Term Papers on Aircraft

Term Paper Title	Aircraft
# of Words	1383
# of Pages (250 words per page double spaced)	5.53

Aircraft

     The extent to which wind shear presents a hazard to aircraft has been well documented in the last ten years. Since some  wind shear can occur in otherwise relatively good weather, the most hazardous kind, a microburst, is associated with rain showers and thunderstorms even thought the parent storm may not be discernible. It was not until the early 1970's that the National Transportation Safety Board was able to obtain the level of data form flight recorders to quantify wind shear. This data became an invaluable tool to assist researchers as well as accident investigators. The physical conditions of wind shear have better defined in the past 10 years. The specific characteristics of microburst wind shear defined are those occurring in the takeoff and landing regime (Harpool 2).
     The key to understanding development of wind shear below the bases of convective clouds is a good knowledge of the characteristics of a typical precipitation-induced downdraft. Not all precipitation-induced downdrafts are associated with critical wind shears. However, there are two types of down drafts that are particularly hazardous to flight operations because of there severity and small size. Professor T. Fulita, an atmospheric scientist from the University of Chicago, coined the term downburst for a concentrated, sever downdraft that induces an outward burst of damaging winds at the ground. He also introduced the term microburst for a downburst with horizontal dimensions of 4km or less (Lester 11-4). Microbursts form by the same process that produce the more common and less intense down drafts; that is, by precipitation drag and cooling due to the evaporation and melting of precipitation particles. In a microburst, the downdraft intensifies with heavy rain and when dry air is mixed into the downdraft causing evaporative cooling and great negative buoyancy. A Microburst may occur in airmass, multicell, and supercell thunderstorms. Isolated, single cell storms present a greater hazard to aviation; because, they are common, small scale, rapidly developing, and they have strong outflows (Lester 11-5). Larger muliticell storms are usually easier to avoid because of there bigger size and because they are usually already identified to be severe.
A microburst is a strong cool core of air descending form the base of a convective cloud. As it reaches the ground it spreads out laterally as a vortex ring which rolls upward along its outer boundary. You could interpret this pattern as a upside down thermal. Not all microbursts are alike; some are accompanied by heavy rain (wet) while others form beneath small verga (dry). Virga is defined as rain showers where the precipitation does not reach the ground. Both types produce extremely dangerous shears which can occur with little or no warning.
     If a stationary microburst spreads inside an undisturbed environment, a perfect starburst outflow with an annular ring of high winds will be observed. In reality, however, the traveling motion of a microburst distorts the airflow form circular to an ellipse shape.

(Lester 6)

The front-side wind intensifies while the back-side wind weakens, resulting in a crescent shaped area of high winds.
     No microbursts form on or near the ground. Instead, they descend from the bases of convective clouds. A microburst with its characteristic winds located above anemometer heights is called a "midair microburst". A midair microburst behind a band of wind damage. This microburst behaves like a steamroller, or a tornado with a horizontal vertical axis, damaging structures and uprooting trees inside a narrow swath. Because of the narrow damage path which occurs with a roaring sound of a rotor microburst, it has been identified as a tornado by mistake.

(Harpool 9)
     Microburst wind shears are short-lived (2 to 5 minutes), small scale, intense downdrafts with vertical velocities that exceed 15 meters per second. They are extremely dangerous to flight because their small rapid changing wind pattern over short distances results in extreme catastrophic performance...

This is ONLY a preview of the article. If you would like to view the entire document, you must subscribe to Digital Term Papers. Please register below now!

Digital Term Papers has over 63,000 essays, term papers, and book notes online. Many paper sites will charge you hundreds of dollars for a single paper. Digital Term Papers only charges $14.95 for a one month membership with instant account activation!

Don't waste anymore time! Join NOW!!!

1 Month (automatic renewal) ($14.95)

3 Months (automatic renewal) ($29.95)

6 Months (one-time billing) ($39.95)

Pay by: