Monday, September 22, 2008

The Ins and Outs

So, my training on the Pensacola bank of scopes continues.

My biggest problem at this point, I think, is actually just that: thinking. I "over think" things, especially when the traffic is slower. Instead of doing and scanning, I sit there mentally going over my LOA's and SOP's and think to myself "Is that the right choice?". I have too many questions at this time that keep me from working it correctly. There's also a lot more coordination on this bank, as you're constantly talking to Jacksonville Center, Mobile Approach, Eglin Approach, and occasionally Houston Center. The end result is that I'm still moving far too slowly for the traffic.

On the Whiting NAS bank of scopes, I'm confident. I know the airspace. I know the rules. I know the procedures. I know the aircraft performance. Obviously I'm no where near as good as the CPC's I work with who have been doing this for 20+ years, but I feel good when I sit down on those scopes. I don't have to think "Ok, what's the proper downwind feed on this runway configuration... and how slow can I get that guy... and how much time is he going to take to turn...." That doesn't happen on Whiting. Over there, I have fun with it, because there I just do it.

On Pensacola... not so much. I'm not comfortable yet, though my comfort level is steadily increasing. I don't ask as many stupid questions as I did before.

Part of my problem has to do with getting used to the general flow of traffic we work with on Pensacola. I don't know what traffic flow is like at other facilities, but in my limited experience I've never heard of anything like the arrangement we have here (outside of maybe Potomac TRACON). Badly chopped up airspace and a lot of MOA's keep it interesting. If anyone can relate to this, please comment on it. I'd love to hear about it.

Tasteful Analogies

I'm sure many of my readers are familiar with the term DSWYE: "Don't shit where you eat." Yeah, it's a nasty saying, one that I've seen used to describe military rifles designed with direct gas impingement, like the "jam-o-matic" M16. However, I think it aptly describes some of our arrival and departure flow.

All high altitude traffic landing at Pensacola Regional - including airliners, corporate jets, etc. - is required to be descending to 11,000 and pointed at a single fix called PENSI, 20 miles north of the airport. It doesn't matter whether they're coming from the east or the west, the rule is the same - 11,000, direct PENSI. That's right: airliners pointed directly at each other from opposite directions descending to the same altitude. It's the kind of situation where if you don't do anything, well... yeah, problems will occur.

Doesn't that make you want to fly into Pensacola? :)

These airplanes are also supposed to - emphasis on the supposed to - be slowing to 250 knots. Doesn't always happen, but generally they're good about it. They're also about 60 miles apart when we start talking to them, so we have room to work with them. The second these airplanes cross our boundary, we're turning them, descending them, or both.

On top of that, our high altitude departures are flying out the same areas through which our inbounds are arriving. The departures will be climbing to 10,000 feet (per our letter of agreement with Jacksonville Center) and angled out the gate (330-340 heading for the NW, 020-030 for the NE). In essence, while we're trying to get our arrivals down, we have departures that are climbing up through them. The "ins" meshing with the "outs". See what I mean now by "DSWYE"?

To make things more interesting, right on top of our airspace is the Pensacola South MOA which is under the control of our Sherman NAS sector. This block of airspace sits directly above our Pensacola sectors and runs from 11,000 up to FL230. So, this basically means that if you get an arrival out of 11,000, you can't turn him southbound until he's AOB 10,000. And if you have a departure climbing to 10,000, you can't switch him until he's out from under the MOA - otherwise, Jax Center (who has control for climb to 15,000) may climb him right into the MOA. This MOA is active quite often, so you need to be paying attention to what the Sherman sector has in it.



So, to sum up:
  • Inbounds: 11,000 /direct PENSI / 250 knots
  • Outbounds (NE): 020-030 heading / 10,000
  • Outbounds (NW): 330-340 heading / 10,000
  • South MOA: Cannot climb or descend through it when active.
Setting Up The Problem

Let's take a look at a color-coded graphical representation of this. Visual Aid time! I kept it simple with just six airplanes in the "problem", and all the colored flight plans below indicate what they'd be doing if there was no other traffic in the airspace.



We have, from lowest altitude to highest:
  • DAL1234, an MD88, released off of runway 17, requesting FL310 with Jacksonville Center.
  • CHQ2223, a Regional Jet, climbing through 6000 to 10,000, northwest bound to Jacksonville Center.
  • KATT613, a T-6 Texan II, departing from NAS Sherman, climbing to 10,000, requesting 17,000 with Jacksonville Center.
  • N2220C, a Piper Seneca, riding the victor airway eastbound level at 9000.
  • EGF789, a Regional Jet, descending out of 13,000 for 11,000, direct PENSI.
  • TRS456, a Boeing 717, out of 14,000 for 11,000, direct PENSI.
KATT613's a single engine turboprop that moves pretty quickly, upwards of 300 knots. DAL1234 is just rolling now while KATT's already airborne. However, the Delta builds speed quickly even in a climb, so even though he gets off the ground later than Katt, there's a significant chance they'll become a DAT (Dead Ass Tie) on their way out. If the Delta winds up behind the Katt at the same altitude, he will eat him up quickly. Center controllers don't really like it when you stuff a fast mover behind a slower-mover.

KATT and DAL are trying to go northeast and are climbing to 10,000. At the same time, you have TRS456 (AirTran) coming in from the northeast, descending to 11,000, direct PENSI. If DAL doesn't climb fast enough or TRS doesn't descend fast enough, there will be conflict. Since DAL is stopped at 10,000 and TRS at 11,000, they won't hit, but Delta will be stuffed down for a bit til he gets out from underneath TRS. And if DAL can't climb, that means we can't descend TRS.

Climbing out to the northwest is CHQ2223, out of 6000, shooting for 10,000 and a handoff to Jax Center. Nearly opposite direction to him is EGF789, inbound, descending to 11,000, direct PENSI. Same thing as DAL vs. TRS: if CHQ doesn't climb fast enough, he'll be held down at 10,000 and EGF will be held up above him.

Right in the middle of it all is N2220C, cruising along at 9000 along our one and only airway. CHQ's current flight path is pointed directly at him, and at this point we're "betting on the come" that he'll top him. On top of that - literally - is EGF, who needs to descend through his altitude. EGF's high speed will close the distance on N2220C significantly.

So, to sum up, we've got multiple potential conflicts here:
  • DAL and KATT racing each other out the northeast
  • DAL and TRS - one descending, one climbing
  • TRS descending through N2220C's altitude, opposite direction
  • DAL climbing through N2220C's altitude, perpendicularly
  • CHQ climbing through N2220C's altitude, opposite direction
  • EGF descending through N2220C's altitude, same direction, 150+ knot overtake
  • CHQ and EGF, opposite direction, one descending, one climbing
  • TRS and CHQ - head on, same altitude, pointed at the same fix
Making it Work

There's no single way to fix things. You have a ton of options available to you as a controller - vectors, altitude changes, speed control. It's just a matter of how you apply these tools.

So let's experiment... Let's see how this would work just using vectors and a couple altitude changes. I'll exaggerate some of the turns for effect:



  1. Leave KATT on an easterly heading for a few more miles to square off his route and then turn him north. This will build in a few more flying miles between him and DAL.
  2. Keep DAL going due north, giving him time to speed up and climb. Once you're sure that KATT won't be a factor, crank DAL on a 020 or 030 heading to slip behind TRS.
  3. Descend TRS to 6000, widening him out a bit north of PENSI. This will dunk him under DAL and under N2220C, and on that heading DAL should pass behind him. Once TRS is below DAL and N2220C, turn TRS towards the airport.
  4. Descend EGF to 5000 and crank him south/southeast. This will ensure he doesn't descend on top of N2220C and get him out of CHQ's way. Once he's below CHQ's altitude, turn him east to base him for Runway 17 at PNS.
  5. Bend CHQ on a more westerly heading - like a 300 - to ensure he'll pass behind N2220C. With EGF on a more southerly route, they should also miss cleanly. Once CHQ has divergence, altitude, and/or lateral separation on EGF and N2220C, crank CHQ to a 340 heading and ship him to center.
This is by no means the only way to approach this. Ask a dozen controllers how to work this and you'll get a dozen answers.

While we're talking about it, there are a couple other things you can do as well using inter-facility coordination.
  • Leave KATT and DAL on their original headings from example 1, but call Jax Center and ApReq higher for KATT. Since their plans diverge 25 miles NE of PNS, if you can get Jax to approve 15,000 the KATT can keep climbing and then turn due east, will the Delta will speed off to the northeast.
  • Or... using the second version of the vectors from example 2, ApReq higher for DAL to get on top of TRS. If Jax can approve a climb to FL230 - the highest altitude they can approve for us- DAL won't have to level off and will continue climbing, topping TRS. If they approve it, we can just issue him the FL230 climb, wait until we're certain TRS will pass underneath him, and switch DAL to Jax.

    That serves two purposes: 1) getting DAL well on his way up to his cruising altitude and 2) allowing us to turn TRS directly to the airport (and away from N2220C) once DAL tops him.
Like I said, that's just six airplanes. Now add in a few more airliner departures and arrivals, four or five Navy trainers and helicopters shooting practice approaches to different runways at PNS, two or three check cargo haulers in and out of PNS, random Cessnas and Tomahawks out in the practice areas, a bizjet or two landing PNS, a few more IFR overflights, and we've got a party! :)

So, that's what I'm working with right now.. I feel like I've been handed a pile of wood, a hammer, and some nails, and told to go build a house. I have all the materials in front of me, but I'm not quite sure how it all fits together yet. I know it can be done, but I'm currently thinking too long and too hard about it, instead of letting it just come naturally.

3 comments:

Anonymous said...

move the enroute down to 70 an get some wiggle room

Wicked Penguin said...

Yup - that'll help, so long as I get him back up to 9000 by the boundary.

Anonymous said...

Looks to me that single arrival fix is killing you. Last place I worked (ANC) we tried to keep the departures away from arrivals 'til we had something - used SIDS and arrival gates a lot. That overflight right at arrival altitude and over your only arrival fix looks like the genesis of a deal.