Ultralight Pilot's Checklist: Weather or Not?

Too hot, too cold, just right. Like Goldilocks, the ultralight pilots know what's 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, listen to weather stations or take a test flight in the sportlight aircraft.

What weather brings the best flight conditions? Before you read about each weather factor listed below, make a prediction how it affects flying with the birds. Then see what 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 air, 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!"

Gusty winds
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 any birds bumping into the plane, which rocks and rolls in bumpy air."

Joe Says: "Our biggest weather problem during the late fall and for most of the migration 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 layer 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 can't 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 weather systems 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 molecules are packed tighter. That means that when the birds (or pilots) breathe cold air, they get more oxygen. Also, the birds' wings work better in cooler air 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."

Journal Questions 
  • 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?
  • Birds 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.

National Science Education Standards

  • Weather changes from day to day and over the seasons. Weather can be described by measurable quantities, such as temperature, wind direction and speed, and precipitation.
  • Materials 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.