The U.S. aircraft register, updated daily
Approved modifications · supplemental type certificate · current · amended

SA00169SE

Install Lycoming IO-540-M1C5 engine and Hartzell HC-C3YR-2UF/FC8468()-6R propeller. Held by Merlyn Products INC., which holds 35 approved modifications in all. Last revised June 2, 2000. System: propeller.

What it applies to

Kind of product
Aircraft
Design holder
Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation
Models
500-B, 500-U, 500-S
Type certificates
6A1, 6A1, 6A1
The FAA's record
On the FAA's site

What an approved modification is

A supplemental type certificate is the FAA's approval of a change to a certified design: a new engine or propeller, avionics, an autopilot, floats, a parachute, a larger fuel tank, an ice-protection kit. The company holding it may sell the kit and the paperwork to owners of the listed models; the modification then becomes part of that aircraft's record. The FAA's list says what was approved and for which models, not how many aircraft carry it.

Source: FAA supplemental type certificates (Dynamic Regulatory System). Register counts from the FAA register of October 21, 2026.