Topic Author
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Joined: Fri Sep 10, 2010 8:50 pm

### "Annual Winds" Calculation In Range Circles

I have seen range charts / maps or range circles from a specific airport (e.g. ORD) for Boeing and Airbus for various aircraft types in their inventories. A notation at the bottom of the page has references to assumptions. One of the assumptions is:

Typical Mission rules:
85% annual winds

What does the term "85% annual winds" mean in this case? Anyone that can help would be much appreciated.

mercure1
Posts: 3619
Joined: Sun Jul 13, 2008 5:13 am

### RE: "Annual Winds" Calculation In Range Circles

Annual equivalent winds are computed from the mean seasonal values of equivalent winds and their standard deviations.

The technique involves an iterative procedure by which wind speeds are determined for any specified probability between 50 and 99 percent.

85% percentile winds would indicate that only 15% of all flts, would experience a headwind greater than the 85% percentile wind, or tailwind component less than the 85% percentile wind.

85% percentile historical winds/temps have been used for ages by Manufacturers and Airlines, to judge the mission capability of a given aircraft.

Mercure

alasizon
Posts: 1062
Joined: Sat Apr 28, 2007 8:57 pm

### RE: "Annual Winds" Calculation In Range Circles

 Quoting mercure1 (Reply 1):85% percentile historical winds/temps have been used for ages by Manufacturers and Airlines, to judge the mission capability of a given aircraft.

Now its worth noting that BBD (Bombardier) quotes all their ranges at zero wind.
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vikkyvik
Posts: 12112
Joined: Thu Jul 31, 2003 1:58 pm

### RE: "Annual Winds" Calculation In Range Circles

 Quoting Alasizon (Reply 2): Now its worth noting that BBD (Bombardier) quotes all their ranges at zero wind.

Is that just a range, or the plot on a range chart, though?

If it's just range (irrespective of airport) then it makes sense to quote with zero wind, because the wind you factor in will differ depending on your origin and destination.

If it's range from a specific airport plotted on a map, or range between specific airport pairs, then you can account for typical winds.

At least that's what makes sense to me!
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alasizon
Posts: 1062
Joined: Sat Apr 28, 2007 8:57 pm

### RE: "Annual Winds" Calculation In Range Circles

 Quoting vikkyvik (Reply 3):Is that just a range, or the plot on a range chart, though? If it's just range (irrespective of airport) then it makes sense to quote with zero wind, because the wind you factor in will differ depending on your origin and destination. If it's range from a specific airport plotted on a map, or range between specific airport pairs, then you can account for typical winds. At least that's what makes sense to me!

They quote their ranges from specific airports around the world with 0 wind, as well as on their payload/range chart, it is quote with no wind.

Though considering the abilities of the CRJ, most aren't flown anywhere near there range. The CSeries, once it gets here, might need to account for 85% Winds.
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vikkyvik
Posts: 12112
Joined: Thu Jul 31, 2003 1:58 pm

### RE: "Annual Winds" Calculation In Range Circles

 Quoting Alasizon (Reply 4):They quote their ranges from specific airports around the world with 0 wind, as well as on their payload/range chart, it is quote with no wind.

Gotcha, thanks!
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