Wencor Group




All repairs are developed in accordance with our FAA-approved Engineering Standards Manual (FES81). FES 81 was initially developed by Fortner’s engineering team in 1981 in support of our issuance of SFAR-36 authority. Our in-house DER’s have continued to update FES to reflect current best practices and FAA Regulatory requirements. Repairs determined to be ‘major’ are accomplished utilizing the expertise of Fortner’s engineering staff and authorized by Fortner’s in-house FAA-DER. Prior to implementation, the engineering staff will test the component to ensure design performance of the Component Processing Package.

The FAA documented Fortner’s ability to utilize this manual for these approvals by including the following wording directly to our Operation Specification:

“Fortner Engineering Standards Manual, FES-81, FAA Approved 06-15-95 (as amended), may be used to establish repairs of aircraft hydraulic components not covered in the applicable manufacturer’s component maintenance manual.”

Fortner Engineering was effectively given authorization to “develop and use major repair data which is not specifically approved by the Administrator” with the issuance by the FAA of SFAR-36 in 1980. In simple terms, this allowed Fortner to develop and implement repairs that were not covered in the OEM’s Component Maintenance Manuals (CMM’s). This industry-recognized practice allowed Fortner to repair, rather than replace, many unserviceable major detail components that remain classified as non-repairable in the CMM.

As SFAR-36 was phased out, Fortner began the on-attrition conversion of these SFAR-36 approved repairs to Designated Engineering Representative (DER) approved repairs with the involvement and concurrence of the local FAA authority. Today all newly developed repair procedures are approved utilizing Fortner’s on-staff DER and are incorporated upon receipt of customer approval.

To date, Fortner has over 1,200 DER / FES-81 approved repair procedures which have saved the airline industry an incalculable amount of time and money.



FAA Operations Specifications


EASA Approval Certification


Boeing Approved
Supplier Certification

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