The 1 in 60 rule

1

• The 1 in 60 rule

2
Introduction

• As is the way with flying, it is important to do
  quick mental calculations in modern aircraft to
  check that the computers are making sense.
• In the Previous chapter we looked at progress
  along track (DST ETA), In this chapter we will
  be looking at progress across track.

3
The 1 in 60 rule

• The 1 in 60 rule states that if an aircraft flies
  a TMG 1 in error from the required track, then
  after 60 miles of flying the aircraft will be one
  mile off the required track.
• This rule can be applied and proven using the
  triangle.

4
Application of 1 in 60 rule
PINPOINT
TMG
Revised Track
10 Track error
Closing Angle
Track Required
A
B

• The Simplest application of the 1 in 60 rule is
  when you take a pinpoint exactly halfway along
  track.
• The triangle above is an example of this. The
  triangle is exactly mirrored. Doubling the track
  error in the other direction will mean that after
  60nm you will be back on track. (assuming the
  wind remains constant)

5
Application of 1 in 60 rule
PINPOINT
? Track error
? Closing Angle
4
40
20
A
B

• This is known as a similar Triangle.
• Triangles are similar if they are identical in
  shape and differ only in size

6
Application of 1 in 60 rule
PINPOINT
? Track error
? Closing Angle
A
B
4
40
20

• We can see that a 20 mile run produces a 4 mile
  error.
• To work out the Track error we must do simple
  multiplication to achieve our magic 60 miles
  along the bottom.
• 20 x 3 60. therefore 4 x 3 12. So Track error
  12

7
Application of 1 in 60 rule

• We can see that a 20 mile run produces a 4 mile
  error.
• To work out the Track error we must do simple
  multiplication to achieve
• our magic 60 miles along the bottom.
• 20 x 3 60. therefore 4 x 3 12. So Track error
  12

8
Application of 1 in 60 rule

• We can see that a 40 mile run produces a 4 mile
  error.
• To work out the Track error we must do simple
  multiplication to achieve
• our magic 60 miles along the bottom.
• 40 x 1.5 60. therefore 4 x 1.5 6. So Track
  error 6

B
6
4
20
40
60
9
Application of 1 in 60 rule
PINPOINT
? TE
? CA
A
B
12
6
40
20
Once you have both the TE and CA you can add them
together to get 18, this is the amount you need
to turn right to regain track by the end of B.