Skip to content
PilotSchool Knowledge Base

Understanding Track Made Good (TMG) and Drift

Introduction

In aviation navigation, accurately determining the Track Made Good (TMG) and calculating drift are critical for maintaining intended flight paths and ensuring compliance with flight plans. This section provides a comprehensive overview of these concepts and their practical applications in the context of pilot navigation for the CASA PPL license.

Key Concepts and Terminology

Track Made Good (TMG)

  • Definition: TMG is the actual path flown over the ground, influenced by wind and other factors.
  • Relevance: It is crucial for ensuring that a pilot follows the planned route to the destination.

Drift

  • Definition: Drift is the deviation from the intended track due to wind or other factors, represented as the angle between the aircraft’s heading and TMG.
  • Significance: Understanding drift is essential for making real-time adjustments and maintaining the planned track.

Calculating Track Made Good (TMG)

Using Automatic Direction Finder (ADF)

  • Process:

    1. Determine Track TO Station: Add the heading (HDG) of the aircraft to the relative bearing from the ADF.
    2. Adjust for Track FROM Station: Subtract or add 180° to convert TO station track to FROM station track.

  • Example Calculation:

    • Given: HDG = 095°, ADF Relative Bearing = 185°
    • Calculation: Track TO Station = 095° + 185° = 280° (TO Station)
    • Convert to FROM Station: TMG = 280° - 180° = 100°
    • Track Error: If the Flight Plan Track (FPT) is 090°, the track error is 10° (right deviation).

Sources: IREX Internet Tutorials - cosmic.com.au, Bob Tait’s Aviation Theory School

Track Error Adjustments

  • Double Track Error Method: Applicable when less than halfway to destination. Correct the heading by doubling the track error.
  • 1-in-60 Rule: A quick estimation technique. If 1 degree of track error occurs after 60 NM, then the error is approximately 1 NM off course.

Calculating Drift

Methods for Drift Calculation

  1. Mental Dead Reckoning (MDR):

    • Employe the clock system to estimate the crosswind impact on drift. Uses angular divisions such as 15°, 20°, and 30° for quick mental calculations.

  2. 1-in-60 Rule:

    • Calculate crosswind drift by applying the formula: (Distance off track × 60) / Distance to station, where a known crosswind component helps predict the angle of drift.

  3. Use of ADF:

    • Determine the drift angle by assessing the difference between the heading and TMG using ADF data.

Practical Application

  • Calculate Maximum Drift:

    • Maximum drift angle = Wind speed / True airspeed (TAS) in nautical miles per minute.

  • Scenario Example:

    • Given HDG = 085° M and ADF = 176° R, calculate TMG as 085° + 176° = 261° M (TO Station).
    • Convert to FROM Station: TMG = 261° - 180° = 081° M.
    • Resultant drift is the difference between HDG and TMG, which is 4° left.

Sources: British Aerobatic Academy, SKYbrary Aviation Safety

Conclusion

Mastery of TMG and drift calculations enables pilots to navigate accurately, making necessary path corrections while ensuring adherence to planned courses. Understanding these concepts not only aids in accurate navigation but also enhances flight safety by minimizing deviations caused by external influences such as wind. Practical application of tools and formulas discussed in this section is indispensable for aspiring pilots seeking the CASA PPL license.