One in Sixty Rule Technique

Wg Cdr Rajagopal

Navigation using the One in Sixty Rule

Index

Use of One in Sixty Rule

  • One in a sixty rule is useful for pilots to quickly calculate alteration of heading
  • One in sixty rule statement states that one unit off-track in 60 units along track mean a track error of 1 degree
  • In other words, if you are 1 NM off-track after a flight of 60 NM, the track error would be 1 degree.

Logic behind One in Sixty Rule

  • Logic of One in Sixty Rule is based on an approximation with an acceptable level of accuracy
  • Calculate the Tan of angles up to 20 Degrees and multiply the value with 60
  • For example, Tan of 10 multiplied by 60 gives 10.56 which is more or less equal to 10
  • Up to 20 Degrees the Angle subtended (z) is almost equal to Tan (Angle subtended) x 60
  • Therefore, Angle (z) = (Opposite side / Adjacent side) x 60
  • Replacing opposite and adjacent sides by distance off-track and distance gone
  • Track error (z) = (Distance off-track / Distance gone) x 60
  • Replacing opposite and adjacent sides by distance off-track and distance to go
  • Closing angle = (Distance off-track / Distance to go) x 60
  • 1 in 60 rule provides acceptable results up to 20 deg only and breaks down beyond 20 degrees

Pilot Navigation using 1 in 60 Rule

  • Alteration of heading an be calculated using Closing angle and Double track error methods
  • 1 in 60 rule can be used to find the required heading alteration up to 20 deg

Closing Angle Calculation

  • Method of finding alter heading to destination by closing angle method involves finding the Closing Angle and Track Error
  • Sum of Track error and Closing angle would give value of Alter Heading
  • The alteration of heading has to be applied in the opposite sense to the heading being flown
  • Alter heading to right if the aircraft has drifted left and to left if the aircraft has drifted right

Double Track Error Calculation

  • Regaining track by Double Track Error method involves single calculation of Track Error only
  • Find the track error using the formula
  • Track error = (Distance off-track / Distance gone) x 60
  • Double of the calculated track error would be the value of the required alteration of heading
  • The alteration of heading has to be applied in the opposite sense to the heading flown
  • Alter heading to right if the aircraft has drifted left and to the left if the aircraft has drifted right
  • Aircraft would regain track after flying the same distance

Best of luck