Principles of Flight Flashcards
1
Q
Air as a fluid
A
- fluids = take the shape of their container and do not resist deformation
- ability to flow
2
Q
Viscosity
A
- property of a fluid that causes it to resist flowing
- high = thick/higher resistance (oil)
- low = thin/lower resistance (water)
- air has very little viscosity
3
Q
Friction
A
- resistance that one object encounters when moving over another
- surface of wing is rough on the microscopic level, causing friction with air
4
Q
Boundary layer
A
- air molecules stick to surface of the wing due to friction
- air molecules near the surface of the wing resist motion and have a relative velocity of zero
- layer of air that sticks to the wing is called the boundary layer
- after boundary layer is formed, friction further increases due to air’s tendency to stick to itself
- when these 2 forces meet = drag
5
Q
Pressure
A
- force applied in a perpendicular direction to the surface of an object
- moves from high to low
6
Q
Atmospheric Pressure
A
- responsible for weather, lift, flight instruments
- air is very light, but still affected by gravity which means it has a weight (force)
- because air is fluid, force acts equally in all directions
- at sea level = 14.70 PSI
- air pressure decreases with altitude
7
Q
Standard Pressure
A
- created because air pressure changes with time and location
- 29.92 inches of mercury and 15° F
8
Q
Standard Temperature Lapse Rate
A
- decrease of 2° C every 1,000 feet up to 36,000 feet
- above 36,000 = constant
9
Q
Standard Pressure Lapse Rate
A
- decrease of 1 “Hg every 1,000 feet up to 10,000 feet
- referred to a ISA
- aircraft instruments are calibrated for standard atmosphere
10
Q
Pressure Altitude
A
- height above the standard datum plane, theoretical level where weight of the atmosphere is 29.92
- achieved by setting altimeter to 29.92
- important for performance calculations
- all aircraft above 18,000 feet use pressure altitude
11
Q
Density Altitude
A
- pressure altitude corrected for non standard temperature
- less dense air causes decreased lift (thinner air exerts less force on wings), decreased power (less air molecules in the engine, decreased thrust (propellers are less efficient)
- hot day = high DA/worse performance, aircraft “feels” like flying at higher altitude, high elevation, high temperature, low atmospheric pressure, high humidity
- cold day - low DA/better performance, aircraft “feels” like flying at lower altitude, low elevation, low temperature, high atmospheric pressure, low humidity
12
Q
Effect of Pressure on Density
A
- density is directly proportional to pressure
- if pressure is doubled = density is doubled
13
Q
Effects of Temperature on Density
A
- temperature is inversely proportional to pressure
- decreasing temperature increased pressure
14
Q
Effects of Humidity on Density
A
- humidity = amount of water vapor in the air
- water vapor is lighter than air = moist air is lighter than dry air = moist air is less dense than dry air
- high humidity = decreased performance
15
Q
Most dense air type vs. least dense air type
A
- most dense = cold dry
- least dense = warm and moist
16
Q
Newton’s 3 Laws of Motions
A
- an object in motion will stay in motion unless acted on by an outside force, an object at rest will stay at rest unless acted on by an outside force
- F = MA
- for every action there is an equal and opposite reaction
17
Q
Bernoulli’s Principle
A
- as the velocity of a fluid increases, its pressure decreases
18
Q
Airfoil Design
A
- airfoil = structure that creates an aerodynamic force when interacting with moving air
- designed to take advantage of Newton’s laws as well as Bernoulli’s principle
19
Q
Camber
A
- curvature of the wing
- large camber = large curve
- small camber = little to no curve
