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

SA00051WI

New nose landing gear scissor fitting. Held by Central Airlines INC, which holds 24 approved modifications in all. Last revised March 26, 1993. System: landing gear.

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; Twin Commander Aircraft Corporation; Twin Commander Aircraft Corporation
Models
690, 690A, 690B, 500-S, 500-U, 500-B
Type certificates
2A4, 2A4, 2A4, 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 5, 2026.