altimeter settings
The questioner, and many of the answerers, seem to be confusing different aspects of altimter settings
The UK has regional pressure settings for atimeter settings regions which are the lowest FORCAST pressures for the areas concerned. The object being that if you are unable to contact ground stations or loose contact setting regional pressure settings will give you a safe terrain avoidance. The settings are a relic of the wartime habit of returning bombers to arrive at the wrong location and impact terrain , often just below mountain tops
RPSs are forecast several hours in advance to be noted when flight planning and only used when no better information is available. They are cover large areas, usually several counties, and have easily remembered names eg TYNE
The transition altitude and the pressure to be set above that altitude are entirely different issues. This is the altitude above which a standard pressure setting is to be used. The level is lower in the UK than the states because our terrain is not as high, anywhere. The standard pressure setting is 1013.25 mbs or 29.2 inches. Modern altimeters show both measures on different parts of the dial. The purpose of the standard pressure setting is nothing to do with terrain but avoids collision. If two aircraft are flying with the standard pressure set and maintaining a flight level a thousand feet apart they will not collide, baring gross altimeter error. The dials may not show an accurate distance above the ground but that does not matter the important thing is the aircraft will be separated by a thousand feet.
Last edited by Tinribs; 10th Sep 2016 at 19:52.