Zenith Aircraft Builders and Flyers
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Accurate cruising speed ??????
When flying with a crosswind at 90 degrees to the plane, will my IAS be an accurate cruising speed if I maintain the 90 degrees ? Will it be pretty much the same as having no wind ? If not, how do I get an accurate cruising speed when the wind is rarely calm in my area ? I'm talking about winds between 4-12 mph.
Thanks,
Jim
Replies to This Discussion
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Permalink Reply by Jay Hancock on
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IAS is the same no matter the wind. If you have a strong sidewind, then you'll be crabbing, and that will reduce your ground speed. How much?
- A 45 degree crab will subtract about 25% of your IAS.
- 25 degrees is about 10%, and
- 10 degrees is about 2%.
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Permalink Reply by James R Depfer Sr. on
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Jay,
I think I asked the wrong question. I guess I should have asked how the wind affects my ground speed at 90 degrees compared to no wind. What I'm trying to determine is what my cruising speed is before a modification and what it is after a modification when I have almost no calm days. How do I eliminate the wind factor in determining the gain or loss in cruising speed ?
Thanks, Jim
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Permalink Reply by Gary Reed on
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Use the wind side of an E6B computer. You will find that a 90 degree crosswind still reduces your ground speed, because of the crab angle to maintain course. Although, the reduction of ground speed is only 1-2 MPH at about 10 MPH of wind
At the speeds that our airplanes fly at, an angle of 98 to 100 degrees (slight tailwind) is required for ground speed to equal airspeed.
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Permalink Reply by Lynn S. Beckhorn on
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Your airspeed remains the same, your groundspeed changes. An E6B flight computer will give you all the answers.
Cheers,,,,,,,,,,, Lynn Once upon a time,"Croc 9"
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Gary & Lynn,
Thanks for the reply. I did find an online "fill-in-the-blank" E6B, and I found the result I was looking for.
Jim
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Permalink Reply by John Austin on
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I've attached a spreadsheet file that should give you the accuracy you're looking for!
John
N750A
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John,
I actually did fill out this form about a year ago. My original question wasn't written correctly. I did find out what I wanted to know about cruising speed for comparing before mod and after mod speeds by using an online E6B app.
Thanks,
Jim
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Permalink Reply by François Balaux on
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Hi
If you want to compare performances before and after a modification, I think you should simply use your IAS and completely ignore ground speed. The IAS is the same no matter the wind angle, and if your plane is faster your IAS will be higher.
However other factors like temperature may have influence the result, on a cool day your plane will be faster.
Regards,
Francois
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