Criteria for an airport weather shutdown? How much leeway?

Factual Questions
#1

The FAA has objective measurements for a shut down, right? “Wind speed steady for x secs of x mph means no takeoffs or landings.”

What about snow? We all know/assume “all flights cancelled because of…” and we look out and see a blizzard. But airport x may have an army of crackerjack snow removal teams and equipment and another airport not.

How much subjective interpretation is employed by the person who makes the shutdown call? (And, who is that person?)

Say, e.g., plane crashes on landing with fatality, lawsuit also says the airport was more dangerous than safe for acceptable landing procedure, the victim family sues airline…airline sues airport?

Victim family sues airport directly? In either case that person who made the call not to shut it down is in the hot seat.

Is this conceivable/has it happened?

#2

Indeed. There will also be differences in runway length and width, elevation, local terrain and obstacles, aids to navigation, etc.

The criteria will thus vary a lot from one airport to another.

#3

FAA doesn’t open or close airports. Local airport management (which may be a municipal government) may open or close a runway or an entire airport based on snow accumulation. Airplanes may choose to use or not an airport / runway which is open based on the reported weather & reported runway condition (snow, water, etc). Different regs apply to private airplanes, including bizjets, than apply to airliners. Different companies and different aircraft have different operating limitations.

All of these lead up to a matrix of different decision-makers making individual decisions under different criteria for different reasons. So the idea there’s some big light switch flipped by one guy using some simple decision criteria is utterly not the way it works.

As to lawsuits, absolutely everybody has sued absolutely everybody else at least once over history. As a rule governments are especially hard to sue. That means the FAA, the weather service, and most airports.
As to how it does work …

As weather deteriorates from fine to simply cloudy the processing rate of the airport is reduced. If the airport is underutilized this may not matter at all and operations continue as normal. OTOH, if the airport is already scheduled to the max, even fairly minor cloudiness can crimp the flow rate enough to matter. Similarly for high winds on a sunny day.

If an airport is expected to become overloaded, or is already overloaded, these folks get involved to trim the flow of aircraft to remain below the airport capacity. http://www.fly.faa.gov/ois/

They do this by ordering departure delays for aircraft going there. This starts with close-in airports who’d otherwise be arriving soon and expands outwards as necessary to trim the “arrival rate” several hours in the future to match expected airport capacity then.

This is your classic “sitting around at the gate waiting for ATC approval to leave” scenario.

If delays get long enough, the airline may choose instead to just cancel the flight.

As the weather gets foggier, some airplanes can’t land; they lack the avionics and crew training necessary to operate to the lowest weather. The airport is fully usable to the airplanes and crews that have the right stuff. This land/no land decision is made by the pilots inflight; nobody on the ground decides anything for them. The weather people report the current weather, ATC passes it along, and the arriving pilots consult their personal / company decision tree and proceed or not as they choose.

For flights still on the ground the airline’s planning staff will be looking at forecasts and current reports. There’s no point in going if there’s little to no chance you can land. OTOH, if you’re coming a long way it might make more sense to leave, e.g., Europe for JFK even though its fogged in now and is still expected to be fogged in 10 hours from now when you expect to arrive. You make this decision (and carry extra fuel) confident that you can land someplace in the US Northeast (maybe even JFK!) and get the folks (and the crew and airplane) much closer to the destination.

Historically Southwest didn’t bother with this lower weather capability since it was expensive and they like cheap. So often they were cancelling all their flights to a foggy city while everybody else was going there just fine. Over the years as they’ve expanded into the northeast and gotten newer airplanes they’ve relented and gained some more of the capability everybody else has. Many RJ operators still have this limitation today.

Fog can also limit takeoffs and the takeoff flow rate. Which in turn can back up into the terminal leading to gridlock there.
Snow: Snow has several synergistically bad effects. It reduces flight and taxi visibility. It reduces braking & steering traction on runways and taxiways. It slows all taxi operations. It requires airplanes to be deiced before takeoff. It requires runways and taxiways and ramps to be closed and plowed over and over as long as snowfall continues. It slows all aspects of ground support, from catering trucks to fuel trucks to the next shift of airline / airport workers even getting to work.

But other than closing an individual runway while the snowplows are driving around on it, snow doesn’t really close airports. It just gums them up to near immobility.
Bottom line:

A lot of the cancellations you see nowadays are not because *one *airplane couldn’t go there and operate just fine. It’s because a *hundred *airplanes can’t all go there the same hour and operate just fine. The industry has realized that a gridlocked big airport is a PR and customer service disaster in the making. Far smarter to avoid it by cancelling vast numbers of flights ahead of time and deal with the passengers elsewhere, not all concentrated at a city they don’t want to be in anyhow.
That’s enough for the overview.

#4

Airports can be closed because of visibility issues, when fog or blizzards, etc. make it hard for the pilots to see to navigate. Sometimes they will close to visual landings but still allow instrumental ones. Thus a 747 can land but a Piper Cub can’t. The newest airline planes do so much automated flying & use electronic gadgets to locate their position that they could land in thick fog. But they have to space planes more, and they move slower (especially taxiing around on the ground), so that reduces capacity, leading to the thing LSLguy mentioned.

Airports can also be closed when runways accumulate too much snow for planes to operate. But the ones in snowy areas (like Minneapolis-St Paul, Detroit. Buffalo, NY, etc.) have a pretty good selection of snow plowing equipment. They usually close one runway and concentrate on keeping another one open when snow gets bad.

Another factor can be snow , rain, or ice that makes runways slippery so that planes require longer distance to stop. Some airport runways are short, and in bad weather may have to restrict landings by heavy, fast planes.

#5

And “heavy”* can vary even for a given aircraft. Full loaded? No passengers? Fuel tanks running low? A pilot flying the same plane in the same conditions might make different go/no go decisions based on what is/isn’t on the plane.

My worst landing experience: Strong winds. Ice storm. Pilot announces that the crew is based there and they’re going to get home for Christmas. Great, got a hero flying the plane.

Very bumpy ride coming in. Long, slow braking. The passengers applauded once we came to a stop.

  • “Heavy” is actually used in pilot lingo to indicate a jet full of passengers.
#6

To put some concrete numbers to all this, these are the general limitations applied in the US.
Maximum geometric tailwind component: 10 knots sustained over most of a few minutes. Measured continuously by anemometer and averaged by a computer.
Minimum visibility measured by laser alongside the touchdown part of the runway. The minimum acceptable value varies by airport and runway with 1800 ft, 1200 ft, 600 ft, and 300 ft being the usual cutoffs. Readings are instantaneous, but are averaged over IIRC 30 seconds. Any given aircraft’s approach & landing is limited by the greatest of the runway’s limit, the airplane’s limit, and the crew’s limit. (Ref my earlier post.)

Note that poor vis could be due to cloud/fog or dense snowfall or dense rainfall or a combination. Fog tends to be uniform minute to minute and long-lived. Heavy rain tends to last just a couple to a few minutes. Snow squalls can last for a couple hours or more with the vis fluctuating up and down a few hundred feet every 30 seconds as thick and thin spots in the snowfall happen to pass through the sensor beam.

Takeoff limits are different (usually higher) values, but conceptually similar.
Snow or standing water depth > 1/2" on the center section of runway or any material accumulation of ice in the same area.

Note we’re trying to measure depth of snow on a surface ~100 feet wide by 1.5 to 2.5 miles long. Anyone who knows anything about snow or rain knows an area that big will not be uniformly covered. Especially not if the wind is whipping. This is measured using the calibrated eyeballs of guys in trucks.
Moderate or heavy freezing rainfall. “Moderate” defined as a rate sufficient to reduce visibility below 1/2 statue mile in daytime.
Windshear or microburst. The exact cut-offs depend on which detection device is in use and other local specifics. But generally speaking abrupt wind shifts in azimuth or speed totaling 20 knots effective delta along the runway alignment triggers the lowest level of warning.

Generally speaking takeoffs & landings are suspended for 10-20 minutes after a severe warning and 5-10 minutes after a less-severe warning. If a thunderstorm will be passing over or near the field the alarms will typically start going off when the severe rain shaft is 5-ish miles away and approaching. These will continue until it’s 3-ish miles away and receding.

If the storm happens to be traveling along the arrival and departure corridors vice 90 degrees to them, that’ll obviously bring things to a halt for even longer as we wait for it to get out of the way. If there happens to be a train of the damn things at 15-20 mile intervals we may be waiting a very long time. My personal record of 6 hours waiting in line to take off was just this scenario. And before somebody jumps up, this was before the current rules on going back to the gate sooner so folks can abandon ship & not be held prisoner.

#7

Just a bump to thank contributors, particularly LSLGuy of course.

Damn but he’s helpful.