly, looking at the instruments
without knowing exactly what you are looking for. With increasing
experience in basic instrument maneuvers and familiarity with the
instrument indications associated with them, you will learn what to look
for, when to look for it, and what response to make. As proficiency
increases, you cross-check primarily from habit, suiting your scanning rate
and sequence to the demands of the flight situation.

You can expect to make many of the following common scanning errors, both
during training and at any subsequent time, if you fail to maintain basic
instrument proficiency through practice:

1. Fixation, or staring at a single instrument, usually occurs for a good
reason, but has poor results. For instance, you may find yourself staring
at your altimeter, which reads 200 feet below the assigned altitude,
wondering how the needle got there. While you gaze at the instrument,
perhaps with increasing tension on the controls, a heading change occurs
unnoticed, and more errors accumulate. Another common fixation is likely
when you initiate an attitude change. For example, you establish a shallow
bank for a 90° turn and stare at the heading indicator throughout the turn,
instead of maintaining your cross-check of other pertinent instruments. You
know the aircraft is turning and you do not need to recheck the heading
indicator for approximately 25 seconds after turn entry, yet you cannot
take your eyes off the instrument. The problem here may not be entirely due
to cross-check error. It may be related to difficulties with one or both of
the other fundamental skills. You may be fixating because of uncertainty
about reading the heading indicator (interpretation), or because of
inconsistency in rolling out of turns (control).
2. Omission of an instrument from your cross-check is another likely fault.
It may be caused by failure to anticipate significant instrument
indications following attitude changes. For example, on your roll-out from
a 180° steep turn, you establish straight-and-level flight with reference
to the attitude indicator alone, neglecting to check the heading indicator
for constant heading information. Because of precession error, the attitude
indicator will temporarily show a slight error, correctable by quick
reference to the other flight instruments.
3. Emphasis on a single instrument, instead of on the combination of
instruments necessary for attitude information, is an understandable fault
during the initial stages of training. You naturally tend to rely on the
instrument that you understand most readily, even when it provides
erroneous or inadequate information. Reliance on a single instrument is
poor technique. For example, you can maintain reasonably close altitude
control with the attitude indicator, but you cannot hold altitude with
precision without including the altimeter in your crosscheck.

Instrument Interpretation
The second fundamental skill, instrument interpretation, requires the most
thorough study and analysis. It begins as you understand each instrument's
construction and operating principles. Then you must apply this knowledge
to the performance of the aircraft that you are flying, the particular
maneuvers to be executed, the cross-check and control techniques applicable
to that aircraft, and the flight conditions in which you are operating.

Tension: Maintaining an excessively strong grip on the control column;
usually results in an over controlled situation.

For example, a pilot uses full power in a small airplane for a 5-minute
climb from near sea level, and the attitude indicator shows the miniature
aircraft two bar widths (twice the thickness of the miniature aircraft
wings) above the artificial horizon. [Figure 4-6] (See attached file: 4-6
Power and attitude equal performance.jpg) The airplane is climbing at 500
feet per minute (fpm) as shown on the vertical speed indicator, and at
airspeed of 90 knots, as shown on the airspeed indicator. With the power
available in this particular airplane and the attitude selected by the
pilot, the performance is shown on the instruments.

Now set up the identical picture on the attitude indicator in a jet
airplane. With the same airplane attitude as shown in the first example,
the vertical speed indicator in the jet reads 2,000 fpm, and the airspeed
indicates 300 knots. As you learn the performance capabilities of the
aircraft in which you are training, you will interpret the instrument
indications appropriately in terms of the attitude of the aircraft. If the
pitch attitude is to be determined, the airspeed indicator, altimeter,
vertical speed indicator, and attitude indicator provide the necessary
information. If the bank attitude is to be determined, the heading
indicator, turn coordinator, and attitude indicator must be interpreted.

For each maneuver, you will learn what performance to expect and the
combination of instruments you must interpret in order to control aircraft
attitude during the maneuver.

Aircraft Control
The third fundamental instrument flying skill is aircraft control. When you
use instruments as substitutes for outside references the necessary control
responses and thought processes are the same as those for controlling
aircraft performance by means of outside references. Knowing the desired
attitude of the aircraft with respect to the natural and artificial
horizon, you maintain the attitude or change it by moving the appropriate
controls.

Aircraft control is composed of four components: pitch control, bank
control, power control, and trim.

1. Pitch control is controlling the rotation of the aircraft about the
lateral axis by movement of the elevators. After interpreting the pitch
attitude from the proper flight instruments, you exert control pressures to
effect the desired pitch attitude with reference to the horizon.
2. Bank control is controlling the angle made by the wing and the horizon.
After interpreting the bank attitude from the appropriate instruments, you
exert the necessary pressures to move the ailerons and roll the aircraft
about the longitudinal axis.
3. Power control is used when interpretation of the flight instruments
indicates a need for a change in thrust.
4. Trim is used to relieve all control pressures held after a desired
attitude has been attained. An improperly trimmed aircraft requires
constant control pressures, produces tension, distracts your attention from
cross-checking, and contributes to abrupt and erratic attitude control. The
pressures you feel on the controls must be those you apply while
controlling a planned change in aircraft attitude, not pressures held
because you let the aircraft control you.

Common Errors in Straight-and-Level Flight

Pitch
Pitch errors usually result from the following faults:

Improper adjustment of the attitude indicator's miniature aircraft to
the wings-level attitude. Following your initial level-off from a climb,
check the attitude indicator and make any necessary adjustment in the
miniature aircraft for level flight indication at normal cruise
airspeed.
Insufficient cross-check and interpretation of pitch instruments. For
example, the airspeed indication is low. Believing you are in a
nose-high attitude, you react with forward pressure without noting that
a low power setting is the cause of the airspeed discrepancy. Increase
your cross-check speed to include all relevant instrument indications
before you make a control response.
Uncaging the attitude indicator (if it has a caging feature) when the
airplane is not in level flight. The altimeter and heading indicator
must be stabilized with airspeed indication at normal cruise when you
pull out the caging knob, if you expect the instrument to read
straight-and-level at normal cruise airspeed.
Failure to interpret the attitude indicator in terms of the existing
airspeed.
Late pitch corrections. Pilots commonly like to leave well enough alone.
When the altimeter shows a 20-foot error, there is a reluctance to
correct it, perhaps because of fear of overcontrolling. If
overcontrolling is the error, the more you practice small corrections
and find out the cause of overcontrolling, the closer you will be able
to hold your altitude. If you tolerate a deviation, your errors will
increase.
Chasing the vertical-speed indications. This tendency can be corrected
by proper cross-check of other pitch instruments, as well as by
increasing your understanding of the instrument characteristics.
Using excessive pitch corrections for the altimeter evaluation. Rushing
a pitch correction by making a large pitch change usually aggravates the
existing error and saves neither time nor effort.
Failure to maintain established pitch corrections. This is a common
error associated with cross-check and trim errors. For example, having
established a pitch change to correct an altitude error, you tend to
slow down your crosscheck, waiting for the airplane to stabilize in the
new pitch attitude. To maintain the attitude, you must continue to
cross-check and trim off the pressures you are holding.
Fixations during cross-check. After initiating a heading correction, for
example, you become preoccupied with bank control and neglect to notice
a pitch error. Likewise, during an airspeed change, unnecessary gazing
at the power instrument is common. Bear in mind that a small error in
power setting is of less consequence than large altitude and heading
errors. The airplane will not decelerate any faster if you stare at the
manifold pressure gauge than if you continue your cross-check.

Trim: Adjusting the aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.

Uncaging: Unlocking the gimbals of a gyroscopic instrument, making it
susceptible to damage by abrupt flight maneuvers or rough handling.

Heading
Heading errors usually result from the following faults:

Failure to cross-check the heading indicator, especially during changes
in power or pitch attitude.
Misinterpretation of changes in heading, with resulting corrections in
the wrong direction.
Failure to note, and remember, a preselected heading.
Failure to observe the rate of heading change and its relation to bank
attitude.
Overcontrolling in response to heading changes, especially during
changes in power settings.
Anticipating heading changes with premature application of rudder
control.
Failure to correct small heading deviations. Unless zero error in
heading is your goal, you will find yourself tolerating larger and
larger deviations. Correction of a 1° error takes a lot less time and
concentration than correction of a 20° error.
Correcting with improper bank attitude. If you correct a 10° heading
error with a 20° bank correction, you can roll past the desired heading
before you have the bank established, requiring another correction in
the opposite direction. Do not multiply existing errors with errors in
corrective technique.
Failure to note the cause of a previous heading error and thus repeating
the same error. For example, your airplane is out of trim, with a left
wing low tendency. You repeatedly correct for a slight left turn, yet do
nothing about trim.
Failure to set the heading indicator properly, or failure to uncage it.

Power
Power errors usually result from the following faults:

Failure to know the power settings and pitch attitudes appropriate to
various airspeeds and airplane configurations.
Abrupt use of throttle.
Failure to lead the airspeed when making power changes. For example,
during an airspeed reduction in level flight, especially with gear and
flaps extended, adjust the throttle to maintain the slower speed before
the airspeed reaches the desired speed. Otherwise, the airplane will
decelerate to a speed lower than that desired, resulting in further
power adjustments. How much you lead the airspeed depends upon how fast
the airplane responds to power changes.
Fixation on airspeed or manifold pressure instruments during airspeed
changes, resulting in erratic control of both airspeed and power.

Trim
Trim errors usually result from the following faults:

Improper adjustment of seat or rudder pedals for comfortable position of
legs and feet. Tension in the ankles makes it difficult to relax rudder
pressures.
Confusion as to the operation of trim devices, which differ among
various airplane types. Some trim wheels are aligned appropriately with
the airplane's axes; others are not. Some rotate in a direction contrary
to what you expect.
Faulty sequence in trim technique. Trim should be used, not as a
substitute for control with the wheel (stick) and rudders, but to
relieve pressures already held to stabilize attitude. As you gain
proficiency, you become familiar with trim settings, just as you do with
power settings. With little conscious effort, you trim off pressures
continually as they occur.
Excessive trim control. This induces control pressures that must be held
until you retrim properly. Use trim frequently and in small amounts.
Failure to understand the cause of trim changes. If you do not
understand the basic aerodynamics related to the basic instrument
skills, you will continually lag behind the airplane.

Explosive Decompression

Decompression is defined as the inability of the airplane's pressurization
system to maintain its designed pressure differential. This can be caused
by a malfunction in the pressurization system or structural damage to the
airplane. Physiologically, decompression's fall into two categories; they
are:

Explosive Decompression - Explosive decompression is defined as a
change in cabin pressure faster than the lungs can decompress;
therefore, it is possible that lung damage may occur. Normally, the
time required to release air from the lungs without restrictions,
such as masks, is 0.2 seconds. Most authorities consider any
decompression that occurs in less than 0.5 seconds as explosive and
potentially dangerous.
Rapid Decompression - Rapid decompression is defined as a change in
cabin pressure where the lungs can decompress faster than the cabin;
therefore, there is no likelihood of lung damage. During an explosive
decompression, there may be noise, and for a split second, one may
feel dazed. The cabin air will fill with fog, dust, or flying debris.
Fog occurs due to the rapid drop in temperature and the change of
relative humidity. Normally, the ears clear automatically. Air will
rush from the mouth and nose due to the escape of air from the lungs,
and may be noticed by some individuals.

The primary danger of decompression is hypoxia. Unless proper utilization
of oxygen equipment is accomplished quickly, unconsciousness may occur in a
very short time. The period of useful consciousness is considerably
shortened when a person is subjected to a rapid decompression. This is due
to the rapid reduction of pressure on the body—oxygen in the lungs is
exhaled rapidly. This in effect reduces the partial pressure of oxygen in
the blood and therefore reduces the pilot's effective performance time by
one-third to one-fourth its normal time. For this reason, the oxygen mask
should be worn when flying at very high altitudes (35,000 feet or higher).
It is recommended that the crew members select the 100 percent oxygen
setting on the oxygen regulator at high altitude if the airplane is
equipped with a demand or pressure demand oxygen system.

Another hazard is being tossed or blown out of the airplane if near an
opening. For this reason, individuals near openings should wear safety
harnesses or seat belts at all times when the airplane is pressurized and
they are seated.

Another potential hazard during high altitude decompression is the
possibility of evolved gas decompression sicknesses. Exposure to wind
blasts and extremely cold temperatures are other hazards one might have to
face.

Rapid descent from altitude is necessary if these problems are to be
minimized. Automatic visual and aural warning systems are included in the
equipment of all pressurized airplanes.

Pitot-Static Systems

Three basic pressure-operated instruments are found in most aircraft instrument panels. These are the sensitive altimeter, airspeed indicator (ASI), and vertical speed indicator (VSI). All three receive the pressures they measure from the aircraft Pitot-static system.

Flight instruments depend upon accurate sampling of the ambient atmospheric pressure to determine the height and speed of movement of the aircraft through the air, both horizontally and vertically. This pressure is sampled at two or more locations outside the aircraft by the Pitot-static system.

The pressure of the static, or still air, is measured at a flush port where the air is not disturbed. On some aircraft, this air is sampled by static ports on the side of the electrically heated Pitot-static head, such as the one in figure 3-1. Other aircraft pick up the static pressure through flush ports on the side of the fuselage or the vertical fin. These ports are in locations proven by flight tests to be in undisturbed air, and they are normally paired, one on either side of the aircraft. This dual location prevents lateral movement of the aircraft from giving erroneous static pressure indications. The areas around the static ports may be heated with electric heater elements to prevent ice forming over the port and blocking the entry of the static air.

Pitot pressure, or impact air pressure, is taken in through an open-end tube pointed directly into the relative wind flowing around the aircraft. The pitot tube connects to the airspeed indicator, and the static ports deliver their pressure to the airspeed indicator, altimeter, and VSI. If the static ports should ice over, or in any other way become obstructed, the pilot is able to open a static-system alternate source valve to provide a static air pressure source from a location inside the aircraft. [Figure 3-2] This may cause an inaccurate indication on the pitot-static instrument. Consult the Pilot's Operating Handbook/Airplane Flight Manual (POH/AFM) to determine the amount of error.

Position Error
The static ports are located in a position where the air at their surface is as undisturbed as possible. But under some flight conditions, particularly at a high angle of attack with the landing gear and flaps down, the air around the static port may be disturbed to the extent that it can cause an error in the indication of the altimeter and airspeed indicator. Because of the importance of accuracy in these instruments, part of the certification tests for an aircraft is a check of position error in the static system.

The POH/AFM contains any corrections that must be applied to the airspeed for the various configurations of flaps and landing gear.

Pitot-static head: A combination pickup used to sample Pitot pressure and static air pressure.

Static pressure: Pressure of the air that is still, or not moving, measured perpendicular to the surface of the aircraft.