AIR NAVIGATION Part 5 The 1 in 60 Rule

Introduction In modern aircraft it is often necessary to do quick mental calculations to check that the navigational computer is still making sense and that we have not fallen into the garbage in - garbage out trap. We have looked at progress along track (DST and ETA); we now need to consider our position across track.

Tracks Track Required The Track Required is normally the line drawn on the map between the departure airfield and the destination, or from one turning point to another on the route. Track Required

Tracks A Pinpoint If for some reason the aircraft drifts off track and we can establish our position using some unique feature (a pinpoint), Pinpoint Track Required

Tracks Track Made Good If for some reason the aircraft drifts off track and we can establish our position using some unique feature (a pinpoint), then the line joining the departure airfield and the pinpoint is known as the Track Made Good (TMG). Track Made Good Pinpoint Track Required

Tracks Revised Track From a pinpoint, which is off the track required, we have 2 options. One would be to regain the required track, but more normally we would draw a line from the pinpoint to the next turning point. This is called the Revised Track. Track Made Good Pinpoint Revised Track Track Required

Tracks Definitions Track Required The planned route. Track Made Good The line joining the departure airfield and the pinpoint Revised Track A line from the pinpoint to the next turning point. Track Made Good Pinpoint Revised Track Track Required

The 1 in 60 Rule The 1 in 60 rule states: If an aircraft flies a Track Made Good 1º in error from the Track Required, then after 60 miles of flying the aircraft will be one mile off the Track Required. Track Made Good Track Required

This can be proved with trigonometry . . . . The 1 in 60 Rule This can be proved with trigonometry . . . . but all we need to know is how to use the triangle. After 60 nm the error is 1 nm for every 1° off track For Example Track Error of 1° 1 nm Track Required 60 nm

The 1 in 60 Rule For Example After 60 nm the error is 1 nm for every 1° off track For Example Track Error of 10° 10 nm Track Required 60 nm

The 1 in 60 Rule For Example After 60 nm the error is 1 nm for every 1° off track For Example Track Error of 15° 15 nm Track Required 60 nm

The 1 in 60 Rule For Example After 60 nm the error is 1 nm for every 1° off track For Example Track Error of 10° 20 nm Track Required 120 nm

The 1 in 60 Rule For Example After 60 nm the error is 1 nm for every 1° off track For Example Track Error of 15° 30 nm Track Required 120 nm

The 1 in 60 Rule The 1 in 60 rule holds good for track errors up to 23º beyond that the difference in length of the two tracks (Track Made Good (TMG) and Track Required) becomes too great and the approximation will not work.

The 1 in 60 Rule The simplest application of the 1 in 60 rule is when a pinpoint is taken exactly halfway along a track. The triangle as the aircraft drifts off track is exactly mirrored by the triangle showing the aircraft regaining track. Pinpoint Track Error Closing Angle Revised Track Track Required A B

The 1 in 60 Rule by twice the track error As the triangles are the same size and shape, it is only necessary to alter heading to the right by twice the track error to ensure the aircraft reaches point B. As the pinpoint is taken halfway along track, the actual distances do not affect the results. Pinpoint Track Error Closing Angle 20° Revised Track 10° 10° Track Required A B

The 1 in 60 Rule Once you understand the method and can do the mental arithmetic, you can omit the drawing of the triangles. Because pinpoints are not always available when we want them, we are often left with awkward numbers that do not lend themselves to mental arithmetic. The solution is to use approximate numbers that are easily handled, either round numbers like 20, 30, 40 or those divisible by 6. Pinpoint Track Error Closing Angle 20° Revised Track 10° 10° Track Required A B

Check Understanding Track revised Track required Track made good What is a line on a map between the departure airfield and the destination known as? Track revised Track required Track made good Heading required

Check Understanding What is meant by the term Track Made Good? A line joining the pinpoint to the next turning point A line joining the departure airfield and the destination A line joining the departure airfield and the pinpoint A line joining the next turning point to the destination

Check Understanding Revised Track Required Track Renewed Track What is a line from the pinpoint to the next turning point called? Revised Track Required Track Renewed Track Track Made Good

Check Understanding 6 6° 12 degrees 9 degrees 6 degrees 3 degrees At the fix point, an aircraft is 6 nm off track, What is the required closing angle? 6 Track error 6° 12 degrees 60 9 degrees 6 degrees 3 degrees

an aircraft is 3 nm off track. Check Understanding After 20 nm of flight, an aircraft is 3 nm off track. What is the track error? 60 2 degrees Track error 9 6 degrees 3 9° 20 9 degrees 60 10 degrees

Check Understanding 3 9 2 6 3 2 If an aircraft flies for 90 nm with a track error of 2o how many miles off track will it be? 9 60 Track error 3 2 6 2° 90 3 2

Check Understanding a. 4° b. 8° c. 16° d. 24° An aircraft flying from A to B is found to be off track at the pinpoint shown below. The pilot calculates the track error as 8°. By how much does the pilot need to turn to reach point B? As the triangles are the same size and shape, it is only necessary to alter heading to the right by twice the track error Pinpoint TMG A B 8° a. 4° b. 8° c. 16° d. 24°

AIR NAVIGATION End of Presentation