{"id":8125,"date":"2024-05-10T18:05:45","date_gmt":"2024-05-10T10:05:45","guid":{"rendered":"https:\/\/tommykwan.com\/blog\/?p=8125"},"modified":"2024-05-12T12:28:00","modified_gmt":"2024-05-12T04:28:00","slug":"mach-number-sonic-subsonic-transonic","status":"publish","type":"post","link":"https:\/\/tommykwan.com\/blog\/aviation\/mach-number-sonic-subsonic-transonic\/","title":{"rendered":"Mach number &#8211; Sonic, subsonic, transonic?"},"content":{"rendered":"<p>Ref FAA PHAK 5-44 to 5-51<\/p>\n<p>Mach number is a kind of true airspeed indication method, it makes relationship with local speed of sound (LSS).<\/p>\n<p style=\"text-align: center;\">Mach number = True Airspeed \/ Local Speed of Sound (LSS)<\/p>\n<p style=\"text-align: center;\">LSS = 39 x sq root of\u00a0 Temperature (K)<\/p>\n<p style=\"text-align: center;\"><em>Note: C + 273 = K<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-8128 aligncenter\" src=\"https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Mach-number-and-LSS.png\" alt=\"\" width=\"507\" height=\"338\" srcset=\"https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Mach-number-and-LSS.png 1351w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Mach-number-and-LSS-300x200.png 300w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Mach-number-and-LSS-1024x683.png 1024w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Mach-number-and-LSS-768x512.png 768w\" sizes=\"auto, (max-width: 507px) 100vw, 507px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>By FAA book&#8217;s definition,\u00a0 &#8220;Sonic&#8221; , &#8220;Subsonic&#8221; , &#8220;Transonic&#8221; and &#8220;Supersonic&#8221; can use speed regime to define:<\/p>\n<ul>\n<li><strong>Subsonic<\/strong> &#8211; Mach number <strong>below 0.75\u00a0 (i.e 500KT)<\/strong><\/li>\n<li><strong>Transonic<\/strong> &#8211; Mach number <strong>0.75 -1.2<\/strong><\/li>\n<li>Supersonic &#8211; Mach number 1.2 to 5<\/li>\n<li>Hypersonic &#8211; Mach number over 5<\/li>\n<\/ul>\n<p><em>Notes: speed of sound is 343 m\/s -&gt; equivalent to 666.7 KT<\/em><\/p>\n<div class=\"embed-container\">\n<blockquote class=\"wp-embedded-content\" data-secret=\"SJYIFHhcKL\"><p><a href=\"https:\/\/tommykwan.com\/blog\/aviation\/mcrit-mach-crit\/\">Mcrit &#8211; Mach Crit?<\/a><\/p><\/blockquote>\n<p><iframe loading=\"lazy\" class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;Mcrit &#8211; Mach Crit?&#8221; &#8212; Tommy&#039;s Diaries\" src=\"https:\/\/tommykwan.com\/blog\/aviation\/mcrit-mach-crit\/embed\/#?secret=H79ky9J6Pn#?secret=SJYIFHhcKL\" data-secret=\"SJYIFHhcKL\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe><\/div>\n<p>&nbsp;<\/p>\n<p>Read More &#8211;<\/p>\n<p>Concept and challenge question: What&#8217;s the <strong>LSS<\/strong> at<strong> 30000 feet<\/strong> in ISA atmosphere?<\/p>\n<ul>\n<li>ISA sea level -&gt; 15C &#8211;&gt; C + 273 = K , i.e 15 +273 = 288 K<\/li>\n<li>Lapse rate 2 (1.98C) \/ 1000 feet &#8211;&gt; i.e (30000\/1000) * 1.98 = 59.4 C lapse<\/li>\n<li>30000 feet temp = 15 &#8211; 59.4 = -44.4 C &#8211;&gt; C+ 273 = K &#8211;&gt; so i.e 228.6 K<\/li>\n<li><strong>LSS = 39 * sq rt of Temp(K) <\/strong>= 39 * sq rt 228.6 = 589.7<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8132 size-full\" src=\"https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Concept.png\" alt=\"\" width=\"1242\" height=\"713\" srcset=\"https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Concept.png 1242w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Concept-300x172.png 300w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Concept-1024x588.png 1024w, https:\/\/tommykwan.com\/blog\/wp-content\/uploads\/2024\/05\/Concept-768x441.png 768w\" sizes=\"auto, (max-width: 1242px) 100vw, 1242px\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Ref FAA PHAK 5-44 to 5-51 Mach number is a kind of true airspeed indication method, it makes relationship with local speed of sound (LSS). Mach number = True Airspeed \/ Local Speed of Sound (LSS) LSS = 39 x sq root of\u00a0 Temperature (K) Note: C + 273 = K &nbsp; By FAA book&#8217;s<a class=\"read-more \" href=\"https:\/\/tommykwan.com\/blog\/aviation\/mach-number-sonic-subsonic-transonic\/\" title=\"Read More\"> <span class=\"button default\">Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[68,64],"tags":[],"class_list":["post-8125","post","type-post","status-publish","format-standard","hentry","category-atpl-knowledge","category-aviation"],"_links":{"self":[{"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/posts\/8125","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/comments?post=8125"}],"version-history":[{"count":12,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/posts\/8125\/revisions"}],"predecessor-version":[{"id":8156,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/posts\/8125\/revisions\/8156"}],"wp:attachment":[{"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/media?parent=8125"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/categories?post=8125"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tommykwan.com\/blog\/wp-json\/wp\/v2\/tags?post=8125"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}