SA1744WE

Installation of oil filter assemblies. Held by Nelson Filter, which holds 3 approved modifications in all. Last revised August 29, 1974. System: engine.

What it applies to

Kind of product: Aircraft
Design holder: Curtiss-Wright Corporation; Douglas Aircraft Co. Inc.; Douglas Aircraft Co. Inc.; Douglas Aircraft Co. Inc.; Lockheed Aircraft Corporation; Lockheed Aircraft Corporation; Lockheed Aircraft Corporation; Martin-Marietta Corporation; Martin-Marietta Corporation; Martin-Marietta Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation; McDonnell Douglas Corporation; S and R Aviation Services Inc; S and R Aviation Services Inc; S and R Aviation Services Inc; S and R Aviation Services Inc; S and R Aviation Services Inc
Models: C-46 Series, Army B-23, Army A-26B, Army A-26C, Lockheed 18, Navy PV-1, Army B-34, 404, 202A, 202, DC-6A (USAF C-118A), DC-6A (Navy R6D-1), DC-3D Series, DC-3A Series, DC-3C Series, DC-4, Army B-25C, Army B-25G, Army B-25H, Army B-25J, Army RB-25
Type certificates: A-772, 2-576, L-3-4, L-3-4, A-723, LTC-13, LTC-13, 1A7, A-795, A-795, 6A3, 6A3, A-669, A-669, A-669, A-762, AL-2, AL-2, AL-2, AL-2, AL-2
On this site: Curtiss Wright C-46 8 registered
Douglas DC-3 155 registered
Douglas DC-6 17 registered
Martin 404 5 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.