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7 Answers

Wind correction angle in IMC

Asked by: 6077 views Aerodynamics, Flight Instructor, Instrument Rating

Hi.

Could you answer below example?

AIRSPEED : 90kts

CROSSWIND : 10kts

Flight rules : IFR

 

What is the WCA and why?

 

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7 Answers



  1. Kris Kortokrax on Oct 04, 2014

    The wind correction angle will be the same as it would be in VMC.
    The airplane doesn’t know the difference.

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  2. Michael Nowakowski on Oct 07, 2014

    You have not included enough information to answer your question.

    What is the wind direction and speed? What is the aircraft heading?

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  3. Michael Nowakowski on Oct 07, 2014

    There is not enough information here. What is the wind direction and speed and what is the heading of the aircraft?

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  4. Mark Kolber on Oct 08, 2014

    Michael,

    Wind direction, aircraft course and wind speed are usual inputs for the typical question of this type, but those three things are used in the calculation in order to determine the crosswind component.

    Namugoni’s question already gives you that part (10 KT crosswind)) so the question is answerable as is.

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  5. Best Answer


    Jim Post on Oct 09, 2014

    Determine your maximum wind correction angle (WCAmax), for a wind speed (WS) of 10 knots, using the formula below at the true airspeed (TAS) that you are flying. This will be the WCA when the wind direction (WD) is 90degrees in relation to the CRS line. The exact maximum wind correction angle is given by: WCA = asin[(WS x sin(AWA/TAS)] assuming (ass u me) the given 10kts is @90º then the sin=1 and formula can be reduced to WCA=asin(WS/TAS)=asin 10/90 =6.38degrees where WS is the wind speed, and TAS is the aircraft’s true airspeed which means that in the worst case scenario when the wind is 90degrees in relation to your desired course (same as AWA=90degrees), the wind correction angle (WCA) is 6degrees for a wind of 10 knots at your true airspeed of 90 knots. The wind correction angle (WCA) is always on the same side of the CRS line as the wind direction (WD). The heading (HDG) to track the course (CRS) will always lie somewhere between the CRS and the wind direction (WD). (+R-L)

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  6. Mark Kolber on Oct 09, 2014

    It is also interesting how close the rule of thumb gets to the answer. The rule of thumb is

    WCA=crosswind / TAS * 60 which in this case comes out to 10/90*60=6.67 degrees

    About 1/4 degree difference. Not too bad for a calculation based on estimates to be flown by pilots and machinery that are not quite that accurate.

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  7. Namugoni on Oct 16, 2014

    thanks all!

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