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 274–285
Page 286Open in PDF

Fuel System, OC X X X X Chapter 28 Rear Compartment OC X X Tank Fuel Heater 3,000 X X FC VA Wing Tank Press. 3,600 X X CAL VA Reducing Valve Rear Compartment Tank 3,600 X X CAL VA Press. Reducing Valve Dual Fuel Quantity 1,500 X X CAL VA Indicators Fuel Transfer Pump 2,400 X X X Replace brushes 1,800 hrs.

Effective date ____________________ Page 5 of 8

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

FAN JET FALCON

OVERHAUL INSPECTION AND CHECK PERIOD HOURS/YRS. PVO VA GV 2GV OTHER Fuel System, Chapter 28 (Cont'd) Fuel Shut Off Valve OC X X X FC EC L.P. Crossfeed Valve OC X X X FC VA L.P. Fuel Pump 2,400 X X X Replace brushes 1,800 hrs.

Hydraulic System, OC X X X X Chapter 29 Hydraulic Pump EO X Engine Driven Transfer Jack 5,400 X X X Electro Pump 7 yrs. X X X Selector Valve Electro Pump 3,600 X X X FC Once a week.

Ice & Rain, OC X X X X Chapter 30

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Instruments, OC X X X X Chapter 31 To be determined by assigned inspector.

Landing Gear, OC X X X X Chapter 32 Main Landing Gear 2,700 5,400 X X X Per AMD SB 431 Nose Landing Gear 2,700 5,400 X X X Per AMD SB 431 Landing Gear Door OC X X X Locks (2 GV Inspection for door locks P/N VTS 431) (1 GV Inspection for door locks P/N VTS 442 or 4422) Parking Brake OC X X Telforce Cable Anti-Skid Detectors 4,800 X X X OP at wheel or brake change Nose Gear Wheel 700 Ldgs Scrap (P/N 9533961) after 700 landings Effective date ____________________ Page 6 of 8

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

FAN JET FALCON

OVERHAUL INSPECTION AND CHECK PERIOD HOURS/YRS. PVO VA GV 2GV OTHER Lights, Chapter 33 OC X X X X All Lights OC X X X X

Page 288Open in PDF

Navigation, OC X X X X Chapter 34 To be determined by assigned inspector.

Oxygen, Chapter 35 OC X X X X Oxygen Bottle ** 3 yrs. X X X (Hyd. or retire appropriate for bottle used) Pressure Reducing 3 yrs. X X X Valve High Pressure Gauge OC X X X Crew Oxygen Mask 3 yrs. X X X Altitude Sensitive 5 yrs. X X X Switch Filler Connection OC X X X Solenoid Valve OC X X X Shut Off Valve OC X X X Pneumatic, Chapter 36 OC X X X X Valve, Nacelle OC X X Deicing Valve, Bleed Air OC X X Valve, Conditioning OC X X Valve, Wing Deicing OC X X Drag Chute, OC X X X X Chapter 39 * F.C. to be carried * 6 mos.

out every time drag chute has been used or at least every 6 mos. in case of nonoperation.

APU, Chapter 49 OC X X X X APU * X X X * See APU Manufacturers recommendation.

Effective date ____________________ Page 7 of 8

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

FAN JET FALCON

OVERHAUL INSPECTION AND CHECK PERIOD

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HOURS/YRS. PVO VA GV 2GV OTHER Doors, Chapter 52 OC X X X X Main L/G Door OC X X X Teleforce Control L/G Door Emergency OC X X X Teleforce Control Passenger/Crew Door 7 yrs. X X X Pneumatic Jack Emergency Exits OC X X X O.P. VA Fuselage, Chapter 53 OC X X X X NOTE 1: Inspect areas in accordance with Fan Jet Falcon Maintenance Manual.

Nacelles, Pylons, OC X X X X Chapter 54 Inspect areas in accordance with Fan Jet Falcon Maintenance Manual.

Stabilizers, OC X X X X Chapter 55 Inspect areas in accordance with Fan Jet Falcon Maintenance Manual.

Windows, Chapter 56 OC X X X X Inspect areas in accordance with Fan Jet Falcon Maintenance Manual.

Wings, Chapter 57 OC X X X X Inspect areas in accordance with Fan Jet Falcon Maintenance Manual.

Powerplant, OC X X X X Chapter 71 Engine Mount EC X X X Effective date ____________________ Page 8 of 8

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OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE

FAN JET FALCON

OVERHAUL INSPECTION AND CHECK PERIOD HOURS/YRS. PVO VA GV 2GV OTHER Engine, Chapter 72 OC X X X X Turbojet Engine * X X X CF 700 Hot Section * X X X Inspection * See engine (G.E.

manufacturer's recommendations) Engine Fuel & EO X X X X Control, Chapter 73 Ignition, Chapter 74 EO X X X X Igniter Plug 300 X X X Engine Hours Engine Air, EO X X X X Chapter 75 Engine Controls, OC X X X X Chapter 76 Throttle Teleforce 3,600 Control in Nacelle Engine Indicating, OC X X X X Chapter 77 T5 Harness EO X X X EPR (PT7) Probe EO X X X EPR Transmitter 3,600 X X X Exhaust, Chapter 78 OC X X X X Oil, Chapter 79 OC X X X X Oil Pressure EO X X X Transmitter Starting, Chapter 80 OC X X X X NOTE 1: Effectivity - Aircraft Serial No. 1 through 53.

Prior to accumulation 4,800 hours time in service or 7 years, whichever occurs first, accomplish Marcel Dassault Service Bulletin No. 159 titled, Fuselage - Reinforcement of Stringer

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Junction on Frame 33.

Effective date ____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 36. OPERATIONS SPECIFICATIONS, AIRCRAFT MAINTENANCE

- HAWKER-SIDDELEY DH-125 SERIES Form Approved.

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

WASHINGTON PART D Page 1 of 7

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE - GENERAL HAWKER SIDDELEY DH-125 SERIES Thorough inspection shall be accomplished in accordance with the applicable procedures as listed in ABC Airlines Maintenance Manual.

Preflight (PF) shall be accomplished each service calendar day.

Inspection shall be in accordance with the applicable procedures listed in ABC Airlines Maintenance Manual.

Period Inspections (PI) the procedure for the performance of period inspections will be accomplished as specified in ABC's Maintenance Manual. Period inspections must be accomplished at intervals not to exceed 160 hours time in service.

Aircraft shall not be utilized in air carrier or commercial operations unless:

a. The aircraft and its component parts, accessories, and appliances are maintained in an airworthy condition in accordance with the schedule of maintenance and inspection functions and procedures set forth in the operator's maintenance manual.

b. OC "On Condition" items will be maintained in continuous airworthiness condition by periodic and progressive inspections, checks, services, repair, and/or preventive maintenance and shall be appropriately described in the operator's maintenance manual.

c. Parts or sub-components not listed below will be checked, inspected and/or overhauled at the same time limits

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specified for the component or accessory to which such parts or sub-components are related.

Abbreviations used in the Hawker-Siddeley DH-125 maintenance specifications are defined as follows:

PF - Indicates "Preflight Inspection" BC - Indicates "Bench Check" EO - Indicates "Engine Overhaul" EC - Indicates "Engine Change" OC - Indicates "On Condition" HYD - Indicates "Hydrostatic Test" C - Indicates "Calibration" Life Limited Components.

Numerous parts, affecting different models of the DH-125 Aircraft, are life limited and listed under Note 3 of FAA Type Certificate Data Sheet ABEU. The limitations must be adhered to as applicable to the various aircraft.

Effective date ____________________ Page 2 of 7

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE HAWKER-SIDDELEY DH-125 SERIES

OVERHAUL INSPECTION AND CHECK PERIOD LNDGS., HOURS OR YRS PF PI OTHER Air Conditioning, OC X X Chapter 21 Air Jet Pump 3,000 X Air Needle Valve OC X APU Supply Check 3,000 X Valve APU Shut-off 3,000 X Valve Auxiliary Heating 3,000 X Valve Cabin Temperature OC X Controller Cabin Pressure OC X Control Fan Operated 3,000 X Venturi Flow Control 3,000 X Valve Initiation Air 3,000 X Valve

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Main Supply Check 3,000 X Valve Outflow and Safety 3,000 X Valve Pneumatic Relay 3,000 X Pressure Regulators 3,000 X Ram Air Check Valves 3,000 X Ram Air Valve 3,000 X Refrigeration 3,000 X By-Pass Valve Refrigeration Unit 2,000 X Turbine By-Pass 3,000 X Valve Auto Pilot, OC X X Chapter 22 Aileron Servo 3,000 X X Air Speed 4,000 X Compensator Compass Amplifier 4,000 X X Computer Amplifier 4,000 X X BC 1 Year Controller, Pedestal 5,000 X X BC 1 Year Elevator Servo 3,000 X X Emergency Disconnect 4,000 X X Instrument Amplifier 4,000 X X Rudder Servo 3,000 X X Servo Mount 5,000 X Steering Computer 4,000 X X Trim Tab Servo 3,000 X X Vertical, Yaw and 4,000 X X Rate Gyros Communications, OC X X Chapter 23 To be determined by assigned inspector.

Effective date ____________________ Page 3 of 7

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE HAWKER-SIDDELEY DH-125 SERIES

OVERHAUL INSPECTION AND CHECK PERIOD LNDGS., HOURS OR YRS PF PI OTHER Electrical System, OC X X Chapter 24

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Alternator 800 X X Alternator Volt. 2 Yrs. X X Control Unit Compass Inverter 1,000 X X Emergency Contactor 4,000 X Field Contactors 3,000 X Generator 2,000 X Contactors Generator Switching 2,000 X Units Ground Contactor 5,000 X Inverters #1 and 1,500 running Hrs. X X #2 Inverter Control 4,000 X Relays Overspeed Relays 3,000 X Overvoltage Relays 4,500 X BC - 2250 Hrs.

Overvoltage Unit 3,000 X Regulators 4,500 X Standby Inverter 1,500 running Hrs. X X Start and Battery 4,000 X Contactor Starter Buss 5,000 X Contactor Starter Generators 800 X X Time Switch 4,000 X Voltage Sensing 4,500 X Unit Voltmeter 10,000 X X Equipment & OC X X Furnishings, Chapter 25 To be determined by assigned inspector.

Fire Protection OC X X System, Chapter 26 Actuator Cartridge OC X Replace 2 Yrs.

APU Fire Detector OC X X Container, Fire OC X X HYD 5 Yrs.

Extinguisher Dual Head Valves OC X Engine Fire OC X X Detection Rear Equipment Bay OC X Overheat Flight Control OC X X Systems, Chapter 27 Airbrake and Lift OC X

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Dump System Flap System OC X X Flap Control Unit 4,500 X Flap Jack Screws 3,000 X Stall Warning OC X X System Stick Shaker System 4 Yrs. X X Trim Control OC X Systems Effective date ____________________ Page 4 of 7

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE HAWKER-SIDDELEY DH-125 SERIES

OVERHAUL INSPECTION AND CHECK PERIOD LNDGS., HOURS OR YRS PF PI OTHER Fuel System, OC X X Chapter 28 Boost Pumps 1,000 X X Check Valves 6 Yrs. X Cross Feed System OC X X Drain Valves OC X X Float Valves 6 Yrs. X X Low Pressure, 4 Yrs. X Transfer and Crossfeed Valves Hydraulic System, OC X X Chapter 29 Accumulators 3,000 X X Aux. Hydraulic OC X Low Level Light Brake Modulator 3,000 X Units Cylinders:

Airbrake 3,000 X Actuating MLG, 4,500 Lndgs X Retraction MLG, Door 3,000 Lndgs X Actuating NLG, 6,000 Lndgs X Retraction NLG, 3,600 Lndgs X Steering

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Wing Flap 3,000 X Actuating Engine Driven Pumps 3,000 X Flap Control Unit 4,500 X Flow Indicator Unit 5,000 X Hand Pump 5,000 X Valves:

Brake 3,000 X Emergency Reducer Brake 3,000 X Control Brake 5,000 X Shuttle Check 5,000 X Gear 5,000 X Extension Restrictor Nose Gear 5,000 X Steering Pump Cut-Out 2,500 X Pressure 5,000 X Regulating Ice and Rain OC X X Protection, Chapter 30 Airframe Deicing 2 Yrs. X Pump Fuel Filter Deice 3 Yrs. X Pump Ice Detector System 4,500 X Pitot Heat System OC X X Windshield Heat OC X X Control Windshield Deicer 3 Yrs. X Hand Pump Wing Deicer Check 3,000/4 Yrs. X Valve Wing Deicer 3,000/4 Yrs. X Compensating Valve Effective date ____________________ Page 5 of 7

OPERATIONS SPECIFICATIONS

AIRCRAFT MAINTENANCE HAWKER-SIDDELEY DH-125 SERIES

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OVERHAUL INSPECTION AND CHECK PERIOD LNDGS., HOURS OR YRS PF PI OTHER Instruments, OC X X Chapter 31 To be determined by assigned inspector.

Landing Gear, OC X X Chapter 32 Anti-Skid System 3,000 Lndgs X X Landing Gear 3,000 Lndgs X Control Unit MLG Assembly 2,000 Lndgs X X MLG Door Assembly OC X X MLG Mechanical OC X Indicator NLG Assembly 3,000 Lndgs X X NLG Door Assembly OC X X NLG Mechanical OC X Indicator Parking Brake OC X X Control Wheels, Tires and OC X X Brakes Lights, Chapter 33 OC X X Anti-Collision OC X X Central Warning OC X X Unit Exit Marking OC X X Landing OC X Navigation OC X Passenger OC X Emergency Wing Ice Lights OC X Navigation, OC X X Chapter 34 To be determined by assigned inspector.

Oxygen, Chapter 35 OC X X Cylinders:

Main *OC X X *(4 Yrs. Hyd Check or cyl.

replacement appropriate to