Some of you may be interested in this paper by John West. The link is to the abstract. Click free pdf link on the right for the full article. http://jap.physiology.org/cgi/content/abstract/81/4/1850
His interest is altitude sickness and high altitude medicine. He accepts that the Standard Atmosphere is a world-wide, year-round approximation. For mountains at specific latitudes climbed at certain times of year, he recommends the Supplements to the Standard Atmosphere, tabulated for January and July in 15° latitude bands. He shows surprising good fits to the correct model. NOTE: Figure 1 is screwed up. I don't know if in original paper or pdf conversion. The temperature scale appears to be associated with the solid lines to the number's right, not the hash mark. The left altitude numbers are associated with the solid line below. I draw your attention to figure 2 showing pressure vs altitude for the Standard Atmosphere and the most extreme supplement bands (remember these are still averages, not worst case day). A pilot is commanded to fly a pressure contour, even if is it called an altitude. Consider two flight levels in the Russian flight level structure, 7800 m and 8100 m. (The 300 m separation is roughly the same as 1000' separation in Western airspace). Go up vertically from the altitude axis to the Standard Atmosphere line, then go horizontally to the 75° Winter and 30° Summer lines, and drop vertically to the altitude axis. You can see the range of true altitudes that may be flown around the world when these flight levels are commanded. The bands overlap roughly ±2 increments (300 m) of altitude. In the same place and time, it works fine as long as everyone follows the same rule. Anyone flying true altitude instead of pressure altitude would be a menace to everyone. ________________________________ From: Michael Payne <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Fri, April 23, 2010 10:40:36 PM Subject: [USMA:47253] Re: Air flight altitudes in meters We put in the local altimeter setting at the Transition Level which is published for each airport elsewhere or a fixed altitude in the US 18000 ft, Australia 15000 ft, Europe around 4-5000 ft. Same with Africa. We have a switch we flip for inHg or hPa. When in North America we use inHg and elsewhere hPa. We do have a separate Radar altimeter which bounces signals off the ground, this only activates at 2500 AGL or below and gives only feet indications. Nowhere do we change things to view kilometers, it's always knots and nautical miles only. This applies even in Russia where Air Traffic Control gives distances to go in kilometers. Regardless, all visibilities outside North America are in meters and kilometers. Mike Payne ----- Original Message ----- > When and where do the pilots key local altimeter data into the flight computers, and in what units (hPa, or km in Eastern countries)? > > What are the units of instrument display(s)? > > Is there a separate *radar* altimeter for clearance of mountain peaks? (in > addition to the "local" altimeter?) > > Gene Mechtly. >
