http://www.jets.dk/cs/forums/15/ShowForum.aspxQuestions about General Aviationen-USCommunityServer 2.0 (Build: 60526.2668)http://www.jets.dk/cs/forums/thread/1246.aspxFri, 10 Nov 2000 17:20:00 GMTa23efcf1-9e75-4ff9-be18-cd9cb68b9485:1246Anonymous0http://www.jets.dk/cs/forums/thread/1246.aspxhttp://www.jets.dk/cs/forums/commentrss.aspx?SectionID=15&PostID=1246*** Posted by run *** <br />Hi Chaco <br /> <br />The reason why you see different numbers is because the Speed of sound changes depending on altitude. You can use the following page to give you the correct number for a certain altitude: <br />&lt;a href='http://www.desktopaero.com/stdatm.html' target='_blank'&gt;http://www.desktopaero.com/stdatm.html&lt;/a&gt; <br />This of course is only for standard atmosphere. As soon as you have a 'non-standard' day these numbers change. <br /> <br />Regards John Raahauge RUN <br />[I have a question about Mach numbers. I am wondering, what is the exact number for Mach of Mach 1. At what speed does it start? Also, why is it that when I read books on plane specs that the Mach numbers are always different from book to book. It seems that some are just guessing. Thanks for any responses. ]http://www.jets.dk/cs/forums/thread/1245.aspxFri, 10 Nov 2000 06:17:00 GMTa23efcf1-9e75-4ff9-be18-cd9cb68b9485:1245Anonymous0http://www.jets.dk/cs/forums/thread/1245.aspxhttp://www.jets.dk/cs/forums/commentrss.aspx?SectionID=15&PostID=1245*** Posted by chaco1 *** <br />I have a question about Mach numbers. I am wondering, what is the exact number for Mach of Mach 1. At what speed does it start? Also, why is it that when I read books on plane specs that the Mach numbers are always different from book to book. It seems that some are just guessing. Thanks for any responses.