DI-SESS-81498A

Structural Design Criteria Report (Helicopters)

Documents information necessary to delineate and expand system mission requirements into specific structural terms, providing a basis for presenting the contractor's interpretation of system requirements for determining airframe structural loads and design.

Approval DateNovember 26, 2019

AMSC NumberN10104

Preparing ActivityAS

Project NumberSESS-2019-054

OPR—

DTIC ApplicableYes

GIDEP Applicable—

Limitation—

Applicable Forms—

Approval Limitation—

Form Version—

DID Formatfree_text

963C CompliantYes

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

Supersedes

DI-RELI-81498

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Description & Purpose

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Application & Interrelationship

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Use & Relationship

The structural design criteria report documents information necessary to delineate and expand into specific structural terms, the system mission requirements. The purpose of this report is to document these specific structural terms and requirements and to provide a basis for presenting the contractor's interpretation of system requirements for the determination of airframe structural loads and subsequent design.

This data item description (DID) contains the format, content, and intended use information for the data deliverable resulting from the work task described in the contract.

This DID supersedes DI-RELI-81498.

Defense Technical Information Center (DTIC), Attn: DTIC-FDAC, Bldg.5, Cameron Station, Alexandria, VA 22304-6145.

Preparation Instructions

1Reference DocumentsNone.

2FormatThe report shall be in contractor format.

3ContentThe report shall contain the following:

3.1A complete list of all deviations requestedfrom the structural design requirements as cited in the contract and the reason for such requests shall be included as an appendix to the report.

3.2Criteria for service loads design spectraincluding planned operational usage (mission and ground profiles), dynamic response methods, summary of design and analysis conditions (flight and ground), discussions of design features which affect determination of mission segments contribution on fracture/fatigue damage, and other data pertinent to service loading conditions or design.

3.3Flight loads design criteria, including three viewsof the helicopter, vehicle physical characteristics descriptions and surface areas, the maximum and minimum gross weights, a weight breakdown of all variable weight items, center of gravity envelopes. The specific design conditions selected for detail analysis together with basis for their selection and method of analysis projected for the various maneuver conditions. Discussions of design features, which affect determination of critical conditions, sources of aerodynamic data, methods and assumptions applied in the calculation of aerodynamic loads, design V-n diagrams, rotational velocities and acceleration, temperature criteria, weights with definitions of each, all possible loading configuration, and an altitude-velocity envelope.

3.4Ground loads criteria, shall be presented forthe terrestrial landing condition and ship deck landing separately. This covers a summary of design gross weights, center of gravity positions, all practicable distributions of variable and removable mass items that will be considered for design. Also, range of touchdown speeds, takeoff speeds, sinking speeds, helicopter touchdown attitudes, terrain roughness, CBR's, load factors, external load configurations, the specific design conditions selected for detailed analyses, discussion of design features which affect determination of critical conditions and other parameters pertinent to the ground loads. Whenever necessary, substantiating data, pertinent references, and additional discussion shall be included to indicate that the range of parameters considered comply with applicable design requirements.

3.5Control system loads, including appropriate summariesof loads to be used for design. Components of the control system, their functions, and operation shall be explained in sufficient detail to show clearly their operation and source loads.

3.6Water loads criteria, presenting the maximumand minimum gross weights, center of gravity envelopes, sea conditions, the specific design conditions selected for analysis and basis of their selection, the methods employed in the analysis of water loads and pressures and their distributions, weight distributions, design load factors, angular velocities and accelerations, store configurations, and other items pertinent to water loading conditions.

3.7For all cargo/personnel carriers a complete detaileddescription of structural design criteria utilized for troop and passenger seats, cargo tie downs, lifters, cargo aerial delivery, cargo jettison, cargo hooks, rescue hoist, mission equipment etc.

3.8Repeated loads and fatigue criteria, including spectraused for design and fatigue methodology report(s). Methods of analyzing mission profile, flight time for each mission, mission distribution and ground-air-ground (GAG) cycles shall be presented. In addition, rotor blade and tail surface fold spectra and landing gear and ground maneuvering/operations fatigue spectra shall also be included.

3.9Miscellaneous flight loads criteria, presenting critical loadsencountered during rotor starting, braking for all rotors, blade trailing edge loads at transonic speeds, limit load factors for design store pylons and other support structures.

3.10Miscellaneous ground loads criteria, presenting discussion ofdesign features which affect determination of critical conditions when helicopter on ground such as towing, jacking, hoisting, rebound and securing. Various landing field condition including ship deck.

3.11Wind loads criteria, covering critical rotor speedfor ground flapping and impact of gust generated by the ship-structure for ship-based helicopters.

3.12Crash loads criteria, presenting the maximum g-loadsalong vertical, lateral and longitudinal directions for crew, passenger, engine, transmission, fuel tank landing gears, and other structural items. Crash energy absorbing consideration for protecting crew during crash will be discussed.

References

DTIC Applicable https://discover.dtic.mil/submit-documents/

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