So you want to modify your airplane from its original design.
Before you begin cutting, drilling, patching or altering your aircraft or any of its parts, you’ll need to obtain an FAA supplemental type certificate (STC) project number. After that, each step must be accomplished in accordance with the regulations.
An STC is the FAAs approval for you to create a design change on an aeronautical product, aircraft, engine or propeller. It is one of the processes the FAA uses to promote safe flight of civil aircraft in air commerce.
Even if you’re certain the fix will make your aircraft fly faster, burn less oil or improve overall efficiency, to maintain your aircraft’s airworthiness certificate you’ll need to receive an FAA STC project prior to beginning any modification work.
1. The first step is to fill out an application Form FAA 8110-12.
Along with the application, you’ll need to provide a detailed program plan called a Project Specific Certification Plan (PSCP) and a compliance checklist. When ready you’ll submit your application to the certification office in your local area.
2. Detailed test and computations.
Once the FAA opens your project, you must provide a detailed test and computations plan according to FAR Part 21 aircraft certification. This plan requires developing engineering design data and showing the FAA how you plan to modify your aircraft. You are responsible for demonstrating that the changed product will comply with applicable regulations and airworthiness standards.
3. Conformities for the test airplane.
You must conduct conformity inspections of each part and installation, which verifies to the FAA that the modification conforms to the design data. The FAA Manufacturing Inspection District Office (MIDO) or a designee must verify that each part and installation is accurate and complete and that you have complied with applicable regulations and airworthiness standards.
4. Accomplish test and computations.
Testing is normally required to demonstrate compliance with the applicable regulations. Component, ground, and flight-testing may be required. Required testing must be accomplished according to a detailed test plan, and the FAA must issue an authorization to accomplish compliance testing through a Type Inspection Authorization of Approved Request for Conformity.
5.Submit your documentation to the FAA.
The FAA requires that the applicant (you) prepare Instructions for Continued Airworthiness (ICA) that details the modification, how to maintain the airplane with the modification, and, if required, flight manual revisions. The FAA must approve major parts of the ICA documents.
The amount of time it takes to receive your STC after submission will depend on the complexity of your project. On average, plan for about two to three months, so be patient. To ensure your application package meets guidelines, schedule and coordinate inspections, meetings, tests and other events during the planning phase as much as possible.
What not to do when applying for a supplemental type certificate.
One sure-fire way to complicate and delay the process is to begin modifying your airplane before receiving your FAA STC project (with a project number). Each step of the modification must be accomplished under conformity! If the modification is not accomplished properly to show compliance with the regulations, then it may have to be re-worked back to its approved configuration.
Half of general aviation accidents are due to maintenance problems where people did not follow procedures and processes correctly. To stay safe and maintain your aircraft’s airworthiness follow these STC application protocols and get professional help when needed. Prior to seeking a modification, it’s a good idea to consult with a Designated Engineering Representative (DER) to find out if the desired change is feasible. You can also get more information about the process from Advisory Circular AC No: 21-40A.
Any individual or company may apply to change a type-certificated aircraft, aircraft engine, or propeller. However, if you want to sell the parts over the counter, you’ll need an additional Parts Manufacturing Authorization (PMA). For complex design modifications, the Aircraft Certification Office may ask that you follow the Original Design Approval Process.
Jimmy Tubbs is an aerospace engineer, A&P mechanic, licensed pilot and FAA Designated Engineering Representative (DER). He has over 50 years experience in GA developing modifications and certifications and working with vendors in more than a dozen countries. Jimmy is Chief Technical Officer for Blue Sky Innovations Group.
Have a question for Jimmy about your STC, or need help with an engineering problem? Just give us a call to schedule a consultation, we’re here to help you navigate the challenges and grow your business. Want to learn more about how to expand your business opportunities? Check out this post on best practices for going global with your GA product or service.