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Thread: About the altimeter setting
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Old 9th April 2016 | 21:18
  #55 (permalink)  
fireflybob
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QNH is atmospheric pressure at aerodrome level reduced to sea level assuming an ISA temp lapse rate (1.98 deg C per 1,000ft)

QFF is atmospheric pressure at aerodrome level reduced to sea level assuming isothermal conditions (i.e. constant temp). Isobars are lines joining places of equal QFF.
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