Pilot Courses of Instruction

Navigation

VOR

Introduction

Designed as the replacement for the old A/N ranges, the VOR has been the standard navigation aide now for over five decades. Briefly stated, the VOR provides a near continuous plan of airways along "radials" from due north of the station (000 degree radial) around to due north again. Radials are measured from the station, generally in whole degrees, and are selected by an "omni bearing selector" (OBS that -- traditionally -- rotates a card, with the track to the station on top of the display and the radial from the station on the bottom of the display (contemporary displays show the radial digitally). Note that the VOR receiver does not know the orientation of the airplane (i.e., what the airplane's heading is), so the display will display the same -- with respect to a given radial -- regardless of which direction the plane is flying at any given time.

Orienting with respect to the VOR

• Tune in and identify

  1. Obtain the correct frequency
  2. Tune-in VOR receiver
  3. Listen to morse code or other station ID to confirm correct station

• To fly directly to the station

  1. Insure the omni bearing flag is reading either TO or FROM (this indicates a usable signal)
  2. Turn the OBS to center the needle with a TO indication; the degrees at the top of the card is the track to the station
  3. Turn towards the heading displayed
  4. As the heading is reached, recenter the needle (the plane will have traveled the radius of the turn and center on this heading

• To intercept a radial to or from the station

  1. Insure the omni bearing flag is reading either TO or FROM (this indicates a usable signal)
  2. Turn the OBS to place the radial to be intercepted (i.e., the course outbound) at the index at the top of the display.
  3. Normally you will know beforehand whether you will be intercepting inbound or outbound, but if in doubt,

     • If the flag says FROM

       , you are past the station with respect to the radial, so you cannot intercept inbound and will be tracking from the station.

     • If the flag says TO

       , you have not yet passed the station with respect to the radial, so you cannot intercept outbound and will be tracking to the station.
     • If flag indications are inconsistent with your intentions or instructions, check to insure that you have the radial, and not the reciprocal, selected on the OBS; if you are actually on the wrong side of the VOR and are under ATC clearance, check with them for clarification.
  4. Turn 90 degrees toward the radial:

     • If the needle is to the right

       , turn to an intercept heading that is 90 degrees greater than the radial
       • e.g., if the radial is 270 degrees, turn to a heading of 360 degrees (left or right turn, which ever is the shortest way around)

     • If the needle is to the left

       , turn to an intercept heading that is 90 degrees less than the radial
       • e.g., if the radial is 270 degrees, turn to a heading of 180 degrees (left or right turn, which ever is the shortest way around)

     • If the needle is centered

       , you are on the radial (recheck the TO/FROM flag to make sure you still have a signal)
  5. When the needle comes unstuck, begin considering a turn to the appropriate heading (based on the rate at which the needle is centering):

     • If tracking outbound from the station

       , turn to the radial heading

     • If tracking inbound to the station

       ,
       1. turn to the reciprocal heading from the radial
       2. in the turn, twist the OBS to place the inbound heading under the index (reciprocal from the radial) at the course index.

Tracking the radial TO or FROM the station

1. Do not alter heading until some persistant wind drift becomes apparent.
2. If a persistant wind drift becomes apparent (i.e., the needle moves left or right and contiues to move), take a 30 degree cut to the needle (i.e., into the wind)
3. Hold heading until aircraft recrosses original bearing (it is unlikely but possible that an additinal cut into the wind would be necessary)
4. Take-out 1/2 of the correction (15 degrees if a 30 degree correction was used)
5. Hold a 15 degree wind correction angle and wait to determine if the needle drifts again
6. Adjust wind correction angle as necessary to to hold the radial

IFR: the Five Ts

The 5 Ts – Turn, Time, Twist, Throttle, and Talk – have been taught to generations of instrument students, myself included. They detail the series of actions taken at various points in an instrument flight where changes in course, heading, altitude, or airspeed occur, or where timing is begun or reporting is made. This is typically in the approach phase of the flight or upon entry into a holding pattern. There is a certain logic to the order, so they are generally presented in this sequence. Not all of the Ts are always needed (e.g., a non-precisison, VOR approach may be from straight-in, so no turn is required), but mentally running through the complete list is always appropriate.

Turn

Turn to the desired heading. You may need to turn to an intercept heading to get on the desired radial or bearing.

Time

Time check for the start of the maneuver if needed (e.g., final approach fix inbound with time to the MAP).

Twist

Twist the OBS to the proper setting if necessary (a new radial or a reciprocal if transitioning to track inbound – but not with an NDB approach!).

Throttle

Throttle back to reduce airspeed or begin descent

Talk

Talk, e.g., to ATC if required (or asked) to report, to announce position inbound at an uncontrolled, etc.

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