Wednesday, 4 February 2009
Monday, 2 February 2009
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Meanwhile, remember some of these Dead-Reckoning (DR) 'tips': See PPL Navigation Ex 18(X).
60/TAS x WS = Max Drift. (60 divided by True Air Speed multiplied by Met Office Windspeed = Maximum Drift in Degrees).
The 1/6ths rule:
0/6 of Max Drift for wind from 0-degrees OFF Track.
1/6 of Max Drift for wind from 10-degrees OFF Track.
2/6 of Max Drift for wind from 20-degrees Off Track.
3/6 of Max Drift for wind from 30-degrees Off Track. Etc up to 6/6 then Max Drift for 70, 80 and 90-degree beam wind.
HWC and TWC (Headwind & Tailwind Component): Use the 120 aide memoire:
Wind from 0, 10 & 20-degrees OFF Track: use 100% of Windspeed. (20+100=120 aide memoire)
Wind from 30-degrees OFF Track: use 90% of Windspeed. (30+90=120 aide memoire)
Wind from 40-degrees OFF Track: use 80% of Windspeed. (40+80=120 aide memoire)
Wind from 50-degrees OFF Track: use 60% of Windspeed. (50 use 60!)
Wind from 60-degrees OFF Track: use 50% of Windspeed. (60 use 50!)
Where, D1=Distance Flown. d1=Distance OFF track. D2=Distance to go to next waypoint.
T.E.1=Track Error in degrees after D1. T.E.1 correction (only) would result in the aircraft paralleling the reqired track to the next waypoint.
Therefore ADD T.E.2 to T.E.1 to fly direct to next waypoint.
60/D1 x d1 = T.E.1 and 60/D2 x d1 = T.E.2. ADD T.E.1 + T.E.2
Flying between waypoints A and B which are 120nm apart. After 40nm the aircraft is 4nm off track. What is the correction angle to fly to B?
D1=40. d1=4. D2=80.
60/40 x4=6-degrees (T.E1). 60/80 x4=3-degrees (T.E.2). Add 6+3=9-degrees correcton angle to fly to B from the OFF-Track position.
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