What is QNE?
The height that will be displayed if on the ground with SPS (1013.25) set on the altimeter
What happens to pressure as altitude increases?
What does an altimeter measure?
Vertical distance above MSL altitude = height + elevation
Vertical distance above a specified datum (e.g. what is the height of B?)
Altitude of a fixed object (e.g. an airfield)
Define flight level
A level measured from SPS (1013.25). e.g. FL60 or FL250
When will flight level and true altitude be the same?
MSL pressure is the same as ISA (1013.25)
What is density altitude?
Pressure altitude / flight level adjusted for temperature (i.e. true altitude) If ISA temp +, density altitude is higher. If ISA temp -, density altitude is lower
How do you work out the pressure lapse rate?
96 x Temp (k) ___________ Pressure (hPa)
What setting is the altimeter set to during take-off and initial climb?
During flight, when is the altimeter changed from QNH and what is it changed to?
Changed from QNH on approaching the transition altitude and changed to SPS (1013.25)
What is the transition altitude?
The altitude at or below which the vertical position of the aircraft is controlled with reference to altitude (i.e. 2,500 ft instead of FL120)
What must the altimeter be set to when flying above the transition altitude?
Why do aircraft above the transition level fly with SPS (1013.25) set?
To ensure safe separation from other aicraft
During flight, when is the altimeter changed from SPS (1013.25) and what is it changed to?
Changed from SPS (1013.25) when descending below the transition level, and changed to airfield QNH.
During approach and landing, what would the altimeter normally be set to?
What is indicated altitude?
Altitude reading on the altimeter
What is true altitude?
The actual altitude of the aircraft with barometric and temperature subscale errors accounted for
At or around MSL, how can barometric subscale errors be adjusted?
27 ft / hPa pressure lapse at MSL 27 x (QNH - subscale)
How do you calculate QNH?
If QFE is above MSL: QFE + Elevation (ft) __________ 27 If QFE is below MSL: QFE - Elevation (ft) _________ 27
What is the transition level?
The lowest flight level available for use above the transition altitude
What is the transition layer?
The layer between the transition altitude and transition level (usually 500 ft)
Does the transition altitude for a given location always have a set value?
Who sets the transition level?
ATC is responsible for ensuring the transition level is always above the transition altitude
May you ever fly level in the transition layer?
What happens to density in colder air?
What happens to density in warmer air?
What happens to pressure levels in colder air?
What happens to pressure levels in warmer air?
What happens to indicated altitude in colder air?
Stays the same
What happens to true altitude in colder air?
What happens to indicated altitude in warmer air?
Stays the same
What happens to true altitude in warmer air?
What happens to surface pressure in colder air?
Remains the same
What happens to surface pressure in warmer air?
Remains the same
Calculate temperature subscale error
4 x Altitude (ft) x ISA-D ________ 1,000 ALWAYS CORRECT BARROMETRIC ERROR PRESSURE FIRST
What is the subscale error rhyme?
4 x T (thousands of feet) x ISA-D, to end with true, end with T (temp)
What is the relationship between QNH and QFF
Where OAT warmer than ISA, QNH > QFF REMEMBER: not hotter, not higher REMEMBER it is reversed when below MSL