PPRuNe Forums - View Single Post - QNH, QFE?, density & pressure alts.
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Old 5th Feb 2003, 18:44
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Chilli Monster
 
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Lump Jockey

You might want to read up on some abbreviations

KIAS - Knots indicated AIR speed.

The only time that can be the same as the Ground speed is when there is zero headwind / tailwind component. Therefore the Ground speed in your post just needs to be referred to as knots.

As for pressure and density altitude. Pressure altitude is based on ISA (international Standard Atsmosphere). Air Density however is also affected by temperature - the hotter the temperature the lower the air density. Not very important in the UK but at hot and high airfields where you can have field elevations of 4000ft with a high outside air temperature your density altitude can be in the region of 5-6000ft. Makes for extremely long take off runs and very slow climb performance.
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