VOR, DME & Ground-Based Navigation
Key concepts for interpreting VOR bearings, sensing, dot values, and flying repeatable intercepts.
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Questions Covered in This Set
11 cards to master
What is a VOR radial?
A magnetic course measured OUTBOUND from the station — one of 360 'spokes' on the wheel. The radial you are physically on defines your position.
Does a VOR indication depend on aircraft heading?
No. The CDI shows the same thing regardless of which way the nose points (unlike the heading-relative ADF). Only the OBS setting and your position matter.
How do you find the radial you are on?
Twist the OBS until the needle centers with a FROM flag — that number is your bearing from the station (your present radial).
You center the needle at 315 with FROM. Where are you and what course flies to the station?
You are northwest of the VOR on the 315 radial; fly 135° to go direct to the station.
What causes reverse sensing, and how do you avoid it?
Setting an OBS roughly 180° opposed to your direction of flight. Avoid it by always setting the OBS to the course you intend to fly and keeping heading within ±90° of it.
Full-scale CDI deflection and value per dot on a VOR?
Full scale = 10°; each of the five dots = 2°.
State the 1-in-60 rule as it applies to VOR error.
1° of course error ≈ 1 NM of lateral error at 60 NM. So one dot (2°) ≈ 1 NM at 30 NM, but only ~0.17 NM at 5 NM.
What is the cone of confusion?
The zone directly overhead the station where the needle swings wildly for up to a minute — normal; hold heading and wait for a solid FROM indication.
List the four-step intercept procedure.
1) Twist to center with FROM to find present radial. 2) Set desired course in OBS. 3) Note which side the needle deflects — course is on that side. 4) Turn to desired course ± intercept angle, toward the needle.
Typical intercept angle choices?
30° default enroute, 20° close-in or on an approach, 45° when well off course; angle ≈ degrees of deviation, capped at 45° and rarely less than 20°.
When should you lead the roll-out on an intercept?
Begin rolling out about one dot before centering — use more lead with larger intercept angles or higher groundspeed.
