Re: Regional Pressures
Pierre,
Your argument about several airfields in close proximity goes against the stabalishd procedures for operations within and under the London TMA. All aircraft ther use the "London QNH" which is the QNH from any suitable airfield within or below the TMA. The differences are according to the CAA not considdered to be significant.
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Farmer 1,
Can you elaborate on your statement: "Using it enables me to remember the Decision Height for every single airfield in the country"?
In my book, the decision height depends on the procedure, system minima and obstacle environment which are not the same for every airfield.
France does not have RPS and has terrain higher than the UK. Ireland does not have RPS and covers an area as big as England if one incluses SOTA and NOTA. Our nearest really remote area - Shanwick OCA does not have RPS. Why not?
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When landing Visually one can see the runway and obstacles - an altimeter is unnecessary. When flying the visual circuit, the altimeter enables one to fly at the published level. That could be done with the altimeter set to QFE, QNH, RPS or 1013 provided that the pilot flies at the appropriate level.
When flying IFR, all the obstacles published are AMSL even close to or on the aerodrome. Thus QNH provides better situational awareness. Until visual provided that the appropriate procedure is followed flying on QNH or QFE makes no difference. Once visual, refer to above comment regarding visual landing.
If however, one uses QFE and does not become visual, failure to reset the QNH at a very busy part of the flight is a) Dangerous and b) one of the most common cause of IR test failures.
I also think that using QNH for take-off, landing and circuit work improves situational awareness with regard to performance. For example take a PPL and get them to do a few circuits on QFE - they take-off at 0, downwind at 1000 and land at 0. No problem. Take them to an airfield 5000ft AMSL (with an altimeterb that could set the QFE). Again they take-off at 0, downwind at 1000 and land at 0.
Would it not be safer to have the PPL sit there and say "heck this airfield is high I better check the figures, lean the mixture and make a best performance take-off as per the POH.
QFE is used because of...........tradition. No other reason.
As Chilli says. Time to bin it.
Regards,
DFC