-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Terry Simpson Sent: Saturday, 2003-12-13 11:18 To: U.S. Metric Association Subject: [USMA:27823] RE: Airplane altitudes
> Of Nick Kocharhook >I've often thought that 33,000 feet is a pretty >strange number for athe cruising altitude It is in 'thousands of feet'. Odd thousands for aircraft going east. Even thousands for aircraft going west. The numeric value does not actually describe altitude, it describes the pressure of the air through which the aircraft is flying. As the surrounding air pressure rises and falls, the aircraft will climb and descend to maintain the same pressure. Are you saying that the plane isn't really at 33 000 ft (10 km) altitude? That the feet are units of pressure, like mmHg is used for blood pressure? That doesn't sound right. Could you elaborate further? There are regions of the world where altitude is expressed in metres. Aircraft change from metres to feet and back as they fly in and out of these regions, of course. There are also regions where both are in use at the same time e.g. military using metres, civilian using feet. Like China and Russia? Can you be more specific? >proximity to 10 km more than just coincidence? It is a coincidence. >And, why don't they tell us that we'll be cruising at 6 and a quarter miles? An excellent question. If I'm not mistaken, the airlines don't use the common mile at all. The use the 1852 m version. Thus, the altitude would be 5.43 nautical miles. * If you use a wide range of values, it is best to stay with the same units. You avoid the changes and conversions as you move up and down the range. * All communication will be in the same expected units so errors are less likely. * Equipment can be a simple. * You do not distribute learning a 'feel' over several different units, your learning of 'feel' is focussed on one. This is one of the key features of the metric system. Each quantity has only one unit. What is the main obstacle to conversion of air traffic to metres at this time? Euric --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.547 / Virus Database: 340 - Release Date: 2003-12-02 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.547 / Virus Database: 340 - Release Date: 2003-12-02
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