AC 121-1A

Change 4Historical

Advisory circular · Standard Operations Specifications - Aircraft Maintenance Handbook

Approved
July 7, 1978
Last reviewed
October 25, 2024
Cancels
AC121-1A CHG 3AC120-21AC120-24A
Family
AC 121-1 · 1 version
Revision
A, change 4
14 CFR parts
1

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 22, 2025.

Show pages 60–71

Effective date December 15, 1962 PAGE 2 of 3 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE VISCOUNT 745D/810 Overhaul Inspection & Period Check Period Equipment & Furnishings, Chapter 25 12,000 Evacuation Chute OC Fire Protection, Chapter 26 12,000 Cylinders * * Hydrostatic and life limits shall be entered here and shall not exceed those set forth in Part 173, Chapter I, Subtitle "B" of CFR Title 49.

Flight Controls, Chapter 27 12,000 Actuator, Aileron Trim Tab 4,500 Drum Assembly - Microswitch Control 7,000 Flap Brake Assembly 4,500 Flap Clutch & Disconnect Assembly 4,500 Flap Gear Box 7,000 Flap Gear Box Drive Motor 2,500 Indicator, Aileron Trim Position 4,000 Transmitter, Aileron Trim Tab Position 4,000 Indicator, Flap Position 6,000 Transmitter, Flap Position 6,000 Fuel System, Chapter 28 12,000 Actuator, Low Pressure Fuel 2,500 Actuator, Plessey Interengine 2,500 Amplifier, Fuel Quantity 2,500 Indicator, Fuel Datum Trim 6,000 Indicator, Fuel Quantity 4,000 Pump, Fuel Boost 4,000 Hydraulic System, Chapter 29 12,000 Actuator, Foot Brake 6,000 Motor, Undercarriage Control Valve 2,500 Unit, Maxaret 3,500 Ice & Rain Protection, Chapter 30 12,000 Actuator, Jet Pipe Flap 2,500 Actuator, Thermal Deice Bypass Valve 2,500

Alternator, Prop Deice 2,500 Indicator, Jet Pipe Temperature 6,000 Inverter, Windshield Deice 2,000 Instruments, Chapter 31 12,000 Clock OC Effective date _____________________ PAGE 3 of 3 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE VISCOUNT 745D/810 Overhaul Inspection & Period Check Period Landing Gear, Chapter 32 12,000 Emergency Air Bottle * Indicator, Brake Pressure 6,000 Switches, Gear 4,000 Switches, Oleo 4,000 Wheels, Tires & Brakes OC Lights, Chapter 33 12,000 Flasher 4,000 Lights, Landing 2,500 Navigation Instruments, Chapter 34 12,000 Altimeter 3,000 ** Compass, Magnetic 6,000 Horizon, Gyro 3,000 Indicator, Air Speed 4,000 Indicator, Outside Air Temperature 6,000 Indicator, Rate of Climb 4,000 Indicator, Turn & Bank 3,000 ** Bench Check every 12 months.

Oxygen System, Chapter 35 12,000 Oxygen Bottle * Fuselage, Chapter 53 12,000 Nacelles, Chapter 54 12,000 Stabilizers, Chapter 55 12,000 Wings, Chapter 57 12,000

* Hydrostatic and life limits shall be entered here and shall not exceed those set forth in Part 173, Chapter I, Subtitle "B" of CFR Title 49.

Effective date _____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 19. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE

- LOCKHEED L-188 A & C Form Approved.

UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.

WASHINGTON

OPERATIONS SPECIFICATIONS PART D Page 1 of 5 pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE LOCKHEED L-188 A & C Overhaul Inspection & Period Check Period Air Conditioning System, Chapter 21 12,000 Air Cycle By-Pass Valve 4,000 Air Cycle Cooling Air Exit Door Actuator 4,000 Air Cycle Heat Exchange O.C.

Air Cycle Cooling Turbine 4,000 Altimeter, Cabin 7,000 Cabin Air Compressor 2,000 Cabin Air Flow Control Valve 2,000 Cabin Pressure Reg. Outflow Valve 5,000 BC 2500 Cabin Pressure Safety Valve 12,000 BC 4000 Cabin Air Duct Shut-Off Valve O.C.

Cabin Air Duct Check Valve O.C.

Cabin Air Pressure Outflow Valve Control 3,500 Cabin Air Pressure Outflow Valve Control Filter 1,500 Cabin Freon Evaporator O.C.

Cabin Aux. Vent Inlet Valve & System O.C.

Cabin Air Warmup Valve Actuator O.C.

Cabin Air Filter O.C.

Cabin Duct Heater O.C.

Cabin Recirculating Fan 4,000 Cooling Air Exit Door Actuator (tunnel) 4,000 Cooling Air Inlet Door Actuator (tunnel) 4,000 Flight Station Recirculating Fan 4,000 Flight Station Freon Evaporator O.C.

Flight Station Duct Heater O.C.

Flight Station Aux. Vent Inlet Valve O.C.

Flight Station Air Filter O.C.

Freon Suction Pressure Throttling Valve 4,000 Freon Condenser Fan 4,000 Freon Condenser O.C.

Freon Compressor 3,000 Lavatory Exhaust Fan O.C.

Manual Control Valve 5,000 Negative Pressure Relief Valve O.C.

Radio Rack Exhaust Fan 1,400 Rate of Climb 7,000 Radiant Heating Panel (floor and wall) O.C.

Radiant Heating Panel (cargo compt.) O.C.

Surge Control Valve 2,000 Temperature Control Box 2,500 Effective date April 1, 1964 PAGE 2 of 5 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE LOCKHEED L-188 A & C Overhaul Inspection & Period Check Period Auto-Pilot System, Chapter 22 May be determined by the assigned inspector.

Communications System, Chapter 23 May be determined by the assigned inspector.

Electrical Power, Chapter 24 OC Battery OC Flight Station Electrical &

Instrument Panels OC Generator, AC 2,000 Generator Control and Protection Components 2,000 Inverter 2,000 Main & Flight Station Distribution Centers, including Wiring, Terminals, Relays, Circuit Breakers, Etc. OC Power Contactors and Reverse Current Relays 2,000 Secondary Electrical Centers, including Wiring, Terminals, Relays, Circuit Breakers, Etc. OC Transformer Rectifiers 2,000 Voltage Regulators 2,000 Equipment & Furnishings, Chapter 25 May be determined by the assigned inspector.

Fire Protection, Chapter 26 OC Cylinder * Discharge Valve Cartridges 3 years Transfer Valve 8,000 Valve, Drain 3,500 Flight Controls, Chapter 27 OC Aileron Trim Tab Control Unit 12,000 Aileron Trim Tab Actuator Unit 12,000 Aileron Push-Pull Tubes, Bellcranks Fittings, etc. 8,000 Asymmetry Detector Shut-Off Valve 6,000 Asymmetry Detector Actuated Flap Actuator Brake 12,000 * Hydrostatic and life limits shall be entered here and shall not exceed those set forth in Part 173, Chapter I, Subtitle "B" of CFR Title 49.

Effective date _____________________ Page 3 of 5 pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE LOCKHEED L-188 A & C Overhaul Inspection & Period Check Period

Flight Controls, Chapter 27, continued Booster Actuators 8,000 Booster Valve Cluster 8,000 Booster Frame Disconnect Mechanism 8,000 Control Column 12,000 Control Cables, Pulleys, Fairleads, etc. O.C.

Elevator Trim Tab Control Unit 12,000 Elevator Trim Tab Actuator Unit 12,000 Elevator Push-Pull and Torque Tube 8,000 Flap Control System 5,000 Hydraulic Load Sensors 8,000 Rudder Pedals 12,000 Rudder Trim Tab Control Unit 12,000 Rudder Trim Tab Actuator & Linkage 12,000 Rudder Push-Pull and Torque Tube Installation 8,000 Wing Flap Main Drive Hydraulic Motor 12,000 Wing Flap Main Drive Gear Box 12,000 Wing Flap Actuators, Linkages, Tracks and Carriages @ 4,000 Fuel System, Chapter 28 Boost Pump, Main 5,000 Boost Pump, Scavange 5,000 Fuel Valves (Crossfeed-Elect.; Shut- Off-Manual) 8,000 Fuel Dump Valves 8,000 Fueling Valve 8,000 Fuel Quantity Tank Units O.C.

Fuel Quantity Indicators 5,000 Fuel Pressure Warning System O.C.

Misc. Valves, Pilot & Vent. 10,000 Overflow Valve 8,000 Transmitter, Fuel Crossfeed 8,000 Hydraulic System, Chapter 29 O.C.

Aux. Pump (DC) 4,000 Hydraulic Motor Pump (AC) 2,000 Heat Exchanger O.C.

Relief Valve, Main System 12,000 Reservoir 12,000 Pressure Switches O.C.

Effective date April 1, 1964 PAGE 4 of 5 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE LOCKHEED L-188 A & C Overhaul Inspection & Period Check Period Ice & Rain Protection, Chapter 30 OC Airfoil Temperature Sensor Amplifier 4,000 Bleed Air Shut-Off Valve 3,000 Control Unit, Temperature 8,000 Fuselage Isolation Valve 8,000 Indicator, Airfoil Temperature 8,000 Indicator, Bleed Air Manifold 8,000 Leakage Detector Valve 3,000 Modulating Control Valves 8,000 Switch Temperature Selector 8,000 Transmitter, Bleed Air Manifold 8,000 Thermostats OC Universals OC Firewall Bleed Air Shut-Off Valve 3,500 Timer, Prop De-Ice 5,000 Windshield De-Fog 8,000 Windshield Wiper Accumulator 12,000 Windshield Wiper Control Unit 4,000 Window Units 12,000 Landing Gear, Chapter 32 Brake Accumulators 12,000 Brake System 12,000 Gear Up-and-Down Locks 10,000 Lockout Cylinder 12,000 Main and Nose Wheels OC Main Gear 12,000 Main Gear Door Actuating Cylinder 10,000 Nose Gear 12,000 Nose Gear Door Actuating Cylinder 10,000 Nose Wheel Steering 12,000 Valve, Shuttle 12,000 Valve, Priority 12,000 Lighting, Chapter 33 May be determined by assigned inspector.

Navigation, Chapter 34 May be determined by assigned inspector.

Oxygen System, Chapter 35 Oxygen Bottle *

* Hydrostatic and life limits shall be entered here and shall not exceed those set forth in Part 173, Chapter I, Subtitle "B" of CFR Title 49.

Effective date _____________________ Page 5 of 5 pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE LOCKHEED L-188 A & C Overhaul Inspection & Period Check Period Doors, Chapter 52 Actuators 4,000 Cylinder, Stair Actuating 4,000 Doors and Emergency Exits 12,000 Valve, Stair Selector 8,000 Fuselage, Chapter 53 Crew Seats and Attachments 8,000 Exterior Covering 12,000 Floor Support Members 12,000 Interior O.C.

Nose Gear Well Area 12,000 Passenger Seats and Attachments 12,000 Structure Around Windows 12,000 Nacelles, Chapter 54 Attachments 12,000 4,000 Main Gear Support Structure 12,000 Skin and Structure Beneath Tail Pipe Shroud 12,000 4,000 Tail Pipe and Shroud 12,000 2,000 Stabilizers, Chapter 55 Attachments and Joints 6,000 Exterior Covering 6,000 Elevator and Tabs 12,000 * 500 Interior Structure 6,000 ** 2,000 Rudder and Tabs 12,000 Vertical, Horizontal and Installation 6,000 Windows, Chapter 56 Cabin 12,000 Windshield Structure 12,000

Wings, Chapter 57 Ailerons and Tabs 12,000 Attach Joints 12,000 Center Wing Section 8,000 Flaps, Structure 12,000 Interior Structure 12,000 Wing to Fuselage Fillets 8,000 * Counter weight bracket Effective date April 1, 1964 ** Inspection Rear Spar Web ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 20. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE

- ALLISON 501-D13 ENGINE AEROPRODUCTS PROPELLER Form Approved.

UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.

WASHINGTON

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

ENGINE MAKE - ALLISON PROPELLER MAKE - AEROPRODUCTS ENGINE MODEL - 501-D13 PROPELLER MODEL - A6441FN606 Overhaul Inspection & Period Check Period Propellers, Chapter 61 Alternator 2000 Regulator 2000 Hub 2500 Blades 2500 Reservoir 2500 Spinner OC Power Plant General, Chapter 71 Engine Mounting System OC Vibration Isolators OC Engine Cowling OC Engine Fire Seal OC Engine, Chapter 72 Compressor/Gearbox 4000 Turbine Section 4000

Engine Fuel and Control, Chapter 73 Temperature Datum Control System 3000 Fuel Control 3000 Engine Fuel Pump 3000 Fuel Flow Meter 3000 Ignition System, Chapter 74 Exciter and Relay EO Ignitor EO Engine Air, Chapter 75 Ducts and Scoops OC Anti-ice System 3000 Speed-sensitive Control 3000 Engine Controls, Chapter 76 Power Lever System and Engine Coordinator Controls and Linkages OC Effective date _____________________

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

ENGINE MAKE - ALLISON ENGINE MODEL - 501-D13 Overhaul Inspection & Period Check Period Engine Indicating, Chapter 77 Tachometer Generator 3,000 Tachometer Indicator 5,000 T. I. T. Indicator 5,000 Torquemeter Indicator 5,000 Torquemeter Phase Detector 5,000 Indicator Oil Temperature 5,000 Indicator Oil Quantity OC Indicator Oil Pressure Gearbox 5,000 Indicator Oil Pressure Engine 5,000 Engine Exhaust System, Chapter 78 Engine Exhaust System OC Engine Oil System, Chapter 79 Engine Oil System OC Actuator Oil Cooler Flap 3,000 Oil Quantity Transmitter OC Oil Pressure Warning Switch OC Oil Pressure Transmitters 5,000

Oil Cooler Flap Position Indicator OC Fuel Oil Heat Exchanger 3,000 Oil Cooler EO Starting, Chapter 80 Engine Starter EO Bleed Air Shutoff Valves 5,000 Isolation and Firewell Valves 5,000 Combustor Assembly 1,800 Air Storage Bottles * Corrosion Inspection 1 year Air Bottle Cooling Valve 5,000 Air Compressor OC Low Pressure Regulator Valve EO * Hydrostatic and life limits shall be entered here and shall not exceed those set forth in Part 173, Chapter I, Subtitle "B" of CFR Title 49.

Effective date _____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 21. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE

- BOEING 707/720 Form Approved.

UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.

WASHINGTON PART D Page 1 of 12 Pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE BOEING 707/720 Overhaul Inspection & Period Check Period Air Conditioning, Chapter 21 O.C.

Ducting, Plumbing, Electrical Conduits O.C.

Turbo Compressor 3,000 Outflow Valves 2,500 Cabin Pressure Controller 5,000 Differential Pressure Indicator 8,000 Vapor Cycle Pack 5,000 Tachometer, Turbo Compressor 3,500 Actuator - Ram Air Damper 7,500 Controller, Cockpit Airflow 7,500

Valve - Pack Shutoff 5,000 Valve - Cabin Temp. Control 7,500 Valve - Cockpit Temp. Control (Hot) 10,000 Valve - Cockpit Temp. Control (Cold) 10,000 Valve - Ram Air Shutoff 12,500 Valve - Wing Shutoff 12,500 Blower - Recirculating 3,500 Controller - Cabin Pressure Manual 5,000 Fan Assembly - Condenser 4,000 Heat Exchanger O.C.

Heaters - Electric O.C.

Indicator - Cabin Temperature O.C.

Indicator - Cabin Rate of Climb 10,000 Pump - Jet O.C.

Relay - Compressor Discharge Overheat 10,000 Relay - Cabin Pressure Warning 10,000 Elements - Temperature Sensing O.C.

Switch - Duct Overheat O.C.

Switch - Pressure Altitude O.C.

Valve - Blower Shutoff 10,000 Valve - Cabin Air Check O.C.

Valve - Cockpit Air Check O.C.

Valve - Turbo Compressor Check O.C.

Electronic Equipment Blower 6,000 Valve - Cabin Pressure Bleed Air Shutoff O.C.

Air Cycle Machine 5,000 Condenser O.C.

Evaporator O.C.

Compressor 10,000 Auto Pilot - Chapter 22 O.C.

Auto Pilot Adapter O.C.

Box - Power Junction 5,000 Control Panel O.C.

Indicator - 3 Axis Trim (Eclipse Pioneer) 7,500 Sero - Stabilizer Trim 5,000 Effective date July 1, 1964 PAGE 2 of 12 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE BOEING 707/720 Overhaul Inspection &