Ultralight Pilot's Checklist: Weather or Not? Clip: Hear why cool air is best for flying. How many reasons can you list? Watch It Now Tips Too hot, too cold, just right. Like Goldilocks, the ultralight pilots know what's best. 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 ultralight. Before you read about each weather factor (named in the subheads below), make a prediction how each one affects flying with the birds. Then see what Joe Duff says! Headwinds Joe says: "Headwinds are a problem because they make flying much harder work for the birds, and they 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!" Tailwinds 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 the wing vortices and they tire easily." Ice 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.)" Fog Joe says: "Fog is a problem because the pilot can't see!" 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 ultralights." 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 ultralights work better and so do the propellers. If the temperature is around 40 degrees F we are happy and so are the birds." Try This! Journaling 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 will find shelter from wind behind a ridge or other obstacle. They also face into the wind and rain. Why? Write your prediction/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 pleased to feature this educational adventure made possible by the Whooping Crane Eastern Partnership (WCEP). This Season Teachers Kids Orientation Registration Search Copyright 1997-2008 Journey North. All Rights Reserved. Questions or comments? Contact us.