NAV 7

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NAV 7
VOR and ADF
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VOR
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VOR Head
TO/FROM indicator or sense indicator Course
Deviation Indicator or left/right needle or Track
Bar Indicator Omni Bearing selector or Course
selector
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C172 INSTRUMENT PANEL
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VHF Receiver
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INSTRUMENT PANEL
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VOT
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COVERAGE - IF AT MRA, 50 NM - RECEPTION
DISTANCE IS 1.23 x v ALTITUDE
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PRINCIPLES OF OPERATIONOperation of the VOR is
based on a phase difference between two signals
a reference phase and a variable phase. The
reference phase, which is omni directional,
radiates from the station in a circular pattern,
the phase being constant throughout 360 degrees.
The variable phase rotates uniformly at 1800 rpm
causing its phase to vary at a constant rate.
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Magnetic North is the reference datum for
measuring the phase difference between the two
signals. At Magnetic North, the two signals are
exactly in phase. At other points around the
compass, the phase difference varies accordingly.
The aircraft equipment resolves the phase
difference and displays it primarily in the form
of angular displacement from Magnetic North as
measured from the VOR station.
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TRACK BAR DEFLECTIONS
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VOR EQUIPMENT CHECKS
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TRACKING AWAY FROM A STATION
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TRACKING TO A STATION
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At the VOR facility, a monitoring system and
two transmitters insure continuous reliable
service. If the VOR signal is interrupted or the
phasing is changed, the monitor system turns off
defective equipment, turns on the stand-by
transmitter, and excites an alarm at the remote
control station. When a VOR is on the air while
servicing is taking place, the station
identification is removed.
VOR RELIABILITY
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FREQUENCY RANGES
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ADF Automatic Direction Finder
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ADF Automatic Direction Finder

• Receiver tune and identify
• LF/MF 2 or 3 letter Morse code
• ILS locator 1 letter Morse code
• Signal also powers bearing indicator
• Antennae
• Loop senses direction of station
• Sense provides info if bearing to or from station
• Bearing indicator
• Points to station relative to nose or axis
• Fixed card 0o is nose and 180o is tail

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ADF

• FUNCTIONS
• AIRWAYS
• AIR ROUTES
• ILS LOCATORS MARKER BEACONS
• MARINE BEACONS
• NDB APPROACHES
• COMMERCIAL BROADCAST

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ADF
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ADF

• LIMITATIONS
• TWILIGHT EFFECT
• JUST BEFORE/AFTER SUNSET/SUNRISE - fly high
• GREATER AT GREAT DISTANCE use less than 350 khz
• TERRAIN or MOUNTAIN EFFECT
• SHORELINE signals crossing at less than 30o
• ELECTRICAL STORMS
• BANK ERROR ALL TURNS
• LOOP ANTENNAE ROTATES TO SENSE DIRECTION OF
  INCOMING SIGNAL AND IS MOUNTED PARALLEL TO NORMAL
  AXIS

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ADF

• ADVANTAGES
• LOW COST INSTALLATION AND MAINTENANCE
• NOT LINE OF LINE OF SIGHT SO GIVES GREATER
  RECEPTION AT LOWER ALTITUDES THAN VOR
• PRIMARY NAVIGATION OVER LONG DISTANCE IN REMOTE
  AREAS

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TRACKING TO THE STATION

• PARALLEL TRACK
• DESIRED TO HEAD
• DETERMINES THE TURN
• LEFT TURN
• DESIRED TRACK INTERCEPT ANGLE INTERCEPT
  HEADING
• RIGHT TURN
• DESIRED TRACK INTERCEPT ANGLE INTERCEPT
  HEADING

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TRACKING FROM THE STATION

• PARALLEL TRACK
• TAIL TO DESIRED
• DETERMINES THE TURN
• LEFT TURN
• DESIRED TRACK INTERCEPT ANGLE INTERCEPT
  HEADING
• RIGHT TURN
• DESIRED TRACK INTERCEPT ANGLE INTERCEPT
  HEADING

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SOME RULES

• WHEN INTERCEPTING A TRACK TO OR FROM A STATION,
  BEARING INDICATOR ALWAYS AWAY
• FROM 0 OR TOWARDS 180
• 2. WHEN TURNING, IF HEADING INDICATOR INCREASES,
  THEN ADF BEARINGINDICATOR (VALUE) DECREASES
• HI LESS, ADF MORE
• WHEN TRACKING, NEEDLE RIGHT? YES, THEN WIND IS
  FROM THE RIGHT SO TURN RIGHT, ETC.
• MAGNETIC HEADING RELATIVE BEARING MAGNETIC
  BEARING TO THE STATION
• MH RB MB TO THE STATION
• MH MB RB
• RB MB - MH