Principles of Flight Flashcards
What is the atmosphere and how is it made up?
The atmosphere is an envelope of air that surrounds the Earth and rests upon its surface. The atmosphere is composed of 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases, such as argon or helium.
What is viscosity?
Viscosity is the property of a fluid that causes it to resist
flowing. High-viscosity fluids are “thick” and resist flow;
low-viscosity fluids are “thin” and flow easily. Air has a low
viscosity and flows easily.
What is the average pressure exerted by the weight of the atmosphere?
Under standard conditions at sea level, the average pressure exerted by the weight of the atmosphere is approximately 14.70 pounds per square inch (psi) of surface, or 1,013.2
millibars (mb).
The thickness of the atmosphere is limited;
therefore, the higher the altitude, the less air there is above. For this reason, the weight of the atmosphere at 18,000 feet is one-half what it is at sea level.
What is the standard atmosphere at sea level?
The standard atmosphere at sea level is a surface temperature of 59 °F or 15 °C and a surface pressure of 29.92 inches of mercury (“Hg) or 1,013.2 mb.
Standard temperature lapse rate is?
Standard temperature lapse rate is when the temperature
decreases at the rate of approximately 3.5 °F or 2 °C per thousand feet up to 36,000 feet, which is approximately –65
°F or –55 °C. Above this point, the temperature is considered constant up to 80,000 feet.
A standard pressure lapse rate is?
A standard pressure lapse rate is when pressure decreases at a rate of approximately 1 “Hg
per 1,000 feet of altitude gain to 10,000 feet.
What is Pressure Altitude?
Pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.92 “Hg (1,013.2 mb) as measured by a barometer.
How is Pressure Altitude determined?
The pressure altitude can be determined by one of the following methods:
1. Setting the barometric scale of the altimeter to 29.92and reading the indicated altitude
2. Applying a correction factor to the indicated altitude according to the reported altimeter setting
Density Altitude is?
Density altitude is the vertical distance above sea level in the standard atmosphere at which a given density is to be found. Density altitude is pressure altitude corrected for nonstandard temperature.
How does density of air affect aircraft performance as the air becomes less dense?
The density of air has significant effects on the aircraft’s performance because as air becomes less dense, it reduces:
* Power because the engine takes in less air
* Thrust because a propeller is less efficient in thin air
* Lift because the thin air exerts less force on the airfoils
As the density of the air increases what happens to aircraft performance?
As the density of the air increases (lower density altitude), aircraft performance increases; conversely as air density decreases (higher density altitude), aircraft performance decreases. decrease in air density means a high density altitude; an increase in air density means a lower density altitude. Density altitude is used in calculating aircraft performance because under standard atmospheric conditions, air at each level in the atmosphere not only has a specific density, its pressure altitude and density altitude identify the same level.
How is density altitude determined?
Density altitude is determined by first finding pressure altitude, and then correcting this altitude for nonstandard temperature variations.
Air density is affected by changes in altitude, temperature, and humidity.
Air density is affected by changes in altitude, temperature, and humidity. High density altitude refers to thin air, while low density altitude refers to dense air. The conditions that result in a high density altitude are high elevations, low atmospheric pressures, high temperatures, high humidity, or some combination of these factors. Lower elevations, high atmospheric pressure, low temperatures, and low humidity are more indicative of low density altitude.
How does Temperature affect Density?
Increasing the temperature of a substance decreases its density. Conversely, decreasing the temperature increases the density. Thus, the density of air varies inversely with temperature. This statement is true only at a constant pressure. In the atmosphere, both temperature and pressure decrease with altitude and have conflicting effects upon density.
