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-   -   CAP 698 Figure 4.1 Wind Component Chart Confusion (https://www.pprune.org/tech-log/612285-cap-698-figure-4-1-wind-component-chart-confusion.html)

aviation1993 16th August 2018 12:30

CAP 698 Figure 4.1 Wind Component Chart Confusion
 
Regarding Figure 4.1 of CAP 698, part f) says that the chart has already accounted for 50% headwind and 150% tailwind

My question is how does it account for the 50% and 150%, because if i resolve the wind components using trigonometry:
Using the same data in the example:
Headwind = 30cos50 = 19.28
Crosswind = 30sin50 = 22.98
Gives the exact same component values from the chart.
Does this mean that trigonometry also accounts for 50% headwind and 150% tailwind? Or am I missing out something here?

Cheers

Goldenrivett 16th August 2018 16:52


Does this mean that trigonometry also accounts for 50% headwind and 150% tailwind?
Definitely not.

The graph 4.1 gives the same HW & TW component when the wind is 50 degs off the runway and 130 degs off. i.e. 19 Kts Head Wind and 19 Kts Tail Wind - so they are not factored on that graph.
The performance chart 4.4 has different scales for Head & Tail wind and the reference line is slightly biased to give a bigger penalty for a tail wind. I think that is what they refer to when they say "the chart has already accounted for 50% headwind and 150% tailwind" - but please check with your instructor.

aviation1993 16th August 2018 23:14

I understand now, the wording was confusing.
But thanks a million! Appreciate it :)


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