Monday, June 11, 2007

Using Weather Radar at ARTCCs

This is another technical article aimed at controllers in ARTCCs. It is a continuation of the Weather Radar at ARTCCs article. Be sure to read that article first.

Let’s get down to the nitty-gritty. The weather display on your radar scope is there to use. The big question is, how ? You’ll hear all sorts of horror stories from your fellow controllers. Most of the stories have been around long enough to be considered legends. The most common ones told are meant to impress you about how much trouble you can get into trying to vector aircraft around thunderstorms. That is true. You can get into a lot of trouble. Unfortunately, this truth has led many to the wrong conclusion and they won’t vector aircraft around weather. I submit to you that not using your weather display to get aircraft around severe weather is more dangerous than using it for the intended purpose. I also know for a fact that the consequences of not acting are just as severe (if not worse) than acting.

From the FAA 7110.65...


a. Issue pertinent information on observed/reported weather and chaff areas. When requested by the pilot, provide radar navigational guidance and/or approve deviations around weather or chaff areas.

(emphasis added)

Part of your job is to “provide radar navigational guidance... around weather.” You’ll never come across a pilot that wants to fly into a thunderstorm (hopefully.) Once you tell them about a thunderstorm you’re depicting on your scope, chances are, they will ask which way looks the best to avoid it. And that is the issue this article will deal with. What is best way to accomplish the job ?

On the most basic level, you’re being asked to use your judgment. Obviously, you want to use good judgment. That requires knowledge and experience. As I tried to point out in the first article in this series, the more information you have -- and the longer you’ve been using it -- the better your judgment will be. The flip side of that coin is -- a lot of good judgment comes from bad experience. You’ll make some mistakes learning this subject just like you made mistakes when you were learning to vector arrivals in trail. Give yourself a lot of room to make mistakes. How much room ? The rule of thumb is to keep at least 20 miles between an airplane and a thunderstorm. It’s an axiom of the aviation world that hail and/or severe turbulence can occur within 20 miles of a severe thunderstorm. I’m sure you’ve all seen airplanes get much closer. That doesn’t mean it’s a good idea.

Route vs. Vector

I know everyone out there is envisioning how hard it would be (i.e. impossible) to keep 20 miles between every airplane and every thunderstorm. Which brings me to the first technique I want to mention. Your first course of action should be to route airplanes around thunderstorms instead of vectoring them around thunderstorms.

I fought this battle for years at Atlanta Center without much success. But I remain convinced that it’s a technique that should be adopted widely. Don’t let enroute airplanes get close enough to an area of thunderstorms that they start deviating all over the place. Put them on a route that will keep them out of the area. And I mean a route -- not a deviation at the pilot’s discretion. Let me give you an example.

The main route into ATL that I worked was J48.ODF.MACEY STAR.ATL. Invariably, thunderstorms would start popping up on J48 between ODF and AVL. It was one of the normal “patterns” I mentioned in the previous article. Most of the aircraft wanted to deviate to the right and that is exactly what most controllers gave them. “Deviate right as necessary, cleared direct ODF when able.” That’s all well and good. Except most controllers would wait until the pilot interrupted them to make the request to deviate and then interrupt them again to tell the controller they were turning back direct ODF. Still, it really wasn’t much worse than my method, which was, as soon as the first ones started deviating (confirming what I was seeing on radar) I started clearing the other aircraft on the route direct HMV..SOT..ODF.MACEY STAR. -- a route that took them west of the thunderstorms. Admittedly, it used to work a lot better back when pilots looked at maps and didn’t have to ask, “Can you spell Holston Mountain for us ?” But that’s another problem and another story.

Where the method of waiting for each individual pilot to decide for himself was proven inferior was when the pilot decided to go left. That took him into two other sectors and head on to the departures coming out of ATL. Failure to use the tool at hand (the weather display), to be proactive and route the planes where the controller wanted them (well clear of the thunderstorms yet contained in his sector) would result in all sorts of mayhem.

You have to be knowledgeable and flexible. You need to know your airspace, how the traffic works in the sectors next to you and how the thunderstorms normally act so you can anticipate what you’ll need to do as they move. The overriding concern (as always) is to be safe (keeping the airplanes well clear), orderly (nailing the airplanes down on a defined route) and then expeditious (you can always shorten the route if time and conditions allow.) How this method would work in your airspace is something you’ll have to figure out for yourself, of course. The point is to control the situation as much as you can. Deviations are just a fact of life controllers have to live with. But if it’s obvious that a whole stream of airplanes will have to deviate, put them where you want them. You’re the controller. Control the situation.

Closer to the Edge

As I mentioned in the previous article, I don’t consider the safety implications of the example above as particularly great. You’re in a situation with professional crews flying with good weather radar in an environment where all the equipment works well. As we move lower and/or closer to the airport, the situation starts getting a little hairier.

One of the reasons I recommend keeping the enroute aircraft so far away from thunderstorms is that, invariably, other aircraft will have to get closer to them. We’ve all seen this. If there’s only one hole in a line of thunderstorms 100 miles long, every aircraft in the sky will head for that one hole and the situation soon becomes unmanageable. Jacksonville Center and Miami Center have to live with that condition on a consistent basis. Most of the time, the rest of us don’t. We do have to deal with the ones that can’t be routed around the weather -- those taking off or landing at airports near the thunderstorms.

You can help yourself and the pilots by careful observation. You -- with a mosaic radar image -- have a much clearer picture of the weather system. An example that comes to mind is a departure paralleling a line of thunderstorms. Their radar image to the side of the aircraft is limited. I don’t know how limited, but I’ve seen many of them pass a perfectly good route through the weather without (evidently) seeing it. If your radar is showing the route as clear, you can advise them of it so they can look for themselves. Many times you’ll have other aircraft approaching it from a better angle that makes it obvious to them. If it looks good to you and it looks good to another aircraft approaching from a different angle, it’s probably a good route to recommend.

Again, it will take some time before you trust your judgment in these situations. But look for them. “Following the leader” is one of best tools you have to deal with thunderstorms. It takes a lot of time to “compare notes” with the pilots in the lead but it will help build your confidence level in dealing with thunderstorms. Be forewarned, it isn’t foolproof. Just like controllers, pilots have varying comfort levels in dealing with thunderstorms. And thunderstorms, by their very nature, change. If the hole looks like it is collapsing, warn the pilots. If thunderstorms start building in another line behind the hole, warn the pilots. This is the scenario that always concerned me the most -- a “sucker hole.” And it’s the one that you, as a controller, are in the best position to see. A pilot will see what he thinks is a hole through the weather, not realizing that there is even more weather just on the other side of the hole. Look for it. If it looks like a poor choice to you, speak up.

At Atlanta Center, we tried to keep a large scale radar loop projected onto the overhead screens along with the TMU Aircraft Situation Display (ASD.) I referred to it constantly to get a bigger “picture” of what the thunderstorms were doing. It’s information that you just can’t get looking only at your radar scope. Use it.

All this just leads us to the situations that inspired me to write these articles. If you’ll look at the data, there isn’t a big problem in the Enroute environment with most of our traffic and thunderstorms. You have to look pretty hard to find any fatalities with airliners and corporate aircraft in this environment. You don’t have to look hard at all to find some fatalities with General Aviation aircraft and thunderstorms. According to the data that I’ve been able to obtain, we’ve had 40 accidents with 74 fatalities -- minimum -- in the last decade with GA vs. Thunderstorms. I expect that figure to get worse as the NTSB finalizes some ongoing investigations.

I’ve already mentioned that I believe NEXRAD -- by itself -- is a poor “tactical” aid in avoiding thunderstorms. At the risk of beating a dead horse, I’ll say it again. The more situations you can solve by thinking strategically -- keeping airplanes well away from an area of thunderstorms -- the better off you are. But in the end, you will be faced with “tactical” situations. Situations where the airplanes are in close to thunderstorms and they will have to skirt the edges or fly through a hole. And sooner or later, you’ll have to face the most dangerous situation out there -- a pilot without any weather radar flying around thunderstorms.

This article isn’t a chance to play the blame game. Controllers shouldn’t have to face this situation but they do. This article is about what to do about it. The first step is to recognize the situation.

Danger, Will Robinson ! Danger !

If you don’t know what types of aircraft don’t have weather radar you need to learn. As a starting point, I’ll say to include anything smaller than a King Air in this category. There are some smaller aircraft that do, even some single engine type aircraft. But at the risk of getting hate mail from pilots, it’s only slightly better than nothing. The same goes for NEXRAD in a tactical situation. This is one area in which you want to err on the side of caution. Assume they don’t have any weather radar until you know better.

The best way to “know better” is to ask. “N12345, do you have weather radar ?” I’d love to tell you that will earn you a simple “yes” or “no.” It usually won’t. You’ll hear all sorts of answers. NEXRAD, Stormscopes, etc. If you don’t know what they are, learn. If you haven’t learned by the time you find yourself is this situation -- assume the worst.

I’ve mentioned this before but I’m going to mention it again, too. The very best thunderstorm avoidance tool is a pilot’s eyes. Never assume a pilot can see a thunderstorm. If I find myself working a General Aviation pilot without radar the first thing I find out is if he is in VFR conditions. “Say flight conditions.” If you’d rather, put it in plain English. “N12345 are you in VFR conditions ?” If the answer is “no”, then that is your goal, to get them back in VFR conditions. Yes, I realize that isn’t always possible but most of the time it is. Vector them to a clear area of the scope. An area with no “slashes” from the ARSR and no dark blue from the NEXRAD. The goal is to turn a “tactical” situation back into a “strategic” situation. Get them away from the thunderstorms and back into VFR conditions. Then route them around the area of storms.

If you can’t get them to VFR conditions, then don’t let them get near any “H”s or into any “checkerboard” areas on the NEXRAD. And if all else fails, never, never-ever let anybody get into a area of “light blue” (extreme rain) on the NEXRAD display. I don’t care if you have to turn the guy around -- 180 degrees -- (and it may come down to that one day), keep them out of it. A thunderstorm that intense can rip an airliner apart. A General Aviation airplane would be lucky to survive it.

I don’t want you to “fly the airplane.” I want you to control the sector and keep the pilot and his passengers alive. There may be a fine line in there somewhere but controllers are use to walking fine lines. Think of it this way. Who has the most experience dealing with thunderstorms, you or the pilot ? Even if we were talking about airline pilots (and we’re not in this situation) you sit in front of a radar scope 8 hours a day, 5 days a week for years on end. In a few years you have experience to match any pilot. You’ve got the radar and the experience -- don’t be afraid to use it. Be cautious but don’t be afraid.

Paying Attention ?

There are a million situations I’d love to cover but I’m nearing the end of your attention span so I’ll just mention one. Let’s say you’ve done all that I suggest. You’ve studied, you’ve paid attention to the trends, you’ve made a habit of warning pilots about what you see and you’ve learned how to vector pilots away from thunderstorms. You’ve got a GA aircraft with no radar on a heading around a thunderstorm that is 30 miles out and it’s time to hand him off to the next controller. The next controller hasn’t done all of the above. Furthermore, he thinks guys like me -- using Center ARSRs and NEXRAD to vector airplanes around thunderstorms -- are idiots and just asking for trouble. He tells you to let the pilot navigate on his own and clear him direct to the next fix on his route of flight “when able.” What do you do now Ollie ?

Go back to the beginning. The beginning of this article. ”Your first course of action should be to route airplanes around thunderstorms instead of vectoring them around thunderstorms.” If you didn’t see that coming, let it be a sign. You have more to learn. I’m not kidding. This is as dangerous a situation as you’ll ever get in as a controller. You’ve got to think all of this out. You may get to be the best controller in the business when it comes to vectoring pilots around a thunderstorm. That won’t help the pilot much when he enters the next sector.

I want you to go to this link on the NTSB’s web site and read this report. Compare what happened with what I’ve said in this article and any of my previous ones . See if there are any flaws in what I’ve said. I’m serious. I’m not perfect. If you see any flaws, sing out. I’ve already received some new information (at least new to me) from my previous article on this subject. Comments, questions and corrections are always welcome. Remember -- secrets and safety don’t mix. Talk about it, share the knowledge, ask questions and never stop learning.

Don Brown
June 11, 2007

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