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I'm looking at forecasted winds aloft on SkyVector for early next week. Specifically, I'm looking at the Pacific Ocean (routed between California and Hawaii) and notice that there are some barbs showing almost 150kt winds at FL300.

Being someone who only has experience flying in lower altitudes with wind speeds I can fathom, this brings up a few questions for me:

  1. Is there a maximum or safe winds aloft value / crosswind for say, a 737 to fly?
  2. How is it reasonable to deal with wind speeds this high when they're other than a direct headwind or tailwind? What if it is a direct crosswind, how is it possible for the airplane to fly without significant navigation issues (or maybe safety issues?) at velocities that high.
  3. In general, how does the significant wind speeds found in the upper altitudes affect flight (contrasted with typical general aviation flight)
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I like to show people videos of planes flying backwards.

These videos show that wind does not have an effect on how well the aircraft stays in the air - no matter how strong it is, it only effects the path taken over the ground. A steady wind makes zero difference to the aerodynamics, whether it is a piper cub or a 747. The aircraft doesn't know what the wind is doing - comparable to you closing your eyes while floating on a smooth flowing river, you wouldn't think you are moving. The stated crosswind limit is only for landing, when you need to be able to fly in a straight line with precision.

I think the big thing you're forgetting is that the wind correction angle is affected by the true airspeed (TAS). The faster the TAS, the less correction is needed for the same wind. Think about it, if you are travelling forward at a faster velocity, it will take a bigger force to knock you off course. 737s have a TAS of about 400-450kts, so whilst a 150kt wind is strong, it's not all that different to a 30kt wind in a GA aircraft. 99% of the time there will be a crosswind component of some kind, but the method of correction for jets is no different to GA - just point the noise into wind as per your calculations.

Back to flying backwards for a minute. The only safety issue would be if the wind were to suddenly stop. The aircraft indicated airspeed would suddenly be 0 and a potentially unrecoverable stall could develop. But one thing many 'ground dwellers' don't appreciate is that the wind - in fair weather - is actually fairly constant when it is not effected by ground obstacles and friction. Generally speaking, the higher you go, the more steady and predictable the wind will be.

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  • $\begingroup$ Any aircraft is in a safety issue when the wind suddenly shifts or goes to zero. Typically, though, this is called turbulence, windshear or even a microburst. Using your analogy imagine floating down water rapids in a canoe vs. a calm river. $\endgroup$ – wbeard52 Jan 7 '17 at 7:53
  • $\begingroup$ Hi @Ben, I think you addressed my question better than I was able to frame it in the first place. Part of my thought was with winds at such a high velocity, I would think the changes in the wind speed or direction would be much more abrupt and significant. Thus creating more wind shear, etc. $\endgroup$ – Ryan Griffith Jan 7 '17 at 14:07
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Is there a maximum or safe winds aloft value / crosswind for say, a 737 to fly?

Crosswind limits are in place for landing not flying. Cross wind limits have to do with how effective the control surfaces are which allows you to fly the plane in such a manner where the fuselage is aligned with the ground track. At altitude winds simply either add to your ground speed or count against it.

How is it reasonable to deal with wind speeds this high when they're other than a direct headwind or tailwind? What if it is a direct crosswind, how is it possible for the airplane to fly without significant navigation issues (or maybe safety issues?) at velocities that high.

Winds are not always a direct head or tail wind (for that matter they often are not) thus you simply need to figure out your course correction. You can check out this video on how to do so. Keep in mind that you are flying through the air and thus moving with it, on the ground you feel wind because you are stationary and it is moving around you.

In general, how does the significant wind speeds found in the upper altitudes affect flight (contrasted with typical general aviation flight)

Its all relative but in general it simply effects time in transit (ground speed). However keep in mind that the planes that fly up there are often faster so 150Kt headwind on a plane that can cruise at 550Kts at FL300 is not all that different from a 35 Knot headwind on a plane cruising at 140kts at 5000ft.

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  • $\begingroup$ Also, if you have a predicted 150 kt westerly wind at FL300, you would try to fly at that level if westbound, higher or lower if eastbound. $\endgroup$ – jamesqf Jan 6 '17 at 19:40
  • $\begingroup$ In any plane with sufficiently precise position information available (all of those capable of cruising FL300 have that) you can get ground track indication and just steer to keep that aligned whatever the heading ends up. Or rather the autopilot steers that way; FL300 is in RVSM airspace where you must use A/P (unless you have special clearance with non-reduced minima, which you usually won't get). $\endgroup$ – Jan Hudec Jan 6 '17 at 20:11

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