New Guidance: Casting and Proof of Structure

The FAA has released two new advisory circulars that may affect the PMA community.  Both advisory circulars are issued by the Transport Aircraft Directorate and apply to Part 25 aircraft (and parts thereof).

• Casting Factors, AC 25.621-1: This AC provides guidance for meeting the requirements of 14 C.F.R. 25.621.
  • This regulation imposes limits and restrictions on casting, and also requires a design approval applicant/holder to have control over the operations of a vendor casting facility.
  • The intention of both the regulation and the AC is to drive greater levels of consistency into casting (or to mitigate inconsistencies).
  • Discusses a means of qualifying a casting process

• Proof of Structure, AC 25.307-1: This AC provides guidance for meeting the requirements of 14 C.F.R. 25.307.
  • This regulation is for the demonstration of compliance for each critical loading condition.
  • The AC provides a list of factors that should be considered in deciding the need for and the extent of testing, including the load levels to be achieved.
  • The AC states that there are four certification approaches to choose from (and provides guidance on each one):
    • Analysis supported by new strength testing of the structure to limit and ultimate load.
    • Analysis validated by previous test evidence and supported with additional limited testing.
    • Analysis supported by previous test evidence.
    • Test only.

We would be interested in hearing from any MARPA member who is affected by one of these new advisory circulars.