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The slaving meter indicates the difference between the displayed heading and the magnetic heading, showing clockwise or counterclockwise errors of the compass card during turns.

The magnetic slaving transmitter is usually mounted in a wingtip to eliminate the possibility of magnetic interference, ensuring accurate heading information.

The torque motor processes the gyro unit until it is aligned with the transmitter signal, allowing for accurate heading indication.

'Free' gyros do not have automatic north-seeking capability and require periodic adjustment to align with the magnetic compass, unlike automatic gyros that self-correct.

The pilot should check the heading indicator frequently (approximately every 15 minutes) and reset it to align with the magnetic compass when the aircraft is straight and level at a constant speed.

The AOA indicator provides the pilot with situational awareness regarding the aerodynamic health of the airfoil, specifically the margin between current AOA and critical AOA at which the airfoil will stall.

The pitot-static system combines static air pressure and dynamic pressure from the aircraft's motion to operate key instruments such as the airspeed indicator (ASI), altimeter, and vertical speed indicator (VSI).

The key instruments that utilize the pitot-static system are:

1. Airspeed Indicator (ASI)
2. Altimeter
3. Vertical Speed Indicator (VSI)

It is important for pilots to understand flight instruments to:

• Safely interpret and operate the instruments
• Recognize errors and malfunctions
• Utilize the instruments to their fullest potential for safe flight operations.

The pitot tube measures the total combined pressures present when an aircraft moves through the air, capturing both dynamic pressure (due to motion) and static pressure (ambient pressure).

The ASI receives total pressure from the pitot tube's pressure chamber and static pressure from the opposite side, allowing it to indicate dynamic pressure by canceling out static pressures.

When dynamic pressure changes, the ASI shows either an increase or decrease in speed, corresponding to the direction of the change in dynamic pressure.

The static chamber is vented to the free undisturbed air, allowing atmospheric pressure to move freely in and out of the instruments, and it connects to the altimeter and VSI to provide static pressure.

The alternate static source provides static pressure in case the primary static source becomes blocked, ensuring the instruments can still function correctly.

When the alternate static source is used, the altimeter indicates a slightly higher altitude than actual due to the lower pressure inside the flight deck compared to the exterior pressure.

The primary function of the altimeter is to measure the height of an aircraft above a given pressure level, providing vital altitude information to the pilot.

The pressure altimeter operates by measuring the atmospheric pressure at its location. As altitude increases, atmospheric pressure decreases, causing the aneroid wafers inside the altimeter to expand or contract, which translates into altitude indications on the dial.

The main components of the altimeter include a stack of sealed aneroid wafers, a mechanical linkage that connects wafer movement to the indicator needles, and a static port for pressure input.

The VSI is chosen to be broken because it is the least important static source instrument for flight, and doing so allows for an alternate method of introducing static pressure into the system.

The indicated altitude is correct only when:

1. Sea level barometric pressure is standard (29.92 "Hg)
2. Sea level free air temperature is standard (+15 degrees Celsius or 59 degrees Fahrenheit)
3. Pressure and temperature decrease at a standard rate with an increase in altitude.

The Kollsman window is a barometric pressure setting window on the altimeter. It allows pilots to set the corrected pressure, ensuring that the altimeter indicates the correct altitude above sea level after adjustments are made.

If an aircraft flies from a high pressure area to a low pressure area without adjusting the altimeter, the indicated altitude will remain constant, but the actual height of the aircraft above the ground will be lower than the indicated altitude, creating a hazardous situation.

Cold air is denser than warm air, so when operating in temperatures colder than standard, the true altitude is lower than the altimeter indication. This means that pilots must anticipate that a colder-than-standard temperature places the aircraft lower than indicated, potentially requiring a higher indicated altitude for terrain clearance.

The aviation axiom is: "GOING FROM A HIGH TO A LOW, LOOK OUT BELOW." This highlights the danger of not adjusting the altimeter when transitioning between different pressure areas.

When the air is warmer than standard, the aircraft is higher than the altimeter indicates. Conversely, extremely cold temperatures can cause the altimeter to indicate a lower altitude than the actual altitude. Altitude corrections for temperature can be computed using a navigation computer.

The Kollsman window allows pilots to adjust the altimeter for variations in atmospheric pressure by setting the pressure scale to match the given altimeter setting, which is defined as station pressure reduced to sea level.

Pilots must adjust their altimeter settings as they progress from one reporting station to another because the altimeter setting is only accurate in the vicinity of the reporting station. Air traffic control (ATC) provides updated altimeter settings, or pilots can obtain local settings from weather broadcasts.

If a pilot does not adjust the altimeter setting, the aircraft may be at an incorrect altitude relative to the traffic pattern. For example, using an outdated setting could result in the aircraft being approximately 250 feet below the proper traffic pattern altitude, leading to potential safety issues during landing.

The difference in altimeter settings indicates how much the indicated altitude may vary between locations. For instance, a difference of 0.25 inches of mercury corresponds to an altitude difference of approximately 250 feet, which is crucial for maintaining safe vertical separation between aircraft.

The pilot should subtract the difference from the indicated altitude, as the actual altitude is lower than what is indicated on the altimeter.

1. Subtract the current altimeter setting from 29.94 'Hg, placing the original setting as the top number.
2. Multiply the difference by 1,000 feet (since 1 inch of pressure equals approximately 1,000 feet of altitude).
3. Subtract this number from the indicated altitude.

A decrease in pressure causes the altimeter to indicate an increase in altitude, interpreting the pressure change as a climb.

Accurate altitude information is vital for clearing terrain and obstructions, especially in restricted visibility, and to maintain safe altitude in accordance with air traffic rules.

1. Indicated altitude - read directly from the altimeter when set to the current setting.
2. True altitude - vertical distance above sea level, often expressed as feet above mean sea level (MSL).
3. Absolute altitude - height above the terrain directly below the aircraft.
4. Pressure altitude - altitude in standard atmospheric conditions.
5. Density altitude - altitude corrected for non-standard temperature.

Absolute altitude is the vertical distance of an aircraft above the terrain or above ground level (AGL).

Pressure altitude is the altitude indicated when the altimeter setting is adjusted to 29.92 "Hg. It represents the altitude above the standard datum plane, where air pressure equals 29.92 "Hg at 15 °C. It is used to compute density altitude, true altitude, true airspeed (TAS), and other performance data.

Density altitude is pressure altitude corrected for variations from standard temperature. When conditions are standard, pressure altitude and density altitude are the same. If the temperature is above standard, density altitude is higher than pressure altitude; if below standard, it is lower. This is crucial for aircraft performance.

The performance of an aircraft is directly related to the density of the air. Key factors include:

1. Power Output: Lower air density results in less power from naturally aspirated engines.
2. Airfoil Efficiency: Fewer air molecules affect the efficiency of airfoils.
3. Takeoff Roll: Lower pressure leads to longer takeoff rolls due to reduced acceleration.

Prior to each flight, a pilot should:

1. Examine the altimeter for proper indications.
2. Set the barometric scale to the current reported altimeter setting from a reliable source (e.g., ATIS, AWOS).
3. Ensure the altimeter indicates the surveyed field elevation of the airport.
4. If the indication is off by more than 75 feet, refer the instrument for recalibration.

The Vertical Speed Indicator (VSI) indicates whether the aircraft is climbing, descending, or in level flight, showing the rate of climb or descent in feet per minute (fpm). If calibrated correctly, it indicates zero in level flight.

The VSI operates as a differential pressure instrument using static pressure. It contains a diaphragm connected to the static line and a calibrated leak. When the aircraft climbs or descends, the pressure inside the diaphragm changes immediately, while the case pressure changes more slowly due to the leak, creating a pressure differential that indicates the rate of altitude change on the instrument needle.

The VSI displays:

1. Trend information - Indicates an immediate increase or decrease in the aircraft's rate of climb or descent.
2. Rate information - Shows a stabilized rate of change in altitude after a brief lag period.

The lag period is the time from the initial change in the rate of climb until the VSI displays an accurate indication of the new rate. It typically lasts 6-9 seconds and can be extended by rough control techniques and turbulence, leading to erratic and unstable rate indications.

During a preflight check, the VSI should indicate a near zero reading prior to leaving the ramp area and again just before takeoff. If the VSI indicates anything other than zero, that indication can be referenced as the zero mark. After takeoff, the VSI should trend upward to indicate a positive rate of climb.

The ASI is a sensitive, differential pressure gauge that measures and indicates the difference between pitot (dynamic) pressure and static pressure, providing the pilot with the aircraft's airspeed.

Indicated airspeed (IAS) is the direct instrument reading obtained from the ASI, uncorrected for variations in atmospheric density, installation error, or instrument error. It is crucial as it serves as the basis for determining aircraft performance, including takeoff, landing, and stall speeds listed in the AFM/POH.

Calibrated airspeed (CAS) is indicated airspeed (IAS) corrected for installation and instrument errors. Errors may occur throughout the airspeed operating range, particularly at low airspeeds, but CAS and IAS are approximately the same at cruising and higher airspeeds. To correct for possible airspeed errors, refer to the airspeed calibration chart.

True airspeed (TAS) is calibrated airspeed (CAS) corrected for altitude and nonstandard temperature. As altitude increases, air density decreases, requiring the aircraft to fly faster to maintain the same pressure difference. Therefore, TAS increases with altitude for a given CAS, or CAS decreases for a given TAS as altitude increases. TAS can be accurately calculated using a flight computer or approximated by adding 2% to CAS for each 1,000 feet of altitude.

Groundspeed (GS) is the actual speed of the airplane over the ground, calculated as true airspeed (TAS) adjusted for wind. GS decreases with a headwind and increases with a tailwind.

The color-coded markings on an ASI indicate various airspeed limitations:

These markings help pilots determine safe operating speeds at a glance.

The lower limit of the white arc (Vso) represents the stalling speed or the minimum steady flight speed in the landing configuration. In small aircraft, this is the power-off stall speed at maximum landing weight with gear and flaps down.

The upper limit of the green arc (VNO) indicates the maximum structural cruising speed. Pilots should not exceed this speed except in smooth air to avoid potential structural damage.

The design maneuvering speed (VA) is the maximum speed at which the structural design's limit load can be imposed without causing structural damage. It varies with weight; for example, VA may be 100 knots when the aircraft is heavily loaded and only 90 knots when the load is light.

The landing gear operating speed (VLO) is the maximum speed for extending or retracting the landing gear in an aircraft with retractable landing gear.

The best angle-of-climb speed (Vx) is the airspeed at which an aircraft gains the greatest amount of altitude in a given distance, typically used during a short-field takeoff to clear an obstacle.

The single-engine best rate-of-climb speed (VYSE) is the best rate-of-climb or minimum rate-of-sink in a light twin-engine aircraft with one engine inoperative, marked on the ASI with a blue line, commonly referred to as 'Blue Line.'

Blockage in the pitot-static system can lead to errors in the ASI reading. A blocked pitot tube affects the ASI accuracy, while a blockage of the static port affects the ASI, altimeter, and VSI. If both are blocked, the ASI may not change with airspeed variations, but will reflect changes in static pressure if the static port is unblocked.

If the pitot tube is blocked and its drain hole remains open, the ASI reading decreases to zero because it senses no difference between ram and static air pressure. This happens quickly, leading to an apparent loss of airspeed indication.

If both the pitot tube opening and the drain hole are clogged simultaneously, the pressure in the pitot tube is trapped, and the ASI will not change with airspeed variations. However, if the static port is unblocked and the aircraft changes altitude, the ASI will reflect changes in static pressure, not airspeed.

When the pitot tube is blocked during a descent, the pressure in the pitot system remains constant. However, the static pressure increases against the diaphragm, causing it to compress and resulting in an indication of decreased airspeed.

If the static system becomes blocked but the pitot tube remains clear, the ASI continues to operate but inaccurately. It indicates a lower airspeed than the actual airspeed when the aircraft is above the altitude of blockage because the trapped static pressure is higher than normal for that altitude.

A blockage of the static system causes the altimeter to freeze at the altitude where the blockage occurred, and the VSI produces a continuous zero indication, meaning it does not show any vertical speed changes.

The pitot tube measures dynamic pressure, which is then compared to static pressure in the ASI's case to determine airspeed. The ASI uses static pressure as a reference and dynamic pressure from the pitot tube to indicate airspeed.

If the static system becomes blocked, the pilot can use an alternate static source if available. Opening the alternate static source introduces static pressure from the flight deck, which is lower than outside static pressure, and may require airspeed corrections as per the aircraft's AOM/POH.

A blocked static system can lead to:

• Inaccurate airspeed indications
• Frozen altimeter
• Constant zero indication on the vertical speed indicator (VSI)

Advantages of Electronic Flight Displays (EFDs) include:

• Improved system reliability, enhancing overall safety
• Reduced costs for equipping aircraft with advanced instrumentation
• Less prone to failure compared to analogue instruments
• Consolidation of flight instruments onto a single screen, reducing panel clutter

On an Electronic Flight Display (EFD), the airspeed indicator (ASI) is displayed as:

• A vertical speed tape located on the left side of the screen
• Larger numbers that descend from the top of the tape as speed increases
• True Airspeed (TAS) displayed at the bottom of the tape
• Color-coded ranges for flap operating range and markings for Vx, Vy, and rotation speed (VR) for pilot reference

The attitude indicator provides a visual reference of the aircraft's orientation relative to the horizon, improving situational awareness during all phases of flight and maneuvers. It receives information from the Attitude Heading and Reference System (AHRS).

The VSI can take the form of an arced indicator or a vertical speed tape, and it is equipped with a vertical speed bug to indicate the rate of climb or descent.

The heading indicator displays the aircraft's current heading and is modeled after a Horizontal Situation Indicator (HSI). It receives data from the magnetometer, which is processed by the AHRS before being displayed on the PFD.

The turn indicator shows the deflection from coordinated flight using a sliding bar that moves left and right below a triangle, with reference provided by accelerometers in the AHRS unit.

The tachometer is usually found on the multi-function display (MFD) and is the only instrument not located on the Primary Flight Display (PFD). In case of a display failure, it can be shown on the remaining screen with PFD flight instrumentation.

The ADC processes pitot static inputs to compute the difference between total pressure and static pressure, generating information necessary to display airspeed on the Primary Flight Display (PFD). It also monitors outside air temperatures and provides data to the autopilot control system.

Trend vectors are magenta lines on the ASI and altimeter that indicate the projected rate of change in altitude and airspeed over a 6-second period. By incorporating trend vectors into their instrument scan, pilots can better control the aircraft's attitude and maintain precise airspeed and altitude.

1. Freely or Universally Mounted Gyroscope: Free to rotate in any direction about its center of gravity, having three planes of freedom.

2. Restricted or Semi-Rigidly Mounted Gyroscope: One of the planes of freedom is held fixed in relation to the base.

Rigidity in space refers to the principle that a gyroscope remains in a fixed position in the plane in which it is spinning, becoming more stable as its speed increases, similar to a bicycle wheel.

Precession is the tilting or turning of a gyro in response to a deflective force, occurring 90° later in the direction of rotation. This allows the gyro to determine a rate of turn by sensing the pressure created by a change in direction.

1. Rigidity in Space: The gyroscope remains fixed in its plane of rotation.
2. Precession: The gyro tilts in response to a force applied, with the reaction occurring 90° later in the direction of rotation.

Precession can cause a freely spinning gyro to become displaced from its intended plane of rotation, leading to minor errors in instruments such as the heading indicator, which may require corrective realignment during flight.

Gyroscopic instruments in aircraft can be powered by vacuum, pressure, or electrical systems. Most aircraft have at least two sources of power to ensure at least one source of bank information is available if one power source fails.

A typical vacuum system consists of an engine-driven vacuum pump, relief valve, air filter, gauge, and tubing. The vacuum pump draws air into the system, which spins the gyros in the attitude and heading indicators, while a relief valve prevents excessive vacuum pressure.

The two types of turn indicators are turn-and-slip indicators and turn coordinators. The turn-and-slip indicator shows the rate of turn in degrees per second, while the turn coordinator indicates roll rate and, once stabilized, the rate of turn.

The inclinometer, which consists of a liquid-filled curved tube with a ball inside, is used to achieve coordination by indicating the quality of the turn and ensuring that the aircraft is properly coordinated during turns.

The turn coordinator indicates the rate and direction of turn, allowing pilots to establish and maintain a standard-rate turn by aligning the miniature aircraft with the turn index.

The canted gimbal allows the gyro to sense both the rate of roll and the rate of turn, providing more accurate information during maneuvers.

A standard-rate turn is defined as a turn rate of 3º per second, indicated by specific marks on the turn coordinator's face.

The turn coordinator does not display a specific angle of bank; it only indicates the rate and direction of turn.

A slip results when inadequate right rudder is applied during a right turn.

The inclinometer depicts aircraft yaw, indicating the side-to-side movement of the aircraft's nose and helps maintain coordinated flight by keeping the ball centered.

'Step on the ball' is a rule to remember which rudder pedal to press to center the ball in the inclinometer during a turn.

To correct for a slip, the pilot should decrease the bank angle and/or increase the rate of turn.

The attitude indicator displays the aircraft's orientation relative to the Earth, showing pitch (nose up or down) and roll (bank angle).

The gyro in the attitude indicator is mounted in a horizontal plane and relies on rigidity in space, resisting deflection of its rotational path to indicate the aircraft's attitude relative to the true horizon.

The yaw string indicates whether the aircraft is in coordinated flight; it trails straight back when coordinated and moves to the right or left during a slip or skid.

The adjustment knob allows the pilot to move the miniature aircraft up or down to align it with the horizon bar, ensuring it suits the pilot's line of vision. Normally, the miniature aircraft is adjusted so that its wings overlap the horizon bar during straight-and-level cruising flight.

If the pitch limits (usually 60° to 70°) or bank limits (usually 100° to 110°) are exceeded, the instrument will tumble or spill, resulting in incorrect indications until it is realigned. However, many modern attitude indicators do not tumble.

The banking scale should be used to control the degree of desired bank, while the relationship of the miniature aircraft to the horizon bar should indicate the direction of bank. Some banking scale indicators move in the opposite direction of the actual bank, which can confuse the pilot.

The attitude indicator is considered the most reliable and realistic flight instrument on the instrument panel, providing indications that closely approximate the actual attitude of the aircraft.

The operation of the heading indicator depends upon the principle of rigidity in space. The rotor remains rigid in space, allowing the compass card to maintain its position relative to the vertical plane of the gyro.

The heading indicator drifts due to precession caused by friction. The amount of drift can be influenced by the condition of the instrument, such as worn or dirty bearings.

The heading indicator may indicate as much as 15° error per hour of operation due to the Earth's rotation, which occurs at a rate of 15° in 1 hour, in addition to precession errors.

The magnetometer in the AHRS senses the Earth's lines of magnetic flux and provides heading information to the Primary Flight Display (PFD) for generating the heading display.

The flux gate compass drives slaved gyros by using the characteristic of current induction from the Earth's magnetic field, allowing for accurate heading information.

The soft iron frame of the flux valve accepts the flux from the Earth's magnetic field each time the current in the center coil reverses, allowing it to demagnetize and accept new flux, which induces current in the pickup coils.

The three pickup coils are connected in such a way that the current flowing in them changes as the heading of the aircraft changes, allowing for accurate heading indication.

A typical remote indicating compass system consists of a pictorial navigation indicator (HSI) and a slaving control and compensator unit.

The critical AOA does not change with weight, bank angle, temperature, density altitude, or center of gravity.

An AOA indicator measures several parameters to determine the current AOA and provides a visual representation of the current AOA along with proximity to the critical AOA, making it visible to pilots.

The angle of attack indicator displays the angle between the wing and the oncoming air, helping pilots understand the aircraft's aerodynamic efficiency and preventing stalls.

1. Any magnet that is free to rotate will align with them.
2. An electrical current is induced into any conductor that cuts across them.

The flexible diaphragm prevents damage or leakage of compass fluid when the fluid expands and contracts due to temperature changes.

The magnetic compass has small magnets that align with the Earth's magnetic field, allowing the pilot to read the direction on the graduated scale opposite the lubber line.

At steeper bank angles, the compass indications become erratic and unpredictable due to the limitations of the float and card assembly.

True directions are measured from the geographic poles, while magnetic directions are measured from the magnetic poles. The difference between them is known as variation.

Variation is the angular difference between true north (geographic North Pole) and magnetic north (magnetic North Pole). It affects how a pilot must adjust their compass readings to obtain true directions.

Deviation is the compass error caused by magnetic fields within the aircraft, which varies based on the aircraft's heading. In contrast, variation is a constant error based on geographic location and does not change with heading.

Swinging the compass is a maintenance task performed by aviation maintenance technicians to minimize deviation errors caused by the aircraft's magnetic fields.

The agonic line is where the magnetic North Pole aligns with the geographic North Pole, resulting in no variation. Pilots flying along this line do not need to adjust their compass readings for variation.

The purpose of swinging the compass at a compass rose is to align the aircraft's compass with known headings, minimizing the difference between the compass indication and the actual aircraft magnetic heading.

The AMT adjusts the compensator assembly by rotating two shafts that affect small compensating magnets. One shaft is marked E-W for east and west adjustments, while the other is marked N-S for north and south adjustments.

The compass correction card records any remaining error after adjustments have been made to the compass, allowing pilots to determine and fly compass headings using the noted deviation errors.

The sequence for applying corrections is: start from the true course desired, determine the magnetic course by adjusting for variation, and then determine the compass course by adjusting for deviation.

The dip angle is the angle created by the vertical pull of the Earth's magnetic field in relation to the Earth's surface. It increases as one moves towards the Magnetic North Pole in a downward direction and increases in an upward direction towards the Magnetic South Pole.

During northerly turns, the magnetic dip causes the compass float assembly to swing in the same direction as the turn, leading to a false northerly turn indication. To correct for this error, the turn should be stopped 15 degrees plus half of the latitude before reaching the desired heading.

In southerly turns, the compass float assembly lags behind the actual turn, resulting in a false southerly turn indication. To correct this lagging error, the pilot should allow the compass to pass the desired heading before stopping the turn, using the rule of 15 degrees plus half of the latitude.

The mnemonic 'ANDS' (Acceleration-North/Deceleration-South) helps remember that when accelerating on easterly or westerly headings, the compass indicates a turn toward north, and when decelerating, it indicates a turn toward south.

When an aircraft accelerates on an easterly or westerly heading, the compass indicates a turn toward north due to the upward tilt of the aft end of the compass card caused by the magnetic dip and inertia.

Compass errors, such as northerly and southerly turning errors, are amplified when the aircraft is close to either magnetic pole, making the compass less reliable for navigation in those areas.

When an aircraft accelerates, the compass needle deflects towards the north. Conversely, during deceleration, the compass needle deflects towards the south.

Oscillation error is a combination of various errors that results in fluctuation of the compass card in relation to the actual heading direction of the aircraft. To set the gyroscopic heading indicator, use the average indication between the swings of the compass.

The vertical card magnetic compass eliminates some errors and confusion by using a dial graduated with cardinal directions and numbers, and it rotates based on a shaft-mounted magnet, providing a clearer reading of the aircraft's heading.

Eddy current damping in a vertical card magnetic compass occurs when flux from the oscillating permanent magnet produces eddy currents in a damping disk, which opposes the flux from the permanent magnet and decreases oscillations.

When starting a turn from a northerly heading, the compass lags behind the turn, meaning it does not immediately reflect the new heading until the turn is completed.

When starting a turn from a southerly heading, the compass leads the turn, indicating a heading change before the aircraft has fully completed the turn.

The OAT gauge provides pilots with accurate air temperature readings, which are essential for understanding the temperature lapse rate with altitude changes.

The sensing element consists of a bimetallic-type thermometer made of two dissimilar materials welded together, twisted into a helix, with one end anchored and the other affixed to a pointer.

The OAT gauge is calibrated in degrees Celsius (°C), degrees Fahrenheit (°F), or both.

Understanding flight instruments is crucial for operating an aircraft with maximum performance and enhanced safety, especially during long-distance flights.