Is a Supplemental Type Certificate Approved Data?


Heather Bennett

Is a Supplemental Type Certificate (STC) Approved Data?

When it comes to aircraft modifications, the Supplemental Type Certificate (STC) plays a vital role in ensuring compliance with aviation regulations. But what exactly is an STC, and is it considered approved data?

Understanding the Supplemental Type Certificate

An STC is a document issued by the relevant aviation authority that approves a modification or alteration to an aircraft’s design or configuration. It grants permission for the installation of a specific modification, allowing an aircraft to deviate from its original type design as defined by the Type Certificate (TC).

An STC typically includes detailed information about the approved modification, such as engineering drawings, specifications, installation instructions, and any necessary flight manual supplements. This documentation provides vital guidance for mechanics, engineers, and pilots involved in implementing and operating the modified aircraft.

The Status of an STC as Approved Data

While an STC itself is not considered “approved data,” it references approved data sources that validate its compliance with applicable regulations. The primary source of approved data for an STC is the Airworthiness Limitations Section (ALS), which contains instructions and maintenance tasks necessary to ensure continued airworthiness after implementing the modification.

The ALS outlines specific inspections, checks, replacements, and other maintenance activities that must be performed on a regular basis to keep the modified aircraft in airworthy condition. These instructions are developed based on engineering analysis and testing conducted during the certification process.

Additionally, an STC may reference other approved documents such as service bulletins, service letters, or manufacturer’s manuals that provide further guidance on maintaining and operating the modified equipment.

The Importance of Approved Data

Approved data is crucial in aviation as it ensures that modifications or alterations to an aircraft are carried out safely and in compliance with regulatory standards. By following approved data, operators can be confident that the modified aircraft will continue to meet the necessary airworthiness requirements.

Furthermore, approved data provides a standardized set of instructions for mechanics, reducing the risk of errors during installation or maintenance. It also facilitates inspections and audits by regulatory authorities, as they can verify compliance with approved data sources.


In summary, while an STC itself is not considered approved data, it references approved data sources such as the Airworthiness Limitations Section and other manufacturer documents. These approved data sources provide detailed instructions for maintaining and operating the modified equipment in a safe and compliant manner.

Understanding the role of STCs and their relationship to approved data is essential for anyone involved in aircraft modifications. By adhering to approved data sources, aviation professionals can ensure the continued airworthiness of modified aircraft while meeting regulatory requirements.

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