Introduction
Due to their inherent criticality, all changes to the design of an aircraft are required to be approved in some form. How this is achieved varies from country to country. Generally, modifications and repairs deemed to be “minor”, such as the installation of a radio or the repair to upholstery, may be approved by the aircraft mechanic or maintenance engineer. However, larger changes, such as changing the type of engine or increasing the maximum weight, are deemed “major” and require formal approval from the applicable authority.
As its name suggests, an STC is a certificate. It defines the product design change, states how the modification affects the existing type design, and lists serial number effectivity. It also identifies the certification basis, listing specific regulatory compliance for the design change. Information contained in the certification basis is helpful for those applicants proposing subsequent product modifications and evaluating certification basis compatibility with other STC modifications.
Under the U.S. FAA’s regulatory system, there are various methods to obtain approval for a major modification or repair to a type-certified aircraft (the following list is not exhaustive):
A data approval issued by a Designated Engineering Representative which is usually issued on a FAA Form 8110-3
A data approval issued by an Organization Designation Authorization Holder using ODA Procedures
A Field Repair, which may be issued on a FAA Form 337, or
A Supplemental (or Supplementary) Type Certificate (STC).
What is an STC?
A Supplemental Type Certificate (STC) is a type certificate (TC) issued when an applicant has received FAA approval to modify an aeronautical product from its original design. As it adds to the existing type certificate, it is deemed “supplemental”.
The STC, which incorporates by reference the related TC, approves not only the modification but also how that modification affects the original design. (To also consider the potential affect on the Maintenance Program â MSG 3 Analysis may be required to develop additional maintenance obligations).
What if it is a Significant Modification?
For complex design modifications, the FAA Aircraft Certification Office (ACO) may ask that you follow the Original Design Approval Process.
An original FAA design approval is a multi-phase process in which an applicant applies for, and the FAA may issue, a type certificate or design approval of a product or a major design change to a product. A product is an aircraft, an aircraft engine or, an aircraft propeller.
The process, if approved, results in the issue of a type certificate, a supplemental type certificate or an amendment to either a type certificate or supplemental type certificate as contained in 14 CFR part 21.
The principles of up-front planning, project management, and documenting the certification process are applicable to all applicants. A major change to the design of a type-certificated product is approved by a separate process and issued on a supplemental type certificate or an amended type certificate.
If a person holds the TC for a product and alters that product by introducing a major change in type design that does not require an application for a new TC under § 21.19, that person must either apply to the appropriate aircraft certification office for an STC or apply to amend the original type certificate under subpart D of this part.
If a person does not hold the TC for a product and alters that product by introducing a major change in type design that does not require an application for a new TC under § 21.19, that person must apply to the appropriate aircraft certification office for an STC.
The application for an STC must be made in the form and manner prescribed by the FAA.
STC Benefits
An STC has the following benefits over other forms of modification or repair approval:
It may be developed and owned by a person other than the aircraft or equipment manufacturer,
It is essentially unlimited in the scope of the modification.
It may cover a single aircraft (serial number) or many types of aircraft.
It may be bought and sold
It has greater recognition and acceptance in foreign countries.
Due to these advantages, many minor modifications are also approved under STCs for increased salability.
STC Owner Privileges
The holder of a supplemental type certificate may –
In the case of aircraft, obtain airworthiness certificates;
In the case of other products, obtain approval for installation on certificated aircraft; and
Obtain a production certificate in accordance with the requirements of subpart G of this part for the change in the type design approved by the supplemental type certificate.
STC Owner Responsibilities
A supplemental type certificate holder who allows a person to use the supplemental type certificate to alter an aircraft, aircraft engine, or propeller must provide that person with written permission acceptable to the FAA.
What are the STC process – major steps?
Applicant applies for STC
Familiarization and preliminary type certification board (TCB) meetings
FAA develops certification program plan
Establishment of certification basis by FAA (Establishment of Certification Basis which is essentially the same as for a change to type design.)
14 CFR 21.115(a), Applicable requirements
Each applicant for a supplemental type certificate must show that the altered product meets applicable requirements specified in 14 CFR 21.101 and,
In the case of an acoustical change, show compliance with the applicable noise requirements of 14 CFR part 36 and,
In the case of an emissions change, show compliance with the applicable fuel venting and exhaust emissions requirements of 14 CFR part 34.
Applicant submits data for approval
FAA design evaluation
FAA and applicant hold specialists and interim type certification meetings, as required
FAA performs conformity inspections
Engineering compliance determinations
Pre-flight TCB Meeting
Applicant performs ground inspections, ground tests, and flight tests
FAA reviews manufacturer’s flight test results and issues TIA (Type Inspection Authorisation)
FAA performs conformity inspections, witnesses tests, performs official certification flight tests and flight standards evaluations
Functional and reliability testing
FAA approves flight manual supplement or supplemental flight manual and holds final TCB meeting
AEG completes continuing airworthiness determination
FAA issues STC
Notes – An STC will be issued only if:
the pertinent technical data have been examined and found satisfactory, all necessary tests and compliance inspections have been completed, and the alteration has been found to conform with the technical data.
An STC will NOT be issued to:
Approve minor changes, or for approval of identical replacement parts, unless the installation of such parts constitutes a major change to the type design
Approve design changes to Technical Standard Order (TSO) approved articles unless the TSO is invalidated for the modified article.
An STC which modifies a TSO article must provide for installation
Combine two or more STCs without additional showing of compliance; or
Manufacturers or applicants outside of the U.S., except as provided for in a bilateral agreement.
Single Issue STC (One-Only STC)
A âOne-onlyâ STC may be issued for a particular aircraft, identified by make, model, and serial number. A one-only STC cannot be amended and the holder is not eligible for production approval. Application for a multiple STC is required for subsequent approvals of the modification.
Non-Interference STC
A non-interference, or no-hazard, STC addresses a convenience function modification that is not required by the applicable airworthiness standards. The STC Limitations and Conditions section specifies the extent, or limitation, of the modification approved by the FAA.
I’ve found a supplemental type certificate that I want to install on my airplane. What do I do now?
You must contact the supplemental type certificate holder to seek written permission. The supplemental type certificate and its related information â all drawings, data, specifications â are the property of the supplemental type certificate holder.
Note – FAA will not release this information without authorization from the owner.
See 14 CFR § 21.120, Responsibility of supplemental type certificate holders to provide written permission for alterations.
I can’t find the supplemental type certificate holder. What do I do now?
If the mail you sent was returned “undeliverable” and there is no phone listing for the holder, please contact the issuing FAA office. Supplemental type certificates are approved and issued through the FAA Aircraft Certification Office (ACO) which serves the geographic area of the supplemental type certificate ownerâs residence.
Where can I find information about STCs installed on my aircraft?
If you need information about supplemental type certificates that have been installed on your aircraft, you may:
Search the Supplemental Type Certificates database in the on-line Regulatory and Guidance Library, or Go to the Aircraft Registration, Records & Reports section, to request copies of records for your aircraft.
Support for the Certification Process
Designated Engineering Representatives (DER) – Engineering and Flight Test designees are responsible for finding that engineering data complies with the appropriate airworthiness standards. These designees are called Designated Engineering Representatives, or DERs.
A DER is an individual, appointed in accordance with 14 CFR section 183.29, who holds an engineering degree or equivalent, possesses technical knowledge and experience, and meets the qualification requirements of Order 8100.8.
A DER may be appointed to act as a Company DER and/or Consultant DER.
Company DERs can act as DER for their employer and may only approve, or recommend approval, of technical data to the FAA for the company.
Consultant DERs are individuals appointed to act as an independent DER to approve or recommend approval of technical data to the FAA.
A Designated Airworthiness Representative (DAR) is an individual appointed in accordance with 14 CFR 183.33 who may perform examination, inspection, and testing services necessary to the issuance of certificates.
There are two types of DARs: manufacturing, and maintenance. DAR-T and DAR-F – A DAR-F primarily inspects/certifies new aircraft that have never been issued an airworthiness certificate (original certification.) A DAR-T inspects/re-certifies aircraft (recurrent certification.) DARs work within their geographic region, a geographic expansion maybe obtained however starting in 2015 some of these expansion request have been denied due to national policy changes.
Acting on behalf of the FAA in the certification of type certificated and amateur-built aircraft for the issuance of airworthiness certificates, special flight permits, import aircraft, export certificates for products and articles, conformity inspections and field approvals for repair and alterations.
Most DARs have limited and/or certain “functions” authorized by the FAA based on their experience and technical background.
Manufacturing DARs must possess aeronautical knowledge, experience, and meet the qualification requirements of Order 8100.8.
Maintenance DARs must hold a mechanic’s certificate with an airframe and powerplant rating under 14 CFR part 65, Certification: Airmen Other Than Flight Crewmembers, or
a repairman certificate and be employed at a repair station certificated under 14 CFR part 145, or an air carrier operating certificate holder with an FAA-approved continuous airworthiness program and must meet the qualification requirements of FAA Order 8100.8, Chapter 14.
The aircraft owner or agent of aircraft owner may contact a DAR directly, the local FAA Flight Standards District Office (FSDO) or Manufacturing Inspection District Office (MIDO) for assistance.
For additional information please see www.sassofia.com or email office@sassofia.com
