Airline-Quality Weather Decisions for the General Aviation Pilot

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I spend a lot of time in the vicinity of poor weather. Especially thunderstorms. It often seems like they have an affinity for me. Of course, it doesn't help that my aircraft is typically loaded to the hilt with bank paperwork that has been deemed to be of extreme importance; as my employer consistently reminds me, if it wasn't time-sensitive, it would be on a truck.

There's no doubt that the types of flying that some cargo pilots do can be among the most difficult there is, as we aren't typically blessed with color radar displays, turbine engines, and state-of-the-art avionics. Furthermore, we're often flying into some backcountry strips that don't necessarily have the same level of facilities enjoyed at the major metropolitan airports. Stir in a thunderstorm or two, or some fog, and you've got a formula for a very long day (or night, as the case may be).

However, with some exceptions, there is a method to a freight pilot's madness. A good understanding of how to deal with different types of weather, the facilities that are available for everyone, and a sensibility built with knowing when to throw in the towel, can help any pilot in nearly any type of equipment fly more efficiently and safely in the vicinity of nasty weather. Trouble is, not all this stuff is taught in ground school.

The Early Bird Gets the Worm

You may be used to showing up at the airport exactly eight and a half minutes before the propeller starts turning on the nice weather days, but on the days when the weather is not cooperating with the production of smooth air and unlimited visibilities, getting to the airport quite a bit earlier to start doing some planning is an absolute must. Depending on the weather system you're dealing with, leaving several hours early or even the night before could be the easiest way of making it from point A to point B without a hitch (and without getting stuck in point K in the midst of the trip). Of course, sometimes because of what or who you're flying, or your own schedule, that may not be feasible. At the very least, showing up an hour earlier than you usually do should give you enough time to get the information you need to work through a challenging meteorological event.

Start out with your conventional weather briefing. The worse the weather is, the more important it is that you speak directly to a FSS briefer, though in all likelihood, you'll be put on hold a lot longer in the process. Getting a DUAT briefing will cover the basic, legal flight-planning requirements, but FSS briefers have been watching the weather all day, and talking to pilots in multitudes of equipment about what's out there. That information isn't put into the text weather briefing, and the insight you get from a real person could give you an idea to make something work that you might not have thought of. Getting a text briefing isn't a bad idea either, especially if you can go through it with the briefer while on the phone. On top of this, being aggressive about getting information is of the utmost importance, so ask the briefer about every intimate detail that might influence your flight. Ask for specific locations of storm cells and their movement, surface observations from nearby airports in addition to your departure and destination, and even for the briefer's own opinion of the weather (you'll be surprised by what you'll get).

Don't stop there. If you have access to the internet, there's a variety of great informational sources out there, including Intellicast, which has the same radar graphics found on the WSI weather stations, ADDS, which has a lot of experimental weather algorithms and data, and the UNISYS Weather Processor, which provides every sort of stability index and forecast data that you've read about in the books but don't generally find advertised on The Weather Channel. Speaking of which, watch The Weather Channel for a few minutes if you can. The most important thing is to soak up as much information as you can get from whatever sources are available.

Plan B ... and C, and D

So your briefing tells you that the visibility could be as low as 1/4 mile, a hailstorm could roll through in the afternoon, or there may be a blizzard. Most forecasts deal with possibilities or temporary conditions, so often you could make the flight without any difficulty on one day and the next time you try you could end up in hot water with nearly the same forecast. When dealing with possible weather conditions, the key is to have a plan B -- and while you're at it, think of as many more as you can. A wise flight instructor I once knew said that if he had three certain ways out of a potentially bad situation, he didn't have any problem trying to get through the first one.

In fact, the FARs require you to have a plan B. FAR 91.103 discusses pre-flight requirements of the pilot-in-command, and among them is determining "... alternatives available if the planned flight cannot be completed."

Thunderstorm View from the Ramp
 
Determining a way out of a poor situation varies with the type of weather you're dealing with. If you're flying into a mountainous area susceptible to upslope fog, perhaps there's less likelihood of lower visibilities in an area outside of the mountains you could get to. Find airports 50 miles either side of your destination and see if the same conditions are forecast; if you've got a solid way out, you can depart with the knowledge that you'll have somewhere to go if the weather goes down the tubes.

With thunderstorms, the worst weather generally comes in lines, so having a few places to land on one side of the line where you can wait for the weather to pass over will generally only delay you a few hours. See how far you can get, land and tie the airplane down, and then plant yourself firmly on the pilot's lounge couch and enjoy some satellite TV (and convince yourself that this is part of your responsibility as a pilot). Once the worst blows over, you'll usually have a clear shot to anywhere on the back side of the poor weather.


Looking Into The Maelstrom

Someday in the not-too-distant future a general aviation cockpit may come loaded with electronic gizmos that rival the supercomputers of a few years ago, and with it may come the data accessible right now through sources like Flight Service and the Internet. Unfortunately for most of us, the most advanced equipment out there is still expensive, often heavy, and carries with it a high learning curve (just look at GPS units, for instance). Fortunately, the best ways to fly around bad weather haven't changed much and are often still the most effective means of traversing the worst stuff out there.

Remember that most bad weather is an isolated event; seldom will you find entire geographic areas covered with thunderstorms or low ceilings (though it happens from time to time). Just like avoiding traffic, see-and-avoid can be the simplest way to work around what's out there.

First off, let's discuss visibility. An often misunderstood concept is the difference between reported visibility of 10 statute miles and nine statute miles; in most instances, there's a lot more of a difference between the two. Most automated reporting stations are not capable (or, at the very least, don't) report visibilities greater than 10 miles. The danger in this is getting used to what "10-mile" visibility looks like (when it could, in fact, be 50 miles or more), and then moving to a "nine-mile" visibility day. Many pilots are surprised by the 80% reduction in visibility that can come with a change of only one mile from the reporting station.

On the days where visibility is much better than 10 miles, getting around isolated thunderstorms can be relatively easy. The rain shafts, lightning, and cumulonimbus clouds can be seen on such days from a sufficient distance to preclude getting stuck in the midst of it. However, this plan of action is predicated on not being in the middle of a cloud deck, or even on top of one. The best idea when there are thunderstorms about is to stay as low as you reasonably can. Sometimes it's a bit more bumpy at 4000 feet than at 8000, but your ability to avoid the turbulence associated with an embedded thunderstorm by far outweighs the mild discomfort below the cloud deck. Of course, if you have the ability to climb well above the resident cumulus buildups (the high teens or twenties), your ability to pick out the culprits is enhanced as well -- just look out for the one that's built up above you.

Though recommendations vary, flying any closer than 10 miles to a thunderstorm (20 for a severe thunderstorm) is pretty unanimously thought of as not being a good idea. As a result, the "see and avoid" plan doesn't pan out so well when the visibility is poor, as it often is in mid-summer when airmass thunderstorms rear their ugly heads. Night flying can be just as difficult, since lightning can be seen for dozens of miles and it's sometimes difficult to determine whether or not you'll fly into the clouds or rain until you're already in the midst of them.

Listen Up ...

Fortunately, an astute pilot has a lot of information at his or her fingertips to help when looking out doesn't necessarily give the picture to make good decisions. Through those trusty old communications radios, there's a wealth of information available to the pilot who doesn't have much else except a whiskey compass and a stopwatch to guide him.

You may be familiar with the obvious ones -- like Flight Service or Flight Watch. FSS can typically be reached aloft through numerous outlets that are depicted on the chart (see the chart legend, as they're depicted differently on NOS, Jeppesen, and Sectional Charts), or when in doubt, try 122.2. Make sure you let them know where you are and what frequency you're listening to, as the briefers are often monitoring a wide geographic area and may not know which outlet you're trying to communicate through. Flight Watch (122.0) is often easier to reach and deals specifically with the weather out there, so they've typically done a great deal of talking to pilots and have the latest scoop, and they're also not busy dealing with flight plans and other pilot services. The same rules apply as before: Make the process interactive, ask questions, and keep the inquiry going until you are confident that you have the necessary information to make solid decisions. In fact, go over a plan of action based on what you hear, and see what the briefer thinks of it. Saying, for instance, "So if I fly directly northbound until reaching the Richmond VOR, then directly to Charlottesville, I should remain clear of the convective activity ..." gives the briefer the opportunity to catch any holes in your idea because of information you might not have gotten in the first place.

En Route Chart
 
Millville FSS Frequencies at Teterboro, N.Y., are 122.65 and 122.2
 
What a lot of pilots don't understand at all is what ATC has to offer. Truth is, what you get when it comes to weather depends on which ATC facility you're talking to, since the equipment differs widely. One could easily get the impression that ATC has no weather capabilities whatsoever.

Fortunately, that's not the truth. Though ATC radar was never constructed with the intention of seeking out precipitation information, it can actually be quite good at it. The problem lay in that the architecture on which ATC radar was built is supposed to eliminate weather information from the screen because it has the tendency to interfere with the primary function of the controller -- to separate traffic. Several suppression circuits take certain types of radar returns (generally those that aren't moving very quickly) and eliminate them from the display. This precludes objects that have no business from being on the screen, such as buildings, birds, and (unfortunately) precipitation, from cluttering the display to the point that the aircraft cannot be discerned from the rest of the garbage on the screen.

This doesn't mean that ATC can't give any information, though. Even early versions of terminal radar (what's called Airport Surveillance Radar 7 or 8, or ASR7 or 8) gives the controller the ability to turn off the suppression circuits and display precipitation information that would otherwise be hidden from the controller. Though the intensity of these returns cannot be discerned, at the very least a controller can give some idea or confirmation of the existence of an area of precipitation. Further, any returns that make it past the suppression circuitry can be inferred to be of relatively high intensity, and should certainly be avoided. Often controllers can be hesitant to give you this information, as it is not entirely reliable (similar returns can be created by low-level temperature inversions or the previously mentioned "ground clutter"). However, if you specifically ask for any information that the controller might have available, while mentioning that you understand that intensity information is limited and accuracy isn't guaranteed, you'll often come out having at least some idea what's coming in the near future.

The best out there right now can be found at the busier terminal radar facilities, such as Raleigh-Durham, Baltimore-Washington, and Philadelphia, to name a few. These facilities have what is called ASR9; the equipment at these facilities was designed to be able to differentiate between differing intensities, and can be of incredible use to a pilot whose cockpit might disappoint Bill Gates.

Just as pilots with sophisticated on-board radar displays do, a controller from an ASR-9 facility can interpret contours displayed on the radar display by selecting lighted buttons at the station, which illuminate when weather information is available (in other words, when there's something to see). The information is classified into the six classic "VIP" levels, and is given to pilots by the number of the intensity, with one being the least intense to six being to weather what nuclear war is to a "minor disagreement."

For comparison's sake, let's discuss the different VIP levels in more depth. On a controller's screen, a Level 1 return would equate to a radar return with an intensity of roughly 30 decibels (dBz) or less, and a Level 2 would provide up to a 41 dBz signal. This is generally equivalent to what you'd see on the ground-based weather displays, such as WSI, as a green band of returns. Levels 3 and 4, the yellow band, provide up to a 46 and 50 dBz return, respectively. Level 5 gives returns up to 57 dBz, and Level 6 is anything above that, both of which make me visibly shiver. As a general rule, it's an incredibly smart idea to stay away from anything above a level 3 return no matter what equipment you're flying, though if there's more room available the controller may steer you clear of any of the returns on the screen.

Orange Thunderstorms
 
To make matters more confusing though, the Center controllers, those from the Air Route Traffic Controller Centers (ARTCCs), have another form of weather information at their fingertips. As AVweb's Don Brown discusses in Air Traffic Chaos, the Center controllers' radar picture is a combination of Hs and slashes, with the H representing the areas of higher-density precipitation. If you'd like to see a picture of it, pull out the trusty AIM and turn to diagram 1-2-3. The slashes begin to appear with returns above 20 dBz. The threshold between a slash and an H is made at 30 dBz, or what would roughly be anything above a Level 1 return from the ASR9. Unfortunately, that's about all you have to work with. In theory, staying away from the Hs should protect you from flying into the nastiest of weather, but should you stray into an area delineated so, there's no guarantee that you'll be flying in Level 2 returns and not Level 5s.

To make matters worse, Center radar tends to be more sensitive to disturbances and inaccuracies due to the frequencies at which it operates and the distances over which it is utilized. Center controllers can be even more hesitant to actively provide the information on their screens as result. In other words, you have to ask. The best strategy to use with Center radar is to get a plan going with the controller around a series of weather, and then ask to step off the frequency for a moment and see what Flight Watch says about your suggested course.

There had to be some good news about Center radar, though -- it packs a punch. Two major advantages of Center radar are its strength of signal (up to 5 million Watts, as compared to the puny 50,000 that most airborne weather radar units are capable of producing), and its relatively low-frequency band. To paraphrase aviation specialist Bruce Croft, the lower frequency range of Center radar acts a great deal like the stereo of the neighborhood punk as his car approaches your house. The bass that is shaking your windows is akin to the frequency range of the ARTCC's radar; the lower frequency travels through interfering objects, like windows or heavy precipitation, more effectively than the more trebly high frequency waves of classical music. Though no good comes from the big speakers in the passing Civic, Center's ability to penetrate through more dense precipitation gives even pilots with airborne displays the ability to see through some angry weather that their displays couldn't depict due to the absorption of their relatively weaker and higher frequency radar pulse (a phenomenon called "attenuation").

Finally, collecting your own weather data can give you some picture of where the good, bad, and the ugly are. Whip out your trusty aeronautical charts and start listening to every ATIS, ASOS, or AWOS that you can find on the map within 50 miles of your route. Turn the squelch off and try your best to pick up stations that are 70 miles or more away from you, and see where the weather is and how it's moving. The raw data you pick up can give you the information necessary to draw your own weather map, which you can then compare with ATC and FSS.

The end result is that by utilizing the real-time information from the controllers paired with what you see outside and what you've learned from other ground-based stations, you can enjoy the same degree of safety and reliability as the big boys, but without a hundred-thousand-dollar radar dish.

Aw, [Expletive Deleted] ...

As you learn the caveats of the system and gain exposure to a variety of meteorological circumstances, you start to find that there's typically a way to get from departure to destination with a little legwork and planning. However, there are certain times where getting there just isn't reasonably possible, no matter who you are. Most pilots aren't around when the airliners go to their alternate, but it does happen and more frequently than you might think.

The most important thing to consider when things start to go downhill is the possibility of landing. Now. If you've got a GPS, hit the nearest button and let ATC know that you're going to put it down at whatever suitable airport comes up on the display. Believe it or not, sometimes the most efficient (and, of course, safest) strategy when facing poor weather gets passed up because a pilot will focus on "finding a way around" or "waiting it out" to the point that other options aren't as feasible any longer. When faced with a line of thunderstorms, for instance, your best bet may be to land and let it pass, which may take an hour, but is typically followed by beautiful, smooth, calm weather.

Compare that with flying 60 or 70 miles out of your way to find a way around. If you do get around, you've wasted nearly as much if not more time than you would have by waiting it out, burned more fuel and turned the tachometer more times, and possibly stressed yourself out to the point that your hair turns gray (if it's not already). If you don't, you've now flown 60 or 70 miles out of your way, burned more fuel and turned the tachometer more times, stressed yourself out, and are now further away from your destination anyhow. Not very effective planning. Shelve the machoistic attitude and grab a bite to eat. Granted, sometimes you'd have come out ahead by staying in the air, but you have to ask yourself if it's worth the three minutes you might get to (hopefully) live through if that's not how it works out.

Keep in mind, too, that if a thunderstorm is just passing over your destination, there might be a lot of people in line who have already been holding before you. It's not unheard of to fly racetracks for an hour after the thunderstorm has completely passed over a busy airport because all the aircraft that were supposed to land during the half hour when it was raining are stacked up in front of you.

Showers Approach an Airfield
 
If you inadvertently blunder into a thunderstorm (and, dear God, never intentionally fly into a thunderstorm!), the most important thing is to slow down. The ideology that ramming the power forward and punching through as quickly as possible has been largely discounted because you may, in the process, tear the wings off of the aircraft. The most important things is to minimize the stress that the aircraft will absorb in the wind gusts and turbulence, so slow down to well below maneuvering speed, or the turbulent air penetration speed if your aircraft has one. If the storm decides to take you for a ride, tell ATC you can't hold altitude, and don't try; just keep the wings level and let the storm take you where it may. Trying to overcome an updraft of the intensity found in a thunderstorm may well overstress the aircraft, and chances are nobody else in their right mind is in your immediate vicinity, so the chances of causing separation problems aren't very large. Since most thunderstorms are relatively localized and narrow occurrences, making a 180 if you've actually entered the storm is generally not be the best idea, depending on your turning radius -- plus, a level turn will increase load factor, making it easier to overstress the aircraft in the process. Turn the lights up all the way to help offset the blinding effects of lightning, keep your focus on the panel, and cross your fingers!

If the visibility is down to nothing at your destination and dawn is hours away, you probably have no other choice than to enjoy the local scenery at another location. Who knows what you may find, though -- one night I ended up in Kankakee, Ill., which was voted the worst place to live in the United States, or at least that's how it was described to me by the hotel van driver, though I never got to see the gazebo David Letterman bought the town to give it some culture. Isn't flying exciting?


And the Credit Goes To ...

You didn't think I knew all this myself, did you? Though a lot of the information contained above was gleaned from getting myself tossed around in the cockpit, a lot of it I learned from numerous other pros out there in the field. My sincerest thanks to Preston Williams and Cindy Zewe from the RDU Air Traffic Control Facility, Bruce Croft, Captain David Gwinn, and Dr. Tom Carney and Professor Mike Nolan of Purdue University. Without their assistance, I couldn't possibly have spoken with the same degree of authority on the subject, nor probably have fared as well in the system myself.


About the author...

Jeremy Jankowski  
 

Jeremy Jankowskiworks as a "freight dog," running cancelled bank checks around in Piper Lances and Senecas in the Southeast, and has recently been named a "Master CFI" by the National Association of Flight Instructors. Previously, he's flown a variety of turbine- and piston-engine aircraft as both a co-pilot and a flight instructor from coast to coast with Purdue University in West Lafayette, Ind., and has also spent time working in the dispatch department of nationally recognized UTFlight, the corporate flight department of United Technologies Corporation. Jeremy used to work as a computer technician in Southeastern Michigan, but doesn't miss it a bit.