G500
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A319/320, 737- Winter Headwinds From N.Y To L.A

Tue Jan 15, 2013 3:36 am

During the winter season when the head-winds are particularly strong flying from say N.Y to California can get tight in a A319/320 and 737-700 due to strong headwinds... I remember JetBlue, Virgin and AirTran had a bunch of diversions a couple of years ago on flights from the East to the West Coast, due to "stronger than predicted winds" .. Even Alaska had to stop a couple of times.

How strong does the head-wind need to be to force a diversion on a narrow-body flying from East to West? I'm guessing over 100 knots on the nose?

I've heard airlines divert into SLC a few times. Looks like SLC is a favorite spot to stop for fuel. As a passenger i'd rather stop there than LAS or PHX
 
jetmatt777
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Tue Jan 15, 2013 7:46 am

Quoting g500 (Thread starter):
I've heard airlines divert into SLC a few times. Looks like SLC is a favorite spot to stop for fuel. As a passenger i'd rather stop there than LAS or PHX

Why does it matter? Gas 'n' go's do not take very long, especially for narrowbodies.

Quoting g500 (Thread starter):
How strong does the head-wind need to be to force a diversion on a narrow-body flying from East to West? I'm guessing over 100 knots on the nose?

Over 150 knots.

Here's a snapshot of the time of this post...

FL240: (24,000 feet)
http://gyazo.com/0c26d006a36e5334f1195eb2a757d6ec.png?1358235853

FL300: (30,000 feet)
http://gyazo.com/dcc28b0a31ef31fb3ea9e3c579710816.png?1358235818

FL360: (36,000 feet)
http://gyazo.com/cc2e9a7bd4045ab4b039f10a118f8d88.png?1358235834


This tool can be found here:

http://www.aviationweather.gov/adds/winds/
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roseflyer
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Tue Jan 15, 2013 10:54 pm

There are a lot of factors involved. If an airplane is not filled to capacity, then the need for a fuel stop goes away. Some airlines are willing to block seats to allow more payload available for fuel (assuming tanks aren’t full). Other airlines prefer a fuel stop and filling all the seats instead of bumping passengers.

As the previous poster pointed out, winds aren’t continuous. Airplane dispatchers will dispatch creative routes where the airplane will cover more ground distance to avoid the winds. A 737NG can fly over 7 hours with full tanks, but they would exceed MTOW to fill the tanks up with a full load of passengers, baggage and cargo along with fuel for an alternate. Flights into SFO see more diversions than LAX because of the need for fuel to cover an alternate (even though OAK and SJC are close alternates) because the weather is so often bad.

In 2003 the FAA increased passenger weights after the Air Midwest crash in Charlotte which caused a lot more fuel diversions and essentially ended AS operating 737-900s on transcon routes because there was less payload available for fuel.
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thegeek
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Wed Jan 16, 2013 1:48 am

Quoting g500 (Thread starter):
Looks like SLC is a favorite spot to stop for fuel.

Is the high elevation of the field a factor with this? Saves time in descent and climb.
 
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Starlionblue
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Wed Jan 16, 2013 3:03 am

Quoting thegeek (Reply 3):
Is the high elevation of the field a factor with this? Saves time in descent and climb.

High altitude means worse take-off performance, and I think that would have a bigger effect than the small time saving. SLC is at 4227 feet. Compared to sea level that's 2 minutes extra climb time.

Fuel is king. If fuel is cheaper at SLC, even by a little, that's the place to go. Not to mention routing.

[Edited 2013-01-15 19:43:53]
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B6JFKH81
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Wed Jan 16, 2013 8:57 pm

Quoting g500 (Thread starter):
I've heard airlines divert into SLC a few times. Looks like SLC is a favorite spot to stop for fuel. As a passenger i'd rather stop there than LAS or PHX

It's not really a diversion....it's a scheduled fuel stop or "tech stop", which is scheduled before the aircraft even departs normally (based on my knowledge). I have been on a few flights that went into SLC (and were briefed by the captain that was going to be the case before departing JFK), we were back in the air within 30 minutes of touching down. You do not get out of the plane. You go to a hard stand, fuel up, go to the de-ice pad, get sprayed, and leave. There could be multiple factors, but I'm sure the price of fuel is a big one when you have to stop to take on more fuel just to complete the flight so cheaper is better at that point.
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DFWHeavy
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Wed Jan 16, 2013 10:49 pm

Also, the 737-700 wouldn't have any issues, any time of year. It's the 737-800/900 that run into issues once in a blue moon....along with baby buses of course.
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B747forever
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Thu Jan 17, 2013 6:34 am

Quoting DFWHeavy (Reply 6):
Also, the 737-700 wouldn't have any issues, any time of year. It's the 737-800/900 that run into issues once in a blue moon....along with baby buses of course.

Exactly. Doesnt both the 737-700 and A319 have longer range capabilities than their larger siblings?
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glen
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Thu Jan 17, 2013 10:38 am

Quoting B747forever (Reply 7):
Exactly. Doesnt both the 737-700 and A319 have longer range capabilities than their larger siblings?

For the same amount of fuel the range of the A319 is considerably better than on the A320 or A321, due to its lower weight.

Things look different if you want to transport the same high payload, for example the max possible load on a A319 (rounded figures):
DOW: 42t, MZFW: 58.5t, MTOW: 68t ; so you have a maximum payload of 16.5t and are then able to take 9.5t of fuel which gives a range of approx. 1750 NM without reserves.


A320:
DOW: 43.5t, MZFW: 61t, MTOW 73.5t ; so with the same payload of 16.5 t you are at a ZFW of 60t and 1t below MZFW and are able to take 13.5t of fuel - 4t more than the A319 and a range of approx. 2100 NM without reserves.

A321:
DOW 49t, MZFW: 71t, MTOW 83t ; so with the same payload of 16.5t you are at a ZFW of 65.5t and 5.5t below MZFW and are able to take 17.5t of fuel - 8t more than the A319 and considerable more than required to compensate the higher fuel burn of the A321, i.e. a range of approx. 2600 NM without reserves.

So for the same payload the A321 has longest range capability amongst the three, or is able to carry more payload for a given distance.
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roseflyer
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Thu Jan 17, 2013 11:17 pm

Quoting glen (Reply 8):
So for the same payload the A321 has longest range capability amongst the three, or is able to carry more payload for a given distance.

That is true, but no airline operates its airplanes like that. The A321 would be loaded up with more passengers, baggage and cargo. So while at the same payload it has more range, when at a normal operational payload it has less range.
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glen
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Fri Jan 18, 2013 7:41 am

Quoting Roseflyer (Reply 9):
That is true, but no airline operates its airplanes like that. The A321 would be loaded up with more passengers, baggage and cargo. So while at the same payload it has more range, when at a normal operational payload it has less range.

Sorry, my text was not very clear in this point - all I wanted to show was that not the A319 has best range when loaded.

May be I should have better left the comparison between the A319 and A320 at max payload, where the A320 is definitely best.

However even loaded up to MZFW, gives the A321 the possibility to load 12 t of fuel, which gives a range of little bit more than 1700 NM without reserves - not far off the A319. The A319 has only good range capabilities if there's not much payload, leaving room for more fuel - profitability would be the other question then...
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roseflyer
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RE: A319/320, 737- Winter Headwinds From N.Y To L.A

Fri Jan 18, 2013 8:08 pm

Quoting glen (Reply 10):


However even loaded up to MZFW, gives the A321 the possibility to load 12 t of fuel, which gives a range of little bit more than 1700 NM without reserves - not far off the A319. The A319 has only good range capabilities if there's not much payload, leaving room for more fuel - profitability would be the other question then...

True, although rarely are A320s or 737NGs loaded up to MZFW. You see that more often on regional jets where landing weight becomes a factor and on their short segments.
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