CESSNA 337G — Supplemental Type Certificate

This document, produced by the FAA Safety Promotion Program Office, addresses the hazards associated with layering multiple Supplemental Type Certificates (STCs) on aircraft, specifically focusing on the Beechcraft G58 Baron. It emphasizes the importance of ensuring compatibility between new modifications and previously approved alterations to maintain airworthiness. The document provides guidance for installers and operators regarding the assessment of compatibility and the responsibilities involved in the installation of modifications. It also references relevant FAA advisory circulars and safety recommendations from the NTSB, highlighting the potential risks and safety issues that can arise from incompatible modifications.

• Installers must assess compatibility of new modifications with existing STCs to ensure airworthiness.
• NTSB recommendations emphasize the importance of education and evaluation in managing STC risks.
• FAA Form 337 must document compatibility assessments for new modifications.
• Installers should seek engineering support if compatibility assessments exceed their expertise.
• Awareness of potential safety issues from incompatible modifications is crucial for safe operation.