In some cases, parts may be classified as exempt.
[FCR 6] Each part classified as exempt shall fit into one of the following categories:
- a. Non-structural parts with no credible failure mode caused by a flaw.
- b. Non-structural parts with no credible potential for causing a catastrophic hazard.
- c. Other non-structural parts approved by the RFCB for exempt status.
[Rationale: Non-structural parts that do not have a credible failure mode caused by a flaw and those with no credible potential for causing a catastrophic hazard do not need to be assessed for fracture criticality because they do not pose a catastrophic hazard.]
Use of an alternative approach requires unique rationale and approval by the RFCB as described in section 10 [FCR 26] in this NASA Technical Standard.
Parts that are identified and shown to meet the exempt classification criteria in documentation cited in the Fracture Control Summary Report (FCSR) in accordance with the requirements listed in section 9 of this NASA Technical Standard comply with fracture control requirements without further activity beyond conventional aerospace verification and quality assurance procedures, unless otherwise indicated in this document.
Exempt parts typically include non-structural items or items that do not have a credible failure mode related to the presence of a flaw, such as flexible insulation blankets, enclosed electrical circuit components/boards, wire bundles, and certain batteries listed in section 6.1.6 in this NASA Technical Standard. The RFCB may accept other items as exempt based on rigorous development programs that establish their safety and functional reliability.
Non-structural parts are generally those not intended to resist loads. A part that may be structural in one system or application may not be in another. Discussion with the RFCB may be necessary.