FAA-listed STC holder

Preferred Improvements LLC STCs

The Jun 30, 2026 FAA DRS snapshot lists 22 selected supplemental type certificates with status Current under Preferred Improvements LLC. The records span 14 public aircraft directories and 8 modification categories. This is a research directory, not a claim that any specific kit or service is currently offered.

listed Current at snapshot

aircraft directories

modification categories

May 22, 2024

latest recorded revision

Recently revised records

Showing the 22 most recently revised records. Category directories provide the complete paginated discovery path.

22 displayed records.

Search every indexed record for this holder. The table below contains the recently revised records shown on this page.

Preferred Improvements LLC supplemental type certificates, aircraft applicability, source status and dates
STC and modification	Aircraft / model / TC	Source status and dates	Holder and authority
ST04605CH Installation of a Garmin GTS 8000 Traffic Alert and Collision Avoidance System (TCAS) II. Other aircraft modifications View record	Boeing DC3C-SC3GTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-R-1830-90CTC A-669	Current at cited snapshot Revised May 22, 2024 Application: Mar 30, 2022	FAA holder: Preferred Improvements LLC FAA authority record
ST04530AT Installation of a wingtip modification on DC3C aircraft (specific models listed). Other aircraft modifications View record	Boeing DC3A-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 12, 2021 Application: May 7, 2019	FAA holder: Preferred Improvements LLC FAA authority record
SA3-307 Installation of 145-gallon fuel tanks. Installation of 252-gallon fuel tanks. Fuel systems View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 7, 2018 Application: Jul 3, 1958	FAA holder: Preferred Improvements LLC FAA authority record
ST04262CH Install placarding to restrict total payload to a maximum of six thousand pounds (6,000 lbs). Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Feb 2, 2018 Application: Apr 25, 2017	FAA holder: Preferred Improvements LLC FAA authority record
ST04244CH Installation and Activation of a Saab Grintek Defense Impi II Asset Tracking System. Other aircraft modifications View record	Boeing DC3A-S1C3GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S4C4GTC A-669	Current at cited snapshot Revised Jan 18, 2018 Application: Feb 1, 2017	FAA holder: Preferred Improvements LLC FAA authority record
SA211CE A.P.U. Installation - Ranger Andover Model V-32D-2-1. Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Jan 24, 1964	FAA holder: Preferred Improvements LLC FAA authority record
SA3-113 Installation of RCA Model AVQ-10 radar antenna swingaway mount SK10136 (SA3-65). Aircraft connectivity View record	Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Sep 11, 1957	FAA holder: Preferred Improvements LLC FAA authority record
SA3-139 Installation of standard C-47 cargo door. Cargo and special mission View record	Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Nov 11, 1957	FAA holder: Preferred Improvements LLC FAA authority record
SA3-15 Installation of wheel well enclosure doors. Landing gear and brakes View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Dec 5, 1956	FAA holder: Preferred Improvements LLC FAA authority record
SA3-422 Installation of bird resistant windshield. Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Sep 18, 1959	FAA holder: Preferred Improvements LLC FAA authority record
SA3-434 Picture window installation and standard window modification. Aircraft structures View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Sep 18, 1959	FAA holder: Preferred Improvements LLC FAA authority record
SA3-461 Installation of electrically driven emergency hydraulic pump. Safety and emergency equipment View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Dec 18, 1959	FAA holder: Preferred Improvements LLC FAA authority record
SA3-52 Radome installation. Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Feb 22, 1955	FAA holder: Preferred Improvements LLC FAA authority record
SA3-78 Alternate Tee-Bolt radome attachment for STC SA3-52 radome installation. Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Dec 13, 2017 Application: Jul 26, 1957	FAA holder: Preferred Improvements LLC FAA authority record
ST04263CH Install placarding to restrict passenger count to a maximum of nineteen (19) and total payload to a maximum of seven thousand five hundred pounds (7,500 lbs). Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618	Current at cited snapshot Revised Dec 11, 2017 Application: Apr 24, 2017	FAA holder: Preferred Improvements LLC FAA authority record
ST04261CH Installation of a Gear Latch & Ground Shift system. Other aircraft modifications View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Nov 20, 2017 Application: Jun 7, 2016	FAA holder: Preferred Improvements LLC FAA authority record
ST565CH Installation of a Fairchild F800 or F1000 digital flight data recorder. Other aircraft modifications View record	Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Mar 9, 2017 Application: Sep 9, 1996	FAA holder: Preferred Improvements LLC FAA authority record
SA3074NM This modification requires that the following two (2) placards be placed on the inside of the forward (L.H.) cargo door in full view of the cargo loading crew: MAXIMUM PAYLOAD CAPACITY -7500 lbs. or less, CARGO LOADING METHOD-Refer to FAA App Oper Handbk. Cargo and special mission View record	Boeing DC3A-S1C3GTC A-669 Boeing DC3C-S1C3GTC A-669	Current at cited snapshot Revised Feb 24, 2017 Application: Jul 23, 1985	FAA holder: Preferred Improvements LLC FAA authority record
SA4-220 Installation of tail wheel cover and fairing. Landing gear and brakes View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Jul 15, 2016 Application: May 3, 1957	FAA holder: Preferred Improvements LLC FAA authority record
SA4-228 Main landing gear doors, actuating system, main landing gear assist bungee, oil cooler fairing and oil cooler fixed section for aircraft with Pratt & Whitney R-1830-75, -92 or -94 engines. Landing gear and brakes View record	Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Feb 25, 2016 Application: May 27, 1957	FAA holder: Preferred Improvements LLC FAA authority record
SA4-230 Installation of aileron gap closure. Flight controls View record	Boeing DC3-G102TC A-618 Boeing DC3-G102ATC A-618 Boeing DC3-G103ATC A-618 Boeing DC3-G202ATC A-618 Boeing DC3A-S1C3GTC A-669 Boeing DC3A-S1CGTC A-669 Boeing DC3A-S4C4GTC A-669 Boeing DC3A-SC3GTC A-669 Boeing DC3A-SCGTC A-669 Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669 Boeing DC3D-R-1830-90CTC A-669	Current at cited snapshot Revised Feb 25, 2016 Application: Jun 6, 1957	FAA holder: Preferred Improvements LLC FAA authority record
ST04050CH Installation of Ice Protection Systems. Other aircraft modifications View record	Boeing DC3C-R-1830-90CTC A-669 Boeing DC3C-S1C3GTC A-669 Boeing DC3C-S4C4GTC A-669 Boeing DC3C-SC3GTC A-669	Current at cited snapshot Revised Feb 12, 2016 Application: Jan 16, 2014	FAA holder: Preferred Improvements LLC FAA authority record

Preferred Improvements LLC STCs

Modification mix

Aircraft represented

Recently revised records

Installation of a Garmin GTS 8000 Traffic Alert and Collision Avoidance System (TCAS) II.

Installation of a wingtip modification on DC3C aircraft (specific models listed).

Installation of 145-gallon fuel tanks. Installation of 252-gallon fuel tanks.

Install placarding to restrict total payload to a maximum of six thousand pounds (6,000 lbs).

Installation and Activation of a Saab Grintek Defense Impi II Asset Tracking System.

A.P.U. Installation - Ranger Andover Model V-32D-2-1.

Installation of RCA Model AVQ-10 radar antenna swingaway mount SK10136 (SA3-65).

Installation of standard C-47 cargo door.

Installation of wheel well enclosure doors.

Installation of bird resistant windshield.

Picture window installation and standard window modification.

Installation of electrically driven emergency hydraulic pump.

Radome installation.

Alternate Tee-Bolt radome attachment for STC SA3-52 radome installation.

Install placarding to restrict passenger count to a maximum of nineteen (19) and total payload to a maximum of seven thousand five hundred pounds (7,500 lbs).

Installation of a Gear Latch & Ground Shift system.

Installation of a Fairchild F800 or F1000 digital flight data recorder.

This modification requires that the following two (2) placards be placed on the inside of the forward (L.H.) cargo door in full view of the cargo loading crew: MAXIMUM PAYLOAD CAPACITY -7500 lbs. or less, CARGO LOADING METHOD-Refer to FAA App Oper Handbk.

Installation of tail wheel cover and fairing.

Main landing gear doors, actuating system, main landing gear assist bungee, oil cooler fairing and oil cooler fixed section for aircraft with Pratt & Whitney R-1830-75, -92 or -94 engines.

Installation of aileron gap closure.

Installation of Ice Protection Systems.