Nav Definitions

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Nav Definitions
2013-09-17 22:17:35

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  1. Great circle
    Circle whos radius is that of the earth and whose plane passes through the centre of the earth.

    the shorter arc is the shortest distance between any two points
  2. Small Circle
    Any circle on the surface whose radius is not that of the earth.
  3. Rhumb Line
    A regular curved line which cuts all Meridians at the same angle
  4. True Poles
    • The extremities of the spin axis of the earth
    • Where all meridians meet
  5. Parallel of Latitude
    • All Small Circles (other than equator)
    • All Rhumb Lines
  6. Prime Meridian
    • Also known as Greenwich Meridian
    • Semi-Great circle passing through the poles and through Greenwich
    • Defines Longitude 00 East or West
  7. Anti-Meridian
    • Lies at 1800 degrees removed east/west from the Meridian in question
    • Prime Anti-meridian is at exactly 180 east/west of Greenwich
  8. International Dateline
    Kind of follows 180 meridian
  9. Graticule
    X Y grid formed by the meridian, equator and parallels of lattitude
  10. Variation
    Difference between true direction and Magnetic direction

    Variation is east when Mag north lies East of True North

    Variation is west when Mag north lies West of True North
  11. Isogonals
    Lines joining points of equal Variation
  12. Deviation
    • A/C specific error in compass. 
    • Compass Swing performed
    • Compass direction +/- deviation gives magnetic direction

    Deviation is east when Compass north lies East of Mag North

    Deviation is west when Compass north lies East of Mag North
  13. Does 1 degree of longitude equal 60 miles?
    Only at the equator. Always true for latitude though.
  14. Departure Formula
    • Distance = d Long x Cos lat

    Only valid for points at the same Latitude!

  15. Earth Convergence Formula
    The angle of inclination between any two meridians at a given Latitude.

    Change of Long(deg) x sin mean Lat
  16. How does Wind effect distance to PNR and ETP?
    ETP always moves into the wind.

    PNR reduces in any wind compared to Nil wind conditions
  17. What Fuel Profile gives the PNR furtherest away
    Best Range Speed
  18. How does Air Density affect TAS
    TAS will increase with lower density

    Increase in height, or an increase in ambient temp and same height.
  19. What Grid referencing system is used for GNSS and FMS

    World Geodesic system 1984

    "Geod" meaning the earth shape
  20. when using departure formula to get Distance between two points on same parallel is the answer a Rhumb Line or great circle
    Rhumb Line
  21. What is the conversion angle
    Difference between the Rhumb line track and the true track at the start and end of the lines.

    Equal to half the earth convergence.

     = 0.5 x d.long sin mean latitude