[USMA:27845] RE: Airplane altitudes

[Michael Payne]

I think what everyone is saying, is that the altimeter is a pressure measuring device, when it is calibrated at the factory, they have an International Standard Atmosphere is it calibrated to, pressure drops with altitude, so what the altimeter gives is the corresponding altitude for a pressure. As the airplane flies from a low pressure region to a high pressure region, the airplane will follow the pressure and it's actual altitude above say, sea level will increase. The amount depends on the intensity of the low or high pressure area. When the airplane nears an airport, you can correct for this constantly changing atmospheric pressure by setting the actual pressure in a small window, the altimeter will then indicate the actual airfield altitude above sea level.     Michael Payne   ----- Original Message ----- From: Mighty Chimp To: U.S. Metric Association Sent: 14/12/03 13:03:01 Subject: [USMA:27832] RE: Airplane altitudes I�m still confused.  If the plane is not at 33 000 feet, then what altitude is it at?  I know you said it may vary to maintain the same pressure, but can we know what range of altitude the plane is actually at?   How did you come up with 33 000 ft = 26.2 kPa?    This is all quite interesting.   BTW, do you have proof of this?   Euric   -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Terry Simpson SSent: Saturday, 2003-12-13 19:02 To: U.S. Metric Association Subject: [USMA:27827] RE: Airplane altitudes   >Mighty Chimp >>The numeric value does not actually describe altitude, >>it describes the pressure of the air > >Are you saying that the plane isn't really at 33 000 ft   Yes, that is what I am saying. The phrase '33 000 feet' means 26 200 Pa.     >That the feet are units of pressure,   Yes (at cruise altitudes).     --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.551 / Virus Database: 343 - Release Date: 2003-12-11     --- Michael Payne --- [EMAIL PROTECTED] --- EarthLink: The #1 provider of the Real Internet.   --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.5551 / Virus Database: 343 - Release Date: 2003-12-11