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

SA1205NW

Installation of a digital Electronics International exhaust gas temperature (E.G.T.) gauge (P/N ET-1). Held by Aero Air, LLC, which holds 12 approved modifications in all. Last revised December 8, 2006. System: engine.

What it applies to

Kind of product
Aircraft
Design holder
Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation
Models
680-T, 680-V, 680-W, 681
Type certificates
2A4, 2A4, 2A4, 2A4
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 12, 2026.