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

SA4-502

Engine mount core assemblies. Held by Dow-Elco INC, which holds 7 approved modifications in all. Last revised January 1, 1960. System: engine.

What it applies to

Kind of product
Aircraft
Design holder
McDonnell Douglas Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation
Models
DC-6 Series, DC-6B (Navy R6D-1Z), DC-6
Type certificates
6A3, 6A4, A-781
On this site
Douglas DC-6 17 registered
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 7, 2026.