101-3 Pressure & Altimetry Flashcards
Two types of barometers
- Mercurial
- Aneroid
QFE
Station Pressure
Actual pressure @ field elevation or wx station
QNH
Altimeter Setting
Sea-level pressure value to which the scale of the altitude is set
Pressure Variation
Pressure lapse rate is 1” hg / 1000’
Only up to 10K, slows past that point
Pressure drops faster in cold air (i.e. faster than 1”/1000’
True Altitude
(TA)
actual altitude above MSL
I.e. Field elevation of airport
Absolute Altitude
Actual altitude above terrain
Indicated altitude
Altitude above MSL as indicated on the altimeter when using the local altimeter setting (below 18,000)
Altimetry Rule 1
When flying HIGH to LOW = Look out below
*the aircraft is lower than the altimeter says
TA < IA
Altimetry Rule 2
When flying LOW to HIGH = reach for the sky
*aircraft is higher than altimeter says
TA > IA
Flying at 14000 @ 29.72
Land at airport w/ elevation of 3000’ @ 29.52 (QNH)
What is IA after landing?
3200 IA
DA relation to PA
- If the atmosphere is warmer than std = DA > PA
-if the atmosphere is colder than std = DA < PA
Pressure Altitude
Altitude indicated on the altimeter when using 29.92” hg as the setting
Density Altitude
Pressure altitude corrected for non-standard temperature
Characteristics of High Density Altitude
Low air density
Decreased performance
Decreased climb rate
Increased take off roll/ray
*Less Dense
*found at high elevation airports
*not good
*High Temp & Low Pressure
Characteristics of Low Density Altitude
High Air density (more dense)
Increased performance
Increased climb rate
Decreased take off roll/RWG
*Low temp + High Pressure
