AVIA- Chapter 8

Instruments in pilot-static system

• Air Speed Indicator (ASI)

• Vertical Speed Indicator (VSI)

• Altimeter

Impact pressure

Used to sense the airspeed of an aircraft

Pilot Tube

Forward pointing tube that senses impact pressure

Air Speed Indicator (ASI)

Only instrument that uses the pilot tube

Static pressure port

Small sensor with a hole located in a place that is relatively undisturbed in terms of air flow

Pilot-Static instruments

Variations in pressure affects . . .

Vertical Speed Indicator (VSI)

In an emergency, when the static port i sblocked, to restore static pressure a pilot is to break the glass of the . . .

Altimeter

Shows the altitude of the aircraft, relative to sea level, based on pressure changes with altitude

Decreases

As an aircraft climbs, the outside air pressure ________

29.92 in/Hg.

The aneroid chamber of an altimeter contains a reference pressure of . . .

Altimeter

As ambient pressure changes, the aneroid will expand or contract in direct response

Climb

When pressure decreases, in a _____, the aneroid expands (altimeter)

Descent

During a ______, as pressure increases, the aneroid will contract (altimeter)

Aneroid (altimeter)

Internal pressure does not change

Case (altimeter)

Sealed except that it is open to static pressure, internal pressure will change as the aircraft climbs or descends

Altimeter will "freeze" reading the pressure of the air trapped in the case

What will happen to the altimeter if the static port becomes covered with ice?

Altimeter will give higher readings than what is accurate (non-pressurized aircraft)

What will happen to the altimeter if the static port is disconnected?

Adjusting the altimeter

Using small knob and a window that allows the instrument to be set for the actual outside air pressure

Kollsman Window

Altimeter

Behaves like a barometer

Altimeter reading will decrease

If you fly from a low pressure area into a high pressure area, how will the altimeter reading change?

Altimeter reading will increase

If you fly from high pressure to low, how will the altimeter reading change?

Altimeter

Air temps. impact the _________ readings

Increase

Cold temperatures ________ the air density (true altitude is lower than the altimeter indicated)

Decrease

Warm temperatures ________ the air density (true altitude is higher than the altimeter indicates)

Ground level

Altimeter settings are adjusted according to barometric pressure readings at . . .

Indicated altitude

Altitude read directly from the altimeter

True altitude

Actual altitude above sea level (MSL) (all altitudes on charts)

Absolute altitude

Actual altitude above the ground (AGL)

Pressure altitude

Altitude indicated when the altimeter is set to 29.92 in/Hg (Used above 18,000 feet)

Density altitude

Pressure altitude corrected for non-standard temperatures

75

Altimeter reading must be correct within __ feet to be considered safe for flight

Vertical Speed Indicator (VSI)

Indicates rate of climb or descent, if the aircraft is in level flight, it will indicate zero (0 fpm)

Vertical Speed Indicator (VSI)

Connected to the static air source

Vertical Speed Indicator (VSI)

Diaphragm is sealed and connected to static pressure

Vertical Speed Indicator (VSI)

Inside of the case is vented to static air through a calibrated vent (slows the equalization of pressure in the case)

Vertical Speed Indicator (VSI)

No power source is required

Vertical Speed Indicator (VSI)

Slowed response to pressure changes causes instrument to indicate when the diaphragm is expanding or contracting

Airspeed Indicator (ASI)

Shows airspeed by comparing pilot tube pressure to ambient pressure

Airspeed Indicator (ASI)

Only instrument that uses both pilot tube and static port air pressures

Airspeed Indicator (ASI)

Pilot pressure increases as the forward speed increases

Vs0 (ASI)

Stall speed, flaps deployed (Bottom of white arc.)

Vs1 (ASI)

Stall speed, flaps retracted (Bottom of green arc.)

White arc. (ASI)

Flap operating range

Vfe (ASI)

Max speed with flaps deployed

Green arc. (ASI)

Normal operating range

Vno (ASI)

Normal operating max speed

Yellow arc. (ASI)

Caution range (smooth air only)

Vne (ASI)

Never Exceed speed

Indicated Airspeed (IAS)

Uncorrected airspeed read directly from the instrument (used for performance data, including takeoff, landing, and stall speeds as listed in POH/AFM)

Calibrated Airspeed (CAS)

Airspeed corrected for installation errors and instrument errors (error greatest at low airspeed)

True Airspeed (TAS)

CAS corrected for altitude and temperature (increases with altitude), can be calculated with a flight computer or estimated by adding 2% for each 1000 ft of altitude

Design Maneuvering Speed - Va

Max speed at which the structural limit load can be imposed without structural damage

Landing Gear Operating Speed - Vlo

Max speed at which the aircraft landing gear may be safely operated (extended or retracted)

Landing Gear Extended Speed - Vle

Max speed at which the aircraft can be safely flown with gear extended

Best Angle of Climb - Vx

Speed at which aircraft gains the most altitude in a given distance

Best Rate of Climb - Vy

Speed at which aircraft gains the most altitude in a given time

Single Engine Best rate of climb - Vyse

Best rate of climb (or minimum sink rate) on a single engine

Minimum Control Speed - Vmc

Minimum speed at which a twin can maintain directional control on a single engine

EFD or EFIS “glass cockpit" display

• Attitude Indicator

• Altimeter

• VSI

• Heading Indicator

• Turn Indicator

• Tachometer

• Slip/Skid Indicator (inclinometer)

• Turn Rate

Air Data Computer (ADC)

• Drives Multifunction Displays

• Takes information from various sensors on board the aircraft and combines all of the data into the display shown to the pilot

Most common Gyroscopic Flight Instruments

• Turn Coordinator

• Heading Indicator

• Attitude Indicator

Gyroscope

A rotating mass designed and mounted to use gyroscopic properties

Primary characteristics of a useful gyro.

Rotor has a high density and is able to rotate at a high speed

Classes of gyro. mount

Universal & Semi-rigid

Universal mount

Allows motion in any direction, has free motion in all three planes

Semi-rigid mounts

Restrict motion in one plane relative to a base, has two planes of freedom

Rigidity in space, and precession

The two fundamental properties of gyroscopic rotation . . .

Rigidity in space

Once spinning, a gyroscope tends to remain fixed in the plane in which it is spinning

As long as rotational velocity remains constant

No matter which direction the base is moved, the axis of rotation tends to remain in the same orientation . . .

precession

The motion of a gyroscope in response to an applied force

90°

When a force is applied to a spinning gyroscope, the reaction occurs ___ later in the direction of rotation (what makes a gyro useful for determining rate of turn)

Vacuum or electric

Gyros are generally powered with ______ or _______ power

Electric gyros.

Powered by simple motors.

Turn & slip indicator and turn coordinator

Two types of turn indicators (both marked to indicate a standard rate turn of 3° per second/ 2 minutes per 360°)

Turn and Slip Indicators

Gyros rotate in the vertical plane along the longitudinal axis of the aircraft, precession causes the pointer to tilt left or right as the aircraft turns.

Turn coordinator

Gyro is canted at an angle, when the aircraft is rolled, the indicator tilts in the direction of roll

Inclinometer

Detects yaw or uncoordinated turns

“Step on the ball”

Simple rule to remember when reading an Inclinometer

Attitude indicator

Represents the aircraft’s relationship to the horizon (indicates both pitch and roll)

Attitude indicator

Adjustment knob adjusts the pitch setting to account for changes in cruise pitch angle (typically used to set the wings in the instrument along the horizon line on the instrument face)

100°-110°

Attitude indicator limits in roll, and from 60-70° in pitch

60°-70°

Attitude indicator limits in pitch

Heading indicator

Depends on the principle of rigidity in space

Heading indicator

Meant to provide a more stable directional indication than the magnetic compass (is stable and provides clear directional guidance)

Heading indicator

It is set to match the magnetic compass when the aircraft is in a level, unaccelerated condition.

Heading indicator

Precession and friction will cause it to drift slowly from the original setting (pilots should compare the readings to the Mag Compass regularly while in flight)

Heading indicator

Reacts to the rotation of the earth (earth rotates at about 15° per hour, so the it will drift up to that much per hour of flight)

Horizontal Situation Indicators (HSI)

Heading indicators that have the ability to correct themselves automatically (have a magnetometer which detects and correct the reference to magnetic north automatically)

Electronci flight displays (EFD)

Use solid state laser gyros that are capable of flight in any attitude without failing (give accurate information in 360 degrees of roll or pitch and do not tumble)

Flux Valve

Larger aircraft may use a magnetic sensor called a ____ _____ which electrically determines the aircraft’s heading in relation to the earth’s magnetic field

Angle of attack indicator (AOA)

Give better situational awareness and stall margin indications than airspeed alone

Angle of attack indicator (AOA)

Indications do not change with weight, bank angle, temperature, density altitude or center of gravity

Magnetic compass

Required to be installed in all US certified aircraft (no matter how sophisticated)

Magnetic compass

Will point to the magnetic north pole (not the geographic north pole)

1,300

The magnetic north pole is located about ____ miles away from the geographic pole

Offset between the magnetic and geographic north pole

Causes the direction of magnetic north to vary from true north depending on where you are on the earth

Magnetic variation

This difference between true directions and magnetic directions is called (must be accounted for if you are to navigate successfully using magnetic compasses)

Isogonic lines

Lines where the magnetic variation is consistent

Agonic line

Any Isogonic Line where the variation is zero