Register

Aircraft Mods

Last year this Twin Cessna visited Yingling Aviation for some extensive modifications.
Gemini Sparkle

Key Takeaways:

  • Aircraft modifications are simplest when an existing Supplemental Type Certificate (STC) or its Approved Model List (AML) covers the desired change, particularly for avionics upgrades.
  • Obtaining new Field Approvals (Form 337) for major modifications is now challenging, often requiring FAA Designated Engineering Representative (DER) involvement and referral to Aircraft Certification Offices (ACOs).
  • For major or novel modifications without existing approvals, a new STC is mandatory, involving a complex, costly, and lengthy process of detailed applications, certification plans, extensive data submission, conformity inspections, and rigorous testing under FAA oversight.
See a mistake? Contact us.

Some aviators are perfectly happy flying what’s available. Others of us yearn for ever better-equipped aircraft. Somewhere in the middle is taking what you’ve got, and modifying it to better suit your mission, or even just your wishes. There are many avenues by which you can modify your aircraft. Let’s explore the most common. (Note: What follows is not intended to be a checklist or cookbook. Instead, the goal is to give you a good understanding of the complex requirements to approve a proposed modification.)

Has It Been Done?

The first step in your journey should be to check to see if anyone has already made the modification you want. You could Google the mod or go to the FAA’s Regulatory and Guidance Library at https://rgl.faa.gov/. For example, if you have a Cessna 340 and want to improve the turbo intercooler, you can check the database to see if the modification already exists. In this case, STC SA4158NM seems to fit the bill. The Supplemental Type Certificate (STC) owner is American Aviation, Inc. in Hayden Lake, ID.

Ready to Sell Your Aircraft?

List your airplane on AircraftForSale.com and reach qualified buyers.

List Your Aircraft
AircraftForSale Logo | FLYING Logo
Pilot in aircraft
Sign-up for newsletters & special offers!

Get the latest stories & special offers delivered directly to your inbox.

SUBSCRIBE