Correcting a discovered track error
| Term | Meaning |
|---|---|
| Track made good | Actual path of aircraft over ground |
| Track error | Angle between required track and track made good, left or right of required track |
| Opening angle | Track error measured from set-heading point (TP 1102, Opening Angle, Ten Degree Drift Lines) |
| Closing angle | Angle, from aircraft position, between old required track and direct line to destination |
Ten-degree drift lines (TP 1102):
- Open from set-heading, close on destination.
- Read opening and closing angles off a pinpoint. Example: 7° left reads opening angle 7°.
- More accurate read: mark mid-angle between drift lines, place pinpoint against mark (TP 1102, Ten Degree Drift Lines).
Before judging: fly 10 to 25 nm. Shorter magnifies the error.
Four methods to correct a track error:
- Visual alteration
- Double the track error
- Opening and closing angle
- Drift compensation
Choosing: consider visibility, landmark quality, distance to destination, pilot experience (TP 1102).
| Position on leg | Methods |
|---|---|
| Before half-way point | Double the track error, or visual alteration |
| Beyond half-way point | Visual alteration, or opening and closing angle (doubling would regain track past destination) |
| Any point on leg | Opening and closing angle, also before half-way point (TP 1102, The Opening and Closing Angle Method) |
Trap: judging the track error before flying 10 nm, when the error is magnified.
References
- TP 1102, Pilot Navigation (Track Errors and Corrections; Heading Corrections; Ten Degree Drift Lines)