To apply for a Supplemental Type Certificate, submit FAA Form 8110-12 (“Application for Type Certificate, Production Certificate, or Supplemental Type Certificate”) together with a complete technical data package to the FAA certification branch office covering your region. Form 8110-2 is not the application — it is the STC itself, an internal FAA document the agency fills out and issues to you once your major design change has cleared engineering review.1Federal Aviation Administration. Form FAA 8110-2 – Supplemental Type Certificate
Confirm You Actually Need an STC
Federal regulations split design changes into minor and major. A minor change has no appreciable effect on weight, balance, structural strength, reliability, or operational characteristics. Everything else is major.2eCFR. 14 CFR 21.93 – Classification of Changes in Type Design If you hold the original type certificate, you can either amend it or apply for an STC. If you don’t hold the type certificate, an STC is your only route.3eCFR. 14 CFR 21.113 – Requirement for Supplemental Type Certificate
STC or Field Approval
Some major alterations qualify for a field approval instead, where a flight standards inspector signs off on a modification for a single aircraft identified by serial number. FAA Order 8900.1 sets out which alterations can go the field-approval route and which require the full STC process.4Federal Aviation Administration. Field Approvals and Supplemental Type Certificates The practical difference is scope: a field approval covers one airframe; an STC can be applied to every aircraft of the same make and model. If you plan to install or sell the modification more than once, the STC is what you want.
What an STC Won’t Cover
The FAA will not use the STC process to approve minor changes, approve identical replacement parts (unless installing them creates a major change), combine two existing STCs without new compliance data, or approve design changes to TSO articles unless the change also addresses installation on a certificated aircraft. Applicants outside the United States cannot receive an STC unless a bilateral agreement with their country provides for it.4Federal Aviation Administration. Field Approvals and Supplemental Type Certificates
Decide Which Type of STC to Request
A standard STC applies to a specific make and model and can be used on any qualifying airframe. A one-only STC covers a single aircraft by make, model, and serial number; it cannot be amended, and the holder is not eligible for a production approval. Extending a one-only modification to other aircraft later requires a new, multiple-use STC.4Federal Aviation Administration. Field Approvals and Supplemental Type Certificates
For a modification that fits many different aircraft models, such as an avionics suite, the FAA allows an Approved Model List STC (AML-STC), which covers multiple models under one certificate. Advisory Circular 20-180 describes one acceptable path to an AML-STC, and applicants may propose alternative methods that meet the same requirements.5Federal Aviation Administration. AC 20-180 – Approved Model List Supplemental Type Certificate (AML-STC) A separate no-hazard or non-interference STC addresses convenience-function modifications not required by airworthiness standards; the STC’s limitations section will note the restricted scope of the approval.
Fill Out FAA Form 8110-12
The application is FAA Form 8110-12, a PDF on the FAA’s website.6Federal Aviation Administration. FAA Form 8110-12 – Application for Type Certificate, Production Certificate, or Supplemental Type Certificate For an STC or amended STC, complete Blocks 1, 2, 3, 4, 7, and 8.
- Block 1 is the applicant name — the person, corporation, or organization as it should appear on the certificate.
- Block 2 is the application type; check STC or Amended STC.
- Block 3 identifies the product as aircraft, engine, or propeller.
- Block 4 is the applicant’s physical address. A P.O. box is not accepted.
- Block 7 is the substantive core: the make and model designations of the product being modified (7a); a description of the modification (7b); the existing STC number if amending (7c); whether data will be sold to others (7d); whether parts will be manufactured for sale under 14 CFR 21.303 (7e); and whether the request is for a one-only STC (7f).
- Block 8 is the signature of the applicant or an authorized certifying official.
The form’s current OMB approval expires October 31, 2026. If you’re applying after that date, pull a refreshed version from the FAA forms library before submitting.
Assemble the Technical Data Package
The form is the easy part. The technical data package proves your modification is safe, and it’s what the FAA actually spends its time reviewing. You must show that the altered product meets the airworthiness requirements in the original type certificate, any special conditions the FAA prescribes, and any applicable human factors requirements.7eCFR. 14 CFR 21.115 – Applicable Requirements The package has two sides.
Descriptive data defines what the modification is and how it gets installed: engineering drawings, material specifications, wiring diagrams, and installation instructions. Substantiating data proves it’s safe: stress analyses, structural load calculations, flight test reports, fatigue evaluations, and any other engineering analyses the certification basis calls for. Acoustical, emissions, or fuel-efficiency changes trigger additional compliance showings under Parts 36, 34, or 38.8eCFR. 14 CFR 21.115 – Applicable Requirements
Every drawing and report has to align exactly with the information on Form 8110-12. Inconsistencies between the application and the data package are one of the easiest ways to trigger delays.
Instructions for Continued Airworthiness
The package must include Instructions for Continued Airworthiness (ICA) — the maintenance manuals and inspection procedures operators need to keep the modification safe in service. Under 14 CFR 21.50, the holder of a design approval for which an application was made after January 28, 1981, must furnish at least one complete set of ICA to the owner of each affected aircraft, engine, or propeller, and must distribute changes to those instructions.9eCFR. 14 CFR 21.50 – Instructions for Continued Airworthiness and Manufacturer’s Maintenance Manuals Having Airworthiness Limitations Sections Any parts you designate as commercial parts must appear on a list in the ICA. Deferring ICA preparation is a common planning mistake; the FAA will not issue the STC without them.
Where to Submit the Application
Send the completed Form 8110-12 and certification plan to the certification branch office with geographic jurisdiction over your primary facility.10Federal Aviation Administration. Guide for Obtaining a Supplemental Type Certificate What used to be called Aircraft Certification Offices are now organized under three regional branches.11Federal Aviation Administration. Certification Branches
- The West Certification Branch covers Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming, with offices in Anchorage, Denver, Los Angeles (Lakewood), and Seattle (Des Moines).
- The Central Certification Branch covers Arkansas, Illinois, Indiana, Iowa, Kansas, Louisiana, Michigan, Minnesota, Missouri, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, Texas, and Wisconsin, with offices in Chicago (Des Plaines), Fort Worth, and Wichita.
- The East Certification Branch covers the New England, mid-Atlantic, and southern states from Alabama through Virginia, with offices in Atlanta (Hapeville), Boston (Burlington), and New York (Westbury).
Contact the office nearest your facility before submitting. Even an informal phone call can clarify what the office expects in the certification plan and save weeks of rework.
What Happens After You Apply
The FAA stands up a certification project and assigns a project manager. The work then moves through familiarization, requirements definition, compliance, and implementation phases.12Federal Aviation Administration. Supplemental Type Certificate Process – Application to Issuance
Expect a familiarization meeting at which you brief the certification team on the modification. The FAA then holds a preliminary Type Certification Board (TCB) meeting to establish the certification basis, identify special conditions, and flag issue papers. You and the FAA jointly develop a Project Specific Certification Plan covering compliance methods, testing schedule, and responsibilities on both sides.
Once the plan is set, you submit engineering data for review. The FAA performs design evaluations, conducts conformity inspections on test articles, and may witness engineering and flight tests. Interim TCB meetings resolve open items. If the modification affects the flight manual, the FAA reviews and approves a flight manual supplement. A pre-flight TCB meeting precedes the FAA’s certification flight tests, and a final TCB meeting closes out compliance findings.
The FAA issues the STC — Form 8110-2 — once it finds that you have met 14 CFR 21.113 and 21.115.13eCFR. 14 CFR 21.117 – Issue of Supplemental Type Certificates The certificate consists of the FAA’s approval of the design change together with the type certificate previously issued for the product. There is no FAA filing fee for the application itself; your costs are the engineering, testing, and any consultant work needed to build the data package and carry the project through.
Timelines vary widely. A simple interior modification can clear in a few months. An engine swap or structural redesign can take well over a year. The biggest variable is how clean the data package is on first submission and how many open issues surface during compliance reviews.
Using a Designated Engineering Representative
You don’t have to send every drawing through an FAA engineer. Designated Engineering Representatives (DERs) are individuals the FAA appoints to approve, or recommend approval of, technical data on the agency’s behalf. A DER holds an engineering degree or equivalent, has relevant technical expertise, and meets the qualification standards in FAA Order 8000.95.14Federal Aviation Administration. Designated Engineering Representatives
A Company DER works for one employer and can only approve data for that company’s projects. A Consultant DER operates independently and can approve data for any applicant. Smaller shops without in-house engineering staff typically hire a consultant DER. Either type reduces the volume of data submittals that need direct FAA engineer review, and that can shorten the compliance phase considerably.