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Instrument Systems
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Instrument Systems
Vacuum System
Pitot-static system
Magnetic System
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Pitot-Static System
Types of Pressure
System components
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Two types of Pressure
Dynamic AirPressure Pitot or ram
pressure
Supplied by pitottube
Location varies
Needs to face
directly into therelative wind
Pressure causedby moving air
Only linked toairspeed indicator
Static Air Pressure
Also, ambientstatic air pressure
Supplied by static
port
Location varies
Needs to be inundisturbed air
Pressure justoutside of theairplane
Linked to all Pitot
Static instruments
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Components of system
Pitot Pressure Lines
Connects pitot tube to airspeed indicator
Needs to run direct Sump in lowest point collects moisture
Static Pressure Lines
Connect to all three Has sump in lowest lines
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Pitot-Static System
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Pitot Static Flight Instruments
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Pitot-Static Instruments
Airspeed Indicator
Altimeter
Vertical Speed Indicator
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Airspeed Indicator
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Airspeed Indicator
Displays the speedof the aircraftthrough the air
Only instrumentthat uses both typesof pressure
Measures thedifference betweenthe two pressures
Greater thedifference thegreater the airspeed
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Airspeed Indicator Operation
Instrument is contained withina sealed case
Pressure sensitive diaphragm
Ram pressure line is connecteddirectly to one side of thediaphragm
Diaphragm expands andcontracts due to ram pressure
Inside of the case is vented tothe static port
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Inside airspeed indicator
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Airspeed Indicator Operation
Diaphragm expands and contracts inproportion to the difference betweenthe two pressures
Measured by mechanical linkage
Linkage is displayed by the hands on theface of airspeed indicator
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Airspeed Indicator
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Airspeed Definitions
Indicated Airspeed
Value read from the indicator
indicated stall speeds remain constant
Uncorrected for installation(position)and instrument error
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Airspeed Definitions
Calibrated Airspeed
Indicated Airspeed corrected for installation andinstrument error
Determine from looking in the POH
True Airspeed
True speed of aircraft through the air
Calibrated corrected for altitude and nonstandardtemperature
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Airspeed Definitions
Ground Speed
Actual speed of the aircraft over theground
True airspeed adjusted for the wind
Found using the E6B
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Airspeed Definitions
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Airspeed Indicator
White Arc
Green Arc
Yellow Arc Red Line
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Airspeed Errors
Position Error Occurs when the static port sense an
erroneous static pressure
Mainly caused by slipstream
Error may be determined by using theairspeed calibration chart
Instrument Error
Errors due to imperfections in theinstrument itself, imperfections withmanufacturing
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Altimeter
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Altimeter
System Operation
Types of Altitude Markings
Errors
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Altimeter
Simply a barometer that measuresstatic pressure of the air around theaircraft.
Uses only the static pressure
Operates by the changes in pressure
Standard pressure at Mean Sea Level in29.92 inches of mercury
Atmosphere declines 1 inch of mercury everythousand feet
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Altimeter Operation
Aneroid wafer
Stack of hollow, elastic metal wafers
Expand and contract as pressure changes This is shown through mechanical linkage
Each pressure setting is a definite size onwindow
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Altimeter Operation
Pressure Window
Kollsman window
Small adjustable
subscale that allowsthe current altimetersetting to be set in
Important to reset
with current Above 18,000
always set at 29.92
O
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Altimeter Operations
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Altimeter Functions
UND Aerospace, 1994
Air moves out
Air moves in
Wafers expand
01
2
3
45
9
8
7
6
W afers contract
01
2
34
5
9
8
76
01
2
3
45
9
8
7
6
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Types of Altitude
Indicated Altitude Read from Indicator
Pressure Altitude
Height above standard datum
Density Altitude
Pressure corrected for nonstandardtemperatures
T f Altit d
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Types of Altitude
True Altitude
True height abovesea level
Airports andobstruction arebased on
Absolute Altitude
Actual height abovesurface
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TrueAltitude AbsoluteAltitude PressureAltitude IndicatedAltitude
Pressure = 29.92" HgStandardDatum Plane
UND Aerospace, 1994
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Altimeter
Alti t E
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Altimeter Errors
Pressure Error
High to Low-Look out below, low to high plenty ofsky
Need to set in current altimeter setting
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Vertical Speed Indicator
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VSI
System Operation
Markings
Errors
V ti l S d I di t
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Vertical Speed Indicator
Provides reference to rate of change
Will show trend away from level quickly
Responds faster then the altimeter
Shows both rate and trend
Uses only static pressure
VSI O ti
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VSI Operations
Expandable Capsule
Directly connected to static port
Connected through mechanical linkage
Calibrated Leak
Instrument Cases connection to the staticport
Allows capsule to change pressure moregradually
VSI O ti
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VSI Operation
Pressure inside of capsule changes thesame as the outside air
Pressure in instrument case changesslower because of calibrated leak.
Gives us the rate
When pressure is equal straight and level
VSI Operations
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VSI Operations
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Types of Information Portrayed
Trend Information
Immediate indicationof an increase or
decrease First Indication
Rate Information
Shows the stabilizedrate of change
Take 6-9 seconds
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Markings
VSI Errors
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VSI Errors
Abrupt changes cause errors
Rough control and turbulent air cause
error
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Vacuum System
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System Operation
Vacuum System
Draws air through the filter system
Moves through Attitude and Headingindicator where it spins gyros
Spins at 18,000 RPM
Air continues into engine drivenvacuum pump
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System Operation
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Gyroscopic Principles
Rigidity in Space
Remains in a fixedplane when spinning
Gimbal instrumentaround gyro to allowit remain in planeable to showchanges in pitch andattitude
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Gyroscopic Principals
Precession
When outside forceis applied to gyro it
will be felt 90degrees in rotationof spinning
Includes friction
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Gyroscopic Instruments
Heading Indicator
Attitude Indicator
Turn Cordinator
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Heading Indicator
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Heading Indicator
Operation
Markings and Use
Limitations and Errors
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Heading Indicator Operation
Relies on Rigidity on Space
Primary source of Heading information
Senses rotation along the verticalaxis Gyro spins in the horizontal axis
Support gimbals drive the compass card
Works through gears and linkage Setting knob
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Heading Indicator Operation
M ki & U
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Markings & Use
Li it ti
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Limitations
Reset every 15 minutes
Pitch - 55 degrees
Bank - 55 degrees
H di E
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Heading Errors
Precession
Can be a negative in Headingindicator
Causes the heading to drift Should check every 15 minutes
Make sure you are in straight and level,unaccelerated flight
Tumbling
Occurs after excessive pitch and roll
Attit d I di t
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Attitude Indicator
Operation
Markings and Use
Limitations and Errors
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Attitude Indicator Operations
Mechanical Substitute for the naturalhorizon
Gives immediate and direct informationof planes pitch and bank
Gyro spins in the horizontal plane
Self erecting mechanisms Vacuum Driven, normally
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Attitude Indicator Operations
M ki & U
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Markings & Use
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Climb
Climb andLeft Bank
Level Flight
Glide
Glide andLeft Bank
Level Flightand Left Bank
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Attitude Indicator Errors Usually very minor
Minor on acceleration and deceleration
Somewhat precesses on turns
Errors are maximum when rolling out of
a 180 degree or 360 degree turn Instrument Tumbling (older AI) Caging mechanism
May take awhile for it to re-erect itself
After 100 degrees of bank and 60 degreesof pitch
T I di t
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Turn Indicators
Two Types
Turn and Slip
Operation Markings
Turn Coordinator
Operation Markings
T rn & Slip Indicator
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Turn & Slip Indicator
L R L R
TURN2 MIN
BANK
Turn Coordinator
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Turn Coordinator
Operation
Like the Turn and Slip
But shows both rate of turn and rate ofroll
Gimbal is set at a 30 degree angle
Allows force to be felt
Allows gyro more movement
Turn Coordinator
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Turn Coordinator
Gyro gimble(mount not shown)
Cantedgyroaxis
Parallel tolongitudinalaxis of a/c
Gyroscoperotor
Indexmarks
Inclinometer
Aircraft
silhouette
Turn Coordinator
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Turn Coordinator
Operation
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Operation
Inclinometer
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Inclinometer
Contains fluid and ball
Kerosene type fluid
Steel ball
Shows the quality of the turn(Coordination)
Shows forces acting ball in the turns
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Quality of Turn
TurnCoordinator
Turn CoordinatorSkid
Slip
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Magnetic Compass
Magnetic Compass
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Magnetic Compass
Construction
Diagram and function
Markings and use Compass Errors
Use of compass
Magnetic Compass Construction
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Magnetic Compass Construction
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The Earths Magnetic Field
Magnetic Pole Geographic Pole
Magnetaligns itselfwith
magneticforce
Lines ofmagneticforce
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Compass Errors
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Compass Errors
Variation
Deviation
Magnetic Dip Northerly Turning Error
Acceleration/Deceleration Error
Oscillation Error
Variation
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Variation
Variation - Angulardifference between true
north and magnetic north.Agonic line - The line where
there is no angular
difference.Isogonic - Lines showing the
angular lines difference.
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Variation
13NorthMagneticPole
GeographicNorth Pole o
Isogonic linesAgonic
line
20
o
15o
10
o
5o
o
0
5o
10
o
15o
20
o
Compass Card
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Compass Card
Deviation
Error due tomagneticinterference withinthe aircraft
Compensatingmagnets in compasshelp to counteract
Called Swinging
Error on compasscorrection card
Compass Card
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Compass Card
For N 30 60 E 120 150
Steer 357 023 050 080 111 145
For S 210 240 W 300 330
Steer 178 213 246 278 307 333
Magnetic Dip
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Magnetic Dip
How it works
Errors it causes
Magnetic Dip
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Magnetic Dip
Most significanterror
Difficult to get
actual readings Magnet in compass
tries to point 3Ds topole
Causes errors inturns andacceleration
How it Works
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How it Works
Magnetic flux lines point downwardat the poles, compass magnets dipto low side of turn
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MagneticDip
AircraftFlight Path
Dip
North PoleNo Dip
Errors it Causes
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Errors it Causes
Acceleration error - ANDS
Northerly turning error
North lags
SOS - south over shoot
Acceleration Error
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Acceleration Error
Accelerate
Will show a turn tothe North
When speedstabilizes compassreturns to accurate
Error greatest onheadings of Westand East
Deceleration
Will show a turn tothe South
Use ANDS Accelerate NorthDecelerate South
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01-185
E6 3
N
N
N N
Constant Airspeed
Accleration
Deceleration
S
15
12
E
Acceleration & Deceleration Errors ~
ANDS
Turning Errors
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Turning Errors
Northerly Error
Initially indicate turn to opposite direction
Southerly Error
Heading will lead the turn
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Questions?