Use of FEA in showing FAR compliance
Use of FEA in showing FAR compliance
(OP)
Can someone provide a reference to the FAR or AC or AMDT that indicates what is required to demonstrate FEA compliance with section 25.307 of the FARs?
Thanks,
jetmaker
Thanks,
jetmaker





RE: Use of FEA in showing FAR compliance
maybe a few more details would help us help you ?
if the structure isn't primary then there shouldn't be much problem. if it is primary, then you need to be more careful. If it is carrying flight loads (from the basic airplane) then you need to account for these, as well as any loads due to your installation.
RE: Use of FEA in showing FAR compliance
In my experience the FAA , CAA (UK) and EASA all buy off on the FEM/FEA provided adequate v&v is included in the documentation. If holes (in the data) are apparent the whole MoC of the aircraft can be cast in doubt, invariably re-doing the FEM (or a part of it) has significant downstream costs in both time and money.
RE: Use of FEA in showing FAR compliance
The analysis I am doing is on ECS and electrical support brackets for flight controls. The analysis covers the basic information that Aerodesign refers to. What I was eluding to is it appears that the DER who will sign off on the work wants checks made against theoretical analyses. Just wondering if there was a doc that said all FEMs need to be verified such that load balances are shown, sample checks against theory, output files included as hardcopy in report, etc.
Thanks.
jetmaker
RE: Use of FEA in showing FAR compliance
i think MSC have a page on quality control checks for FEMs (i'll see if i can find it)
RE: Use of FEA in showing FAR compliance
go to ... http://ntrs.nasa.gov/search.jsp
search for NASA-CR-4675,
most of what it says has already been said, but at least you have a proper reference
RE: Use of FEA in showing FAR compliance
AC 20-107A Composite Aircraft Structure
AC 25-10 Guidance for installation of miscellaneous, nonrequired electrical equipment
This advisory circular (AC) sets forth a method of compliance with the requirements of Part 25 of the Federal Aviation Regulations (FAR) pertaining to installations of miscellaneous, nonrequired electrical equipment in transport category airplanes. It is for guidance purposes and provides an example of a method of compliance that has been found acceptable. It covers FAR 25.307.
AC 25.21 CERTIFICATION OF TRANSPORT AIRPLANE STRUCTURE
Background. Section 25.307 of the FAR was recodified from § 4b.202 of Civil Air Regulations (CAR) in 1964. During recodification, the text was revised for the purpose of technical clarification, but the intent of the requirement remained the same. Prior to adoption of part 4b of the CAR, a similar requirement existed in CAR 04, where § 04.3 required proof of compliance with the strength and deformation requirements of § 04.2.
The Civil Air Regulations (CAR) are on my web site at: http://www.stacheair.com under Repair Stations.
Stache
RE: Use of FEA in showing FAR compliance
AC25-10 restates regarding 25.307 "Structural analysis was allowed only if the structure conformed to that which experience had shown the methods to be reliable."
According to the DERs I support, their FAA advisors interpret this to mean that (complex) FEA work must be correlated to test data in order to establish a method which can be considered reliable. The method may then be applied to similar structures.
Given the wide variety of FEA methods (different types of elements, constraints, element sizes, etc. may constitute different methods), the burden of showing correlation to test can be tedious.
I would be very interested in hearing experience of anyone obtaining structural approval via FEA without correlating test results.