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Cyclic & Collective > Ch. 5 Air, Wind, & Weather > Flashcards

Ch. 5 Air, Wind, & Weather Flashcards

1
Q

What is correctly known as the distance above the ground?

A

Height

Height is taken from Above Ground Level (AGL)

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2
Q

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

A

Altitude

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3
Q

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 _____.

A

Saturated; 100%

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4
Q

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

A
  • At sea level
  • Air temperature of 15 degrees C (59F)
  • Air pressure is 29.92” (mercury)
  • Assumed no wind or water vapor
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5
Q

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?

A

Indicated Air Speed (IAS)

IAS is read on the airspeed indicator instrument

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6
Q

_____ is the rate of change in temperature with altitude.

A

Lapse rate

It is how quickly rising air cools

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7
Q

What is the standard lapse rate?

A

1.98C per 1000’

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8
Q

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

A

Pressure altitude

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9
Q

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

A

More

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10
Q

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?

A

Dew point

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11
Q

What is density altitude?

A

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

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12
Q

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

A

1,000

Standard barometric pressure is 29.92” of mercury.

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13
Q

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

A
  • 500’

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

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14
Q

Aircraft performance is poorer under what conditions?

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

3 highs, 1 low

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15
Q

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.

A

Higher

Aircraft performance is poorer at higher temperatures & altitudes.

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16
Q

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

A

Power

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

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17
Q

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

A

Less

High density altitude = thinner air

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18
Q

Define relative humidity

A

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

19
Q

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

A

Low

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

Don’t get confused with the terms

20
Q

As humidity increases, density altitude _____.

A

Increases

21
Q

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

A

1,000’

22
Q

What term describes rain falling but not hitting the ground?

A

Virga

23
Q

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

A

Calibrated Airspeed (CAS)

IAS = Indicated Airspeed

24
Q

True Air Speed (TAS) is what?

A

CAS corrected for non-standard temperature & pressure

TAS is the real airspeed

25
Q

Which port measures both static & dynamic pressure?

A

Pitot tube (or port)

26
Q

Static ports measure _____ pressure that is independent of motion.

A

Static

Air has mass & always exerts a force.

27
Q

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

A

Decrease

28
Q

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

A

Airspeed Indicator (ASI)

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

29
Q

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

A

10-15 knots

30
Q

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 _____.

A

Downwind

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

31
Q

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

A

10 - 15 knots

32
Q

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

A

15

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

33
Q

Moored boats & seaplanes normally point _____.

A

Into the wind (unless anchored at both ends)

34
Q

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

A

10 - 15 knots

35
Q

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.

A

Upwind; downwind

Such as when hovering over grass.

36
Q

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

A

Slower

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

37
Q

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

A

Lee

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

38
Q

Birds always takeoff & land into the _____.

A

Wind

39
Q

What is upslope flow?

A

Air that flows toward higher terrain & hence, forced to rise.

If this is strong enough, thunderstorms can develop.

40
Q

What is wind shear?

A

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.

41
Q

What are the 4 common sources of wind shears?

A
  1. Frontal activity (front = change in weather)
  2. Thunderstorms
  3. Temperature inversions (small layer/gap of warm air sandwiched between cold)
  4. Surface obstructions
41
Q

What are the 4 common sources of wind shears?

A
  1. Frontal activity (front = change in weather)
  2. Thunderstorms
  3. Temperature inversions (small layer/gap of warm air sandwiched between cold)
  4. Surface obstructions
42
Q

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.

A

5,400’

The pressure is lower, so the pressure altitude is higher.

AMSL: Above Mean Sea Level

43
Q

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.

A

Less

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

Cyclic & Collective (6 decks)

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