Pressure And Altimetry Flashcards
(17 cards)
What are the 5 different altimeter subscale settings
QFE, QNH, QFF, SPS, RQNH
You are 120 ft above MSL and QFE is set, what will the altimeter read
Zero Feet
You are on an airfield at 150ft elevation, you have QNH set. What will the altimeter read?
Elevation of airfield = 150ft
Where does temp error occur
Any altitude above airfield elevation/ starting point
If SPS (1013hPa) is set then what will the altimeter be reading
The pressure altitude at that flight level from MSL
Where can QFE, QNH, QFF be the same
On an airport at MSL
What is variable surface pressure and how does it effect altitude
If you maintain a constant altitude on the altimeter then
True altitude will increase when flying towards a surface with a higher pressure
LOW to HIGH look to the SKY
What happens if air temp varies from ISA
Colder then True Alt is LOWER
Warmer then True Alt is HIGHER
Temp error correction equation
4 x (°C change from ISA) x (1000s of feet)
If flying through a valley how does the venturi effect the pressure
There will be a reduction in static pressure so the altimeter will over read
Therefore you will be lower than indicated = danger
If you fly over a hill with a constant altimeter reading what acc happens
It will descend in terms of true height
Because…
The air flow speeds up over the hill causing a venturi effect, so altimeter will over read, so a descent correction might occur
Surface wind us…
The contanst movement over wind over the surface measured at 10m above the ground
What’s an isobar
A line on a chart that connects two places of equal atmospheric pressure
The same QFF
What is a col
A point that lies in between two high or two low pressure areas
As there is no temp gradient at this point then strong winds cannot occur
What does High to Low look out Below mean
Then moving from an area of high pressure to low pressure then the altimeter will over read so you think you are higher than you are
Could crash!
