8900.1 CHG 0



Section 5 Approve Area Navigational Systems


4-1452 OBJECTIVE. This section provides guidance for approving area navigational systems.

4-1453 GENERAL. The aviation safety inspector (ASI), may need to refer to specific advisory circular(s) (AC) and regulations for individual systems in order to accomplish this approval.

A.  Approvals. Field approval for an Area Navigation System (RNAV) should not be considered unless the applicant has provided previously approved data. This data must be in the form of a Type Certificate (TC) or Supplemental Type Certificate (STC) for an airplane or rotorcraft of like or similar configuration using approved system components.

1)   For Title 14 of the Code of Federal Regulations (14 CFR) part 121 operators, inertial navigation systems and Doppler’s must meet the requirements specified in 14 CFR part 121, appendix G, before formal approval. Under these requirements an STC must be obtained by the applicant.
2)   Installation approvals of other types of area navigation equipment should be obtained with an STC. However, approval can also be obtained by submission of substantiating data with either a Federal Aviation Administration (FAA) Form 337 or an air carrier engineering authorization.
3)   The applicant must furnish all of the installation data necessary to determine the adequacy of the installation. Such data should include the following:

·    Manufacturer’s instructions

·    Electrical schematics and failure protection

·    Installation information and/or photographs

·    Substantiation of structural changes

·    Determination of capability of electrical system and failure protection to handle additional load

·    Any other data determined necessary for approval

4)   FAA-approved manufacturer service bulletins which lists approved instructions for the installation of certain RNAV may be used.
a)   In some cases, the facility making the installation has demonstrated its ability to install this equipment on a representative number of similar type installations through field approvals.
b)   References to previous approvals on FAA Form 337 would constitute previously-approved data and may not require a separate field approval. In this case, a letter from the Flight Standards District Office (FSDO) or General Aviation District Office authorizing the installation facility to perform similar installations would be appropriate.
c)   Alterations which do not differ appreciably from previously approved changes may not require new or additional approval.

B.  Visual Flight Rules (VFR) Operation. An installation may be approved for Visual Flight Rules (VFR) operation after meeting the provisions discussed above. The aircraft should be placarded to limit the use of the RNAV to VFR only, unless the aircraft itself is limited to VFR.

C.  Instrument Flight Rules (IFR) Approval. Systems do not require VFR approval before IFR approval. An application for Instrument Flight Rules (IFR) approval should contain data substantiating that the equipment and installation meet the criteria in Air Circular (AC) 90-45, appendix A, Approval of Area Navigation Systems for Use in the U.S. National Airspace System, current edition.

D.  Original VFR Approval Changes to IFR Approval. Operators have installed RNAVs in a variety of aircraft for use in VFR operations only. Operators have the option of upgrading these systems to allow for IFR operations as well.

1)   When such a request is received, an FAA Form 337 should be prepared on which the approval for IFR operations will be properly documented. Item 8 of FAA Form 337 should provide at least the following information:

·    Reference to FAA Form 337 which recorded the original VFR RNAV installation

·    Data to confirm that the requirements of AC 90-45, appendix A, paragraphs 2 and 3, have been met

·    If a flight test is conducted, a statement to document the modes of IFR operation for which the system is being approved

2)   The data approval stamp, properly completed, should be placed in block 3 of FAA Form 337.
3)   If the aircraft has an FAA-approved flight manual, a supplement to the manual may be prepared and submitted for approval, in accordance with regional procedures.
a)   An additional copy of FAA Form 337 detailing the original installation must accompany the flight manual supplement approval request.
b)   The date of the flight manual supplement must not be later than the approval for return to service date, as shown on FAA Form 337.
4)   If the aircraft does not have an FAA-approved flight manual, then information on equipment operating limitations and manufacturer’s operating instructions must be provided to the pilot by means of a placard.


A.  Prerequisites.

·    Successful completion of Airworthiness Inspector Indoctrination course for General Aviation and Air Carrier Inspections, or previous equivalent

·    Identification and authorization to perform field approvals by the regional Flight Standards Division

B.  Coordination. Engineering assistance should be obtained for a field approval unless the aviation safety inspector (ASI) has previous experience with area navigation installations and feels competent to make such an approval.


A.  References (Current Editions).

·    Title 14 CFR part 121, appendix G

·    AC 20-101, Omega and Omega/VLF Navigation Systems Approvals for Use in the Conterminous United States and Alaska

·    AC 20-121, Airworthiness Approval of Airborne Loran-C Systems for Use in the U.S. National Airspace System

·    AC 25-4, Inertial Navigation Systems

·    AC 90-45, appendix A, current edition, Approval of Area Navigation Systems for Use in the U.S. National Airspace System

·    AC 120-31, Operational and Airworthiness Approval of Airborne Omega Radio Navigation Systems as a Means of Updating Self-Contained Navigation Systems

·    AC 120-33, Operational Approval of Airborne Long-Range Navigation Systems for Flight Within the North Atlantic Minimum Navigation Performance Specifications Airspace

·    AC 120-37, Operational and Airworthiness Approval of Airborne Omega Radio Navigational Systems as a Sole Means of Long Range Navigation Outside the United States

·    AC 121-13, Self-Contained Navigation Systems (Long-Range)

·    This book’s Volume 4, Chapter 9, Section 1, Perform Field Approval of Major Repairs and Major Alterations

B.  Forms. FAA Form 337, Major Repair and Alteration

C.  Job Aids. None.


A.  Follow the Procedures Detailed in the Applicable AC(s).

B.  Review the Operator’s Data. Review STC(s) and installation data, as applicable. Extra consideration must be given to the following:

·    Manufacturer’s instructions and limitations, including necessary modification and calibration of all units in the system and previously installed equipment.

·    Interface with auxiliary equipment, sensor inputs, meter loading and sensitivity, etc.

·    Any reasonable probable failure of the equipment which would cause a flight hazard or affect the normal operation of required equipment to which it is connected.

·    Display location.

C.  Conduct Inspections, as necessary.

1)   Conduct a conformity inspection to ensure the installation conforms to the approved data.
2)   Monitor the ground operational/functional check performed by the installing agency.
3)   Ensure that the aircraft is appropriately placarded regarding the limitations of the equipment.

D.  Review FAA Form 337.

1)   Ensure that certification dates of flight and/or bench tests are provided.
2)   Ensure that limitations on types of approval are clearly stated in block 8 of FAA Form 337 and on any required approved operations specifications.

E.  Review the Operator Training Programs. Ensure that the operator establishes training programs on the new equipment and reviews the existing programs on associated equipment. In addition, accomplish the following:

·    Conduct spot checks of the training records

·    Observe the actual training sessions

·    Ensure that the training emphasizes the new equipment, new maintenance techniques, and new procedures and standards


A.  File PTRS Data Sheet.

B.  Completion of this task may result in the following:

·    Approval of the installation of the equipment

·    If the facility making the installation has demonstrated its ability to install the equipment on a representative number of similar type installations through field approvals, an approval letter sent by the FSDO or General Aviation District Office authorizing the installation facility to perform similar installations


RESERVED. Paragraphs 4-1459 through 4-1475.