Using a VOR VHF omnidirectional range

a mechanical cockpit vor indicator



oceanside vortac in california

if pilot wants approach vor station due east aircraft have fly due west reach station. pilot use obs rotate compass dial until number 27 (270°) aligns pointer (called primary index) @ top of dial. when aircraft intercepts 90° radial (due east of vor station) needle centered , to/from indicator show . notice pilot sets vor indicate reciprocal; aircraft follow 90° radial while vor indicates course vor station 270°. called proceeding inbound on 090 radial. pilot needs keep needle centered follow course vor station. if needle drifts off-center aircraft turned towards needle until centered again. after aircraft passes on vor station to/from indicator indicate , aircraft proceeding outbound on 270° radial. cdi needle may oscillate or go full scale in cone of confusion directly on station recenter once aircraft has flown short distance beyond station.

in illustration on right, notice heading ring set 360° (north) @ primary index, needle centred , to/from indicator showing . vor indicating aircraft on 360° course (north) vor station (i.e. aircraft south of vor station). if to/from indicator showing mean aircraft on 360° radial vor station (i.e. aircraft north of vor). note there absolutely no indication of direction aircraft flying. aircraft flying due west , snapshot of vor moment when crossed 360° radial. interactive vor simulator can seen here.

testing

before using vor indicator first time, can tested , calibrated @ airport vor test facility, or vot. vot differs vor in replaces variable directional signal omnidirectional signal, in sense transmitting 360° radial in directions. nav receiver tuned vot frequency, obs rotated until needle centred. if indicator reads within 4 degrees of 000 flag visible or 180 flag visible, considered usable navigation. faa requires testing , calibration of vor indicator no more 30 days before flight under ifr.

intercepting vor radials

on course deviation indicator select radial , needle , to/fr flag shows our position.

there many methods available determine heading fly intercept radial station or course station. common method involves acronym t-i-t-p-i-t. acronym stands tune – identify – twist – parallel – intercept – track. each of these steps quite important ensure aircraft headed being directed. first, tune desired vor frequency navigation radio, second , important, identify correct vor station verifying morse code heard sectional chart. third, twist vor obs knob desired radial (from) or course (to) station. fourth, bank aircraft until heading indicator indicates radial or course set in vor. fifth step fly towards needle. if needle left, turn left 30–45° , vice versa. last step once vor needle centred, turn heading of aircraft radial or course track down radial or course flown. if there wind, wind correction angle necessary maintain vor needle centred.

aircraft in nw quadrant vor indicator shading heading 360 090 degrees

another method intercept vor radial exists , more closely aligns operation of hsi (horizontal situation indicator). first 3 steps above same; tune, identify , twist. @ point, vor needle should displaced either left or right. looking @ vor indicator, numbers on same side needle headings needed return needle centre. aircraft heading should turned align 1 of shaded headings. if done properly, method never produce reverse sensing. using method ensure quick understanding of how hsi works hsi visually shows mentally trying do.

in adjacent diagram, aircraft flying heading of 180° while located @ bearing of 315° vor. after twisting obs knob 360°, needle deflects right. needle shades numbers between 360 , 090. if aircraft turns heading anywhere in range, aircraft intercept radial. although needle deflects right, shortest way of turning shaded range turn left.