FCA787
Topic Author
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Headwinds Question

Sun Nov 12, 2006 6:36 pm

Hi

I have a question about headwinds.

I have been a flight from JFK-LHR a few months ago and it took approx 8hr30mins as their as alot of headwinds the captain said, but I also have done this flight about 2 yrs ago and it took just over 6hrs?.

Has anyone ever been on a flight that has had to put down and refuel because of headwinds?

How long could headwinds potentially prolong a flight by?

Is their a specific flight that is operated regular that you know has to put down regular because of hadwinds?

Do headwinds vary from times or the year? Is their a particular bad time for them?

Cheers
 
flyboy2001
Posts: 94
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RE: Headwinds Question

Sun Nov 12, 2006 7:33 pm

Well, as a private pilot, I don't deal with those kinds of extremes but my understanding is this... certain routes will nearly always encounter strong headwinds in one direction and a tailwind in the other. Crossing the Atlantic means dealing with the Jetstream but, depending where the Jetstream is flowing that week, one may encounter more or less of it. Flightplans will be made to take advantage of a strong tailwind or avoid a vicious headwind. However, at some point during the year, it is conceiveable that you could find a flight which can't avoid a trans-oceanic track with bad headwinds because of distance/fuel considerations or ETOPS rectrictions.

I've never heard of a flight that had to put down and refuel due to enroute headwinds, most likely because the winds aloft are pretty well predicted and airlines will route their planes around the winds or fuel them for a longer time in the air.

If the flight is long enough, a 100kt headwind can add quite a bit of time to your flight. A simplified example: If your 500kt jet hits a 100kt headwind, the effective forward progress is at 400 kts. Carry that forward, say... 10 hours and you've gone 4000 nm, when you wanted to have done 5000. That's an extra 2.5 hours still to go.

That said, I have never been on any flight that varied as much as your 6 hour vs. 8.5 hour journey!

Hope this helps!  Smile
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Goldenshield
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RE: Headwinds Question

Sun Nov 12, 2006 7:48 pm

Quoting Flyboy2001 (Reply 1):
I've never heard of a flight that had to put down and refuel due to enroute headwinds, most likely because the winds aloft are pretty well predicted and airlines will route their planes around the winds or fuel them for a longer time in the air.

There are times when an enroute diversion is needed when, in the opinion of the PIC or dispatcher, the flight cannot be completed with the fuel remaining. The chance of this happening is pretty rare, but it does happen, and he may, or may not, be correct.

Also, here in the U.S., winds aloft are published twice a day, so when a flight is planned and departs when another chart is due out, planned and actual can very well vary signifigantly.

Quoting Flyboy2001 (Reply 1):
However, at some point during the year, it is conceiveable that you could find a flight which can't avoid a trans-oceanic track with bad headwinds because of distance/fuel considerations or ETOPS rectrictions.

There are times when you just have to suck it up and fight the wind. Case in point, last month, the jet stream pretty much spread itself out over the eastern half of the U.S. There was no avoiding from Atlanta to Maine.

Quoting FCA787 (Thread starter):
Do headwinds vary from times or the year? Is their a particular bad time for them?

In the summer, the jet stream tends to hang out closer to the poles, rarely venturing south (or north, in the Southern hemisphere.) In the winter, the cooler air brings the jetstream out to play for the winter causing all kinds of problems, like bad winds, and CAT, among other things.

Quoting FCA787 (Thread starter):
Is their a specific flight that is operated regular that you know has to put down regular because of hadwinds?

While no airline wants to have a fuel stop, there are times when one may be called for. If the winds are bad enough on a certain route, and the fuel required to depart is greater than the tanks can hold, there is most definately going to be a fuel stop.

[Edited 2006-11-12 11:51:19]
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flyboy2001
Posts: 94
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RE: Headwinds Question

Sun Nov 12, 2006 8:13 pm

Quoting Goldenshield (Reply 2):
There are times when an enroute diversion is needed when, in the opinion of the PIC or dispatcher, the flight cannot be completed with the fuel remaining.

Well how 'bout that... Nice to get a Dispatch POV. How frequent (or infrequent) are these instances?
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Goldenshield
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RE: Headwinds Question

Sun Nov 12, 2006 8:35 pm

Quoting Flyboy2001 (Reply 3):
How frequent (or infrequent) are these instances?

There are too many variables to give an accurate number, but you are looking in the range of 1:500,000+ for unplanned fuel diversions in a commercial operation.
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OPNLguy
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RE: Headwinds Question

Mon Nov 13, 2006 1:56 am

Quoting FCA787 (Thread starter):
Do headwinds vary from times or the year? Is their a particular bad time for them?

To illustrate what Goldenshield mentioned, here's a prog chart for later today.

As you can see, the heavy green lines indicate the location and orientation of the jetstream winds, and for this specific chart time of 00Z, and where they're anticipated to be at that time. The jetstream is constantly in motion, and the location and orientations change. Two days from now, the jetstream could be blowing on a straight line from LAX-JFK, or oriented some other way.

The green triangle barbs are 50 knots of speed, and the green lines are 10 knots, so if you had 2 triangles and 2 lines, that speed would be 120 knots. The yellow dashed lines indicate areas of turbulence, which we dispatchers seek to avoid, or plan the the flights to stay under.

http://i34.photobucket.com/albums/d143/OPNLguy/HISIGPROG.jpg
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futurecaptain
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RE: Headwinds Question

Mon Nov 13, 2006 2:16 am

So, it looks like a flight from JFK-LHR today could have anywhere from 120-150 knots of tailwind today.
The flights going in the opposite direction will be fighting this same wind. Ouch.

[Edited 2006-11-12 18:16:47]
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OPNLguy
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RE: Headwinds Question

Mon Nov 13, 2006 2:43 am

Quoting Futurecaptain (Reply 6):
The flights going in the opposite direction will be fighting this same wind. Ouch.

Not necessarily. If they flew that exact opposite direction, sure, but westbound flights are normally planned on routes that take them out of the jetstream as much as possible so they'll save time/fuel...
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Ncfc99
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RE: Headwinds Question

Mon Nov 13, 2006 4:26 am

A couple of years ago I flew LGW-SFB. Outbound was 9.5 hours due to weather, northerly routing over southern greenland and down the east coast. Inbound the arriving flight was late, bad weather over the Atlantic again but the captain needed to make up time so we went straight through the weather and encountered bad turbulance. 7 hours to get home. Not nessissarily due to headwinds but a 2.5 hour flight difference due to weather.
 
Tristarsteve
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RE: Headwinds Question

Mon Nov 13, 2006 4:34 am

Quoting OPNLguy (Reply 7):
Not necessarily. If they flew that exact opposite direction, sure, but westbound flights are normally planned on routes that take them out of the jetstream as much as possible so they'll save time/fuel...

Briefly the North Atlantic tracks are set twice a day. Early morning for Westbound and late afternoon for Eastbound. Specific airlines' flight planning offices calculate the best track for the day, and the Atlantic controllers work out a mean, and then publish the five tracks for the day. Eastbound flights look for the best tailwinds, and Westbound flights look for the smallest headwinds. The Eastbound and Westbound tracks will be hundreds of miles apart.
I am not invloved because the transatlantic track from ARN is North of the tracks and joins them usually over Canada.
 
PPVRA
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RE: Headwinds Question

Mon Nov 13, 2006 4:37 am

I've heard that sometimes AR aircraft flying MAD-EZE have to stop at GRU for refuelling due to headwinds. I don't think it hapens very often, however.
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Ralgha
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RE: Headwinds Question

Mon Nov 13, 2006 6:25 am

Quoting Goldenshield (Reply 2):
Also, here in the U.S., winds aloft are published twice a day, so when a flight is planned and departs when another chart is due out, planned and actual can very well vary signifigantly.

The winds aloft forecasts are usually way off. They get the general direction right, but the speed varies widely.
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chksix
Posts: 336
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RE: Headwinds Question

Mon Nov 13, 2006 6:59 am

Quoting OPNLguy (Reply 5):
o illustrate what Goldenshield mentioned, here's a prog chart for later today.

Would such a map be available online?
I'd like to plan my "virtual" flights better but have not been able to find jetstream info anywhere.
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Ralgha
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RE: Headwinds Question

Mon Nov 13, 2006 10:00 am

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
 
OPNLguy
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Joined: Tue Jun 15, 1999 11:29 am

RE: Headwinds Question

Mon Nov 13, 2006 12:01 pm

Quoting Ralgha (Reply 13):
http://adds.aviationweather.gov

...and click the tab for "Prog Charts"

...and on the right side, click on "Hi Level"

...and go down to "Mercator" and mouse-over the area you want to cover...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
chksix
Posts: 336
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RE: Headwinds Question

Mon Nov 13, 2006 4:53 pm

Thanks!  Smile
That was the page I had missed. Didn't think global data was available there.

A followup question: The jetstreams are labeled with a FL, the question I have is how close to that FL do I have to fly to use the jetstream? If I fly higher, at what level will I leave the jetstream?

In short, how "thick/deep" are the jetstreams?
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Goldenshield
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RE: Headwinds Question

Tue Nov 14, 2006 1:19 pm

Quoting Ralgha (Reply 11):
The winds aloft forecasts are usually way off. They get the general direction right, but the speed varies widely.

And yet, you'd be surprised at just how accurate flight plans made from them can be.

Quoting Chksix (Reply 15):
A followup question: The jetstreams are labeled with a FL, the question I have is how close to that FL do I have to fly to use the jetstream? If I fly higher, at what level will I leave the jetstream?

The green lines on the charts just show the centerline of a projected path of the jetstream. They can in fact be hundreds of miles wide and thousands of feet deep.
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OPNLguy
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Joined: Tue Jun 15, 1999 11:29 am

RE: Headwinds Question

Tue Nov 14, 2006 9:44 pm

Quoting Chksix (Reply 15):
In short, how "thick/deep" are the jetstreams?

In my experience, flight planning at FL220, FL240, or FL260 usually gets you under the core of the strongest winds....
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
bond007
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RE: Headwinds Question

Tue Nov 14, 2006 10:58 pm

Quoting Goldenshield (Reply 2):
There are times when an enroute diversion is needed when, in the opinion of the PIC or dispatcher, the flight cannot be completed with the fuel remaining. The chance of this happening is pretty rare, but it does happen, and he may, or may not, be correct.

Although a month or two ago, there was a whole bunch of East Coast - West Coast flights over a period of a few days, that had to stop for fuel somewhere on the way. The winds were extremely strong. I seem to remember a few airports getting some unusual visitors!


Jimbo
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chksix
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RE: Headwinds Question

Wed Nov 15, 2006 1:29 am

Thanks Goldenshield and OPNLguy  Smile

It'll make the virtual flights a bit more realistic...
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