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During the Vietnam War, the Army (my alma mater) found that the Huey helicopter had a few shortcomings.\u00a0 I guess that’s to be expected; it was the first time the Army used helicopters in a major way in a real war.\u00a0 The Huey was susceptible to small arms fire (and big arms fire, too, for that matter) and it was noisy.\u00a0 On a clear night, you could hear a Huey coming in from a long way out with its characteristic “wop wop wop” signature as it beat the air into submission.\u00a0 That “wop wop wop” sound was actually the rotor tips breaking the sound barrier on the left side of the helicopter, so the Army knew it had to do something to get the blade tip speed below the speed 0f sound on its next-gen helicopter.\u00a0 Another big problem was small arms fire; a single .30-caliber AK-47 bullet through a Huey rotor blade would destroy the blade’s structural integrity (and there were a lot of AK-47 rounds in the air in those days).\u00a0 When that happened, the helicopter and its crew were lost.\u00a0 There could be no autorotation (you can’t autorotate without a blade) and you couldn’t bail out.\u00a0 The next-gen helicopter blades would have to be impervious to small arms fire.<\/p>\n
Fixing the blade tip speed problem was simple.\u00a0 Instead of having two blades like the Huey, the Apache went to four blades.\u00a0 That cut the rotor speed and let the blade tips go subsonic.\u00a0 “Wop wop wop” no more.\u00a0 Easy peasy.<\/p>\n
The structural integrity issue was the more significant challenge. The engineers at McDonnell Dougas (the Apache prime contractor) designed a blade that had four spars that ran longitudinally (with the length of the blade) contructed of AM455 stainless steel (a special blend used on the Apache and, at the time, nowhere else).\u00a0 The spars had overlapping epoxy-bonded joints that ran the length of the blade.\u00a0 The idea was that a hit anywhere on the blade (up to and including a 23mm high explosive Russian anti-aircraft round, roughly the explosive equivalent of a hand grenade) would damage that spar, but the remaining three spars would hold the blade together.\u00a0 \u00a0It worked.\u00a0 An Apache blade actually took a blade hit from an Iraqi ZSU-23\/4 and made it back to base.<\/p>\n So here’s the problem:\u00a0 The Army specified a blade life of 2200 hours (blades on a helicopter are like tires on a car…they wear out), but our blades were only lasting about 800 hours before the blades’ bondline epoxy joints holding the spars together starting unzipping.\u00a0 \u00a0It wasn’t a catastrophic failure (the helicopter could still fly home), but the blades had to be repaired.\u00a0 The Army would send the blades back to McDonnell Douglas, and McDonnell Douglas sent them back to us at Composite Structures for refurbishment.\u00a0 If they couldn’t be repaired, we sold McDonnell Douglas a new blade (back in the 1990s, each blade cost just north of $53,000, and McDonnell Douglas put a hefty markup on that when they sold the blade to the Army).\u00a0 When they could be repaired, we still charged a hefty fee.<\/p>\n When I entered the picture as the plant manager, I learned that both Composite Structures (my company) and McDonnell Douglas (my customer) had made half-assed efforts to fix the blade problem, but neither company was financially motivated to eliminate it.\u00a0 We were making good money selling and repairing blades and so was McDonnell Douglas.\u00a0 \u00a0The Army, however, was taking it in the shorts.<\/p>\n This was also a major problem for me as the manufacturing guy.\u00a0 I didn’t like having to make two blades to get one good one.\u00a0 We were rejecting one of every two blades we made for spar disbonds in the factory.\u00a0 You read that right:\u00a0 We had to make two blades to get one good one.\u00a0 Because of this, we were in a severe past due delivery condition, and my mission was to correct that situation.\u00a0 So we went to work on solving the problem.\u00a0 We found and fixed plenty of problems (blade cure profile issues, cleanroom assembly shortfalls, epoxy shelf life and pot life issues, nonconforming components issues, and contamination issues), but the blade disbonds continued.\u00a0 McDonnell Douglas continued to pound us for quality issues, all the while secretly smiling all the way to the bank as they continued to sell twice as many blades as they should have been selling.<\/p>\n We went through everything and finally concluded that there had to be a design issue with the blades; specifically, that the bondline width where the spars were glued together had too much variability.\u00a0 If that glue line was small enough, we reasoned, it wouldn’t hold up and the blade would disbond.\u00a0 We asked McDonnell Douglas about that (McDonnell Douglas was responsible for the design; we were building it to their engineering drawings), but they kept blowing us off.\u00a0 The bondline width wasn’t dimensioned on the McDonnell Dougas drawings.\u00a0 The other parts were, and McDonnell Douglas’ idea was that if the blade parts met their drawing requirements, the bondline width would be okay.\u00a0 \u00a0That’s what they hoped for, anyway.\u00a0 But you know what they say about hope.\u00a0 You can poop in one hand and hope in the other, and see which one fills up first.<\/p>\n I asked for a meeting with our company and McDonnell Douglas on the blade failures, and they wouldn’t meet with us.\u00a0 So I sent out another invitation, and this time I included the Army.\u00a0 McDonnell Douglas was livid when the Army quickly said yes; now, the McDonnell Douglas wizards had to meet with us on this issue.\u00a0 That meeting started about like I expected it to, with McDonnell Douglas tearing us a new one on the blade failures, telling us our quality was terrible, and basically letting me and the rest of the world know that, in their opinion, things had gone downhill since I had taken over as plant manager (no matter that this 50%-rejection-rate blade issue had existed for a dozen years prior to my arrival).\u00a0 I patiently explained the issues we had found and corrected, and then emphasized that the problem with blade separations had continued unabated.\u00a0 I then asked the McDonnell Douglas program manager about the bondline width and the fact that this apparently critical requirement was not on their engineering drawings.\u00a0 He denied it was the issue and went off about our poor quality again.\u00a0 When he ran out of steam, I asked the question about the bondline dimension yet again, and specifically, how narrow the bondline could be and still provide an adequate joint.\u00a0 There were more accusations about our lousy quality (the guy only knew one tune and he loved singing it), and I again waited for him to finish.\u00a0 When I asked the question a third time, before McDonnell Douglas lit up about our poor quality again the Army representative asked “yeah, how narrow does it have to be before the blade fails?”<\/p>\n The McDonnell Douglas guy stared at me like cobra looks at a mongoose (I’ve only seen this in YouTube videos, but I’m pretty sure the analogy is a good one).\u00a0 He sputtered and stammered and I think I saw a little spit fly from his mouth.\u00a0 “If you make it to the drawing it will be okay,” he said.\u00a0 I mean, under the circumstances it was the only thing he could say.\u00a0 I almost felt sorry for him, in the same way you feel sorry for a rat when a red-tailed hawk is swooping down with talons extended.\u00a0 You feel bad, but you look forward to seeing the hawk doing his thing.<\/p>\n The Army guy sensed this was something big. “How low?” he asked again.\u00a0 If there is such a thing as a perfect impersonation of a deer caught in the headlights, the McDonnell Douglas dude was nailing it.\u00a0 It was what we in the literary world call a pregnant pause, one of those “what did the President know, and when did he know it?” moments.\u00a0 As I type this, I can remember the scene like it happened 10 minutes ago, but it’s been close to 30 years.<\/p>\n “0.375 inches,” the McDonnell Douglas dude finally answered.\u00a0 He actually said the zero in a half-assed attempt to add engineering gravitas to his answer. “As long as they build it to the print, they’ll be okay,” he added, with a “so there” smirk.\u00a0 He was answering the Army man, but the smirk was all for me.<\/p>\n What the McDonnell Douglas guy didn’t know was that my guys could see the bondline width in an x-ray, and we x-rayed every blade returned for repair.\u00a0 And I guess he didn’t realize how easy it was to do a tolerance analysis to show what the drawings allowed the bondline width to be.<\/p>\n What happened next was one of those moments I’ll remember for the rest of my life.\u00a0 I looked my engineering guy and my QA guy.\u00a0 They knew what I wanted.\u00a0 They both left the room.\u00a0 Fifteen minutes later they were back.\u00a0 \u00a0My engineering guy handed me the results of his tolerance analysis.\u00a0 The McDonnell Douglas engineering drawings tolerance stackups allowed the bondline width to go as low as 0.337 inch.\u00a0 \u00a0The QA guy had even better information.\u00a0 All the blades that had been returned to us for spars unzipping (which was the only reason we ever saw a blade returned) had bondline widths less than 0.375 inches (McDonnell Douglas’ admission for the lower limit) but above .337 inches.\u00a0 In other words, our quality was fine.\u00a0 The failed blades met the McDonnell Douglas engineering drawings but were below the value I had finally prodded McDonnell Douglas into revealing.<\/p>\n I could have been more diplomatic, I guess, but that wasn’t me.\u00a0 I shared that information with the room.\u00a0 The Army rep smiled.\u00a0 “I think you guys might want to continue the meeting without me,” he said.\u00a0 And then he left.<\/p>\n The McDonnell Douglas guy exploded as soon as the door closed.\u00a0 He was apoplectic (I looked that word up; it means overcome with anger and extremely indignant, and that was him).\u00a0 McDonnell Douglas had been screwing the Army for years with a deficient design and now it was out in the open.\u00a0 They were potentially exposed to defective design claims from the Army (and from us) for hundreds of millions of dollars.\u00a0 Think about it:\u00a0 12 years of Apache blade production, a 50% failure rate in production, a blade life of only 800 hours (against the Army’s spec requirement of 2200 hours), and the fact that we and McDonnell had factored all that waste into our pricing.<\/p>\n Fortunately for McDonnell Douglas, the Army wasn’t interested in suing them (all they wanted was good blades).\u00a0 \u00a0My boss wasn’t interested in pursuing a claim against McDonnell Douglas, either, as they were our bread and butter and he wanted to keep the business.\u00a0 We fixed the problem by holding the blade components to tighter tolerances (tighter than McDonnell Douglas had on their drawings) so the bondline width would always be above the magical 0.375 inch, and we never had a blade unzip in production again.\u00a0 McDonnell Douglas did not correct their drawings, as it would have been an admission of guilt on their part that would absolutely guarantee a loss if the Army ever took them to court.<\/p>\n So there you have it:\u00a0 The Apache main rotor blade failures, all caused by sloppy engineering at McDonnell Douglas.\u00a0 It’s hard to believe that the blades had a 50% failure rate and didn’t meet the Army’s specified blade life for a dozen years before the problem was fixed, but that’s what happened.\u00a0 It’s also hard to believe that nobody at McDonnell Douglas went to jail for it.<\/p>\n Never miss an ExNotes blog:<\/p>\n","protected":false},"excerpt":{"rendered":" By Joe Berk Like that photo you see above?\u00a0 Yeah, me, too.\u00a0 I took it on the parade grounds at Fort Knox, Kentucky, a few years ago.\u00a0 \u00a0I used to run the Composite Structures plant that made rotor blades for the Apache helicopter.\u00a0 It was one of the best jobs I ever had. We recently … Continue reading “The Apache Main Rotor Blade Failures”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":20900,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[392],"tags":[3332,3330,3331,3328,3334,3335,3333],"class_list":["post-20893","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-back-in-the-day","tag-ah-64","tag-apache","tag-apache-main-rotor-blade","tag-defense-industry-war-stories","tag-helicopter-blade-failures","tag-heliicopter-blade-quality-and-manufacturing-issues","tag-huey-helicopter"],"jetpack_featured_media_url":"https:\/\/exhaustnotes.us\/blog\/wp-content\/uploads\/2023\/01\/DSC0498-900.jpg","jetpack_sharing_enabled":true,"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/posts\/20893","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/comments?post=20893"}],"version-history":[{"count":22,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/posts\/20893\/revisions"}],"predecessor-version":[{"id":21135,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/posts\/20893\/revisions\/21135"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/media\/20900"}],"wp:attachment":[{"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/media?parent=20893"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/categories?post=20893"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exhaustnotes.us\/blog\/index.php\/wp-json\/wp\/v2\/tags?post=20893"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/exhaustnotes.us\/blog\/wp-content\/uploads\/2023\/01\/apacheblade1.jpg\")
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