Thursday, September 18, 2008

Weather Days

You're heading into work soon at your radar facility. As you're getting dressed, you look out the window to find that it's overcast and the sky outside looks like:

It's definitely a bad day to be ramp rat, but how will this affect you in your radar room? To get the full idea, you jump on your favorite weather site or channel, and get the following forecast for the day:

Thunderstorms. Heavy rain. Gusting winds. Low ceiling. Reduced visibility. General nastiness.

From what I've heard from the "big facility" folks, a forecast like that is enough to give some people the shakes. Instead of relatively orderly flow patterns of airliners in and out of their airports, you've got chaos. Airliners tunneling through the weather, Boeings and Airbuses doing the "holding pattern dance", and pilots electing to take their alternates as the fuel runs low. Ground stops and flow control notices go banging out of printers nationwide as Traffic Management Units go to work instituting methods of slowing the inbounds until the traffic already in the vicinity gets handled.

Around here, it's a very different story. We love days with atrocious weather.

While we do have airliner traffic - something between 20-40 a day, mostly regional jets - the majority of our traffic is military. And not just plain military, but military trainers. Practicing navigation, aerobatics, and approaches is essential to the Navy's syllabus, but it's not essential that it gets done in adverse conditions. Most of our military trainers are single engine props and light helicopters which have limited IFR capability compared to large and heavy airliners. When the weather gets nasty, the Navy simply doesn't fly.

The main reason is that none of these pilots have to go anywhere. These pilots don't have to get 250 passengers to their connections at Dulles or 20 tons of FedEx packages to Memphis for sorting. All they need to do is get a check mark on a training syllabus, and while it's better to do that in a timely fashion, it's not something that needs to be done rain or shine. While the T-34s, TH-57s, T-6s, and all the other "T" airplanes are excellent aircraft, what's light turbulence to a large MD-88 is going to knock those "T's" around.

Marginal Insanity

Now, when I said "we love weather days", I'm talking about days where it's crappy conditions from morning to night. The Navy sees that they're not going get any worthwhile flying in, so they just keep their birds on the ground. This makes it easy for us, since now all we're working with is a little bit of commercial traffic that come two or three at a time every half hour.

On the flipside, the worst days around here are when the weather starts off nice and then goes to hell. Why, you ask? Well, on that beautiful clear mornin, the Navy will have launched all of its aircraft and their T-34s and helos will be out, frolicing in their training areas. But then, Mister T-Storm rolls into the area in the afternoon, along with his friends Low Overcast and Low Visibility. So, you may have started out with a blue sky, but what you end up with is Marginal VFR. And somewhere out there are all these Navy birds that need to make their way home through it.

The majority of our T-34 arrival and departure traffic is VFR and on a beautiful day they're procedurally separated vertically to prevent the inbounds from going head-on with the outbound. However, toss in Mr. Overcast at 2200 feet and now you have:
  • Outbounds stopping their climb at the same altitude as the inbounds, aimed right at them.
  • Reduced visibility that destroys the effectiveness of traffic calls.
  • Pilots deviating from assigned courses and altitudes at all times.
  • Pilots requesting higher to punch through a hole, requiring either case-by-case coordination with the sector above or a negotiated agreement.
  • Course rule traffic that would have been separated by altitude from other sectors now need to be handed off and/or coordinated.
And with Overcast's buddy Reduced Visibility you have:
  • Haze and misting that makes traffic harder to see for the pilots.
  • Lost pilots that can't see their VFR fixes on the ground.
In ATC, you already need to be flexible. But when the weather rolls in, you're constantly changing your plan to coordinate with other sectors and other facilities to keep your traffic safe from the perils of uncooperative weather.

And, that's just with regular marginal VFR on a cloudy day. But when the weather gets even worse in the middle of an operational day, the Navy can drop a bomb on you. Read on.

Weather Recall

You're working Whiting and the day is very marginal VFR. All throughout the day, they've been launching aircraft to the different practice areas, so there's fifty-odd T-34s milling around within 50 miles or so, to the south, west, northwest, and due north. Sooner or later those guys will be coming back. And in the past few hours, there's been weather building in the area.

Suddenly, you hear a transmission go over Guard (emergency) frequency. "All TWA-5 aircraft, contact your base for instructions," it says, or something to that effect. Then you hear the shoutline from North Whiting's tower go hot, asking for your supervisor. A minute later your sup walks over and tells you "Whiting's doing a weather recall."

In short, the weather recall is exactly what it sounds like. The weather's going to pot and the Navy has recalled every single one of their aircraft. Rather than coming in a few at a time like they normally do after they finish their training assignments, they will all be turning tail and headed directly for you en masse. Similar altitudes, inbound from all directions, all requesting IFR pick-ups and vectors to the same TACAN approach.

Unfortunately for us controllers, the Navy seems to wait until the last possible minute to recall their airplanes. By the time they finally get in our airspace, the thunderstorm that caused the recall is near or right on top of the field. Not only are you dealing with dozens of pop-up IFR aircraft, all of which need clearing, vectoring, and sequencing, but the weather conditions are causing all kinds of issues.

A lot of times three or four T-34s will come back in a cluster, only a mile or two between each aircraft. Since they're requesting IFR clearances, you need to pry them apart using altitude or lateral separation to get your 3 miles, 1000 feet, or divergence. Once they're separated, you can start clearing and vectoring them.

Once you find out there's a recall in effect, it's a good idea to call for a handoff to handle the stripmarking work and a position split so you can focus on the arrivals only. Weather recalls are very big deals around here, and they're rare, so not many people have experience with them. There are CPC's in the building that have never seen one, and for us new guys it can be a daunting experience.

What it boils down to is an insanely busy and hectic hour that will truly test you. On the good side of things, all the aircraft you're dealing with are of the same type. This makes speed control and vectoring much easier. They're also small maneuverable aircraft, so their course changes are very quick, simplifying "squeeze plays".


Anonymous said...

Great article!

Anonymous said...

I see that the Navy and Air Force have many things in common! It drives me nuts when they launch knowing full well that the weather is going to go to hell in a matter of minutes. So they fart around in some special use airspace for fifteen minutes only to say "Uh, approach...we are going to have to RTB." So you have 30 or so f-15's and 22's requesting non-standard ILSs and PARs simultaneously, and they have to be radar monitored via single frequency approaches...what a pain in the ass! Sometimes i just want to MAKE them divert...