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
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.)