Pressure Altimeter Flashcards
(21 cards)
Why do we use an altimeter
Terrain avoidance
Aircraft separation
Performance indicator
Land (esp in poor weather)
Important conversion for m - ft
1m = 3.28ft
How does a pressure altimeter work
It converts pressure changes into a mechanical movement
What is an aneroid capsule
A small flexible chamber which contains a vacuum or very low presshre
How is the altimeter calibrated
To give a linear representation of the non linear atmospheric distribution, it uses ISA as its calibration conditions
What are the 5 main components of a simple altimeter
Aneroid capsule
Leaf spring
Gearing
Pointer
Casing
What are the advantages of a servo altimeter
Improved accuracy at higher altitudes
The friction in conventional linkage if reduced
Digital readout/ warnings are incorporated
What is the difference between a simple and sensitive altimeter
The sensitive one has more aneroid capsules
What are the three different types of display
Three point altimeter
Counter drum altimeter
EFS- electronic flight system
What is QFE
The pressure observed at the airfield elevation if you were standing on it now
If QFE is set the altimeter will read 0 on the ground
What is QNH
The QFE plus the pressure difference due to the elevation of the airfield from mean sea level
If QNH is set then altimeter will read the elevation from sea level when on ground
What SPS
Standard pressure setting which is used by all aircraft after the transition layer of the atmosphere
1013.25hPa
What is height
The vertical distance above a datum or the vertical dimension of an object
(QFE set for height above an aerodrome)
What is altitude
The vertical distance above Mean Sea Level
(QNH set)
What is indicated altitude
The altitude indicated on the altimeter which assumes ISA conditions (doesn’t take into account temp variations)
What is true altitude
The indicated altitude corrected for temp variations from ISA conditions
What is pressure altitude
The surfaces of constant pressure which are separated by specific pressure intervals
RADALT is what
The height above the surface immediately below using a radio altimeter
What is density altitude
The height in ISA conditions that has density corresponding to the actual density now
DP = PA +/- (120ft x 1°C change from ISA)
If temps are colder than ISA what do you do to pressure altitude
Subtract from it
If temps are warmer than IsA what do you do to pressure altitude
Add to it
