U.S. Department of Transportation Federal Aviation Administration Advisory Circular AC 121-1A DATE: 7/7/1978 AC No: 121-1A Change: 4 Date: 7/7/78 Initiated by: AFS-320 Subject: STANDARD OPERATIONS SPECIFICATIONS - AIRCRAFT
MAINTENANCE HANDBOOK
1. PURPOSE. This handbook provides procedures acceptable to the Federal Aviation Administration which may be used by operators when establishing inspection intervals and overhaul times. A list of sample Operations Specifications
- Aircraft Maintenance, General, for aircraft currently being used in air transportation, is incorporated in this document to further aid the operator in preparing his program.
2. CANCELLATION. This advisory circular cancels:
a. Advisory Circular 120-21, Aircraft Maintenance Time Limitations, dated 6/24/66.
b. Advisory Circular 120-24A, Establishment and Revision of Aircraft Engine Overhaul and Inspection Periods, dated 2/25/69.
c. Advisory Circular 121-1, Standard Maintenance Specifications, dated 12/15/62.
3. HOW TO ORDER THIS HANDBOOK. This publication is furnished free of charge. Additional copies may be ordered from:
Department of Transportation Distribution Operations Unit, TAD 484.3 Washington, D.C. 20591 Identify the publication in your order as:
FAA AC No. 121-1A, Standard Operations Specifications - Aircraft Maintenance Handbook Dated: June 26, 1973
4. CHANGES TO THIS HANDBOOK. Revised pages to this Advisory Circular will be transmitted by Advisory Circular Changes.
If you order the basic handbook, we will put your name on the mailing list to receive changes.
/s/ C. R. Melugin, Jr.
Acting Director, Flight Standards Service
TABLE OF CONTENTS Page No.
CHAPTER 1. INTRODUCTION. 1
1. Purpose. 1
2. Eligibility. 1
3. Cancellation. 1
4. Definitions. 1
5. General. 2
6. Revision of Time Limitations - General. 5
7. Airframe - Revision of Time Limitations. 6
8. Powerplant and Associated Appliances - Revision 6 of Time Limitations.
9. Appliances - Revision of Time Limitations. 7
10. Reliability vs. Hardtime Conversion. 7
11. Emergency Equipment. 7
12. Avionics and Instruments. 7
13.-15. Reserved.
CHAPTER 2. PRORATION. 9
16. Purpose. 9
17. Application. 9
18. Scope and Limitations. 9
19. Data Required. 11
20. Proration Formula. 13
21.-25. Reserved.
APPENDIX 1. ADDITIONAL PRORATION SAMPLE DATA. (30 pages) FIGURE 1. TRANSFER OF AIRCRAFT FROM A BLOCK/PATTERN SYSTEM TO A ONE-TIME OVERHAUL. 1 FIGURE 2. TRANSFER OF AIRCRAFT FROM A BLOCK/PATTERN SYSTEM TO A BLOCK/PATTERN SYSTEM. 5 FIGURE 3. TRANSFER OF AIRCRAFT FROM A ONE-TIME
OVERHAUL TO A BLOCK/PATTERN SYSTEM
(BUYERS APPROVED OH TIME LIMIT HIGHER THAN PREVIOUS OPERATORS). 9 FIGURE 4. TRANSFER OF AIRCRAFT FROM A ONE-TIME
OVERHAUL TO A BLOCK/PATTERN SYSTEM (BUYERS APPROVED OH TIME LIMIT LOWER THAN PREVIOUS OPERATORS). 13 FIGURE 5. FORMAT FOR PRESENTATION OF PRORATION DATA ON AIRCRAFT BEING TRANSFERRED. 17 FIGURE 6. TRANSFER OF PREVIOUSLY PRORATED AIRCRAFT. 19 FIGURE 7. PROCEDURE FOR CONVERTING CALENDAR
OVERHAUL (MONTHS) TO HOURS SINCE OVERHAUL FOR PRORATION PURPOSES. 21 FIGURE 8. METHOD OF DEPICTING AREAS, SECTIONS, COMPONENTS ETC., THAT ARE TIED TO A SPECIFIC BLOCK. 23 FIGURE 9. OPERATIONS SPECIFICATIONS -- PREFACE PAGE FOR AIRCRAFT ON PRORATED TIME. 25 FIGURE 10. OPERATIONS SPECIFICATION, AIRCRAFT MAINTENANCE -- GENERAL. 27 FIGURE 11. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE -- PREFACE PAGE FOR AIRCRAFT ON PRORATED TIME. 29 * FIGURE 12. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE -- PREFACE PAGE FOR AIRCRAFT
UTILIZING A PREVIOUS OPERATORS PRORATED TIME. 30 * APPENDIX 2. STANDARD SPECIFICATIONS FIGURE 1. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- AVIONICS (ALL AIRCRAFT). 1 FIGURE 2. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- DART 510 AND DART 525. 3 FIGURE 3. WITHDRAWN -- CHG 1.
FIGURE 4. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- PRATT AND WHITNEY R2000 SERIES. 7
FIGURE 5. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- PRATT AND WHITNEY R2800 AND R-2800C-CA-CB SERIES. 9 FIGURE 6. WITHDRAWN -- CHG 1.
FIGURE 7. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- WRIGHT 1820 AND PRATT AND WHITNEY R-1830 SERIES. 13 FIGURE 8. WITHDRAWN -- CHG 1.
FIGURE 9. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- WRIGHT AERO C18 SERIES. 17 FIGURE 10. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- WRIGHT AERO TC18 SERIES. 19 FIGURE 11. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- CONVAIR CV-240/340/440. 21 FIGURE 12. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- CURTISS WRIGHT C46 SERIES. 25 FIGURE 13. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-3 SERIES. 29 FIGURE 14. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-4 SERIES. 33 FIGURE 15. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-6, DC-7. 35 FIGURE 16. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE - LOCKHEED L-049/749/1049/1649. 39 FIGURE 17. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - MARTIN M-202/404. 43 FIGURE 18. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - VISCOUNT 745D/810. 47 FIGURE 19. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - LOCKHEED L-188 A & C. 51 FIGURE 20. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE - ALLISON 501-D13 ENGINE AEROPRODUCTS PROPELLER. 57 FIGURE 21. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - BOEING 707/720. 59 FIGURE 22. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-8/F AND DC-8-61/61F. 75 FIGURE 23. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - LOCKHEED MODEL 382. 109 FIGURE 24. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - CONVAIR CV-880. 123 FIGURE 25. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - FAIRCHILD F-27. 135 FIGURE 26. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - CONVAIR CV-990. 145 FIGURE 27. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - JET COMMANDER 1121. 159 FIGURE 28. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-8-62/62F. 173 FIGURE 29. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE - DOUGLAS DC-8-63/63F. 185 FIGURE 30. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- LOCKHEED MODEL 300 (C-141A). 197 FIGURE 31. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE -- LOCKHEED JETSTAR - MODEL 1329. 211 FIGURE 32. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- SHORT TURBO-SKYVAN 225 (SC-7).
FIGURE 33. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- SIKORSKY S-61L/N HELICOPTER. 233 FIGURE 34. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- LEAR MODEL 24/24B/25. 251
FIGURE 35. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- FAN JET FALCON - 20. 263 FIGURE 36. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- HAWKER-SIDDELEY DH-125 SERIES. 273 FIGURE 37. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- HFB 320 HANSA JET. 283 FIGURE 38. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- BOEING 727. 301 FIGURE 39. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- DOUGLAS DC-9. 319 FIGURE 40. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- HAWKER-SIDDELEY 748 SERIES 2A. 331 FIGURE 41. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE -- FAN JET FALCON - 10. 343 FIGURE 42. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE -- GATES LEARJET MODELS 35/36. 355 * FIGURE 43. OPERATIONS SPECIFICATIONS, AIRCRAFT
MAINTENANCE -- SOCIETE NATIONALE
INDUSTRIELLE AEROSPATIALE (SNIAS) NORD-262A AND 262A/M-298. 369 *
STANDARD OPERATIONS SPECIFICATIONS - AIRCRAFT MAINTENANCE CHAPTER 1. INTRODUCTION
1. PURPOSE. This document prescribes, for air carrier aircraft of 12,500 pounds or over certificated takeoff weight, reasonable methods of determining initial overhaul time limits and period inspection intervals for both new and used airframes, powerplants, propellers, and appliances. Under the provisions of Federal Aviation Regulations 121 and 127, the FAA approves for each aircraft, "Operations Specifications - Aircraft Maintenance," which contain maintenance intervals for airframes, powerplants, propellers, and appliances. Such approved overhaul time limits and maintenance intervals apply only to the aircraft used by each individual air carrier and are not transferable from one air carrier to another.
2. ELIGIBILITY. Standard Operations Specifications - Aircraft Maintenance, or Maintenance Review Board time limits, may be applied to aircraft being placed in FAR 121, 127, and 135.2 operations.
3. DEFINITIONS. Terms as used in this document are defined as follows:
a. Aircraft. An aircraft is any contrivance now known or hereafter invented, used, or designed for navigation of or flight in the air, including airframes, powerplants, propellers, and appliances.
b. Previous Operator. Previous Operator is the last operator who utilized the aircraft prior to its sale or lease.
c. Seller. Seller is the same as Previous Operator.
d. New Operator. A new operator is a person who acquires an aircraft, through purchase or lease, for operation in accordance with his operating certificate, and who HAS NOT had a previously approved maintenance program for such type aircraft.
e. Buyer. A "Buyer" is a person who acquires an aircraft, through purchase or lease, for operation in accordance with his operating certificate, and who HAS an approved maintenance program for such type aircraft.
f. Approved Time Limits. Approved time limits are those which appear on the carrier's approved "Operations Specifications - Aircraft Maintenance," FAA Form 1014.
(OMB 04-R0075)
g. Maintenance Review Board. A Maintenance Review Board is a body of FAA maintenance specialists organized to evaluate and establish inspection and overhaul time limits for transport aircraft intended for use in U.S.
air carrier operations.
h. Maintenance Review Board Reports. That document formulated by the Maintenance Review Board that provides an acceptable initial maintenance program for a specific aircraft or powerplant.
i. Proration. A process by which an operator calculates the time since overhaul on a newly acquired airframe and its installed powerplants, propellers, and appliances when his approved overhaul time differs from that of the previous operator.
j. On Condition. Items and appliances listed as "On Condition" must be restricted to components on which a determination of continued airworthiness may be made by inspections, measurements, or tests. These "On Condition" functions are to be performed within the time limitations prescribed for the inspection or check. Performance tolerances and wear or deterioration limits shall be contained in the air carrier's maintenance manual. If an item or appliance cannot be maintained in a condition of continued airworthiness by use of "On Condition" procedures, it must be placed on specific time limitation control or be controlled by an acceptable standard for determining time limitations (e.g., hard time or condition monitoring).
Additional criteria to be used in determining the eligibility of an item or appliance for "On Condition" are:
(1) Perceptibility of wear or other deterioration of moving parts.
(2) Adaptability to inspection for detection of corrosion and internal structural integrity when such parts or areas have an appreciable effect on continued airworthiness.
k. Direct Inclusion. A process by which the buyer places a newly acquired aircraft into his approved maintenance program for that type aircraft utilizing the existing times of the airframe, powerplants, and appliances.
4. GENERAL.
a. Three acceptable means currently in use for establishing initial maintenance programs are as follows:
(1) Advisory Circular 121-1A, Standard Operations Specifications -- Aircraft Maintenance.
(2) Maintenance Review Board Reports.
* (3) Advisory Circular 120-17A, Maintenance Control by Reliability Methods. *
b. Maintenance Review Board reports, which are formulated at the time of equipment manufacture, are valid only until such time as the limits are published in AC 121-1A. This transfer of limits from the MRB report to
AC 121-1A is accomplished only after sufficient satisfactory service experience has been accumulated that warrants an updating or revision of the original MRB limits.
c. When a non-air carrier aircraft is acquired (e.g., one operating under FAR Part 91, the military, or foreign), the initial time limits for the new operator will be those set forth in the Standard Operations Specifications - Aircraft Maintenance or the MRB report, whichever is applicable. The time remaining to overhaul for the new operator will be the difference between the actual TSO and the newly approved time limit providing the actual TSO is the lower of the two figures.
d. When a non-air carrier aircraft is acquired (e.g., one operating under FAR Part 91, the military or foreign), the initial time limits for the buyer may be established by using either direct inclusion or proration in accordance with the provisions of Chapter
2. In this type of situation, if proration is to be used, the times shown in the Standard Operations Specifications - Aircraft Maintenance or the MRB report (whichever is applicable to the aircraft in question) are to be used as the seller's approved overhaul time and this figure will serve as the basis for the proration computation.
e. In the event an air carrier aircraft is acquired by a new operator or buyer, up to 30 hours of time may be accumulated under FAR Part 91 without the provisions of the above paragraph c being invoked.
f. The times listed in AC 121-1A (as in the case of MRB reports) are recommended starting times. They may be reduced if an investigation of the proposed operation indicates that lower time limits are advisable in the interest of safety.
g. Higher starting times may be approved providing sufficient justification is provided to the assigned maintenance inspector by the operator. In making this determination, consideration shall be given to the following:
(1) Type of intended operations (geographical areas of operation).
(2) The operator's experience in handling aircraft equal in complexity to the new equipment.
(3) The scope and depth of training provided for maintenance personnel on the new aircraft.
(4) The competency and capability of the carrier's maintenance and quality control organizations.
(5) The adequacy of the maintenance and inspection programs.
(6) The adequacy of all facilities and equipment required for the maintenance of the equipment involved.
(7) Calendar time vs. utilization on the aircraft to be transferred. Long periods of idle storage time or extremely low utilization over a period of time can and often does have an appreciable ill effect on the integrity of an aircraft. Careful consideration must be given to this time element by the assigned inspector prior to putting the aircraft on a new certificate. Acceptance checks, which are a necessary part of the certification procedure must take into account the effects of calendar time and assure that the product is airworthy.
(8) Industry-wide service history.
(9) Previous operator's use of a reliability program.
h. Appliances of the same make and basic models as those currently in use by an operator and which are installed in a newly acquired aircraft of a different type are eligible for approval at the operator's approved overhaul time providing it can be determined that environmental factors will not have an adverse effect on them.
i. For those aircraft not listed in AC 121-1A or an MRB document, the basic principle followed by the Administrator will be that the inspections, checks, maintenance, or overhaul be performed at times well within the expected or proven service life of each component of the aircraft.
In determining what the expected or proven time limitations of an aircraft or any of its components might be, the Administrator will consider the following factors:
(1) Geographical area or areas of operation.
(2) Engine operating power, procedures, etc.
(3) Number of landings, long haul vs. short haul.
(4) Maintenance organization and inspection procedures.
(5) Other operators' service experience.
(6) Manufacturer's recommendations.
(7) Service history.
Special reliance will be placed on service experience, including the information obtained from tests, inspections, or measurements that were performed while accumulating service experience. The maintenance program should specify the maintenance checks, inspections, and overhauls to be performed and the times at which they will be accomplished.
j. An aircraft maintained in accordance with the provisions of a reliability program may be incorporated into another operator's maintenance system by direct inclusion under the terms of the previous or present operator's reliability program, if the PMI/PAI determines that the maintenance controls established relate realistically and responsively to operating experience.
NOTE: It is intended that the specific needs of the operator, in terms of operating philosophy, recordkeeping practices, statistical and data processing, be thoroughly evaluated prior to program approval. Areas of program compatibility to be considered are: (1) Adequacy of organizational structure; (2) Suitability of data collection and analysis system; and (3) Timeliness of corrective action program. Additional information that may prove useful can be found in AC 120-17A.
* k. In the event an operator and the assigned PMI/PAI cannot reach an agreement in the application of either program, the assigned inspector should contact the regional office for guidance. If further guidance is needed the Chief, Air Carrier Airworthiness Branch, AFS-230, Washington, D.C., should be contacted by the regional office. *
5. REVISION OF TIME LIMITATIONS - GENERAL.
a. The inspection and overhaul time limitations applicable to airframes, powerplants, propellers, and appliances are normally revised on the basis of service experience unless controlled by a reliability program in accordance with AC 120-17A.
b. Increases in such time limitations may be made as often as the operator can submit proper justification and substantiation to warrant a time increase. The justification should indicate that such increases will not adversely affect airworthiness of the aircraft.
When the service records indicate that any component or subcomponent consistently requires repair, adjustment, or other maintenance because of damage, wear, or deterioration, within the current time limitations, the operator will be responsible for initiating corrective action.
c. Time limitations may be established in terms of hours of operation, cycles, multiples of engine overhaul periods, or multiples of inspection periods.
d. Time limitations for components on which deterioration is not necessarily a function of operation hours, such as electronic units, emergency flotation equipment, etc., may be established in terms of calendar months.
6. AIRFRAME - REVISION OF TIME LIMITATIONS.
a. The increases of time limitations for overhaul or major inspections of airframes are normally based on evaluation of all pertinent service records and/or examination of at least one aircraft, of the model involved, that has been operated within five percent of the currently approved time limitation; or
b. Any other method acceptable to the assigned principal maintenance inspector such as industry experience, etc., may also be used when sufficient justification can be furnished by the operator.
c. When a pattern or block overhaul type of maintenance system is used, it will be permissible to reschedule individual items in another block or pattern, if performance and condition of the specific item warrants such an increase.