This last Tuesday (May 26, 2009), the cadets had a class on the Air Environment (Module 3). For each NCO and Airman promotion (besides the one between Airman Basic and Airman, and the Wright Brothers’ Award), the cadets must take aerospace tests. There are 3 about airplanes and air, and 3 about space and space craft. This particular module is about weather.
The first section of this module is about the basic factors that affect weather. The first is the radiation from the sun. This causes the air to heat up and rise, making air currents. Because of the way the Earth rotates around the sun, the amount of heat that each part of the Earth gets is different. In addition to the winds we feel everyday, there are winds that are at approximately 30,000 feet MSL. This is called the jet stream, which travels from the west to the east between 120-150 miles per hour. This affects mainly military and commercial aircraft, while at cruising altitude. The surface winds affect all aircraft during take off and landing, and private aircraft at cruising altitude.
The next section is about the main elements of weather, wind, temperature, and pressure. Wind is measured by miles per hour and the Beaufort Scale. The Beaufort scale makes a comparison of wind speed and affects on the surrounding environment. One way that wind affects us on the ground (besides blowing our stuff and hair all over the place) is by wind chill. Wind blows warm air away from our bodies, thus making us feel colder. Temperature is another thing that affects weather. Heat is basically the energy within a molecule or substance. Temperature affects airplanes, because heat causes the air to become thinner, which causes the engine to have a richer mixture. This causes the airplane to use much more runway than usual. High temperatures can cause heat stroke, heat exhaustion, and dehydration in humans. Cold temperatures can cause frostbite and hypothermia. Cold temperatures cause icing within airplane carburetors’ and on the body of an airplane. Carburetor icing can occur at temperatures as high as 70 degrees Fahrenheit. The last basic element of weather is pressure. Atmospheric pressure is measured with either an aneroid barograph or a mercurial barometer. In an airplane the atmospheric pressure must be entered into the altimeter, because it affects how high the altimeter thinks the airplane is.
The next section talks about the various types of clouds. Clouds affect airplanes in such ways as visibility, icing, and precipitation. Clouds keep VFR (the kind of flying were one looks outside of the cockpit for guidance) pilots grounded. If the clouds are thick enough, they can even keep IFR (the kind of flying where one only uses the instruments to fly the plane) pilots on the ground. A pilot should never fly anywhere close to thunder clouds. Thunder clouds and the things that go with them (lightning, hail, strong winds) will literally tear an airplane to pieces. Various science companies will fly airplanes into thunderstorms, very few make it out alive.
The last section talks about fronts and extreme weather. Fronts are the boundaries between two air masses. Two colliding air masses cause many of the weather changes we see every day. Extreme weather includes such things as thunderstorms, tornadoes, and hurricanes.