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Week 3 > Atmospheric Density > Flashcards

Flashcards in Atmospheric Density Deck (21)
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1
Q

More humid air, more

A

Water vapour

2
Q

Low density air is better or worse for aircraft?

A

Worse. Reduced ac performance. Risk terrain impact. More Rwy distance required.

3
Q

Density is

A

Mass of air within a given volume

4
Q

What affects density?

A

Temperature, pressure & humidity

5
Q

density altitude formula

A

ISA dev x 120=… (above or below the pressure altitude)

Pressure altitude = indicated altitude with 1013hPa set in subscale.

6
Q

Humidity is & what does it do?

A

Water vapour
& it
Drives weather

7
Q

Latent heat absorbed & released example

A

Ice to gas

Gas to ice

8
Q

Sublimation

A

Phase change from solid to gas or from gas to solid.

9
Q

Condensation relies on:

A

Condensation nuclei to bind to.

If no c nuclei, moisture droplets.

Cloud condensation nuclei

10
Q

Saturation

A

Only happens when air contains maximum amount of water vapour.

11
Q

Cold air can hold less water than warm air because:

A

Because cold air is more compact

12
Q

Humidity units

A

Absolute Humidity (AH)

Humidity Mixing Ratio (HMR)

13
Q

AH

Absolute Humidity

A

amount of water vapour in volume of air

G/m^3

14
Q

Humidity Mixing Ratio

HMR

A

How much air & water mixed together.

15
Q

Dew point

A

Temperature you must cool air at, for it to become saturated. (At constant pressure).

16
Q

Dew point lapse rate

A

-0.5⚫️C per 1000ft upwards

17
Q

TEMP & DP close together

A

Cloud / fog likely to form.

18
Q

Cloud base formula

A

(T-Dp) x 400

19
Q

You measure humidity using:

A

Psychrometer = Wet & dry bulb thermometer
(Evaporation from wet bulb causes temp to drop)
Find this in the Stevenson screen

20
Q

Relative Humidity formula

A

Actual water vapour content (wvc)
————————————————- x100
Saturated water vapour content (SWVC)

WVC=what’s actually in the air
SWVC = what it could hold

21
Q

Temperature on RH

RH increases with a

A

Decrease in temperature