- The Late Douglas Adams
One may think the same about the sky. Look up at it and you'll see a blue infinity with no boundaries, no barriers - just emptiness. Maybe a bird or two looking for an unwitting target for their digestive pyrotechnics, maybe a small cloud that wants to go grow up one day to be a huge cumulonimbus. Typically, though, it's a vast expanse of nothing but air.
However... throw a few planes in there and start looking at it through a radar scope, and things will change quite a bit. Then add a few more planes in there and point them at the first batch of planes. Finally... put imaginary walls up and try to keep those airplanes from smacking into those walls without permission. Now we're having fun!
We have nine sectors at our facility, the smallest of which - the "Z" sector - is approximately 10 miles by 10 miles wide (at its widest point) and reaches from the surface to a mere 3000 feet. It also has a corridor starting at about 3.5 miles wide that extends to the northeast directly into Eglin Air Force Base's airspace. The sector is designed to serve South Whiting Naval Air Station, otherwise known as one of the U.S. Navy's largest helicopter training bases.
While we do have other sectors that are about as small, those are only used for arrival sequencing into our other two airports. This is the only one that's consistently used for both arrivals and departures.
Here's what it looks like:
This sector can get very busy with IFR and VFR traffic arriving and departing South Whiting as well as multiple VFR aircraft operating out of Milton airport, right in the middle of the sector. Also, a majority of the Navy aircraft want multiple practice approaches to runway 32.
I created an illustration showing a fairly busy session on "the Z". Each circle represents the 3 mile wide circle around an aircraft, and each color is a different altitude: 3000 feet is pink, blue is 2200 feet, and 1700 is green.
Note: While the two "blue" VFR aircraft don't technically require the 3 miles, I left the circles around them so they're easier to see.
It's really interesting working this sector. While you deal with the same factors you deal with in other sectors - altitude, sequencing, approaches, etc. - you've got a lot less room to work with.
- Altitude: The ceiling is a stratospheric 3000 feet and our MVA is barely over a thousand feet below it at 1700. When you're dealing with IFR aircraft, that means you only have have those two altitudes available if you want to maintain your 1000 foot vertical separation. If you have VFR aircraft, you've got a third for them: 2200.
As with everything in ATC, you need to plan accordingly and use your "tools" wisely. As an example, inbound aircraft heading southwest will typically be handed off at 4000 feet, while your northeast outbounds will want to climb to 3000 or 5000. If you don't get your outbound climbing and your inbound descending quickly enough, they could feasibly fly into each other's face.
- Lateral Separation: The main block of airspace is 10 miles at its widest point, and the "neck" stretching to the northeast is a little over 3 miles wide at its narrowest point. In short, you've got very little wiggle room for lateral separation. However, being that we're a terminal facility, we get to take advantage of terminal course divergence rules:
5-5-7. PASSING OR DIVERGING
a. TERMINAL. In accordance with the following criteria, all other approved separation may be discontinued, and passing or diverging separation applied when:
1. Aircraft are on opposite/reciprocal courses and you have observed that they have passed each other; or aircraft are on same or crossing courses and one aircraft has crossed the projected course of the other and the angular difference between their courses is at least 15 degrees.
2. The tracks are monitored to ensure that the primary targets, beacon control slashes, or full digital terminal system primary and/or beacon target symbols will not touch.
In short: as long as the route of one aircraft is guaranteed to pass behind another or both aircraft have courses diverging by 15 degrees or more, we can have less than 3 miles of separation. Our friends over at the En Route Centers don't have that luxury.
- Approach Requests: South Whiting is one of the two most-used airfields in our airspace for practice approaches. Its primary runway has ILS, GPS, RNAV, TACAN, PAR, and ASR approaches available for use by the South Whiting-based helicopters and the fixed-wing T-34s out of North Whiting. What's good about this is that it familiarizes you with the idiosyncrasies for each type of approach.
You also learn to manage dissimilar aircraft in tight quarters using speed control and sequencing. For example: if you've got a helo 10 flying miles from the runway and a T-34 15 flying miles away, who will be first? Well, the helo tops out at about 100 knots whereas the T-34 cruises at about 180. It then becomes simple mathematics: while the T-34 has 50% more distance to fly, it's going 80% faster.
- Frequency Management: The PAR and ASR approaches are two types of Ground Controlled Approaches (GCAs) both of which require an aircraft to be "talked down" to the runway by a Navy ground controller. Basically, they make a transmission every few seconds (5 for PAR, 15 for ASR) that fine tunes the aircraft's approach. I don't know the exact phraseology, but it's along the lines of "You're left of final... You're right of final... You're on course." The main difference between two is that ASR provides only lateral corrections, while PAR does both vertical and lateral. It's so accurate that a good PAR/ASR controller can talk a plane down in nearly any kind of weather conditions.
Now, we obviously can't have a GCA controller talking on our main frequency for 2 minutes straight every 5 seconds. Therefore, when an aircraft comes in for a GCA we assign them one of 4 GCA-only frequencies that are used only for approach purposes. This becomes a complication when you have more than 4 aircraft coming in for GCA approaches. Now you need to keep track of who's on what freq, which freqs have cleared now that an aircraft has landed, who's not going to need a freq anymore because they're done with their GCA practice, and who hasn't been assigned a button yet.
I won't go into the specifics, but suffice it to say it takes a combination of accurate stripmarking, datablock scratchpad entries, and situational awareness to keep things straight.
- Borrowed Airspace: If you notice on the sector map, there are three areas to the southeast that are not shaded in yellow. These areas are owned by Eglin AFB, our eastern neighbor, but are usually on loan to us. However, they'll take them back several times a day and apply different separation rules to them. The most troublesome is the hot boundary. Translation: they'll be running IFR aircraft inside those airspace blocks right up to the boundary, so we need to keep our IFR aircraft a minimum of 3 miles away from the boundary instead of the usual 1.5. VFR aircraft are unaffected and can run right up to the boundary.
Those areas are only given to us up to 3000 feet. If you've got an inbound from the northeast at 4000 feet who needs to go south to get to the final, you need to make sure he's at or below 3000 feet when he crosses that line into those areas. If he descends too slowly and crosses that boundary at 3500, you've just had a deal.
- Hot Boundaries: Now go back and look at the map. You'll see that Whiting's runway final depiction runs right into those areas I just mentioned. However, the approaches are designed to have a dogleg that runs nearly north/south, starting about 5 miles out from the airport. But...that dogleg is less than a mile from the boundary!
What this boils down to is that we cannot give IFR aircraft any approaches if the boundary is hot. We usually have to tell the pilot something along the lines of "Navy123, the restricted areas have gone active. In order to continue with this practice approach you will need to cancel IFR." The Navy pilots are familiar with this situation and will usually comply. The weather around here is typically good and it's usually a non-issue.
As a contingency - in the case of a combination of true IFR conditions and a hot boundary - we do have a separate helicopter-only TACAN approach that runs north/south a mile west of Milton airport. The fixed wing aircraft have their own full TACAN at North Whiting.
- VFR Pop-ups: Milton is a very busy little uncontrolled training airport, to the point that on some days we feel like calling ourselves "Milton Approach". Overall, the Cessnas and Pipers that come off there are pretty innocuous and they usually take care of themselves. We issue traffic calls and altitude restrictions as needed to keep them informed of the swarm of Navy traffic around them, but they pretty much stay out of trouble.
- My one pet peeve is the following: inevitably, when I've got a busy pattern full of Navy helos and T-34s, a student pilot will call up, "Pensacola... approach....Warrior 1...2..3...4........5... Off Milton at.... 1000 feet... uh...Five miles south of... uh....Milton. Request....requesting flight following to... the beach... the beach practice area."
Now, I'm a pretty fresh private pilot. Mic fright sucks. I've had it. I still have it. I can relate and I'm in no way angry at them. But man... they always pick the worst possible time to call! However, considering the tight nature of the sector, by the time they're done one Navy guy's blown through final, another Navy guy's missed his turn, and yet another's about to run into another sector. Now I'm playing catch-up, calling out point-outs to other sectors and Eglin, and the whole plan needs to readjusted.
Of the three sectors I'm training on, it's physically the smallest but by far the most challenging. But when you get it running smoothly, it feels really good.