# STC SA4558NM

- Type: Supplemental type certificate
- Status: Current, Reissued
- Holder: Northrop Grumman Systems Corporation, United States
- Description: Installation of LTN-92 Inertial Navigation Systems
- Applied: February 28, 1989
- Status date: February 22, 2016
- Product: Aircraft, Large Airplane
- Certification basis: Part 21, Part 25
- Data sheets: [TCDS A20WE](https://openairdocs.org/tcds/A20WE)
- Certificate PDF: https://openairdocs.org/files/sha256/bf/10/bf101ff2937edefeb82e22fe38857fe04a36a294a79611621191ab7f23853b1f
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/7F207AA062C93C5D86257F6B005C8028.0001
- DRS record last changed: December 6, 2025
- Page: https://openairdocs.org/stc/SA4558NM

## ADs that name it (0)

None.

## Approved models (1)

- The Boeing Company 747-100 Series ([TCDS A20WE](https://openairdocs.org/tcds/A20WE))

## What the certificate says

Read from the PDF's text layer, without the form's printed wording; the layout is lost and the order can differ. The PDF is the record.

This Certificate issued to Northrop Grumman Systems Corporation 21240 Burbank Blvd.

Woodland Hills, CA 91367-6675 Part 25* of the Federal Aviation Regulations.

(For Certification Basis see T. C. Data Sheet No. A20WE.)

A20WE

The Boeing Company

747-100 Series Description of Type Design Change : Installation of LTN -92 Inertial Navigation Systems in accordance with FAA Approved Litton Systems, Inc. Top Installation Drawing No. 454065-05, Revision A, dated July 25, 1989, or later FAA approved revision of this drawing.

Litton Airplane Flight Manual Supplement, Document No. 464882, Revision N/C, FAA Approved on August 11, 1989, or later FAA approved revision, is required as part of this installation.

Limitations and Conditions : The approval of this change in type design applies only to the above listed models airplanes. This approval should not be extended to other aircraft of this model on which other approved previously approved modifications are incorporated unless it is found by the install er that the interrelationship between this change and any of those previously approved modifications will introduce no adverse effect upon the airworthiness of the aircraft . If the holder agrees to permit another person to use this certificate to alter t he product, the holder shall give the other person written evidence of that permission.

Date of application : February 28, 1989

Date of issuance : August 11, 1989

Date reissued : March 30, 2015, February 22, 2016

Date amended : June 29, 1994

(Signature) Supervisor, Technical & Administrative Support Staff Los Angeles Aircraft Certification Office (Title)

## Every issue (2)

- February 22, 2016: Reissued, Current. [certificate](https://openairdocs.org/files/sha256/bf/10/bf101ff2937edefeb82e22fe38857fe04a36a294a79611621191ab7f23853b1f)
- March 30, 2015: Reissued, Historical. [certificate](https://openairdocs.org/files/sha256/55/7e/557ea5df5bb3b1affad191c723262029168e8a510597a3d7151574b5392cb7b0)

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.