Principles of Flight Flashcards
Define viscosity
The property of fluid that causes it to resist flowing
Define friction
The resistence that one surface or object encounters when moving over another
Define pressure
The force applied in a perpendicular direction to the surface of an object
What is the average pressure exerted by the weight of the atmosphere at sea level
14.7 PSI or 1,013.2 millibars
At what altitude is the weight of the atmosphere one-half of what it is at sea-level?
18,000 ft above sea level
What is the standard atmosphere conditions at sea-level?
59ºF or 15ºC and surface pressure of 29.92 hg or 1,013.2 mb
What is the standard temperature lapse rate?
Decrease of 3.5ºF or 2ºC per thousande feet up to 36,000 ft MSL
What is the lapse rate above 36,000 ft MSL?
Constant, up to 80,000 ft MSL
What is the standard pressure lapse rate?
Decrease of 1 hg per thousand feet up to 10,000 ft MSL.
What is pressure altitude?
The height above a standard datum plane, which is a theoretical level where the weight if the atmosphere is 29.92 hg as measured by a barometer.
How can pressure altitude be determined?
- Setting the barometric scale of the altimeter to 29.92 and reading the indicated altitude
- Applying a correction factor to the indicated altitude according to the reported altimeter setting
What is density altitude?
The vertical distance above sea level in the standard atmosphere at which a give density is to be found. Density altitude is pressure altitude corrected for nonstandard temperature.
As air becomes less dense, explain the performance of the aircraft
- Reduces power because the engine takes in less air
- Reduces thrust because the propeller is less effecient in thin air
- Reduces lift becuase the thin air exerts less force on the airfoils (wings)
As the density of the air increases ____
The lower the desity altitude and the aircraft performance increases
As the density of the air decreases ____
The higher the desity altitude and the aircraft performance decreases
A decrease in air density means ___
A high density altitude
A increase in air density means ___
A lower density altitude
How is density altitude determined?
Finding the pressure altitude and then correcting it for non-standard temperature variations
What conditions result in a high density altitude?
- High elevation
- Low atmospheric pressure
- High temperature
- High humidity
What conditions result in a low density altitude?
- Low elevation
- High atmospheric pressure
- Low temperature
- Low humidity
At a lower pressure, the column of air contains a ___
Smaller amount of air
Explain the effect of pressure on density
When air is compressed, a greater amount of air occupy a given volume
Explain the effect of temperature on density
Increasing temperature of air decreases its density
Explain the effect of humidty on density
As water content of the air increases, the air becomes less dense, increasing density altitude
What is Newtan’s First Law
Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impessed on it
Explain Newtan’s First Law in English
Nothing start or stops moving until some outside force causes it to do so
What is Newtan’s Second Law
Force is equal to the change in momentum per change in time. For a constant mass, force equal mass times acceleration
Explain Newtan’s Second Law in English
When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force
What is Newtan’s Third Law
For every action, there is an equal and opposite reaction
Explain Newtan’s Third Law in English
In an airplane, the propeller moves and pushes back the air, the air pushes the propeller in the opposite direction, forward
What is Bernoulli’s Principle?
States that as the velocity of a moving fluid increases, the pressure within the fluid decreases
Explain how lift is generated on the air foil (wings)
- The increase in speed of air on top of the wing produces a drop in pressure on top of the wing (Bernoulli’s Principle)
- The downward, backward flow from the top surface of an airfoil creates a downwash
- The downwash meets the flow from the bottom of the airfoil at the trailing edge
- The reaction of this donward backward flow results in an upward force on the airfoil (Newtan’s Third Law)
