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Long Jump!

by Bruce Comstock

Several years ago I studied Long Jump weather in detail and subsequently made a 645-mile BFA Long Jump flight in a Cameron N-105 using 36 gallons of fuel. The following is what I would suggest to someone planning to make a Long Jump flight starting anywhere in the Midwest. If you're not planning to takeoff in the Midwest, I'm not sure I can help. If you want to go more than 500 miles, you probably should take off somewhere in the Midwest.

Plan to make the flight in January or February, though late December might work. Look for a strong upper level low centered over eastern Canada. By upper level I mean from below 10,000 feet (700 mb) on up. Look for a strong pressure gradient, indicated by tightly packed isobars or, as we shall see, by tightly packed "isoheights".

Look also for a lower level high extending from the surface up to less than 10,000 feet to provide suitable takeoff conditions. You will probably find the strongest winds aloft somewhat towards the leading edge of this lower level high.

Check the prog charts for both takeoff and landing times. You will see that the "surface" high will move almost as fast as the wind at 10,000 feet. This will allow you to take off and land near the center of the same surface high pressure area, but maybe 500 miles from where you started! Ok, ok, so you don't believe this -- watch the charts and you'll see this is the way it works! If you're really sceptical, I'll send you copies of charts documenting at least four different instances of this weather situation.

The result of all this is that it's possible to take off in about 10 knots, cruise at up to 100 miles per hour at altitude, and land in about ten knots -- all under a crystal clear sky in brilliant, warm, sunshine. The flight is every bit as safe as any other flight in calm surface conditions and clear weather -- probably safer because there are no power lines up there. I made my record-setting Long Jump flight in these conditions and I suspect it is one of the more sedate Long Jump flights ever made.

Ok, so where do you get these mysterious weather charts. How do do you read them? How hard are they to interpret?

The easiest way to get these is to subscribe to an aviation weather information service that allows you to order weather information from a touch-tone phone and receive it over a fax machine. Typically, it costs nothing to subscribe, and info costs maybe $1.25 per page. Before I did the Long Jump flight I subscribed to three different services: JeppFax, AvFax, and ZFX. I pretty much settled on ZFX, but maybe you would prefer one of the others. To subscribe to ZFX, call 1 800 876-1232. Charline French is the Sales Coordinator and has extended excellent service to me on several occasions over the past several years.

When you subscribe, ask to be sent a copy of the National Weather Service (NWS) Difax Transmisson Schedule. This is a list of what weather charts are transmitted when each day. They will automatically send you a pocket guide which details how to get from them all the regular aviation weather information products, but you will also want to look at the charts to recognize the right weather for your flight far enough in advance.

After you've got everything else ready for your flight, start ordering chart 2038 each morning. This is a 60-hour prog four-panel chart for sea level, 850 mb (5000 feet), 700 mb (10,000 feet), and 500 mb (18,000 feet). It will show you conditions forecast for a launch two days later at 12Z, which is a lot like sunrise in the Midwest.

Don't be scared of these charts. A picture is worth a thousand words. All you have to do is look for a surface high in which to take off and land, and a strong upper level low shown by the 700 mb chart. The lines on the upper level charts are heights above sea level where the pressure exists, not isobars, but you can read them just like isobars. That is, the air flow is almost exactly parallel to the isoheights, and the speed is faster where the isoheights are the closest together. Look for isoheights that are really close together for the fastest upper level winds.

After you identify a potential flight situation, start gearing up for the flight. The day before the flight you can get a 36-hour chart which will show a one-day-fresher prognosis for your takeoff time. As the takeoff time approaches, you can supplement the chart information with all the usual aviation weather information products with which you are doubtless already familiar.

So basically it's all quite simple.

A few additional comments. I believe 10,000 feet (about 700 mb) is typically about the best altitude to fly a Long Jump flight. As you fly higher, your fuel consumption will probably increase faster than wind speed, so the miles per ever-so-precious Long Jump gallon decreases. As you fly lower the speed will typically decrease faster than your fuel consumption decreases, and, furthermore, if you go too slow -- even if your miles per gallon is better -- you will run out of daylight before you run out of fuel. Sometime these will not be the case. Be prepared to assess your miles per gallon in flight, make quick decisions, and adjust your altitude accordingly. Take a GPS and calculator and know how to use them for this purpose. Practice does make perfect.

Be patient waiting for the right weather. It is better to be down here wishing you you were up there than up there wishing you were down here. You can't force the weather and get away with it -- ever. Get good at interpreting the weather and go when Mother Nature presents you with what you need. If you do your homework and are patient, she will.

Prepare thoroughly and carefully for your flight. Who was it who said: "I believe in luck. The harder I work the luckier I get."?

The best of luck to all of you planning Long Jump flights. (See again the 2nd paragraph above.)


 
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