ASTM F3114-21

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F3114 − 19 F3114 − 21
Standard Specification for
Structures
This standard is issued under the fixed designation F3114; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification addresses the structural requirements that apply to all portions of the airframe regardless of component,
system, or structure.
1.2 This specification was originally conceived for small airplanes as defined in the F44 terminology standard but may find broader
applicability. Use of the term aircraft throughout this specification is intended to allow the relevant CAA(s) to accept this standard
as a means of compliance as they determine it to be appropriate, whether for small airplanes or for other types of aircraft.
1.3 The applicant for a design approval must seek individual guidance from their respective CAA body concerning the use of this
standard as part of a certification plan. For information on which CAA regulatory bodies have accepted this standard (in whole
or in part) as a means of compliance to their Small Airplane Airworthiness Rules (hereinafter referred to as “the Rules”), refer to
ASTM F44 webpage (www.ASTM.org/COMMITTEE/F44.htm) which includes CAA website links.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
F3060 Terminology for Aircraft
F3061/F3061M Specification for Systems and Equipment in Small Aircraft
F3083/F3083M Specification for Emergency Conditions, Occupant Safety and Accommodations
F3093/F3093M Specification for Aeroelasticity Requirements
F3115/F3115M Specification for Structural Durability for Small Aeroplanes
F3116/F3116M Specification for Design Loads and Conditions
3. Terminology
3.1 See Terminology F3060 for more definitions and abbreviations.
This specification is under the jurisdiction of ASTM Committee F44 on General Aviation Aircraft and is the direct responsibility of Subcommittee F44.30 on Structures.
Current edition approved Nov. 1, 2019May 1, 2021. Published December 2019May 2021. Originally approved in 2015. Last previous edition approved in 20152019 as
F3114–15.–19. DOI: 10.1520/F3114–19.10.1520/F3114-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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4. Strength
4.1 Loads—Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate
loads (limit loads multiplied by prescribed factors of safety).
4.2 Factor of Safety—Unless otherwise provided, a factor of safety of 1.5 must be used.
4.3 Strength and Deformation:
4.3.1 The structure must be able to support limit loads without detrimental, permanent deformation. At any load up to limit loads,
the deformation may not interfere with safe operation.
4.3.2 The structure must be able to support ultimate loads without failure for at least three seconds, except local failures or
structural instabilities between limit and ultimate load are acceptable only if the structure can sustain the required ultimate load
for at least three seconds. However when proof of strength is shown by dynamic tests simulating actual load conditions, the three
second limit does not apply.
4.4 Proof of Structure:
4.4.1 Compliance with the strength and deformation requirements of 4.3 must be shown for each critical load condition. Structural
analysis may be used only if the structure conforms to those for which experience has shown this method to be reliable. In other
cases, substantiating load tests must be made. Dynamic tests, including structural flight tests, are acceptable if the design load
conditions have been simulated.
4.4.2 Certain parts of the structure must be tested as specified.
4.5 Mass Balance—The supporting structure and the attachment of concentrated mass balance weight used on control surfaces
must be designed for:
4.5.1 24 g normal to the plane of the control surface;
4.5.2 12 g fore and aft; and
4.5.3 12 g parallel to the hinge line.
4.6 Canard or Tandem Wing Configurations:
4.6.1 The forward structure of a canard or tandem wing configuration must:
4.6.1.1 Meet all requirements of this standard, Specifications F3116/F3116M, F3093/F3093M, F3083/F3083M, and F3115/
F3115M applicable to a wing; and
4.6.1.2 Must meet all requirements applicable to the function performed by these surfaces.
4.7 Windshields and Windows:
4.7.1 The internal panels of windshields and windows must be constructed of a nonsplintering material, such as but not limited
to:
4.7.1.1 Nonsplintering safety glass; or
4.7.1.2 Synthetic resins.
4.7.2 The design of windshields, windows, and canopies in pressurized airplanes must be based on factors peculiar to high altitude
operation, including:
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4.7.2.1 The effects of continuous and cyclic pressurization loadings;
4.7.2.2 The inherent characteristics of the material used; and
4.7.2.3 The effects of temperatures and temperature gradients.
4.7.3 On pressurized airplanes, if certification for operation up to and including 25 000 ft is requested, an enclosure canopy
including a representative part of the installation must be subjected to special tests to account for the combined effects of
continuous and cyclic pressurization loadings and flight loads, or compliance with the fail-safe requirements of 4.7.4 must be
shown.
4.7.4 If certification for operation above 25 000 ft is requested, the windshields, window panels, and canopies must be strong
enough to withstand the maximum cabin pressure differential loads combined with critical aerodynamic pressure and temperature
effects, after failure of any load-carrying element of the windshield, window panel, or canopy.
4.7.5 In the event of any probable single failure, a transparency heating system must be incapable of raising the temperature of
any windshield or window to a point where there would be:
4.7.5.1 Structural failure that adversely affects the integrity of the cabin; or
4.7.5.2 A danger of fire.
4.7.6 In addition, for Level 4 airplanes, the following applies:
4.7.6.1 Windshield panes directly in front of the pilots in the normal conduct of their duties, and the supporting structures for these
panes, must withstand, without penetration, the impact of a 2-lb2 lb bird when the velocity of the airplane (relative to the bird along
the airplane’s flight path) is equal to the airplane’s maximum approach flap speed.
4.7.7 The windshield and side windows forward of the pilot’s back when the pilot is seated in the normal flight position must have
a luminous transmittance value of not less than 70 %.
4.8 Landing Gear:
4.8.1 For Level 4 airplanes, the following general requirements for the landing gear apply:
4.8.1.1 Each airplane must be designed so that, with the airplane under control, it can be landed on a paved runway with any one
or more landing-gear legs not extended without sustaining a structural component failure that is likely to cause the spillage of
enough fuel to constitute a fire hazard.
4.8.1.2 Compliance with the provisions of this section may be shown by analysis or tests, or both.
4.9 Testing—The suitability of each questionable design detail and part having an important bearing on safety in operations must
be established by tests.
4.9.1 Wings—The strength of stressed-skin wings must be proven by load tests or by combined structural analysis and load tests.
4.9.2 Control Surfaces:
4.9.2.1 Limit load tests of control surfaces are required. These tests must include the horn or fitting to which the control system
is attached.
4.9.2.2 In structural analyses, rigging loads due to wire bracing must be accounted for in a rational or conservative manner.
4.9.3 Pressurization Tests—Strength test. The complete pressurized cabin, including doors, windows, canopy, and valves, must be
tested as a pressure vessel for the pressure differential specified in Specification F3116/F3116M.
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5. Mass and Mass Distribution
5.1 Load Distribution Limits—The load distribution limits may not exceed any of the limits at which the structure is proven.
5.2 Leveling Means—There must be means for determining when the airplane is in a level position on the ground.
6. Materials, Processes, and Methods of Fabrication
6.1 Materials and Workmanship:
6.1.1 The suitability and durability of materials used for parts, the failure of which could adversely affect safety, must:
6.1.1.1 Be established by experience or tests;
6.1.1.2 Meet approved specifications that ensure their having the strength and other properties assumed in the design data; and
6.1.1.3 Take into account the effects of environmental conditions, such as temperature and humidity, expected in service.
6.1.2 Workmanship must be of a high standard.
6.2 Fabrication Methods:
6.2.1 The methods of fabrication used must produce consistently sound structures. If a fabrication process (such as gluing, spot
welding, or heat-treating) requires close control to reach this objective, the process must be performed under an approved process
specification.
6.2.2 Each new aircraft fabrication method must be substantiated by a test program.
6.3 Material Strength Properties and Design Values:
6.3.1 Material strength properties must be based on enough tests of material meeting specifications to establish
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