James R. Frysinger wrote: >"Nikolay O. Malyarov" wrote: >>You know what puzzles me here in Canada (among a few other things) >> - is that the visibility given in the current conditions is >>a direct conversion from miles (6.4 km, 16.1 km, 24.1 km). >>Additionally, ceiling is given in feet. > >Sure! The customers are the airline industry members.
That would also be my guess. >ICAO, I believe, is the organization that specifies that. No it isn't. It is the Canadian aviation authority that specifies it. Canada is not compliant with the relevant ICAO convention. ICAO 'specifies' SI and 'permits' non-SI units for only some vertical measures. Note that horizontal distances must be SI. Most countries use SI (plus the SI permitted nautical miles and knots) for aviation horizontal distances and use feet and fpm for vertical measures. For example, see the horizontal/vertical distinction in this UK air accident report: http://www.aaib.dft.gov.uk/bulletin/feb01/gboxy.htm Of course, feet and fpm are non-standard/unusual and are limited to the exceptional cases of some aircraft vertical operations. You will see kite flying and balloon regulations in metres. Some countries such as Russia are more pro-SI and use metres for aircraft vertical operations in full compliance with ICAO. Countries that use statute miles or feet for horizontal distances are non-compliant with ICAO (e.g. USA and Canada). See: http://www.icao.int/icao/en/assembl/a33/resolutions_a33.pdf http://www.icao.int/icao/en/assembl/a32/wp/063.pdf Unfortunately Annex 5, Fourth Edition of the Chicago Convention is not available online without charge.
