{"id":308,"date":"2008-01-26T13:05:29","date_gmt":"2008-01-26T20:05:29","guid":{"rendered":"http:\/\/pwoodford.net\/blog\/?p=308"},"modified":"2023-02-01T06:59:13","modified_gmt":"2023-02-01T13:59:13","slug":"308","status":"publish","type":"post","link":"https:\/\/pwoodford.net\/blog\/?p=308","title":{"rendered":"Air-Minded: Old Bones"},"content":{"rendered":"<p>Boy, does this make me feel old:<\/p>\n<p>In early November 2007, the nose and cockpit section of a Missouri Air National Guard F-15C broke away from the rest of the aircraft during a training flight.&nbsp; The pilot ejected and survived.&nbsp; Here&#8217;s a simulation of what happened:<\/p>\n<p><\/p><center><iframe loading=\"lazy\" src=\"http:\/\/www.youtube.com\/embed\/2R7BWrqmgac\" width=\"420\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/center><p><\/p>\n<p>Following the mishap, the USAF grounded its entire fleet of F-15s, including the newer air-to-ground F-15E models. The F-15Es have all been returned to flight status, I believe, but of the 300-plus air-to-air F-15s (the A, B, C, and D models) still in service, 163 remain grounded, possibly for keeps.<\/p>\n<p>The problem?&nbsp; Faulty longerons, support structures connecting the cockpit area to the fuselage.<\/p>\n<p>The Missouri ANG jet was about 25 years old at the time of the mishap.&nbsp; Some of the oldest F-15s in service are 30 years old.&nbsp; Any F-15 pilot will tell you that virtually every air-to-air F-15 has been overstressed during its career; most of the older jets have been overstressed again and again.&nbsp;&nbsp;Overstress incidents are tracked, of course, and the aircraft involved are inspected afterward.&nbsp; But what about over-Gs that occured before airframe stress recording devices were retrofitted in the mid-1980s?&nbsp; Most of those were probably never reported.<\/p>\n<p>Overstressed longerons can&#8217;t&nbsp;simply be replaced; they&#8217;re part of the basic skeleton of the aircraft.&nbsp; About the only way to fix the problem is to rebuild the aircraft from scratch.<\/p>\n<p>In 1981 I investigated an F-15 airshow crash in The Netherlands.&nbsp; The pilot had smacked into the ground in a flat attitude, and the jet didn&#8217;t look all that bad afterward.&nbsp; True, the cockpit had broken away from the fuselage (in exactly the same place as Missouri ANG jet), but it looked like it would be a simple matter to bolt it together and return it to flight status.<\/p>\n<p>We called in a structural engineer, who turned out to be a young, smallish woman.&nbsp; She crawled inside the wreckage, looked around, and crawled back out.&nbsp; &#8220;This airplane will never fly again,&#8221; she said. &#8220;The longerons are bent.&#8221;&nbsp; I&#8217;m ashamed to say&nbsp;the colonel in charge of the investigation sent her packing and told the USAF to send us an older&nbsp;male engineer.&nbsp; The male engineer came two days later and made the same report.&nbsp; Bent longerons = no fixee.<\/p>\n<p>I&#8217;m not so naive as to think&nbsp;the USAF isn&#8217;t exaggerating the scope of the problem in order to get more money for additional F-22s.&nbsp; Of course it is.&nbsp; But I do think&nbsp;bad longerons will be a showstopper for air-to-air F-15s, and eventually air-to-ground F-15Es too.&nbsp; You can only over-G an airplane so many times.<\/p>\n<p>I started flying F-15s in 1978 and flew them into the mid-1990s.&nbsp; They were new when I started, and still felt new when I quit.&nbsp; Now all of a sudden they&#8217;re old and breaking apart.<\/p>\n<p>My own longerons aren&#8217;t feeling so hot, reading about all this.<\/p>\n<p><em>Credit where credit&#8217;s due:<\/em> an excellent ongoing discussion of the F-15 grounding saga is available at the <a href=\"http:\/\/www.defensetech.org\/\" target=\"_blank\" rel=\"noopener\">Defense Tech blog<\/a> &#8211; look for individual articles under the &#8220;fast movers&#8221; category.<\/p>\n\n\n<p><em>\u2014<a href=\"https:\/\/pwoodford.net\/blog\/?page_id=14450\"><strong> back to the Air-Minded Index<\/strong><\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Boy, does this make me feel old: In early November 2007, the nose and cockpit section of a Missouri Air National Guard F-15C broke away from the rest of the aircraft during a training flight.&nbsp; The pilot ejected and survived.&nbsp; Here&#8217;s a simulation of what happened: Following the mishap, the USAF grounded its entire fleet [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1960,3,14],"tags":[157,593],"class_list":["post-308","post","type-post","status-publish","format-standard","hentry","category-air-minded","category-flying","category-military","tag-air-minded","tag-aviation-accident"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/308","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=308"}],"version-history":[{"count":5,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/308\/revisions"}],"predecessor-version":[{"id":32753,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/308\/revisions\/32753"}],"wp:attachment":[{"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=308"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=308"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pwoodford.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=308"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}