Cirrus -
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For me with my planes, the problem is that the "3rd altimeter" is metric...
You probably fly with a 3rd altimeter in feet - a good cross-check. Fully agree with your ideas. I flew many contracts with different companies, most if not all of them had altimeter procedures same or very similar to the one I described.
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I remember American Airlines had an extra altimeter they kept on QNH, since they flew QFE for takeoff and landing (in US airspace...!) until the 1990s... Eastern Airlines used QFE as well. I got trained to use QFE OR QNH as early as my PPL days as a teenager... and PanAm had excellent optional QFE procedures training for Russia/China operations. Was required for all pilots operating these routes.
Denti -
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Of course if you cannot use a QFE procedure, apply your QNH procedure. The last time I went to Moscow (2005) - I did use QFE/Metric - I believe it can be quite dangerous to "convert" QFE to suit a "QNH" procedure in that airspace. I recall many "horror stories" about wrong altimeter settings and erroneous levels or heights to maintain in Russia or China airspace, at least with old "classic" avionics. If your NG equipment permits, of course, must be a great convenience. Meters for QNE levels and QFE heights, meters/second for winds, or rates of climb, kilometers/hour for speeds... is much of a headache even if I am quite proficient in flying with such numbers, TRANS LVL and TRANS HEIGHTS...
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In Russia/China, I always decided to be PNF and being extra careful in my conversions, just telling the PF "what to do next"... unless you do fly that airspace and these procedures twice a month. I never had problems.
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Happy contrails
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