1. Air is fluid
Viscosity
air and liquid has viscosity, different flow rate
due to their different viscous.
Friction
friction exists between two materials that
contact each other, the boundary layer on the
wing caused by friction.
Pressure
the force applied in a perpendicular direction
to the surface. High concentration flows to low
concentration.
the force is exerted equally in all directions,
and effect on bodies within the air is call
pressure.
the weight of the atmosphere at 18,000 ft is
one-half what it is at sea level.
pressure will changed due to time and location.
2. Atmospheric Pressure
air has mass, and is affected by
attraction of gravity, it has weight,
then it has force.
standard atmosphere at sea level is a surface
pressure of 1013.2 mb, and surface temperature
is 15 Celsius.
a standard temperature lapse rate is when the
temperature decrease at the rate of 2 Celsius
per 1000 ft up to 36,000 ft, which at about -55
Celsius.
a standard pressure lapse rate is when the
pressure decreases at the rate of 1 Hg per 1000
ft, gain to 10,000 ft.
1. power, because the engine takes in less air.
the density of air effects on the
aircraft's performance
2. thrust, because a propeller is less efficient in
thin air.
3. lift, because the thin air exerts less force on
the airfoil.
high density altitude with high elevations, low
pressures, high temperatures and high humidity.
4 Principles of flight
3. Density altitude
effect of pressure on density
density is proportional to pressure, at a
constant temperature.
effect of temperature on density
temperature converses to pressure, at a
constant pressure.
water vapor is lighter than air, moist air is lighter
than dry air.
humidity refers to the amount of water vapor
contained in the atmosphere, and is expressed
as a percentage of the maximum amount of
water vapor the air can hold.
effect of humidity (moisture) on
density
warm air holds more water vapor, while cold air
holds less.
100% of humidity is called saturated air
humidity is not really important factor in
calculating density altitude and aircraft
performance, but it is a contributing factor.
According to Newton's Third Law: for every
action, there is an equal and opposite reaction.
4. Theories in the production of lift
how airplane can fly based on
Newton's basic law of motion and
Bernoulli's principle of differential
pressure.
the force of equal and opposite reaction
pushes against the engine and forces the
airplane forward.
Bernoulli's Principle states that as the velocity
of a moving fluid increases, the pressure with
the fluid decrease.
5. Airfoil design
6. Pressure distribution
a positive pressure lifting action from
the air mass below the wing, and a
negative pressure lifting action from
lowered pressure above the wing.
leading edge flaps and trailing edge flaps,
when extended from the basic wing structure,
change the airfoil shape into the classic
concave form, thereby generating much greater
lift during slow flight conditions.
the downward backward flow from
the top surface of an airfoil creates
a downwash, and meets the flow
from the bottom of the airfoil at the
trailing edge.
applying Newton's Third Law, this reaction
results in an upward forward force on the airfoil.
aerodynamic force acts through the
center of pressure (CP).
high AOA, the position of the CP moves forward
while at low AOA the CP moves aft.