Page 104 - ภาษาอังกฤษสำหรับสายวิทยาการอุตุนิยมวิทยา
P. 104
99
SECTION 2. ICING
l. General
a. Aircraft icing affects an aircraft's flight characteristics. When icing is severe, it can cause an
aircraft to be unable to continue flying. Ice that forms on the outside surfaces of an aircraft
increases the weight of the aircraft and changes the shape of surfaces on which it forms.
Icing can also occur in the engine equipment that leads outside atmospheric air to the
engine. Icing inside these parts reduces the flow of air to the engine. The amount of air
entering the engine can be so reduced that the engine can no longer produce the required
power or it stops completely. Icing is so dangerous to aircraft that many aircraft have
equipment to prevent: the formation of ice.
b. Four forces act on flying aircraft: the downward force, weight; the downward force, lift;
the resistance of the air, drag; and the force oves it forward, thrust. Icing affects all four fo It
decreases the lifting force as increases the weight of the aircraft. result of the extra weight
and the change of shape of the lif surfaces. on surfaces causes changes in the flow of air
around aircraft and results in increased drag. The decrease in lift and the increases in drag
and weight result in a decrease in the forward movement produced by thrust.
2. Structural Icing
The ice that forms on the outside surfaces of the aircraft is clas- sified as structural icing. The
rate of structural ice accumulation is affected by the shape, size, speed through the air, and
angle to the air of the stiucture, such as the wing. Some aircraft are less affected by ice than
otgers, but ice affects the flying performance of all arcraft. Although ice may form on any
exposed surface of the aircraft, ice on structures such as the wings has the largest effect on
flight character- istics. Two conditions are enecessary for serious ice accumulation on aircraft:
