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 142–153
Page 154Open in PDF

Effective date _____________________ ---------------------------------------------------------------- MAINTENANCE ZONES - CONVAIR 880 - 22-99001 [FIGURE NOT INCLUDED] NOTES:

1. WING TO

FUSELAGE

FAIRING OMITTED FOR CLARITY.

2. C.S.S. MEANS

CENTER SPAR STATION.

3. F.S. MEANS

FUSELAGE STATION.

4. W.S. MEANS WING STATION.

UN-PRESSURIZED FUSELAGE AREAS ABOVE FLOOR COMPT.

1. RADOME 20. COCKPIT

2. NOSE WHEEL WELL & GEAR 21. ENTRANCE & SERVICE - FWD

3. AIR-COND (LH) 22. FUSELAGE - PASSENGER

4. AIR-COND (RH) 23. ENTRANCE & SERVICE - REAR

5. WHEEL WELL - LH & GEAR 24. LAVATORY & PRESS DOME

6. WHEEL WELL - RH & GEAR 25. FAIRING - ANTENNA - TOP

7. TAIL SECTION - FUSELAGE

8. TAIL CONE FUEL TANKS

30. WING - NO 1 AUX FUEL TANK

BELOW FLOOR COMPT'S - LH

10. NOSE SECTION 31. WING - NO 1 MAIN FUEL TANK

11. ELECTRONIC - ELECTRICAL - LH

12. BAGGAGE - FWD 32. WING - NO 2 AUX FUEL TANK

13. WATER - LH

14. OVER WING 33. WING - NO 2 MAIN FUEL TANK

15. HYDRAULICS - LH

16. BAGGAGE - REAR 34. WING - FUEL TANK - CENTER

17. AFT FUSELAGE - BELOW FLOOR SECTION

35. WING - NO 3 MAIN FUEL TANK WINGS - L.E. & TIPS - RH

40. WING TIP - LH 36. WING - NO 3 AUX FUEL TANK

41. LEAD EDGE - OUTBD - LH - RH

42. LEAD EDGE - CENTER - LH 37. WING - NO 4 MAIN FUEL TANK

43. LEAD EDGE - INB'D - LH - RH

44. LEAD EDGE - INB'D - RH 38. WING - NO 4 AUX FUEL TANK

Page 155Open in PDF

45. LEAD EDGE - CENTER - RH - RH

46. LEAD EDGE - OUTBD - RH

47. WING TIP - RH HORIZONTAL STABILIZER

60. HORIZ STAB - OUTBD - LH WINGS - TRAILING EDGE & REAR SPAR 61. ELEV. TABS & BAL BD'S - LH

50. WING - TRAILING EDGE - LH 62. HORIZ STAB - INBD - LH

51. WING - FLAP & SPOILER - OUTBD 63. HORIZ STAB - INBD - RH

- LH 64. ELEV. TABS & BAL BD'S - RH

52. WING - AILERON & BAL BD - LH 65. HORIZ STAB - OUTBD - RH

53. WING - FLAP & SPOILER - INBD

- LH VERTICAL STABILIZER

54. WING - FLAP & SPOILER - INBD 70. VERT STAB

- RH 71. VERT STAB - INSUL STRIP &

55. WING - AILERON & BAL BD - RH CAP

56. WING - FLAP & SPOILER - OUTBD 72. RUDDER, BAL BD'S & TABS

- RH

57. WING - TRAILING EDGE - RH PODS & PYLONS

81. ENGINE #1 POD

82. ENGINE #2 POD

83. ENGINE #3 POD

84. ENGINE #4 POD

85. ENGINE #1 PYLON

86. ENGINE #2 PYLON

87. ENGINE #3 PYLON

88. ENGINE #4 PYLON ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 25. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE

- FAIRCHILD F-27 Form Approved.

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

WASHINGTON

OPERATIONS SPECIFICATIONS PART D Page 1 of 7 Pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Air Conditioning System, Chapter 21 12,000 Altimeter, Dual Pressure 3,000 Air Cycle Machine 3,000 Blower, Cabin (Roots) 2,200

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Circuit - Cabin Temperature Sensing 3,000 Controller, Cabin Pressure 5,000 Controller, Cabin Rate 5,000 Controller, Cabin Temperature 5,000 Delivery Silencer 10,000 Fan, Combustion 2,000 Heater System 3,000 Indicator, Cabin Blower Pressure 7,500 Recirculating Fan 1,000 Transmitter, Cabin Blower Pressure 6,000 Valve, ACM Turbine Bypass 2,000 Valve, Spill 3,000 Auto Pilot, Chapter 22 12,000 Controller, Altitude 2,000 Capstan, Primary Servo 2,000 Capstan, Trim Servo 2,000 Computer Coupler 2,000 Followup 2,000 Servo, Primary 2,000 Servo, Trim 2,000 Trim Indicator 4,000 Communications, Chapter 23 12,000 May be determined by the assigned inspector.

Electrical Power, Chapter 24 12,000 Ammeter, D.C. 8,000 Battery O.C.

Circuit Breakers 12,000 Control Panel A.C. 2,000 Control Relay D.C. 2,000 Control, D.C. Generator 1,000 Generator, D.C. 1,400 Generator, A.C. Brushless 2,000 Generator, Emergency A.C. 1,300 Inverter 1,800 Power Failure, A.C. 2,000 Effective date _____________________ PAGE 2 of 7 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Electrical Power, Chapter 24 Period Check Period

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(continued) Relay, Main Contactor 1,000 Voltmeter, D.C. 7,000 Equipment and Furnishings, Chapter 25 12,000 Emergency Equipment 6 mos.

Fire Protection, Chapter 26 12,000 Control Box, Fire Detection 4,000 Cartridges, Discharge Valve 2 years Cylinders (Water and CO2 Hand Extinguisher) * Cylinders (Engine) * * 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 Cables System OC Control Surface Assembly 12,000 Control Interior Structure 12,000 Control Exterior Covering 12,000 Control Stick Shaker 2,000 Flap Transmitter Position and Indicator 5,000 Flap Actuator 1,000 Lift Transducer 1,500 Stall Warning Indicator 1,500 Switch Asymmetry 12,000 Summing and Relay Unit OC Tension Regulator 10,000 Fuel System, Chapter 28 12,000 Indicator Fuel Quantity and Power Unit 12,000 Indicator Fuel Quantity Repeater 12,000 Pump, Fuel Boost 1,200 Switch, Differential Pressure 6,000 Switch, Pressure Fuel Warning 6,000 Tank Unit, 13.41" Fuel Quantity 12,000 Tank Unit, 20.00" Fuel Quantity 12,000 Tank Unit, 16.25 12,000 Valve, Hot Air Gate 3,000 Valves, Electrical and Manual 12,000 Effective date _____________________ Page 3 of 7 Pages

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OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Ice and Rain Protection, Chapter 30 12,000 Ammeter, Deicing 8,000 Control Windshield Temperature 3,000 Control Panel A.C. 3,000 Deicer Fixed Installation and Lines 12,000 Deicer Boots O.C.

Deicing Cycling Timer O.C.

Ejector, Deicer Boot Assembly 5,000 Gauge, Deicing Suction 5,000 Gauge, Deicing Pressure 5,000 Voltmeter A.C. 7,000 Valve Suction Relief 2,000 Windshield Wiper Assembly O.C.

Instruments, Chapter 31 12,000 May be determined by the assigned inspector.

Landing Gear, Chapter 32 10,000 Nose Landing Gear Assembly 10,000 Attach Points 10,000 Under Carriage Main Gear 10,000 Drag Strut Main Gear 10,000 Lock Strut Main Gear 10,000 Brake Assembly O.C.

Anti-skid Device 750 Cable Nose Gear Retract O.C.

Nose Gear Fork 10,000 Nose Gear Strut 10,000 Indicator, Landing Gear Position 10,000 Nose and Main Wheels O.C.

Main Gear Retract Strut 5,000 Uplock Main Gear 5,000 Nose Gear Actuator 2,000 Nose Gear Uplock 2,000 Nose Gear Steering Actuator 1,500 Valve Steering Shutoff 3,000 Valve Steering Followup 1,500 Valves Pressure Reducing 2,500 Valve, Selector Landing Gear 3,000 Valve, Selector Solenoid Landing Gear 1,500

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Valve, Brake 1,500 Valve Brake Emergency 3,000 Effective date _____________________ PAGE 4 of 7 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Landing Gear, Chapter 32 (continued) Valve Rapid Exhaust 1,500 Gearbox Nose Gear Steering 4,000 Nose Gear Centering Cylinder 1,000 Nose Gear Air Motor 2,500 Actuator Main Gear Uplock 6,000 Actuator Nose Gear Uplock 2,000 Gauge, Brake Pressure 6,000 Hydraulic Pressure Relief Valve 5,000 Hydraulic Pressure Switch 5,000 Hydraulic Solenoid Valve 5,200 Hydraulic Pump and Motor 5,000 Relay Hydraulic Steering 3,000 Rectifier OC Lights, Chapter 33 12,000 May be determined by the assigned inspector.

Navigation, Chapter 34 12,000 May be determined by the assigned inspector.

Oxygen, Chapter 35 12,000 Oxygen Bottle * Pneumatic System, Chapter 36 12,000 Air Compressor 1,400 Bottles * Inspect for Corrosion 1 year Chemical Dryer Housing 4,300 Gauge, Pneumatic Brake Pressure 5,000 Gauge, Pneumatic Emergency Pressure 5,000 Gauge, Primary Pressure 5,000 Separator, Moisture 1,500 Switch High Pressure Cutoff 1,500 Unloader 1,500

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Valve Pressure Reduction (1000-100) 1,500 Valve Isolation 3,000 Valve Back Pressure 2,000 Valve Manual Discharge 3,000 * 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 5 of 7 Pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Doors, Chapter 52 12,000 Doors, Pax and Cargo 6,000 Emergency Exits 12,000 Retract Cylinder Cabin Door 5,000 Valve Pressure Reducing 3,000 Fuselage, Chapter 53 12,000 Attach Points 12,000 Exterior Covering 12,000 Interior Structure 12,000 Nose Cap Attach Points 12,000 Belly Interior Overhaul 6,000 Belly Interior, Lavatory and Galley 3,600 Nacelles, Chapter 54 12,000 Interior Structure 12,000 Exterior Covering 12,000 Stabilizers, Chapter 55 12,000 Dorsal Fin Structure 12,000 Vertical Stabilizer and Installation 12,000 Horizontal Stabilizer and Installation 12,000 Windows, Chapter 56 12,000 Windshield Assembly and Installation 12,000 Windows 12,000 Wings, Chapter 57 12,000

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Outer Section Interior Structure 12,000 Exterior Covering 12,000 Control Hinge Points 12,000 Flap Track and Installation 12,000 Center Section Exterior Covering 12,000 Interior Structure 12,000 Fuselage Attach Points 12,000 Flap Tracks and Inst. 12,000 Cables, Pulleys and Fairleads O.C.

Effective date _____________________ Page 6 of 7 Pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Propellers, Chapter 61 Propeller 2,600 Spinner 2,600 Propeller Control Unit 4,100 Feathering Pump 4,200 Alternator Prop Control 1,500 Corrector Motor 2,000 Propeller Brake 1,000 Propeller Controls and Installation 2,600 Powerplant General, Chapter 71 Engine Mount 3,000 Magnaflux 6,000 Cowling and Installation 3,000 Engine, Chapter 72 Air Intake Assembly 3,000 Engine 3,000 * * Sample one hot section inspection at 2000 hours, one engine overhaul at 2400 hours and one engine overhaul at 2700 hours.

Engine Fuel and Control, Chapter 73 Fuel Control Unit 3,000 Fuel Pump 3,000 Fuel System (Nacelle Forward Firewall) 3,000 Fuel Trimmer Actuator 3,000

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Indicator, Fuel Flow Dual 5,000 Indicator, Fuel Pressure Dual 8,000 Indicator, Fuel Trim 7,500 Transmitter Fuel Pressure 3,800 Transmitter Fuel Flow 1,900 Transmitter Fuel Trimmer Position 7,000 Engine Controls, Chapter 76 Engine Controls and Installation 3,000 Cables, Pulleys and Fairleads O.C.

Controls (Nacelle Aft Firewall) 12,000 Pedestal (cockpit) 12,000 Engine Indicating, Chapter 77 Generator Tachometer 5,000 Indicator Tachometer 5,000 Effective date _____________________ Page 7 of 7 Pages

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE FAIRCHILD F-27 Overhaul Inspection & Period Check Period Engine Indicating, Chapter 77 continued Indicator, Tail Pipe Temperature 7,500 Indicator, Torque Pressure 7,500 Transmitter Torque Pressure 3,000 Exhaust, Chapter 78 Exhaust Tail Pipe 3,000 Oil System, Chapter 79 Oil Radiator and Installation 3,000 Indicator Oil Pressure Dual 7,500 Indicator Oil Temperature Dual 5,000 Switch Oil Pressure Warning 7,000 Transmitter Oil Pressure 7,000 Starting, Chapter 80 Ignition Harness Assembly 3,000 Igniter 3,000 Starter 3,000 Starter Relay 1,500 Water Injection, Chapter 82

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W/M Tank and Installation 6,000 W/M Control Unit 3,000 W/M System (Nacelle Aft Firewall) 6,000 W/M Pump 3,000 W/M Filter 600 W/M Pressure Warning Switch 6,000 W/M Tank Indicator 5,000 W/M Valves Electrical and Manual 12,000 Accessory Gearbox, Chapter 83 Gearbox 2,200 Drive Shaft 1,400 Effective date _____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 26. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE

- CONVAIR CV-990 Form Approved.

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

WASHINGTON

OPERATIONS SPECIFICATIONS PART D Page 1 of 11 Pages

AIRCRAFT MAINTENANCE CONVAIR CV-990 Overhaul Inspection & Period Check Period Air Conditioning, Chapter 21 12,500 Controller, Cabin Pressure 6,000 Condenser, Conditioned Air Modulating 5,000 Fan, Electronic Equipment Cooling 6,000 Fan, Freon Pack Condensor 6,000 Fan, Recirculating 6,000 Indicator, Cabin Compartment Air Flow 10,000 Indicator, Cabin Temperature 10,000 Indicator, Turbo Compressor Bearing Temperature 10,000 Indicator, Turbo Compressor RPM 10,000 Heater, Electric Flight Deck Air 6,000 Heater, Cabin Air 6,000 Pack, Freon Refrigeration 5,000

Page 164Open in PDF

Sensor, Conditioned Air Temperature 5,000 Turbo Compressor 3,000 Valve, Air Turbine Drive-Shutoff 5,000 Valve, Condenser Air Ground Shutoff 10,000 Valve, Outflow Cabin Pressure 3,000 Valve, Ram Air Shutoff 10,000 Auto Pilot, Chapter 22 12,500 Accelerometer - Linear, Horizontal and Vertical 5,000 Amplifier, Servo Auto Pilot 5,000 Computer, Automatic Cutoff 5,000 Computer, Yaw Command 5,000 Computer, Pitch Command 5,000 Computer, Roll Command 5,000 Computer, Pressure 5,000 Controller, Auto Pilot 5,000 Coupler, Trim 5,000 Drum-Servo Bracket 6,000 Indicator, Trim 5,000 Rack Assy., Gain Calibrator & Relay 5,000 Rack, Stabilization Computer 5,000 Relay, Trim Valve Solenoid Control & Cockpit 5,000 Servo & Drive - Aileron & Rudder 6,000 Servo & Drive - Elevator 6,000 Communications, Chapter 23 12,500 May be determined by the assigned inspector.

Effective date _____________________ PAGE 2 of 11 PAGES

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE CONVAIR DC-990 Overhaul Inspection & Period Check Period Electrical Power, Chapter 24 12,500 Ammeters, A.C. & D.C. 10,000 Battery OC Constant Speed Drive 1,500 Contactor, External Power 10,000 Contactor, Line and Bus Tie 6,000 Contactor, Load Reduction 6,000 Controller, C.S.D. Load 10,000

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Frequency Meter 10,000 Generator 2,000 Panel, Control 6,000 Panel, Sync, Bus Protector 6,000 Relay, A.C. Monitor, Pilot's Essential Bus 6,000 Relay, A.C. 28 v. Lighting Transfer 6,000 Relay, Essential D.C. Bus Connector 6,000 Relay, Phase Sequence 6,000 Relay, Power Failure Detector 6,000 Relay, Reverse Current 6,000 Relay, Tie Control 6,000 Relay, Tow Power Contactor Transfer 6,000 Relay, 28 v D.C. Battery 6,000 Static Exciter 6,000 Transformer - Rectifier - Battery Charger 6,000 Voltmeters, A.C. & D.C. 10,000 Wattmeter, A.C. 10,000 Equipment and Furnishings, Chapter 25 12,500 Evacuation Slides 6 Mos.

Fire Protection, Chapter 26 12,500 Agent Container & Actuator Assy. * Cartridge 3 years replace Control Box, Fire & Overheat Warning Alarm Bell 5,000 Fire Extinguisher - Hand (CO2) * Fire Extinguisher - Hand (Water) 5 years Valve, Three Way 10,000 * 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.

Flight Controls, Chapter 27 12,500 Actuator, Flap Control - Inboard & Outboard 12,500 Actuator, Horizontal Stabilizer Trim 10,000 Actuator, Inboard and Outboard Spoiler Deactivation 8,000 Actuator, Leading Edge Flap 10,000 Actuator, Outboard Spoiler 6,000 Effective date _____________________ Page 3 of 11 Pages