Pilot's Checklist: Weather or Not?
too cold, just right. Like Goldilocks, the ultralight pilots know
best when cranes must fly with ultralight planes. Each morning around
sunrise the pilots decide whether or not to fly. They look at the windsock,
flight in the sportlight aircraft.
brings the best flight conditions? Before you read about each weather
factor listed below, make a prediction how it affects flying with
pilot Joe Duff says.
Joe says: "Headwinds are a problem because they make flying much
harder work for the birds. Headwinds slow or set back progress in the
similar to paddling a canoe upstream. Birds fly at speeds between 32
and 38 MPH. If we have a head wind of, say 10 MPH, we are slowed to 22
MPH — and
at that speed, we don't get anywhere!"
Joe says: "Tailwinds are great because they help push the bird along
and speed up the progress. Flying with tailwinds is similar to paddling
a canoe downstream. A tailwind of, say 10 MPH, boosts our speed to 42
MPH — and then we REALLY move!"
Joe says: "If there is a gust factor, the aircraft bounces around
and the birds are not able to get close enough to benefit from air currents
(vortices) off the the wings
and they tire easily. When we fly, the lead bird is only about six inches
away from the wing tip, and that's too close for comfort. No one wants
bumping into the plane, which rocks and rolls in bumpy air."
Says: "Our biggest weather problem during the late fall and for most
is moisture. If it’s warm, the moisture produces fog, and if
it’s cold, we get frost."
Joe says: "Fog
is a problem because the pilot can't see!"
Ice (Frost) on the Wings
Joe says: "Ice on wings is a problem because it forms a rough surface
that the air can't stick to. A layer of air called the boundary
forms along the top of the wing and allows the wing to create lift. The
ice disturbs this layer and the lift is destroyed and the aircraft
fly. (Most often the ice forms thicker on one wing than the other and
the aircraft rolls before it crashes.)"
Rain and Lightning
Joe says: "Rain and lightning are problems because most often
they are accompanied by high winds and up-and-down drafts. These
are very dangerous for all aircraft — and especially sport-lights."
Temperatures: Too Hot, Too Cold, Just Right
Joe says: "In order to lead birds we need cold air to keep them
from overheating but more often than not these cooler temperatures
add a thick
layer of frost to our wings that delays our departure by an hour
or more. If the air is warmer it frequently produces early morning
fog and the
results are the same. But that's not all. The warmer the air, the
less oxygen and more water we breathe — and the harder the
birds have to work. Cold air is denser than warm air and the oxygen
tighter. That means that when the birds (or pilots) breathe cold
air, they get more oxygen. Also, the birds' wings work better in
because cooler air is thicker (denser, with tightly packed molecules).
The wings of the sport-light aircraft work better and so do the propellers.
If the temperature is around 40 degrees F., we are happy — and
so are the birds."
- Make a
list of choices you make that depend on the day's weather. Circle the
things you must postpone until more favorable weather. How do you keep
informed about the weather when making your plans?
in the wild are alert to weather. They will find shelter from wind
behind a ridge or other obstacle.
They also face into the wind and rain. Why? Write your thoughts
in your journal. Then compare
your answer with ours.
Science Education Standards
changes from day to day and over the seasons. Weather can be described
by measurable quantities, such as temperature, wind direction and speed,
can exist in different states?solid, liquid, and gas.
Journey North is presented by Annenberg Learner.
Partial funding for this news update has been made possible through Operation Migration by the National Fish and Wildlife Foundation and the Southern Company through the Power of Flight Program.