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ADS 27 2006 Edition, May 2, 2006
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REQUIREMENTS FOR ROTORCRAFT VIBRATION SPECIFICATIONS, MODELING AND TESTING
Published By:US Army (ARMY)
Page Count:31
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This standard practice presents the vibration related requirements for the development and qualification of rotorcraft, rotor craft subsystems, and equipment to be installed on rotorcraft, including external stores. Gunfire induced vibration qualification, when appropriate, should be in accordance with the vibration tests of MIL-STD-810. The development process follows the engineering System Specification (system procurement) or Production Specification (item procurement). Prior to a Request for Proposal (REP) release, the Government defines its engineering specification based on MIL-STD-961. Competing contractors base their proposed engineering specification on the Government specification, their interpretation of the specification and the peculiarities of their proposed hardware. The contractual engineering specification is negotiated based on cost, technology, and specification considerations between contractors and Government prior to contract award. The companion document to the engineering specification is the Airworthiness Qualification Specification (AQS) which describes the analysis and testing required at each step of the development process to show that the contractor's design will be able to meet the intent of the engineering systems specification. The AQS is negotiated in concert with the engineering specification and should reflect state-of-the-art design, analysis, and testing techniques. Equipment to be developed and qualified requires different development and qualification strategies depending on the complexity of the system or item and trade-offs between development costs, production costs, rotorcraft weight penalties associated with over-design and performance and reliability penalties associated with under-design. In general, the development strategy as reflected in the system and qualification specifications should at least reflect the following considerations:

a. Are a limited number of systems needed or is a large production quantity required? 

b. Is component qualification being conducted for installation on one rotorcraft or several kinds of rotorcraft?

c. Are total systems, rotorcraft and components, being procured as a package?

d. Is a rotorcraft component change likely to influence the rotorcraft vibration environment and/or component dynamic loading (i.e., a rotor. system change or a large suspended store) ?

Section 4 presents some general vibration criteria applicable to rotorcraft and rotorcraft subsystems. Section 5 gives detailed vibration specifications for rotorcraft and rotorcraft subsystem development. The analytical and model test efforts required early in the development process to predict vibration levels and help insure compliance with the specifications are described in Section 5. The rotorcraft ground and flight tests and the equipment level vibration tests which are required to substantiate compliance with the specifications prior to production are also described in Section 5.