Thread: QNH or QFE ?
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Old 11th Aug 2018, 15:39
  #60 (permalink)  
Join Date: Nov 2005
Location: River Thames & Surrey
Age: 70
Posts: 7,872
Originally Posted by chevvron View Post
The altitude encoder transmits a reading based on 1013.2 hpa which is then converted by the radar display on the ground which has the current QNH fed into it and updated when necessary.
It is a requirement that the controller MUST cross check what you see on your altimeter with what is displayed on the SSR label; a +/- 200ft difference is allowed.
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