desertjets
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How Are WX Diversion Airports Picked

Tue May 13, 2003 9:44 am

When the destination airport has a groundstop for weather related reasons, how are the diversion alternates picked and choosen?

I ask this question b/c I have a story to go with it. I was flying on Frontier from Denver to Washington National on an August afternoon last year. While waiting for the 30 minute warning that tells us to sit down and buckle up, we are dancing about the sky dodging the thunderstorms. About 20 minutes before we are supposed to land, the Captain comes on saying that all 3 DC area airports have a groundstop in effect. He goes onto say that we do not have enough gas to keep in the hold pattern. So we divert. Now we fly about 40-45 minutes back to Indianapolis. Now my question is, why did we divert to Indy? Surely CVG, CMH (we overflew it on the way back), PIT, CLE and several other airports that would presumably be open would be just as good as diversions.


My theory on this is that IND was the closest F9 outstation, hence why the divert all the way back to Indy.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia
 
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RE: How Are WX Diversion Airports Picked

Tue May 13, 2003 10:00 am

The alternate airports are (generally) designated before the aircraft departs, and is a function of -
(1) weather
(2) airport served by that airline - fuel contracts is one consideration
(3) airport where alternative travel can be easily arraged (surface or air)
(4) airport with sufficient hotel rooms if overnight necessary
(5) adequate runways (a 747 can be too big for some small airports)
xxx
Where the airplane goes is generally decided by the dispatchers in contact with the airplane's flight crew... unless an emergency would exist, or if the captain disagrees with the dispatcher as to the selection of the alternate.
xxx
Happy contrails  Smile
(s) Skipper
 
OPNLguy
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RE: How Are WX Diversion Airports Picked

Tue May 13, 2003 10:24 am

As a dispatcher, I pick alternates all the time, and like most things associated with aviation, there are numerous variables involved.

First, and a minor point, was the captains use of the term "groundstop". ATC might have stopped taking arrivals, but "groundstop" is what occurs to the flights destined to BWI/DCA/IAD from other points, i.e. ATL-DCA was stuck at ATL.

Back to alternate selection, etc. Most simply stated, destination alternates need to be specified when the destination is/is forecast to have less than a 2,000 cloud ceiling or less than 3 miles visibility. (I'm leaving thunderstorms out of the equation for the moment.) If I was releasing a XYZ-DCA flight with, say, a 1,800 foot ceiling at DCA, I'd specify IAD as the alternate, since it doesn't require much fuel to get there. It's almost a certainty that the flight will get into DCA as planned, and in this case, IAD is what we refer to as a "paper" alternate. "Paper" alternates are commonly airports that an airline doesn't fly into normally, i.e. "off-line" alternates.

Now, when it comes to thunderstorms, or for that matter, fog, any of which could drastically increase the chances of not being able to land, alternate selection and use becomes less "what-if" and more "when". Off-line diversions are usually not preferable, as there is nobody at the diversion airport working for your airline, and you're then at the mercies of another airline (who may be dealing with their own diversions) or a fixed-base operator (FBO). On-line diversions are preferable, since their avoid some of these problems, and you also then have company personnel in place to handle passengers should the flight have to cancel.

In the case of your Frontier flight, they also serve one of the NYC airports (LGA, I think) but quite often, the weather that 's causing the problems at DCA is also entailing problems getting into NYC, hence the use of IND. The dispatcher would have had the option of changing the alternate from IND to IAD, or Richmond VA (RIC), assuming the weather permitted, so as to use some of the fuel for getting to IND for use in holding, since IAD and RIC are closer, but that increases the risk of diverting off-line, perhaps one they didn't want to take. Another factor, for some airlines, not necessarily Frontier, is that other airports like CVG and CMH, might already have other divereted flights, and not be able to be handled.

There are still some other factors, undiscussed, but those are the major ones applicable to your situation.

Hope this helps...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
sushka
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RE: How Are WX Diversion Airports Picked

Tue May 13, 2003 12:00 pm

As a GA pilot I use the 123 rule in picking an alternate:
1 hour before to 1 hour after
2000 feet ceiling
3 miles visibility

If it is less than that then you pick an alternate. The alternates also have different rules depending on if the airport has a precision, non-precision, or no approach at all.
Pershoyu Spravoyu Litaki!
 
desertjets
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RE: How Are WX Diversion Airports Picked

Tue May 13, 2003 12:49 pm

Thanks Skip and OPLN... very helpful and informative as usual.

Now I only go with what the captain tells me. Once we got on the ground in Indy and were refueled, the captain said we were waiting for a release time from ATC... so it seems that there was a flow control procedure (hope that is the correct term) for DCA and the other DC metro airports.

I had no idea where the weather was and what areas it was affecting. So Indy might have been the closest that was not under the severe weather gun at the time. Though given the desire to go to the airline's outstation for a divert, it makes more sense.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia
 
OPNLguy
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RE: How Are WX Diversion Airports Picked

Tue May 13, 2003 10:52 pm

There's anoher factor for the NY/DC metro airports sometimes (although not your flight, as described), in that sometimes you'll never get close enough to hold in the NY/DC area near your intended destination. The airspace is so congested up in that corner of the country, so there's not alot of available holdinging fixes. It doesn't take many aircraft to fill them up, and before you know it, Cleveland Center (ZOB) won't even handoff to DC (ZDC), and you'll hold in -their- (ZOB) airspace. If traffic backs up really bad, you won't even get into ZOB's airspace, and you'll be holding in someone else's, Chicago (ZAU), or Indy (ZID) most likely. In such a a situation, ATC isn't going to let you divert to an alternate that's close to your intended destination, so something underneath your flight path (IND, CVG, CMH, DAY, CLE, DTW) is more likely.

Once you diverted to IND, there was a generalized flow control for DCA once you were ready to get going again, but ATC gives preference to diverted flights. When filing your flight plan IND-DCA, the dispatcher enters "DVRSN" in the remarks section (field #11), and that alerts ATC so they can get the diverted flight out ahead of others there that were just groundstopped.

It's fun, it's dynamic, and it's never the same way two days in a row.....  Big grin
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
kellmark
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RE: How Are WX Diversion Airports Picked

Wed May 14, 2003 12:03 am

One other comment to the other excellent ones. In the US it is also necessary that any alternate that is chosen be listed officially in what are called the Operations Specifications (Ops Specs) of the airline. That means that they are FAA approved airports for which the airline has operating weight limits and approach plate information,etc. This doesn't mean that the airline has to serve that airport regularly, but it does have to have the airport specified and authorized by the FAA. It is possible that some of the other airports that you overflew back to IND were not listed by Frontier as alternates in their Ops Specs. But I suspect the more important issue was the ATC situation, as OPNL Guy has stated.
 
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Bruce
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RE: How Are WX Diversion Airports Picked

Wed May 14, 2003 12:58 am

Must be easy to pick a company outstation in the east or west coast for southwest because they have so many of them....but if you are southwest and flying over the big "hole" in their route map - the rocky mountain region - you are pretty much screwed because they dont serve anyone in ND, SD, WY, CO, MT I guess they'd go to BOI or GEG or all the way down to ABQ?

slightly off topic but southwest really needs to get a Colorado destination. They are missing out on a fast growing region and skier's paradise.

bruce
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OPNLguy
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RE: How Are WX Diversion Airports Picked

Wed May 14, 2003 1:25 am

Alan,
Yeah, didn't mention that for simplicity's sake, ditto for aircraft type..

Bruce,
The "hole" is SWA's route system is not all that much a problem.

As far as destination alternates, BOI/SLC (the west end of the "hole") and MCI/OMA (the east end) all have plenty of alternates (online and offline) with 30-60 minutes of those 4 airports. It's rare that I ever need to use one that's in "the hole" as a destination alternate. Sometimes, I will have to use one as a takeoff alternate, but that's only slightly more probable.

As far as "enroute" alternates going across the "hole" in the route system, we have numerous offline airports approved in our Ops Specs. We don't often go to them (for the traditional purposes, i.e. engine shutdowns) and are more likely to drop into one of them due to a passenger medical emergency. In the last year, I've seen transcons across the "hole" drop into DEN, CUS, PUB, RAP, and CYS, and everyone was for a pax medical issue.

SWA will eventually serve Colorado, but darned if anyone knows when it will be...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
OPNLguy
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RE: How Are WX Diversion Airports Picked

Wed May 14, 2003 1:28 am

COS, not CUS, (fat fingers...)
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
srbmod
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RE: How Are WX Diversion Airports Picked

Sun May 18, 2003 4:29 am

Some of the typical WX diversion airports for ATL are:
TYS
CHA
BHM
MGM
MCN
AGS
JAN
BNA
MEM
CLT
CAE
GSP
MOB

 
ba299
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RE: How Are WX Diversion Airports Picked

Sun May 18, 2003 6:19 am

OPNLguy said the most right phrase about aviation:
It's fun, it's dynamic, and it's never the same way two days in a row.....
 
TheGov
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RE: How Are WX Diversion Airports Picked

Sun May 25, 2003 12:39 pm

In the late 80's, MEM was chosen by JAL as their diversion point when they began service to ATL. We (DL) had to be checked out (Ops Specs, I guess) by JAL to be sure that we could handle their 747s. In addition, MEM was also the diversion city for B-Cal and LH for their service to ATL. In my four years in MEM, B-Cal dropped in twice and LH once.
Also, to be slightly off topic, remember, 9/11 brought about a number of airlines landing in cities that they did not serve.
Always a pallbearer, never a corpse.
 
kellmark
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RE: How Are WX Diversion Airports Picked

Mon May 26, 2003 7:30 am

An air carrier can deviate from approved airports when the captain/operational control center/dispatcher believes it is required. But then it becomes an emergency. And that is what 9/11 was. People wound up all over the place.
 
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Bruce
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RE: How Are WX Diversion Airports Picked

Mon May 26, 2003 9:01 am

i wonder why HSV isn't a diversion airport for ATL? We're only 143 miles west-northwest, and we have a runway big enough for a loaded 747 (our cargo 747 operates daily).

bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens

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