NAV 7 VOR and ADF

VOR

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

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

VOR RELIABILITY 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.

FREQUENCY RANGES

ADF – Automatic Direction Finder

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

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

ADF

ADF LIMITATIONS TWILIGHT EFFECT TERRAIN or MOUNTAIN 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 PARALLEL TRACK DESIRED TO HEAD DETERMINES THE TURN LEFT TURN DESIRED TRACK – INTERCEPT ANGLE = INTERCEPT HEADING RIGHT TURN DESIRED TRACK + INTERCEPT ANGLE = INTERCEPT HEADING

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

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