Ice and Snow Removal Essay
Ice and Snow Removal
Ice can affect an airplane’s engine two ways. First, it can form in the carburetor of the engine, blocking the travel of the fuel-air mixture through the carb and possibly resulting in engine failure. Second, ice can also form over the air inlets through which the stream of air must flow on its way to the intake system of the power plant (Eichenberg, 2001 p. 14). Deep inside of the carb, there is a little passageway through increase in its temperature because the compression physically forces the molecules of the gas closer to each other.
When the compressive force is removed, as it is when the fuel-air mixture travels back into a wide opening of the venturi, the temperature of the gas drops. Cooling occurs because the compressive force has been removed and the molecules spread out; hence, molecular activity (heat) declines. A small flapper that controls how much fuel air mixture is allowed to go into the cylinders is placed in or very near the venturi tube. This flapper device is called a “throttle place. ” When you push in or pull out the throttle control in the cockpit, the action is to move the throttle plate in the carburetor.
In turn, the throttle plate is regulating the amount of the fuel-air mixture that is being fed to the intake system of the engine: more flow, more power; less flow, less power. It works the same way in a car engine (Andersland and Ladanyi, 2004 p. 242). When the air is colder than freezing, ice loves to form on the edges of hard objects that are placed in the stream of the air laden with water vapor.
Moreover, the temperature drop in the carburetor can be as much as 90F and the freezing point of water is 32°F, carburetor ice can be a possibility anytime (Lankford, 2000 p. 68); hence, the removal of ice and snow is necessary . Discussion Ice Formation and the Processes Involved In understanding the concepts of ice and snow removal, it is essential to understand the process behind the rationale of ice formation in these structures to further comprehend the rationale behind the mechanics of ice and snow removal. Icing on the airframe of an airplane is deadly, although severity cannot be overemphasized (Andersland and Ladanyi, 2004 p. 242). Any accumulation is a situation that must be dealt with immediate concern especially is it has been prior to plane functioning.
The course of action the pilot takes depends upon many factors, including but certainly not limited to whether the airplane has any ice-protection equipment. Normally the water in the air is in a gaseous state, and we refer to it as water vapor. Water vapor will change to the liquid state at a certain temperature (determined by atmospheric conditions) and become visible, and such temperature is considered as the dew point (Eichenberg, 2001 p. 14). When the dew point is lower than the ambient temperature, the vapor remains a gas, and the water molecules may not be evident in the air.
When much vapor is contained in the air that the air cannot hold any more, the humidity has reached or very nearly approached the 100% level (Ashford, Stanton, & Moore, 1997 p. 312). When humidity hits 100 percent, dew point and temperature will be the same, and water vapor will start becoming visible. The formation may evidently become fog, clouds, rain, drizzle, or other forms (Eichenberg, 2001 p. 16). Airplanes can fly just fine through most visible moisture as long as the temperature at the flight level is warm enough that the water do not freeze.
However, when the ambient temperatures are cold enough that the water in the air is already frozen, it generally will not adhere to the airframe: hence, structural icing is not generally a problem in those conditions. Water can exist in the liquid state at temperatures below 32F. It is called super cooled water (Ashford, Stanton, & Moore, 1997 p. 313). The science behind this phenomenon is complex, and it is essential to understand that super cooled water can be present even though the temperature outside the airplane below freezing.
When a droplet of super cooled water hits the airplane, the surface tension on the outside of the droplet breaks (Andersland and Ladanyi, 2004 p. 247). Since the airframe is cold and at or below freezing, if the ambient temperature is likewise, the droplet freezes to the airframe upon impact, and ice forms. Ignore the friction heating that occurs on the leading edges of the airframe, when though the space shuttle gets red hot from friction as it reenters the atmosphere, it will not gain any similar effect in a small airplane (Andersland and Ladanyi, 2004 p.246).
At speeds faster than about 400 knots, ice seldom adheres to airframes, but does not go that fast either. When your light airplane goes through the applicable atmospheric conditions, ice will form on it (Lankford, 2000 p. 64). Airframe icing can also occur when the clouds or other visible moisture and the surface of the airplane are at a temperature slightly warmer than freezing and the water is not super cooled. As water droplets hit the airframe and splatter, they cool slightly (Eichenberg, 2001 p. 16).
Expect airframe ice in temperatures as warm as about 34°—36°F. Ice that forms on the structure of the airplane falls into three classifications: rime, clear, and mixed. Rime ice is cloudy in appearance due primarily to the fact that it contains air entrained within the ice (Ashford, Stanton, & Moore, 1997 p. 312). Clear ice is smooth and much more transparent than is rime because it has little if any air trapped inside. On the other hand, mixed ice is a combination of rime and clear types. The Dangers of Ice and the Rationale for its Removal
Ice and snow removal in air crafts post various risks that may affect the passengers and the crew present especially during flight. Our discussion about the effects of ice on the airframe and dealing with icing encounters assumes that flying an airplane that is not approved for flight into known icing conditions. Only a very few light, single engine airplanes are so approved, while the greatest majority of light planes cannot be flown into icing conditions, either legally or safely (Ashford, Stanton, & Moore, 1997 p. 314).
Accumulations of ice on the airframe do three things, none of which is positive: airfoils change shape, weight is added, and drag increases The worst part of airframe ice is the simple fact that all three negatives act together—you never get just one or two of them (Eichenberg, 2001 p. 16). When ice accumulates, the airplane needs to carry more weight, with a wing that has far less lifting power than it will when clean of ice, and the airplane’s increased drag must be overcome by a propeller that cannot produce its normal thrust, since it is contaminated with ice too (Andersland and Ladanyi, 2004 p.
248). This combination has effects that are exponential in the decreased performance of the airplane. Any amount of Ice on the wings, tail surfaces, and propeller changes the shape of the affected surface. This change of shape changes the airfoil and alters its characteristics. Ice never accumulates exactly the same way twice, so when flying an airplane, not approved for known icing conditions, and get into ice with it (Kazda and Caves, 2007 p. 112).
When a factory seeks certification of an airplane for flight into known icing, any experiments and analyses are performed that do not done for a lightplane, which is not going to be certified for known icing (Ashford, Stanton, & Moore, 1997 p. 313). The manufacturer will do, or contract to have done, what is known as an impingement analysis. This means that, through the use of computer models and scientific analysis, engineers will look at the airfoils and determine where water droplets of certain sizes will affect the leading edge.
After the impingement analysis is completed, the airplane will be flown in natural icing conditions as a part of its certification trials (Vinson, & Rooney, 2006 p. 72). Often, a model of the wing will be put into a wind tunnel that can spray water droplets onto it, and further test the results of the impingement analysis. Moreover, the airplane will be flown behind a tanker that sprays water onto it so the flight test people can see how the entire deicing system works in flight (Eichenberg, 2001 p. 18).
None of these steps is taken when certifying an airplane that will not be approved for flight into known icing (Andersland and Ladanyi, 2004 p. 248). Such is the reason for precarious position when getting into ice in a typical light plane, which has never been tested or certified for known icing. Nobody knows what shape the airfoils will take as Ice builds on them. As the accumulation progresses, the shapes of the wing, tail surfaces, and prop are continually changing (Kazda and Caves, 2007 p. 114).
No one knows the handling qualities, stall speeds, stall characteristics, reduction of prop thrust, or any of the other performance parameters of what is now a totally new and different airplane (Ashford, Stanton, & Moore, 1997 p. 314). Ice adds mass to the entire airframe where it adheres. Mass equals weight; therefore, an airplane encountering ice gets heavier as the ice grows. Ice is also very heavy. Water weighs about 64 pounds per cubic foot, and recall that clear ice will be very close to the weight of water (Andersland and Ladanyi, 2004 p. 246). Rime and mixed ice will be a little lighter, but not by much.
As the buildup occurs, the drag penalty increases, and again the effects grow at exponential rates. Even small parts of the airplane, like radio antennae, once coated with ice, become producers of large amounts of drag (Vinson, & Rooney, 2006 p. 71). Snow and Ice Removal in Ground Areas Occasionally, some will find an airport that will use sand on a runway and other paved areas, but sand can wreak havoc when ingested into turbine engines, it can also be picked up by propellers and heavily abrade them With the increasing jet and turboprop fleets, sand is not used much anymore.
Most airports do a very good job of plowing snow from the areas where airplanes operate (Eichenberg, 2001 p. 16). However, plowing alone cannot remove all of the snow, and is little help at clearing ice from the paved areas. Even though the modern chemicals do some good, a runway cannot be rid of ice like a road can where salt is used. Pilots have to expect and deal with ice on the ground.
University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 20 April 2017
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