Supplemental Type Certificate
By Eric Barnhill – MyAnnual.net
A Supplemental Type Certificate (STC) is a Type Certificate (TC) that is issued to modify an aircraft (or component) from its original design.
Example: I have a Cessna 175, it originally came with a Continental GO-300 engine. I wanted to put a Lycoming 0-360-A1A engine on that airframe.
I found a company that had jumped through all the hoops with the FAA to get that application approved. I then purchased the right to use their STC to modify my aircraft.
The same goes for sun visors, glare shield covers, propellers, exhausts, etc.
Usually when you purchase an approved component for a certified aircraft the right to use that component (STC) on an aircraft listed in the Approved Model List (AML) comes with the component, but not always.
You, (or your mechanic) must be very careful to follow all the installation instructions and any other instructions that come with the STC. Usually a FAA FORM 337 (Major Repair and Alteration) must be filled out and submitted to the FAA. The work must be done by an A&P Mechanic (or someone working under the supervision of a A&P Mechanic), a repair station, or an approved manufacturer. The form is signed by both the person doing the work, and an A&P Mechanic with Inspection Authorization (IA), or equivalent.
The form is then submitted to the FAA and it goes into the permanent records for that aircraft.
Here is the link to the FAA STC Registry, click on Make, Just like the TCDS list, it lists all the manufacturers. Chose a manufacturer and then a model and it will list all the STCs for that model.
Word of warning! There are a lot of STC owners out there that either have lost interest or aren’t around anymore that will not respond to your inquiries concerning STCs that they own. I know, I have sent numerous letters to STC holders and received no response. I recommend that if you want to modify your certificated aircraft, search for the part (or process) you want to change on the internet. Most manufacturers own a STC for installation of their part or know who does.
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