Principles of Flight

Question 1

Are gases, like air, considered fluids?

Answer 1

Yes

Question 2

Viscosity is the property of a fluid that causes it to…

Answer 2

resist flowing.

Question 3

High-viscosity fluids are “thick” and resist flow; low-viscosity fluids are “thin” and flow easily. Air has a ____ viscosity and flows ________.

Answer 3

low

easily

Question 4

Friction is the…

Answer 4

resistance that an object feels when it moves over another object

Question 5

The layer of molecules that adhere to the wing surface due to friction is called what?

Answer 5

Boundary layer

Question 6

Once the boundary layer of air adheres to the wing by ________, further resistance to the airflow is caused by the viscosity, the tendency of air to ______ to itself. When these two forces act together to resist airflow over a wing, it is called ______.

Answer 6

friction
stick
drag

Question 7

Pressure, in physics terms, is the force applied in a ___________ direction to the surface of an object. If the pressure on one surface of the object becomes less than the pressure exerted on the other surfaces, the object will move in the direction of the _______ pressure.

Answer 7

perpendicular

lower

Question 8

Under standard conditions at sea level, the average pressure exerted by the weight of the atmosphere is approximately ____, or ______.

Answer 8

14.7 psi

1013.2 millibars (mb)

Question 9

The ICAO Standard Atmosphere, or International Standard Atmosphere (ISA), is ____ and a surface pressure of ______.

The standard lapse rate is when termperature decreases ____ per ______ and pressure decreases ____ per ______.

Any temperature or pressure that differs from the standard lapse rates is considered…

Answer 9

15* C
29.92 inches of mercury (“Hg)

2* C per 1,000’
1 ”Hg per 1,000’

nonstandard temperature and pressure.

Question 10

All aircraft instruments are calibrated for the ________ ___________.

Answer 10

standard atmosphere

Question 11

The density of air has significant effects on the aircraft’s performance because as air becomes less dense it reduces:
- ______ because the engine takes in _____ air
- ______ because a propeller is _____ efficient in thin air
- _____ because the thin air exerts ____ force on the airfoils

Answer 11

Power
less

Thrust
less

Lift
less