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Old 14th Sep 2017, 16:30
  #37 (permalink)  
whowhenwhy
 
Join Date: Oct 2001
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The 'unelected few who rule the industry' come from a variety of aviation related organisations including airlines, civil ANSPs (not just you know who), MOD, GA and the CAA. They receive briefing papers on the subjects to be discussed ahead of the meeting and you'd hope that they might discuss the issues with their peers. That said, they attend the PWG as themselves, not to represent their organisations.

In relation to the topic of conversation, agree that the unit used is immaterial (millibars or hectopascals) but there continues to be a fairly valid reason for its inclusion and it's not just to mitigate against the acts of our colonial cousins. It's something that has been seen in a number of international carriers; albeit infrequently. That said, there have been occurrences where a controller has persevered with obtaining a full readback of the QNH value and the units and the pilot has still set the QNH in inches of mercury

In previous years I'd mention something about Darwin at this point but I've been trying to act more responsibly

The problem that you have is that we don't gather any evidence to demonstrate how often this has proved effective in preventing a level bust. In order for the CAA to remove the requirement to state the units they'd need to produce a solid safety argument that it was no longer required and I don't think that it would be possible to demonstrate an equivalent level of safety given the absence of evidence. Maybe with enhanced Mode S with reliable barometric pressure setting downlinks so that ATS could identify incorrect altimeter settings but the BPS reliability isn't quite there yet.
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