Atmospheric Density Flashcards
More humid air, more
Water vapour
Low density air is better or worse for aircraft?
Worse. Reduced ac performance. Risk terrain impact. More Rwy distance required.
Density is
Mass of air within a given volume
What affects density?
Temperature, pressure & humidity
density altitude formula
ISA dev x 120=… (above or below the pressure altitude)
Pressure altitude = indicated altitude with 1013hPa set in subscale.
Humidity is & what does it do?
Water vapour
& it
Drives weather
Latent heat absorbed & released example
Ice to gas
Gas to ice
Sublimation
Phase change from solid to gas or from gas to solid.
Condensation relies on:
Condensation nuclei to bind to.
If no c nuclei, moisture droplets.
Cloud condensation nuclei
Saturation
Only happens when air contains maximum amount of water vapour.
Cold air can hold less water than warm air because:
Because cold air is more compact
Humidity units
Absolute Humidity (AH)
Humidity Mixing Ratio (HMR)
AH
Absolute Humidity
amount of water vapour in volume of air
G/m^3
Humidity Mixing Ratio
HMR
How much air & water mixed together.
Dew point
Temperature you must cool air at, for it to become saturated. (At constant pressure).
