Design, Implementation, and Flight Testing of a Stability Augmentation System for Coaxial Ultralight Rotorcraft

Design, Implementation, and Flight Testing of a Stability Augmentation System for Coaxial Ultralight Rotorcraft | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Design, Implementation, and Flight Testing of a Stability Augmentation System for Coaxial Ultralight Rotorcraft Benjamin Rothaupt, Walter Fichter, Benedikt Grebing This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8745267/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This paper describes the first ever flight demonstration of a stability augmentation system using electromechanicalinline actuators in a rotorcraft without hydraulic force ampflification. A coaxial ultralight helicopter equipped with the stability augmentation system is used as a flight demonstrator. The paper covers the synthesis of requirements for the system, the design process and architecture of the system, technical challenges,the algorithms including the control laws, safety features, flight testing, and flight test results. The flight test campaign includes scaled down versions of well established mission task elements for handling qualities evaluation adapted from literature. Measurement data and pilot feedback indicate that the stabilization is effective and workload is reduced. The flight demonstration proves that the proposed system can be integrated safely into small rotorcraft despite the space and weight limits and the actuation force requirements.To emphasize the scientific contribution of the flight demonstration, the paper also includes a brief discussion of the dynamics of reversible control trains, a qualitative explanation of the expected actuator feedback forces, and a description of the associated challenges and open questions. Main Author ORCID: 0009-0007-9240-9629 rotorcraft coaxial reversible control train inline actuators stabilization handling qualities Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8745267","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":591757450,"identity":"ba0d2769-7c2f-41cf-b49e-326d142171fa","order_by":0,"name":"Benjamin Rothaupt","email":"data:image/png;base64,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","orcid":"","institution":"University of Stuttgart","correspondingAuthor":true,"prefix":"","firstName":"Benjamin","middleName":"","lastName":"Rothaupt","suffix":""},{"id":591757451,"identity":"6fe33adc-911c-4749-b264-1161fc2f0361","order_by":1,"name":"Walter Fichter","email":"","orcid":"","institution":"University of Stuttgart","correspondingAuthor":false,"prefix":"","firstName":"Walter","middleName":"","lastName":"Fichter","suffix":""},{"id":591757452,"identity":"adbc0546-4be3-4731-886a-d1f2101f29b2","order_by":2,"name":"Benedikt Grebing","email":"","orcid":"","institution":"edm aerotec GmbH","correspondingAuthor":false,"prefix":"","firstName":"Benedikt","middleName":"","lastName":"Grebing","suffix":""}],"badges":[],"createdAt":"2026-01-30 23:08:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8745267/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8745267/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102886082,"identity":"0be44d4d-cdde-44c0-a140-1c778c137e9f","added_by":"auto","created_at":"2026-02-18 02:46:29","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9138963,"visible":true,"origin":"","legend":"","description":"","filename":"RothauptSASforULH.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8745267/v1_covered_bc9022dc-6aad-4b0c-b450-38a248e88942.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Design, Implementation, and Flight Testing of a Stability Augmentation System for Coaxial Ultralight Rotorcraft","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"rotorcraft, coaxial, reversible control train, inline actuators, stabilization, handling qualities","lastPublishedDoi":"10.21203/rs.3.rs-8745267/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8745267/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper describes the first ever flight demonstration of a stability augmentation system using electromechanicalinline actuators in a rotorcraft without hydraulic force ampflification. 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