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We recently had some forest fires in Athens, Greece while the weather was very windy. The news said it had 8 beaufort of wind speed (34-40 knots, 38–46 mph) and in these conditions it's dangerous to fly the "canadairs" (I think we have Canadair CL-215 and Bombardier 415).

Is this true? What is a wind speed over which one wouldn't want to fly such a plane?

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  • $\begingroup$ Please cite a reference where the firefighting aircraft were grounded due to WX $\endgroup$ – rbp Jul 21 '15 at 19:25
  • $\begingroup$ The live news kept repeating this. Only 2 helis and 3 aircrafts were trying to help. One of the aircrafts fell nearby. The chief of the town and president of an organisation "protecting" the mountain said that "with these temperatures and 9 Beauforts no system exists that can put out the fire". spay.gr/index.php/newslist/44-2015-07-20-09-46-16 $\endgroup$ – cherouvim Jul 21 '15 at 19:49
  • $\begingroup$ From that article via Google translate: "the intensity of air (9 Beaufort), no system can extinguish such intensive fire." This is not an aircraft limitation but a problem of the wind making it impossible to extinguish the fire, with aircraft or any other means. I'm going to vote to close as off topic. $\endgroup$ – rbp Jul 21 '15 at 20:22
  • $\begingroup$ @rbp in the end, authorities where just watching the fire and the wind do their thing claiming that is very risky to use airplanes in these conditions. I'll try to find written "documentation" of this in order to satisfy your criteria. $\endgroup$ – cherouvim Jul 22 '15 at 1:31
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The problem is not the wind speed per se, but the combination of factors.

Let's start from the data; this is the METAR for Athens on the 17th of July, the day of the fires:

METAR LGAV 171220Z 03026G38KT CAVOK 32/10 Q1016 NOSIG=

I have highlighted the wind speed data. It says that the wind at Athens airport was on average at 26 kts, with gusts up to 38 kts

  • 26 kts of wind at high altitude would not be a problem for a CL-215

  • 26 kts of wind near ground (to drop the water it has to do low passes) and at low speed (it has to go as slow as possible to be precise) can be highly dangerous, as proximity with the ground increases turbulence. Let's also consider the mountainous terrain around Athen (and the fires were on the side of a mountain), windshear and turbulence were probably quite strong. (See also this question: When crossing a mountain ridge at low height above terrain what consideration is given to turbulence? )

  • 26 kts was the average wind speed, gusts were up to 38 kts, increasing the risks of such operations.

In addition to the above, let's remember that these aircrafts have to fly over fires, that will create additional turbulence through the rising hot air column that they generate. (thanks to David Richerby)

I do not think that a hard limit for such operation exists, as said above is the combination of windspeed, terrain configuration and mission that determines if an aircraft can perform it or not.

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  • $\begingroup$ Wow, thanks for the detailed answer. Is it possible to find the metar data for a specific long/lat? $\endgroup$ – cherouvim Jul 21 '15 at 8:41
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    $\begingroup$ @cherouvim METAR is connected to a meteorological station, so usually you can have METAR for airports and a few other locations, but not for an arbitrary lat/long location. remember, METAR is measured data. $\endgroup$ – Federico Jul 21 '15 at 8:45
  • $\begingroup$ makes sense. Thanks. $\endgroup$ – cherouvim Jul 21 '15 at 8:46
  • $\begingroup$ Downvoted: (1) Va and wind speed have nothing to do with each other (2) there is no turbulence over water because water is not a source of convection. $\endgroup$ – rbp Jul 21 '15 at 19:03
  • $\begingroup$ @rbp (1) try to fly in winds with speeds comparable to your Va (2) usually the fires to be estinguished are not in the middle of the sea. $\endgroup$ – Federico Jul 21 '15 at 19:07

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