**60 DIVIDED BY TRUE AIR SPEED X WINDSPEED.**

__Maximum Drift:__*60/TAS X WS.*

**Q.**What IS Maximum Drift?

**A.**It is the maximum drift possible with a given wind strength at a given TAS. The Drift Angle that the aircraft would experience IF the wind was directly ACROSS i.e. at 90-degrees to the Track.

**Q.**How is this useful to ME?

**A.**Having calculated the Maximum Drift, it is easy to calculate the Drift Angle for a given Wind Direction relative to the aircraft track.**We only consider ANGLES OFF from 0 to 60 and this is done by using 1/6ths**

__Fraction of Max Drift:__*Rule:*

*0-degrees OFF = 0/6*

*10-degrees OFF = 1/6*

*20-degrees OFF = 2/6*

*30-degrees OFF = 3/6*

*40-degrees OFF = 4/6*

*50-degrees OFF = 5/6*

*60-degrees OFF = 6/6*

__Example 1:__**True Air Speed (TAS) = 90kts.**

**Wind Speed = 27kts.**

**Max Drift = 60/90 x 27 = 18-degrees.**

*Assume*Wind Direction r*elative*to the Aircraft Track is 20-degrees OFF*.*

*Therefore*Drift Angle = 18-degrees X 2/6 = 6-degrees

__Example 2:__**True Air Speed (TAS) = 100kts.**

**Wind Speed = 40kts.**

**Max Drift = 60/100 x 40 = 24-degrees**

*Assume*Wind Direction*relative*to the Aircraft Track is 30-degrees OFF.

*Therefore*Drift Angle = 24-degrees X 3/6 = 12-degrees.

*Now apply the Drift Angle*to the Track to get the Heading.

__Example 3: (__*Illustrated on the 1:500,000 ICAO Aeronautical Chart above*)**True Air Speed (TAS) = 90.**

**True Track = 030**

**W/V = 050/27**

**Max Drift = 18**

**Actual Drift = 6**

*The wind is blowing from the*__Right__, therefore the Heading is 036-degrees.

__Example 4:__**True Air Speed = 100**

**True Track = 140**

**W/V = 350/40**

**Max Drift = 24**

**Actual Drift = 12**

*The wind is blowing from the Left, therefore the Heading is 128-degrees.*

__Cross Wind Component (XWC__) :

*MAX DRIFT - which is an 'angle' has been addressed above. Let's now have a look at CROSS WIND COMPONENT (XWC) which is a 90-degree vector:*

*The 1/6ths Rule above applies.***We will consider**

*Assume that the aircraft that you are flying today has a 12 knot Cross Wind Limit (XWC).*__only__winds up to 60-degrees OFF the runway (RW) Track:

0-degrees OFF RW = 0/6ths of Wind Strength

10-degrees OFF RW = 1/6th of Wind Strength

20 = 2/6

30 = 3/6.......etc to >>>> 60 = 6/6ths of Wind Strength

**If the Runway is**

__Example 1:__**RW23 [**(

*say)*233-deg Magnetic = 230-deg True (Var 3-deg West)

**],**and the Wind Vector is

**260/22**

*i.e. 30-degrees OFF*, then the

**XWC**is 3/6 X 22 =

**11kts**.

**If the Runway is**

__Example 2:__**RW35 [**(

*say)*348-deg Magnetic = 351-deg True (Var 3-deg West)

**]**, and the Wind Vector is

**310/18**

*i.e. 40-degrees OFF,*then the

**XWC**is 4/6 X 18 =

**12kts**.

*I think that is the MAX DRIFT & XWC dealt with!*

## No comments:

Post a Comment