# AC 121-13 CHG 2: Self-Contained Navigation Systems (Long Range) - Type: Advisory circular (guidance, not mandatory unless a rule or AD requires it) - Status: Historical - Approved: December 21, 1970 - Last reviewed: October 25, 2024 - Family: AC 121-13 - Cancels: [AC 121-13 CHG 1](https://openairdocs.org/ac/121-13-CHG-1), [AC 121-10](https://openairdocs.org/ac/121-10), [AC 121-11](https://openairdocs.org/ac/121-11) - 14 CFR parts: 123, 121 - Pages: 12 - PDF: https://openairdocs.org/files/sha256/47/97/479757b30ae5c151e462b3a6ae2bc808dc72c1978393d498e2a3876d52d16ecf - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/20E9E974EC0E1D44862569EA00777BCC.0001 - DRS record last changed: November 22, 2025 - Page: https://openairdocs.org/ac/121-13 ## Versions - [AC 121-13 CHG 2](https://openairdocs.org/ac/121-13) (Historical), approved Dec 21, 1970, 12 pages ## Text Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 CONSOILDATED REPRINT - NOVEM3m 142 (Includes Changes 1 and 2) AC NO: AC IX- 13 wm : 10/14/69 **ADVISORY** CIRCULAR DEPARTMENT OF TRANSPORTATION FEDERAL AVUkTlON ADMINISTRAT SUBJECT: SELF -CONTAINED NAVIGATION SYSTEMS (LONG RANGE) ~-~~~- 1 l PURPOSE. This Advisory Circular states an acceptable means, not the only means, of compliance with the referenced Sections of the FAR as they apply to persons operating under Parts 121 or 123 who desire approval of Doppler RADAR navigation systems or Inertial Navigation Systems (INS) for use in their operations. 2 l REFERENCES. Federal Aviation Regulations 121.355, 121.389, 121.411, 121.412, 121.413, 121.415, 121.417, 121.418, and AC 25-4. l L 3 0 CANCELLATION. Advisory Circulars 121-10 and 121-11 dated 3/23/67 are canceled. 4 l INFORMATliOX. Doppler RADAR and Inertial Navigation Systems (INS) are self-contained navigation systems which are not continuously dependent on information derived from ground-based or exterior aids. However, exterior aids, such as LORAN and CONSOL or Celestial Navigation are required for periodic updating of Doppler. Updating of Inertial is permissible if the operator so desires, provided the updating technique is demonstrated and approved, and accounted for in the determination of the absolute accuracy of the system. Requests for approval of INS as the sole means of navigation, or in combination with other selfcontained aids, may be made. Adequate terminal ground-based radio navigational aids are necessary to support either INS or Doppler approvals. Under the provisions of FAR Sections 121.355 and 121.389, codcpit navigation over international routes previously requiring a . navigator okay be approved using Doppler RADAR or Inertial Navigation Systems. 3. GENERAL. The operator desiring approval for use of Doppler RADAR or . Inertial Navigation Systems should contact the local Air Carrier District Office or International Field Office for advice in the preparation of an initial written request for FAA evaluation of its proposal. The information needed is described in item 6 of this Initiated by: A.FS-220 ### Page 2 Page 2 AC 1219 13 10/14/69 circular. Thirty days saould be allowed for review and evaluation of the initial request. Subsequent to approval of the initial request, the operator may submit an application for approval of operations specifications, en route flight procedures following the guidelines established in item 7 of this circular. 6 l INITIAL REQUEST FOR EVALUATION. The initial request for evaluation of an operator proposal for use of Doppler RADAR or Inertial Navigation Systems should contain information concerning the following: a. Experience. Prior to presenting its initial request, an operator should have accumulated sufficient experience with the equipment to establish a history of the accuracy and reliability of the system it proposes to use. The applicant may include previous or: related operational experience of other operators, and-operational experience gained during type certification of the aircraft. Once a particular . system has received an equipment approval, evaluation and approval fn subsequent similar installations may be adjusted or omitted to avoid duplication of the lengthy accuracy and reliability data gathering process involved in the issuance of the original approval. A comprehensive mumary of this experience should be provided to rrhaw competenky in the operation and maintenance of the equlpmnt and feasibility of the proposed operation. . . , . - 1, b. Training i’rogram, The operator should outline the training program he plans to set up to comply with Sections 121.411, 121.412, 121.413, 121.415, 121.417, and 121.418. Under these rules, the training program for Doppler or Inertial Navigation Systems is acceptable if: (1) It encompasses all phases of the operation and the responsibilities of flight crewmembers, dispatchers and maintenance personnel. (2) Its technical content, for pilots, covers: (a) Theory and procedures, limitations, detection of malfunctions, pre-flight and in-flight testing, cross-checking methods, etc., . relating to the operation; (b) The use..of computers, an explanation of all systems, compass limitations at high latitudes, a review of navigation, flight planning and applicable meteorology; ( 1 C The methods for updating by means of reliable fixes; and, (d) The actual plotting of fixes. Par 6 ### Page 3 AC 12143 CHG-2 u/21/50 (3) Its recurrent training program includes training and line checks using tne selt-contained navigation system. ( 1 4 Eacu pilot assigned as an operating crewmember completes as many trips over a route or area (either In actual operation, or in a simulator, or training device,approved for conducting the required pilot training and qualifications in the use of these systems) a under the supervision of a check airman, as may be necessary to: * ( 1 a Ensure his qualification in the system; and, (b) Enable certification of his proficiency in the system, as required by Section 121.401. (5) Training of‘flight crewmembers is acceptable during evaluation flights. c. Maintenance Program. The applicant should provide an outline of the training to be given maintenance personnel on the new equipment, proposed intervals for inspection and overhaul, test and inspection procedures as specified in Subpart L of FAR 121, the stationing of spare parts and test equipment, and revisions to the maintenance manual. L *I? d 0 Equipment Installation. (1) The installation should include a navigation computer for each Doppler RADAR or Inertial Navigation System required. Cockpit arrangement should be such as to afford easy viewing and mnipuI.ation of necessary controls consistent with priority of existing equipment. (2) Dual Inertial Navigation Systems (including navigational computers and reference units) are acceptable under FAR 121.355 when installed in accordance with the criteria set forth in AC 25-4. Dual Doppler RADAR equfpment (including dual antennas or a combined antenna designed for dual operation) are also acceptable, For Doppler, a single operating transmitter with a standby capable of operation is acceptable in lieu of two operating tfansmitters. (3) When dual Doppler is installed, it will be permissible to utilize single heading source information to both equipments, . providing a compass comparator system is installed, and Operational procedure6 call for frequent CrOSS-Check6 Of all compass heading indicators by crewmembers. . Par 6 ### Page 4 Pa&$ 4 AC 12143 CHG.1 7/3mo * (4) Currently, other navigational aids are considered necessary to update the Doppler RADAR, such as LORAN, CONSOL, IME, VOR or ADF. Such facilities should be available for the proposed route and the cockpit arranged so as to afford.easy manipulation of the necessary controls. If a si.ngle LORAN is used for this purpose, it should be accessible to both pilots at their duty stations. (5) Cockpit arrangements should provide for adequate lighting, suitable charts, plotting, necessary forms and related equipment l e. Operations Manual. Revisions to the Operations Manual should outline all normal and emergency procedures relative to use of the proposed system. Detailed methods for continuing the navigational function with partial or complete equipment failures, and methods for determining the most accurate system when an unusually large divergence occurs should be included. f. Minbnum Equipment List (MEL& A proposal for revising the operator’s approved MEL should be included. Items which are not required to be opera tfve for dispatch, including existing items which can affect the operation of the proposed equipment, should be fully justified on the basis of an acceptable Level of safety. be as spkifically itemized in the Any exceptions should ‘*Remarks” column of the minimum equipment list for the aircraft concerned. In any event, the. * ’ - ” a. operator’s MEL should not authorize items to be inoperative that are . 1 not authorized by the Master MEL- If the proposal submitted by the operator should include such items, they should be referred to the proper FOEB with complete justification and recommendations for necessary action. * Routes or Areas. (1) Each route or area being proposed for self-contained cockpit navigation should be analyzed with respect to length, mgnetic compass reliability, availability of en route aids, and adequacy of gateway and terminal radio facilities to support the system used. Every available facility, including radar, should be used to ensure navigational accuracy, particularly where a route is proximate to restricted airspace. (2) Routes based &n heading information from slaved magnetic compasses will not be authorized for Doppler navigation in areas having a weak or unreliable earth magnetic field. If free-gyro operation is proposed s detailed procedures for transition to, and use of thfs form of navigation, should be applied* . (3) The use of INS into airports at latitudes above 76O 30’ should be covered by procedures for high latitude platform realignment. )ar 6 ### Page 5 AC 1210 13 10/14/69 (4) Precise coordinates accurate to within one minute of arc should be established for a designated geographic fixed position on each airport to be used for the establishment of alignment and insertion of present position data in the aircraft’s INS prior to takeoff. h l Demonstration of Operational Ability. The operator should provide a schedule of flights which shows his ability to use cockpit navigation in his operations, instead of a navigator or a previously approved specialized means of navigation. During these flights, the pilots should navigate the aircraft using the self-contained system and their navigational duties should not encroach significantly on other required duties. The pilots should be relieved of any workload associated with any previously approved specialized means of navigation. This should be done by adding a navigator or other navigationally qualified flight crewmember as appropriate. This additional flight crewmember should track the flight independent of the Doppler or Inertial System, and give the information obtained to the pilot-in-command. The pilot-in-command decides if changes in course are necessary to remain within allowable navigational limits. Self-contaFneB systems should not be used in Pert8 121 or 123 operations until the agency approve8 anrended operations spectficationti (see paragraph 7.a.). Systems installed and approved during type certification of the aircraft may secure operational approval during L the afrcraf t proving flights. * . _ .L’ i . Equipment Accuracy and Reliability. (1) Self-contained navigation unite should be maintained within the accuracies appropriate for the specific sir route structures in which they are to be used and the accuracy tolerances specified in the operator* s mai.ntenance manual. Specifically, the accuracy appropriate for use over the North Atlantic has been considered a8 a maxim error of + 20 nautical miles cross-track and + 25 miles .long-track for 952 of the flights completed. - (2) Compass heading information to the Doppler RADAR should be maintalned to an accuracy of 2 1.0 degree snd total eystem deviation should not exceed 2 degrees. 3 . FM evaluation #ho&d ensure: (1) Adequacy of operational procedures. (2) Operational accuracy and reliability of equipnrent and feasibility of the system over proposed routes or arem. _ - Par 6 I 9. ### Page 6 Page 6 AC 1210 13 10/14/69 (3) AvailabilLty of terminal, gateway, area and en route groundbased alds to support the self-contained system. (4) Acceptability of cockpit workload. (5) Adequacy of flight crew qualifications. (6) Adequacy of maintenance training and placement of spare parts. k 0 FM observations : (1) Air carrier operations inspectors will observe sufficient flight or simulator qualification checks given to the first flight crews qualified during an Initial evaluation program to ensure valid appraisal of the items listed in paragraph 6.3. (2) Inspectors will observe enough flight checks after operational approval to ensure that the operator maintains the overall quality of his msfntenance and training programs. (3) When the operator applies for additional routes or areas, inspectors will observe enough flights to ensure the adequacy of the terminal, gateway, area and en route facilities to . ) . - support the self-contained system. .# (4) Carriers will be expected to make available to the agency, records of accuracy and reliability for the systems being evaluated for a reasonable period before and after the operational evaluation. 7 l o REQUEST FOR APPROVAL. 8. The operator may forward a request for approval of its proposal following FAA observation of a representative number of satisfactory pilot qualifkation checks and resolution of all items arising during the initial evaluation program. Final FAA approval is indicated by approval of amended operations specifications, en route flight procedures o defining the new operations. Approval Is llmfted to those routes or areas over which the adequacy of the equipment and the ,feasibility of cockpit navigation has been deasbns tra ted. b l Proposed operations specifications authorizing cockplt navigation . should contain the following: (1) Specific points (gateways) fixed by an acceptable ground-based navigational ald where use of Doppler RADAR navigation will commence and tennlnate. Par 6 F ### Page 7 AC 121-13 10/14/69 (2) Latitude limits for the system used. Type heading reference authorized for Doppler navigation, i.e., Slaved Magnetic Compass or Free Gyro, (3) Requirement that pilots be qualified in the rmvfgatioml system. (4) Specific nmrigation equipment that may be inoperative for dispatch. go. The appropriate Air Calrrier District Office (ACDO) or Intemstional Field Office (IFO) advises PS-400: (1) When an application for evaluation is received; (2) When any problem areas exist; and, (3) Concerning the status of the program as it prOgressesa b. Before approving the U6e of Doppler or Inertial navigation over any route or area, the ACDU or IF8 coordinates its recoumendations with FS-400r . Par 7 ### Page 9 Ac 121-13 Attachment 1 10/14/69 Page 1 ### Page 11 OEPARTMFNT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION Form Approved OPERATIONS SPECIFICATIONS - EN ROUTE FLIGHT PROCEDURES Budget Bureau No. WROR3.1 . OPERATION AUTHORIZED TYPE OF AIRCRAFT AUTHORIZED SPECIAL REQUIREMENTS ----p ROUTE OR ROUTE SEGMENT MOCA MEA MAA OTHER tYPE NAVIGATION pproved routes and oceanic reas will be listed here. xample: robisher to Churchill t6 Edmonton or iorth Atlantic Ocean over North Eastern and EFFECTIVE DATE NAME OF AIR CARRIER 1 Khcrc3 a navigator or special cockpit navigation and rquipmcnt is XYZ AIRLINES, INC. rc*q\birc(l, SO qppccify; ie Navie;ator, Cockpit (Ilopplct - Loran), flncrt iill). FAA Form 8400-t (:3-w) --- 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.