{"id":2366,"date":"2019-10-15T13:21:54","date_gmt":"2019-10-15T17:21:54","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/?p=2366"},"modified":"2026-03-26T12:03:34","modified_gmt":"2026-03-26T16:03:34","slug":"aircraft-certification-analysis-from-the-conceptual-design","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/aircraft-certification-analysis-from-the-conceptual-design\/","title":{"rendered":"Aircraft Certification: analysis from the conceptual design"},"content":{"rendered":"\n<p>The benefits of using aircraft analysis and simulation in the certification process of aerospace structures is extensive. Organizations using simulation and analysis tools effectively and maximizing their capabilities find they can achieve certification faster and with drastically less total cost than those who do not.<\/p>\n\n\n\n<p>The certification of\nan entire aircraft structure is extremely complex. There are different aspects\nan applicant for structural approval must consider to prove that the strength\nof that structure sufficiently meets the design goals of the entire system. <\/p>\n\n\n\n<p>All aspects of the structural certification are subject to\nthe Federal Aviation Regulations which spell out the requirements of the\nstructure depending on the type of aircraft. Engineers must adhere to these\nrequirements by looking at every possible condition and operating environment\nthat the aircraft could possibly operate and demonstrate by analysis or test\nthat each production copy will perform as intended and without any structural\nfailure.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Requirements and Criteria Begin in Preliminary Design<\/h2>\n\n\n\n<p>Fundamental analysis begins very early in the stages of\nconceptual design. The structure necessary to support the entire aircraft\ndepends on the design mission of the aircraft in question. How high and fast\nwill this aircraft need to fly?&nbsp; What is the\npayload, people or cargo, and how much payload will it need to carry?&nbsp; How far will it need to fly to deliver that\npayload?&nbsp; These are the fundamental\ndesign criteria that affect the type and size of aircraft an airframe manufacturer\nwill need to address as early as possible.<\/p>\n\n\n\n<p>Once the type and size of aircraft is determined the\nmanufacturer typically designs the outer aerodynamic shape of the aircraft; the\nbasic airfoil shape that will meet the mission, the planform area of the wing,\nthe volume and shape of the fuselage, and the airfoils and size of the\nempennage, the \u201ctail\u201d of the plane.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Loads and Static Strength<\/h2>\n\n\n\n<p>The next large scale general step in substantiating the\nstructure takes the aerodynamic general arrangement definition of the new\nairplane. Conducting a comprehensive analysis evaluates what aerodynamic loads\nare applied to the aircraft at all the various points of the airspeed or flight\nenvelope.<\/p>\n\n\n\n<p>Figure 1 shows an example of a flight envelope for a propeller-driven\nplane. The Load Factor (n) is calculated based upon the various design\nairspeeds for the particular aircraft. The various speeds listed are:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Vs = stall speed<\/li><li>Va = maneuver speed &#8211; this is the highest speed\nat which the maximum deflection of the controls can be applied<\/li><li>Vc = cruise speed<\/li><li>Vd = dive speed<\/li><\/ul>\n\n\n\n<p>These speeds are input to a Loads Analysis, which evaluates the\nmaximum loads and the associated aircraft condition and configurations.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"1000\" height=\"567\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/19\/2019\/10\/Blog-1-Image1.jpg\" alt=\"Figure 1-Example of an Aircraft Flight Envelope\" class=\"wp-image-2367\" srcset=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/19\/2019\/10\/Blog-1-Image1.jpg 1000w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/19\/2019\/10\/Blog-1-Image1-600x340.jpg 600w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/19\/2019\/10\/Blog-1-Image1-768x435.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><figcaption> Fig. 1: Example of an Aircraft Flight Envelope <\/figcaption><\/figure>\n\n\n\n<p>What engineers must do is analyze and find the biggest, worst\ncase forces that will shear, twist and bend, such as bend up, down, forward,\nand rearward, ALL the various parts of the structure. They must investigate\nwhat the loads are at all the various aircraft weights, centers of gravity, at\nhigh and low speeds. At each of these points on the envelope the engineers must\ndetermine the loads associated with certain aspects, such as gear up\/down, the\nflaps up\/down, and every possible combination of the configurations.<\/p>\n\n\n\n<p>The critical design loads and the critical conditions are\nthe highest load for each and every combination of points on the envelope and\neach condition. There are literally hundreds of combinations of points and\nconfigurations on the flight envelope to evaluate and investigate.<\/p>\n\n\n\n<p>For example, the critical condition for wing spanwise\nbending \u2014 imagine pulling straight up on the tips of the wings and holding\nfixed where the wing attaches to the fuselage \u2014 is at a heavy weight in the\ncabin when there is little fuel in the wings and the aircraft is at the maximum\nprescribed gust load. At the point, the wing is lifting up, and the gust is\npushing the aircraft down so the wing bending is the highest in this condition.<\/p>\n\n\n\n<p>From there, aircraft analysis of the actual physical structure\nensures the static strength is sufficient in every possible operating point the\naircraft could see in service. The critical loads are then called the \u201cdesign\nlimit\u201d loads.\n\nIn\ngeneral, the FAA requires static-testing of the structure and that a minimum\nload of 1.5 times the design limit load (the ultimate load) be applied. While\nthe structure may flex, it can show no failure, not even a crack, or any evidence\nof permanent deformation; this would indicate the structure entered a critical\narea in its material property limits. While all of this is happening, there are\nongoing detail design changes to the physical structure. Robust and disciplined\nconfiguration management is absolutely critical at this stage.\n\n\n\n<\/p>\n\n\n\n<p><strong>About the authors<\/strong><\/p>\n\n\n\n<p><strong>Dave Chan<\/strong>\u00a0<em>is a technical account manager supporting the aerospace, defense and federal business for Siemens PLM Software. His career with Siemens PLM Software started in 1996, and he has driven customer success with the adoption of digitalization and digital engineering solutions for numerous commercial and federal customers. Dave has been in the engineering software business for more than 22 years. He has a bachelor\u2019s degree in industrial engineering from Lehigh University.<\/em><\/p>\n\n\n\n<p><em><strong>John Cunneen<\/strong> is a business development consultant for Siemens PLM Software\u2019s Aerospace, Defense, Federal, and Marine division. He leads efforts to uncover, develop, and respond to industry and government requirements pertaining to all aspects of product and system lifecycle management and provides thought leadership to customers. John has been an avid general aviation pilot since 1987, earned a Bachelor of Science in aerospace engineering from Arizona State University in 1989, and has been a key part of Siemens PLM Software since 1999.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn how simulation and analysis tools can make the aircraft certification and aircraft analysis smoother.<\/p>\n","protected":false},"author":17199,"featured_media":2368,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[1],"tags":[],"industry":[113],"product":[],"coauthors":[],"class_list":["post-2366","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","industry-aerospace-defense"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/19\/2019\/10\/Blog-1-Image-2.jpg","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/posts\/2366","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/users\/17199"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/comments?post=2366"}],"version-history":[{"count":6,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/posts\/2366\/revisions"}],"predecessor-version":[{"id":2377,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/posts\/2366\/revisions\/2377"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/media\/2368"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/media?parent=2366"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/categories?post=2366"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/tags?post=2366"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/industry?post=2366"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/product?post=2366"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/thought-leadership\/wp-json\/wp\/v2\/coauthors?post=2366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}