NAV 7

VOR and ADF

VOR

TO/FROM indicator or sense indicator

Course Deviation Indicator or left/right needle or Track Bar Indicator

Omni Bearing selector

or Course selector

VOR Head

C172 INSTRUMENT PANEL

VHF Receiver

INSTRUMENT PANEL

VOT

COVERAGE- IF AT MRA, 50 NM

- RECEPTION DISTANCE IS 1.23 x √ ALTITUDE

PRINCIPLES OF OPERATION

Operation 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.

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.

TRACK BAR DEFLECTIONS

VOR EQUIPMENT CHECKS

TRACKING AWAY FROM A STATION

TRACKING TO A STATION

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

FREQUENCY RANGES

ADF – Automatic Direction Finder

ADF – Automatic Direction Finder

Receiver tune and identifyLF/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 indicatorPoints to station relative to nose or axis

Fixed card 0o is nose and 180o is tail

ADF

FUNCTIONSAIRWAYS

AIR ROUTES

ILS LOCATORS – MARKER BEACONS

MARINE BEACONS

NDB APPROACHES

COMMERCIAL BROADCAST

ADF

ADF

LIMITATIONSTWILIGHT 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

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

TRACKING TO THE STATION

1. PARALLEL TRACK

2. DESIRED TO HEADDETERMINES THE TURN

3. LEFT TURN DESIRED TRACK – INTERCEPT ANGLE = INTERCEPT HEADING

4. RIGHT TURN DESIRED TRACK + INTERCEPT ANGLE = INTERCEPT HEADING

TRACKING FROM THE STATION

1. PARALLEL TRACK

2. TAIL TO DESIREDDETERMINES THE TURN

3. LEFT TURN DESIRED TRACK – INTERCEPT ANGLE = INTERCEPT HEADING

4. RIGHT TURN DESIRED TRACK + INTERCEPT ANGLE = INTERCEPT HEADING

SOME RULES 1. 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

3. WHEN TRACKING, NEEDLE RIGHT? YES, THEN WIND IS FROM THE RIGHT SO TURN RIGHT, ETC.

4. MAGNETIC HEADING + RELATIVE BEARING = MAGNETIC BEARING TO THE STATION

MH + RB = MB TO THE STATIONMH = MB – RBRB = MB - MH