Ch. 5 Air, Wind, & Weather

Question 1

What is correctly known as the distance above the ground?

Answer 1

Height

Height is taken from Above Ground Level (AGL)

Question 2

What is the distance above Mean Sea Level (MSL)?

Answer 2

Altitude

Question 3

When a volume of air has all the water vapor it can handle at that particular temperature, it is said to be _____ & the relative humidity is _____.

Answer 3

Saturated; 100%

Question 4

What is the ISA (International Standard Atmosphere) “standard day”?

Answer 4

• At sea level
• Air temperature of 15 degrees C (59F)
• Air pressure is 29.92” (mercury)
• Assumed no wind or water vapor

Question 5

What type of airspeed is the measure of the difference between the static air pressure & the total pressure of the air entering the pitot tube?

Answer 5

Indicated Air Speed (IAS)

IAS is read on the airspeed indicator instrument

Question 6

_____ is the rate of change in temperature with altitude.

Answer 6

Lapse rate

It is how quickly rising air cools

Question 7

What is the standard lapse rate?

Answer 7

1.98C per 1000’

Question 8

_____ is altitude measured against a standard barometric condition of 29.92” of mercury.

Answer 8

Pressure altitude

Question 9

Cold air is _____ (more/less) dense than warm air.

Answer 9

More

Question 10

What is the temperature where a body of air will be saturated & water vapor will start to fall out of the air, & clouds will form?

Answer 10

Dew point

Question 11

What is density altitude?

Answer 11

It is the measure of the density of air corrected for ambient temperature.

Question 12

Pressure decreases at a rate of 1” per _____’ of altitude gain.

Answer 12

1,000

Standard barometric pressure is 29.92” of mercury.

Question 13

A barometric pressure of 30.42” at sea level gives a pressure altitude of _____’.

Answer 13

• 500’

30. 42” is higher than standard, so the pressure altitude is lower.

Question 14

Aircraft performance is poorer under what conditions?

Answer 14

• Higher altitudes
• Higher temperatures
• Higher humidity
• Lower pressure

3 highs, 1 low

Question 15

When temperature is _____ (higher/lower), the aircraft performs as if it’s at a higher altitude & is said to be at a higher density altitude.

Answer 15

Higher

Aircraft performance is poorer at higher temperatures & altitudes.

Question 16

Understanding density altitude is important because it affects the _____ required by any airframe in nearly every situation.

Answer 16

Power

Density altitude doesn’t have the same effect on turbine engines compared to piston.

Question 17

The higher the density altitude, the _____ (more/less) lift the blades will produce with everything else being equal.

Answer 17

Less

High density altitude = thinner air

Question 18

Define relative humidity

Answer 18

The percentage of moisture that air holds relative to the amount it can hold.

Question 19

High density or a lot of molecules of air per cubic feet is a _____ density altitude.

Answer 19

Low

Whereas low density (fewer molecules) is high density altitude.

Don’t get confused with the terms

Question 20

As humidity increases, density altitude _____.

Answer 20

Increases

Question 21

A good rule of thumb is in high humidity & high temperatures, add _____’ to the density altitude.

Answer 21

1,000’

Question 22

What term describes rain falling but not hitting the ground?

Answer 22

Virga

Question 23

What is the airspeed after the IAS is corrected for errors due to the position of the pitot & static ports?

Answer 23

Calibrated Airspeed (CAS)

IAS = Indicated Airspeed

Question 24

True Air Speed (TAS) is what?

Answer 24

CAS corrected for non-standard temperature & pressure

TAS is the real airspeed

Question 25

Which port measures both static & dynamic pressure?

Answer 25

Pitot tube (or port)

Question 26

Static ports measure _____ pressure that is independent of motion.

Answer 26

Static Air has mass & always exerts a force.

Question 27

As altitude increases, pressure & density decrease, resulting in a _____ of static pressure.

Answer 27

Decrease

Question 28

Only the _____ uses both dynamic & static pressure to calculate a reading.

Answer 28

Airspeed Indicator (ASI) Vertical Speed Indicator (VSI) & altimeter use only static pressure.

Question 29

Windsocks indicate a relative wind strength when fully stuck out. Varying from _____ to _____ knots.

Answer 29

10-15 knots

Question 30

Most deciduous trees turn their leaves in a strong wind so the silvery-colored underside shows: if you can see this, you are probably heading _____.

Answer 30

Downwind If the leaves look normally green, you're probably flying into the wind.

Question 31

With wind strong enough & grass long enough, grass can show waves like water. The wind needs to be _____ to _____ knots for this to happen.

Answer 31

10 - 15 knots

Question 32

Whitecaps on water means the wind is probably at least _____ knots.

Answer 32

15 Waves will be hitting the shore at the downwind side & may show shadows (smooth, unruffled surface) on the upwind (lee) side.

Question 33

Moored boats & seaplanes normally point _____.

Answer 33

Into the wind (unless anchored at both ends)

Question 34

A 45 degree angle of smoke rising from a small to moderate wood fire shows about _____ to _____ knots of wind.

Answer 34

10 - 15 knots

Question 35

The downwash pattern of the helicopter can indicate wind direction. If visible, the downwash will be shortened on the _____ (upwind/downwind) end & stretch out a long way behind on the _____ (upwind/downwind) side.

Answer 35

Upwind; downwind Such as when hovering over grass.

Question 36

When approaching to land, expect the wind speed close to the ground to be _____ (faster/slower) than at 100' AGL.

Answer 36

Slower A sudden drop-off of wind speed close to the ground is because friction decreases as height above ground increases.

Question 37

Trees shelter the area downwind from the wind & induce downdrafts in their immediate _____.

Answer 37

Lee Lee = sheltered side of something or side away from the wind

Question 38

Birds always takeoff & land into the _____.

Answer 38

Wind

Question 39

What is upslope flow?

Answer 39

Air that flows toward higher terrain & hence, forced to rise. If this is strong enough, thunderstorms can develop.

Question 40

What is wind shear?

Answer 40

Change in wind speed and/or direction over a short distance. This change can be horizontal or vertical & is most often associated with strong temperature inversions or density gradients.

Question 41

What are the 4 common sources of wind shears?

Answer 41

1. Frontal activity (front = change in weather) 2. Thunderstorms 3. Temperature inversions (small layer/gap of warm air sandwiched between cold) 4. Surface obstructions

Question 41

What are the 4 common sources of wind shears?

Answer 41

1. Frontal activity (front = change in weather) 2. Thunderstorms 3. Temperature inversions (small layer/gap of warm air sandwiched between cold) 4. Surface obstructions

Question 42

At 5,000’ AMSL, (taken from a map elevation & set on the altimeter) the pressure is found to be 29.52”, so the pressure altitude would be _____’ if 29.92” were set on the sub-scale altimeter.

Answer 42

5,400’ The pressure is lower, so the pressure altitude is higher. AMSL: Above Mean Sea Level

Question 43

Humidity decreases the density of a volume of air because the mass of a molecule of water vapor is _____ than the average mass of the gases that make up air.

Answer 43

Less Adding water vapor displaces other gases, decreasing the overall weight per unit volume.