,5.- ..,- .$ MIL-H-5440G .,. 28November1975 SUPERSEDING ...

,5.- ..,- .$‘

.. ,.

\

MIL-H-5440G28 November 1975SUPERSEDINGMIL-H-5440F18 January 1972

MILITARY SPECIFICATION

HYORAULICSYSTEMS,AIRCSAFT, TYPES I AND II, OESIGNAND INSTALLATION REQUIREMENTS FOR

This specificationis approved for use by all Departmentsand Agencies of the Department of Defense.

1.1 - This specificationcovers the design and installationrequirementsfor types I and 11 aircraft hydraulic systems.

1.2 Classification.types and classes, as

TxPE

Type IType II .-

Classes

1.500 pounds uer

Aircraft hydraulic systems shall be of the ‘followingspecified:

-54” to +71°c (-65” to ~160°F) temperature range-54” to ~135°C (-65° to +275°F) temperature range

square inch (PSi); where the cutout pressure at themain prksure controlli~gdevice is 1,500 psi

3,000 psi; where the cutout ,pressure at the main pressure controllingdevice is 3,000 psi.

2. APPLICABLE 00CUMENTS

* 2.1 The following documents, of the issue in effect on date of invitation forbids or request for proposal, form a part of this specificatkm to the extentspecified herein:

SPECIFICATIONS

Federal

MM-A-1617 Adhesive, Rubber Base, General Purpose

FSC 1650

Downloaded from http://www.everyspec.com

MIL-H-5440G

Military

MIL-B-50B7

MIL-W-508BMIL-A-5498MIL-C-5503

MIL-F-5508MIL-F-5509MIL-P-551OMIL-J-5513MIL-G-5514MIL-P-5516MIL-V-5519MIL-R-5520MIL-T-5522

MIL-V-5525MIL-V-5527MIL-V-552BMIL-V-5530MIL-H-5606

MIL-P-5954MIL-P-5994

MIL-H-6083MIL-T-6845

MIL-T-7081

MIL-F-7179

MIL-P-7858MIL-M-.7997

MIL-G-8348

MIL-T-8504

MIL-V-B566MIL-8-8584MIL-D-8706

MIL-H-8775

2

Bonding, Electrical, and Lightning Protection, forAerospace SystemsWiring, Aircraft, Selection and Installation of

Accumulators, Aircraft Hydropneumatic PressureCylinders; Aeronautical, Hydraulic Actuating, GeneralRequirements forFuses, Aircraft Automatic Quantity Measuring, HydraulicFittings, Flared Tube, Fluid ConnectionPacking, Preformed, Straight Thread Tube Fitting BossJoints, Hydraulic SwivelGland Design; Packings, Hydraulic,.General Requirements forPacking, Preformed, Petroleum Hydraulic Fluid Resistant, 160”FValves, Regulating Fluid PressureReservoirs, Aircraft, Hydra”lic, Non-Separated TypeTest Procedure for Aircraft Hydraulic and Pneumatic Systems,General

Valves, Aircraft Power BrakeValves; Aircraft, Hydraulic Thermal Expansion ReliefValves, Hydraulic Controllable CheckValves, Aircraft Hydraulic ShuttleHydraulic Fluid, Petroleum Base; Aircraft, Missile, andOrdnancePump Unit, Hydraulic, Electric Motor Driven, Fixed DisplacementPump, Hydraulic, Electric-Motor-Driven, Variable Delivery,General Specification forHydraulic Fluid, Petroleum Base, for Presemation and Testing

Tubing, Steel, Corrosion-Resistant (304), Aerospace VehicleHydraulic System, l/B Hard ConditionTube, Aluminum Alloy, Seamless, Round, Drawn, 6061, AircraftHydraulic QualityFinishes and Coatings: Protection of Aerospace WeaponsSystems, Structures and Parts, General Specification forPump, Hydraulic, Power Driven, Fixed ,DisplacementMotors, Aircraft Hydraulic, Constant Displacement, GeneralSpecification forGage Assemblies, Air Pressure, Dial Indicating Chuck TyDe.Self-ContainedTubing, ..Steel,Corrosion-Resistant (3o4), AerospaceHydraulic Systems, Annealed, Seamless and WeldedValves; Aircraft Hydraulic Flow RegulatorBrake Systems, wheel, Aircraft, Design ofData and Tests, EnszineerinE: Contract Requirements

Aircraft and Missiles,Aircraft Weapon Sy~tems -Hydraulic System ‘Components,Specification for

..-

Vehicl,e

for

General


MIL-H-5440G

MIL-F-8785MIL-R-8791

MIL-V-8813

MIL-F-8815

MIL-H-8891

MI L-R-8931MIL-c-8956MIL-S-9395

MIL-F-9490

MIL-F-18280MIL-F-18372

MIL-v-19067

MIL-v-19068MIL-P-19692MIL-c-25427

MIL-H-25579

MIL-V-25675MIL-P-25732MIL-V-27162

MIL-H-27267MIL-F-27272

MIL-H-38360

MIL-V-81940MIL-H-83282

MIL-F-83296

MIL-H-83298

MIL-F-83300

Flying Qualities of Piloted AirplanesRetairier,Packing, Hydraulic, and Pneumatic Tetrafluoro-ethylene Resin -”Valves: Aircraft, Hydraulic Pressure Relief, T~e IISystemsFilter and Filter Elements, Fluid Pressure, Hydraulic Line,15 Micron Absolute and.5 Micron Absolute, Type II Systems,General Specification forHydraulic Systems, Manual Flight Vehicles, Type III, DesignInstal1ation and Data Requirements for

.Accumulators,Hydraulic, Cylindrical, 3,000 PSI, AircraftType 11 SystemsReservoirs: Aircraft and Missile, Hydraulic, Separated TypeClamps, Loop, Tube SupportSwitch Pressure (Absolute Gauze and Differential) GeneralSpecification fo;Flight Control Systems - Design, Installation and Test of,Piloted Aircraft, General Specification forFittings, Flareless Tube, Fluid ConnectionFlight Control Systems; Design, Installation and Test of,Aircraft (General Specification +--)Valves, Check, Controllable, Hydraulic, Aircraft, Type IISystemsValves, Shuttle, Hydraulic, Aircraft, Type II SystemsPumDs. Hydraulic. Variable Delivery, General Specification forCoupling-Assembly, Hydraulic, Self~Sealing, QuickDisconnectHose Assembly, TetrafIuoroethylene, High Temperature MediumPressure, General Requirements forValves, Check, Miniature, Hydraulic, Aircraft and MissilePacking, Preformed, Petroleum Hydraulic Fluid Resistant, 275°FValves, Servo Control, Electro-Hydraulic, General SpecificationforHose Tetrafluoroethylene, High Temperature, Medium PressureFittinz, Tetrafluoroethylene, Hose, High Temperature, MediumPressu~&, General Requirements forHose Assembly, Tetrafluoroethylene, High Temperature, HighPressure, Hydraulic and PneumaticValve, Sampling and 81eed, Hydraulic, Type 11 SystemsHydraulic Fluid, Fire Resistant Synthetic Hydrocarbon 8ase,AircraftFittings, Tetrafluoroethylene Hose, High Temperature,HighPressure (3OOO psi), Hydraulic and PneumaticHose,,Tetrafluoroethy lene, High Temperature, High Pressure(3000 psi), Hydraulic and PneumaticFlying Qualities of Piloted V/STOL Aircraft

3


MIL-H-5440G

STANDARDS

Federal

FED-STD-791 ‘Lubricants, Liquid Fuels and Related Products; Methods ofTesting

Military

MIL-STD-1247

MS21105

MS21344

MS33515

MS33566

MS33583K33584MS33611MS33620MS33656

MS33657

Markings, Functions and Hazard Designations of Hose, Pipe,and Tube Lines for Aircraft, Missile, and Space SystemsClamp, Loop, Cushioned, Wedge, Fluid Resistant, SOO”F, CresType 1.11,Class BFittirigs- Installation of Flared T~be, Straight ThreadedConnectors, Design Standard forFitting End, Standard Dimensions for Bulkhead Flareless TubeConnectionsFittings, Installation ‘ofFlareless Tube, Straight-ThreadedConnectorsTubing End - Double Flare, Standard.Dimensions forTubing End - Standard Dimensions for FlaredTube Bend RadiiChart, Hose SelectionFitting End, Standard Dimensions for Flared Tube Connectionand Gasket SealFitting End, Standard Dimensions for Bulkhead Flared TubeConnection

1

Air Force-Navy Aeronautical

AN929 Cap Assembly, Pressure Seal Flared Tube FittingAN6240 ‘Filter - Hydraulic Replaceable Element Vent Type

PUBLICATIONS

Navy I)epartmentSpecification”

SD-24 General Specification for Design and Construction of AircraftWeapon Systems

vol. I Fixed Wing Aircraftvol. 11 Rotary Wing Aircraft

Navy Department Technical Manual

NAVAIR 01-lA-17 Aviation Hydraulics Manual

4

—


IJIL-H-5440G

Air Force Systems Command Design Handbook

AFSC DH 2-2 Crew Stations and Passenger Accommodations

(Copies of specifications, standards, drawings, and publications required bycontractors in connection with specific procurement functions should be obtainedfrom tbe procuring activity or as directed by-the contracting officer.)

* 2.2 Other publications. The following documents form a part of this speci-fication to the extent specified herein. Unless otherwise indicated, the issuein effect on date of invitation for bids or request fOr proposal shall aPPIY.

Society of Automotive Engineering, Inc. Aerospace Recommended Practices andAeronautical Standards

Coiled TubingGraphic Symbols for Aircraft Hydraulic and Penumatic SYStemS

ARP 584AS 1290

(Appl~cation for copies should be addressed to the Society of AutomotiveEngineering, Inc., 400 Commonwealth Orive, Warrendale, Pa 15096.)

National Aeros~ace Standards Association, Inc. Standard

NAS 1638 Cleanliness Requirements for Parts Used in Hydraulic Systems

(Application for copies should be addressed to the National Aerospace StandardsAssociation, Inc., 1321 Fourteenth St., N .!’l., Washington, D. C. 20005.)

3. REQUIREMENTS

3.1 Materials. Materials used in the manufacture of hydraulic systems inmilitary aircraft shal1 be of high quality, suitable for the purpose, and shallconform to applicable Government specifications. Materials confOTIII1ngto con-tractor’s specifications may be used, provided it can be clearly demonstratedthat they are at least equivalent to Government specifications with respect tooperating characteristics and that a savings in weight or cost can be accom-plished. Contractor’s specifications must be satisfactory to the Governmentand contain provisions for adequate tests. The use of contractor’s specifi-cations will not constitute waiver of Government inspection.

3.2 Design. The hydraulic systems and components thereof shall be designedto operate satisfactorily under al1 conditions that the aircraft may encounterwithin the structural limitations of the aircraft, including forces or condi-tions caused by acceleration, deceleration, zero gravity (g), negative g, or anyflight attitudes obtainable with tbe aircraft, structural deflection, vibration,or other environmental conditions. (For Navy use only, see Navy Departmentpublications SD-24, Volumes 1 and 11.) The hydraulic system(s) shall be con-figured such that any two fluid system failures due to combat or other damage

5


MIL-H-5440G

which cause loss of fluid or pressure will not result in complete loss offlight control. For fixed-wing aircraft, the surviving system(s) shall providesufficient control to meet the level 3 flying qualities of MIL-F-8785 forconventional takeoff and landing and MIL-F-83300 for vertical takeoff andlanding. For rotary-wing aircraft, the surviving system(s) shall provide suf-ficient control for return to the >ntended landing area (including shipboardareas and land)

* 3.3 Fluid. Fluid conforming to MIL-H-5606 shall be used for hydraulic systemsand associated ground equipment. MIL-H-83282 hydraulic fluid shall be usedinstead of MIL-H-5606 when specified by the procuring activity.

3.4 Packings. MIL-G-5514 shall be used as a guide for packing installations.

3.4.1 Type I systems. Packings shall conform to MIL-P-5516 or MIL-P-25732(excluding boss applications) . Packings used in bosses shall conform toMIL-P-551O.

3.4.2 Type 11 systems. Packings conforming to MIL-P-25732 shal1 be used with-in tbe performance constraints reflected by qualification requirements and testsof MIL-P-25732. Nonstandard packing may be used subject to approval of theprocuring activity. The major performance constraints of MIL-P-25732 are summa-rized in 3.4.2.1 and 3.4.2.2.

3.4.2.1 For maximum fluid temperature of 107”C (225”F). If the maximum fluidtemperature does not exceed 107”C (225”F), the standard seal is suitable for thenormal life reflected by emdurance test B of MIL-P-25732.

3.4.2.2 For maximum fluid temperature between 107° and 135°C (225” and 275”F).If maximum fluid temperature is between 107° and 135°C (225° and 275”F), the lifeexpectancy of the standard seal shall be reduced proportionally from the normallife reflected by e“dura”ce test 8 of MIL-P-25732 to the reduced life reflectedby endurance test A of MIL-P-25732. (The total accumulated time of exposure to13S°C (275”F) during qualification tests is approximately 80 hours.) The reducedlife expectancy shall be clearly defined in all appropriate publications. Pack-ings used in bosses shall be subjected to the,approval of the procuring activity.

3.4.3 8ackup rings. Backup rings shall conform to MIL-R-B791.

3.5 Hydraulic system data submittal and approval. Hydraulic system data sub-mittal and a’mroval requirements for a sDecific model aircraft will be coveredby a contrac~’with the ‘appropriate procu~ing activity. Typical information anddata required are listed in 6.2. The data shall be furnished in accordance withMIL-D-8706 or in accordance with appropriate line items of the Contractor DataRequirements List (DD Form 1423), as applicable.

6


MIL-H-5440G

3.5.1 Service-contractor conferences. The contractors shall confer with thehydraulic engineers of the applicable service on the proposed hydraulic systemsduring the early stages of design in order to take advantage of exchange ofinformation and to coordinate development programs. The first conference shall

take place at the time when the preliminary schematic diagram is established forthe aircraft. Other conferences shall take place during the appropriate develop-ment phases of the aircraft.

* 3.5.2 Functional mockup and simulator. A functional mockup and simulator ofthe hydraulic system or systems shall be constructed to determine system per-formance. Arrangement shall be made for the application of simulated flightloads and forces. Prototype components or suitable laboratory models may be

used for systems development testing. However, prior to the first flight, test-ing shall be accomplished on the simulator with all components incorporated,including flight instrumentation, tubing and fittings, identical to thoseinstalled in the first flight aircraft. Pending the availability of productioncomponents, prototype components or suitable laboratory models may be used.One test on the simulator shall simulate a mission profile so as to duplicatean actual aircraft condition. Items shall operate in sequence for a check onunusual back pressure, surges, temperature, pump pulsation, etc. The systemshall simulate startup, flight-control checkout, door closing, braking, steering,flap retraction, gear retraction, and power flight control under takeoff, cruise,

approach, landing, and taxi conditions. Al1 emergency modes and system failure

conditions as required by 3.2 shall be demonstrated. The functional mockupshall be used to determine the performance of the hydraulic system prior to thefirst flight of the aircraft and to evaluate any significant changes to be madeto the system during production of the aircraft.

* 3.6 General system design. Hydraulic systems shall be as simple and foolproofas possible and in accordance with design, operation, inspection, and maintenanceobjectives specified in the aircraft design requirements. For Navy aircraftNAVAIR 01-1A-17 shal1 be used as a guide for the maintenance aspects of tbe designof the aircraft.

* 3.6.1 Fluid temperature limitations. The hydraulic system(s) shal1 be capable

of operating under any condition encountered within the operating envelope,including the conditions specified in 3.6.1.1 and without exceeding the follow-ing bulk fluid temperature limits in any portion of the system(s):

a. Type I - 71°C (160”F)

b. Type 11 - 13S°C (275”F)

Operation at these temperaturesor component performance except

shall not result in any degradation of system(s)as noted .in 3.4.2.2.

7


I *

●

MIL-H-5440G

3.6.1.1 Climatic extremes. Ground operation, flight operation and storageclimatic extremes shall be in accordance with the weapon system procurementspecification.

3.6.2 Fire hazards. The hydraulic system shall be integrated with othersystems that will eliminate or isolate the system(s) from fire hazards causedby proximity of combustible gases, heat sources, bleed-air ducts or electricalequipment, etc. Hydraulic lines and equipment located in the vicinity of heatand ignition sources that will cause spontaneous ignition or sustained fire ofhydraulic leakage from these lines of equipment shall be protected by devicessu,chas firewal1s, shrouds, or equivalent means that will prevent fluid ignition.

3.6.3 Strength

3.6.3.1 Additional loads. All hydraulic systems and components which are sub-jected, during operation of the aircraft, to structural or other loads which arenot of hydraulic origin shall withstand such loads when applied simultaneouslywith appropriate proof,pressure as specified in table 1, without exceeding theyield point at the maximum operating temperature.

3.6.3.2 Accelerated loads. Actuating cylinders and other components and theirattaching lines and fittings, subject to accelerated loads, shall be designedand tested on the basis of a pressure equal to the maximum pressure that willbe developed, without exceeding the yield point at the maximum operating temp-erature.

3.6.4 Pressure limitations

3.6.4.1 System pressures. System pressures shall be in accordance with table 1.Peak pressure resulting from any phase of the $ystem operation shal1 not exceed135 percent of the main systep, subsystem, or return system pressure when measuredwith electronic equipment, or equivalent. Lines, fittings, and equipment inreturn circuits shall be designed for one-half the nominal system pressure.

3.6.4.2 Back pressure. The system shall be so designed that proper function-ing of any unit wil1 not be affected.by the back pressure or changes in theback pressure in the system. The system or systems shall also be so designeuthat malfunctioning of any unit in the system will not render any other sub-system, emergency system, or alternate system inoperative because of backpressure.

3.6.4.3 Brakes. Back pressure resulting from the operation of any unit whilethe aircraft is on the ground shall create no greater back pressure at the brakevalve return port than 90 percent of that pressure “hich will cause contact ofbraking surfaces. In addition, supply pressure to the brake system shal1 notdrop below the maximum brake-operating pressure during the operation of anyother subsystem in tbe aircraft during taxiing, landing, or takeoff.

8


MIL-H-5440G

TABLE 1, SySt C. Pressures

Percent

Ch.racterist ics Nominal systmo Pressure system Remarks I

C18SS 1500 class 5000 ‘re’’”re

a. Regulator cutout pressure 1,500

b. upper limit .f .peratin~ 1,250for all units (regularcut-in press.rc)

c. Maximum system relief 1,900valvesetting,atmaximumsystemflow

3,000

2>600

3,8S0

Automatic pressure regulator Accumulator system [closedcenter]

T1

Cpen-center-tne system[constant-deliverypump)

a. Systemdesignpressure 1,500 3,000 --- ReliefvalveFull -fl.$,

b. Upperlimitfor full- 1,350 2,700 setting

flow system pressurec System Relief “,1”, 1,500 3,000 MI L-v-8813 “nits

setting, u maximum‘system flow

Closed- or open-centersystem(variable-volurn.pump)

.. Pump unloading pre,s”re 1,500 S,ooo --- syst.. desi!w Pr.. $,, r.b. Maximm limit of full-flow 1,450 2,9S0

s)’stcm pl’e$,”rec Maim.. system relief 1,900 3,85o --- MIL-V-8813 units

valve setting, atmaximum system flow

Thermal relief ..1.. setting (maximum]

a. Equal to system relief 150 150 --- . . .valve setting plus . . .“,1”. s noted

Proof me.wre [minimum)

a. Lines, fittings aridhoses

b. Coulponent,.cmtZ.<.%.*air and fluid under

pr.s..r.c. ~P $..ti..a.d

casedrain linec.mpo”ent s andreservoir

(1) Non-pressurizedreservoirs

[2) Bootstrap re-servoirs

(3) Gas pressurizedreservoirs

3,000

3,000

50

. .

6,000

6,000

so

...

200

200

. . .

Proof” pressure “al”,,for hose to be i.accordance with theapplicable detailspecification.

MIL-A-S498 or MIL-A-8897, as applicable,

150% of reservoir op-erating press”:..

200% of reservoir op-erating p.ess. r..

. ,

9


I

MIL-H-5440G

TABLE 1. system Pressures (cot ,dl

PercentCharacteristics Nominal System Pressure system Remarks

class 1500 Class 3000 P,.,, ”,.

Proof pressure [minimum) (cent ,d)

d. Componentsundersystem pressureonly snd pressurecircuits (i.clud -ing lines, fitting+and hoses)

e . Components underreturn pressureonly and returncircuits (includ-ing lines, fitting,and hoses)

a.

b,

c.

d.

e.

Lines,fittings andhoses

Components containingairand fluid ..de,

w-,...Pump s.ct ion and

case drain 1in.components andreservoir

(1) Non-pressurizedreservoir

(2] Bootstrap re-servoir

(3) Gas pressurizedresew. i.

Componentsundersystem pressure0“17

camp.” ent s ill returncircuits (incl.d-ing lines, fittingsand hoses)

Collapse press.re of partssubject t. suction

2,250

1,125

4,S00

2,250

B.=st pressure (minimum)

6,000

6,000

100

...

3,750

2,250

;0external

12,000

12,000

100

. . .

7.s00

4,500

50 external

150

75

400

400

. . .

250

150

. . .

Except hose, whichshall b. 125$ ofnominal system pres-sure

Burst pressure valve,for hoses t. be inaccordance with theapplicable detail,necif icati on.MiL-A- 5498 or MIL-A-8897 as applicable

300* of reservoiroperatinz pressure.

400% of reservoiroperating pressure.

Except hose > whichshal 1 be 250% ofnominal system pres-sure.

. . .

10


*

*

MIL-H-5440G

3.6.4.4 Pressure regulation. Systems employing power-operated pumps shal1utilize a pressure-regulating device and an independent means of limiting ex-cessive pressure. When the pump-driving mechanism is in contil.:us operation,such as engine or transmission drives, a variable-displacement pump shall beused. When the pump is driven by an electric motor, a pressure switch may beused to deactivate the electric motor as the primary method of pressure regula-tion. In any case, an independent safety relief valve shall be provided.

3.6.S Reservoir pressurization. Type 1 systems requiring pump inlet pressuri-zation may utilize reservoirs of the nonseparated pressurized type (gas andhydraulic fluid in contact) or the separated (airless) type. Type 11 systemsshall be designed so that air does not contact the fluid during the normalfunction of the system(s) The reservoir pressure shall be adequate to preventcavitation at the inlet to the pump under all operating conditions.

3.6.5.1 Reservoir bootstrap pressurization. Reservoir pressurization shall bemaintained in the event normal system pressure (reservoir bootstrap pressure)

I 1s lost.

3.6.6 Fluid velocity limitations. Tubing size and maximum fluid velocity foreach system shall be determined considering, but not limited to, the following:

a. Allowable pressure drop at minimum required operating temperatures

b. Pressure surges caused by high fluid velocity and fast response valves

c. Back pressure in return lines, as it may affect brakes and pump-case drainlines

d. Pump inlet pressure, as affected by long suction lines, and a high responserate variable-volume pump. Consideration should be given to both pressuresurges and cavitation.

3.6.6.1 Fluid flow effects. The systems shall be so designed that malfunction-ing of any unit or subsystem will not occur because of reduced flow, such ascreated by single-pump operation of a multi-pump system, or reduced engine speed.The systems shall also be so designed that increased flow will not adverselyaffect the proper functioning of any unit or subsystems, such as increased flowrate caused by accumulator operation or units affected by airload operation.

3.6.6.2 Acceleration effects. System and component operation shall not beadversely affected by the maximum (positive and negative) g loadings obtainablewith the aircraft. Consideration shall be given to determine the effect of gon the actuated service, the fluid columns, other large fluid masses, the massof the operating controls, and any other unit or subsystems that could beaffected by the g capabilities of the aircraft.

3.6.? Subsystem isolation. Two or more subsystems pressurized by a commonpressure source, one of which is essential to flight operation and the othernot essential, shall be so isolated that the system essential to flight opera-tion wil1 not be affected by any damage to the nonessential system.

11


MIL-H-5440G

3.6.8 Ground test provisions. Each hydraulic system shall include a set of

self-sealing couplings for attachment of ground test equipment. System ground

test provisions shall be so designed that pressurization of any hydraulic systemin the aircraft is not necessary in order to test another hydraulic system. Inparticular, use of only one hydraulic test stand shall be necessary to test thesystem, without use of Y connections between the test stand and the aircraft oruse of a second ground test stand connected to another hydraulic system in theaircraft. (For filtration requirements, see 3.11.9.) A central ground servicingstation shall be provided for each system that includes connections for attach-ment of ground test equipment for system checkout and flushing, reservoir bleed-ing, reservoir fill, and accumulator air-nitrogen charging.

* 3.6.8.1 Ground test connections. A set of self-sealing couplings consistingof bulkhead halves and protective caps shall be provided at a convenient loca-tion in the aircraft, easily accessible from the ground, for attachment ofground test equipment. The ground connections shall be compatible with thoseconnections supplied on ground test units in use by the procuring activity.Connections on ground test units are as follows:

Pressure connections on ground test units

Aeroquip T150S1-8D coupling halfAeroquip E1S5-25-8D nutAeroquip 155S9-8D dust plugAeroquip T150S1-120 coupling halfAeroquip E155-25-120 nutAeroquip 155S9-12D dust plugAeroquip E155-25-160 nut (Air Force only)Aeroquip T150S1-16D coupling half (Air Force only)Aeroquip 155S9-16D dust plug (Air Force only)

Suction connections on ground test units

Aeroquip T150S1- 160 coupling halfAeroquip E155-25-16D nutAeroquip 155S9-160 dust plugAeroquip B140S1-20D coupling halfAeroquip El45-25-2oD nutAeroquip 145S9-200 dust plugAeroquip B140S1-24D coupling half (Air Force only)Aeroquip E145-25-24D nut (Air Force only)Aeroquip 145S9-24D dust plug (Air Force only)Aeroquip T150S1-120 coupling half

Aeroquip E155-25-12D nut

Aeroquip 155S9- 12D dust plug

12


MIL-H-5440G

Electric-motor-driven pumps used in emergency or auxiliary systems shall not be

used for ground test purposes unless the motor is designed for continuousopet-ation.

3.6.8.1.1 Reservoir supercharging connection. When reservoirs are normallypressurized by either compressed air or nitrogen, a ground supercharging con-nection shall be provided and shall consist of a fitting end in accordancewith MS33656-4 or MS33657-4 for attachment to a ground supercharging unit. Aprotective cap in accordance with AN929 with a safety chain shall be providedto protect the end connection when not in use.

3.6.8.1.2 Reservoir filling connection. Reservoirs shall be filled by low-pre<sure replenishment methods. The reservoir filling connection for Navyaircraft shall be a suitable check valve with an MS33656-6 or MS33657-6fitting end for attachment to ground filling equipment. A protective capin accordance with AN929, with a safety chain, shall be prOvided to PrOtectthe end connection when not in use. Unless otherwise specified by the pro-curing activity, direct pouring of fluid into the reservoir (includingin-flight fluid replenishment provisions) shall not be provided.

3.6.8.2 Ground test data. The following data shall be attached in a permanentmanner on the aircraft near the ground test connections:

Set ground test reservoir pressurizing valve to psi. ~/Set ground test stand relief valve to psi. ~1Set ground test stand volume output to gpm. ~/Set ground test stand pressure compensator to psi. AlUse hydraulic fluid conforming to ~/Ground test stand output filter shall be microns absc~ute. ~/(Any other precautions or information considered necessary. )

1/ The contractor shall fill in these values.—

Caution note: The aircraft manufacturer shall provide a caution note stipu-lating the maximum safe flow for landing-gear retraction checks during the timethe aircraft is on jacks.

3.6.9 Removal of entrapped air. Suitable means, such as bleeder valves, shall

be provided for removal of entrapped air where it interferes with the properfunctioning of the hydraulic system. Disconnection of lines or loosening oftubing nuts does not constitute suitable means. Equipment and system configu-ration shall, insofar as practicable, be designed to automatically scavenge freeaiT to a reservoir or other ‘collectionpoints where operation wil1 not be affec-ted and where release can be conveniently accomplished. (See 3.11.4.)

3.6.9.1 System air tolerance. The system shall be designed and configured such

that the presence of entrapped air shall not cause sustained loss of system pres-sure or degradation of system performance during all conditions of intendedIircraft operation.

13


MIL-H-5440G

3.6.10 Power Pumps. The hydraulic system pump(s) shall be compatible withthe installed aircraft system and shall not cause abnormal or undesirableeffects on the installed system in the aircraft. In each system, the primarypump applications which normally require continuous operation shall be providedwith at least two qualified pump designs from separate manufacturing scmrces.All pumps qualified for a given application shall be physically and function-ally interchangeable and shall be compatible with the system and with each otherto allow mixed use in multiple pump systems.

3.6.10.1 Emergency power pumps. Hydraulic pumps fequired to provide emergencypower for direct application to flight controls or other e>sential hydraulicflight requirements shall not be used for any other function.

3.6.10.2 Multiple pumps, engine-driven. Multiple engine aircraft hydraulicsystems using engine-driven pumps shall have pumps driven by at least twoengines. A sufficient number of engine-driven pumps, augmented where necessaryby pumps driven from other sources of power (e.g., electric motors, auxiliarypower units, ram-air turbine, or pneumatic drives), shall be provided to assureoperation of control surface boost or power systems with any minimum combina-tion of engines which will maintain flight and to assure operation of powerbrake systems and any other services needed during taxiing with any minimumcombination of engines wbicb may be used for taxiing.

3.6.10.3 Pump pulsation. For all power-generating components (engine pumps,power packages, transfer units, etc), pump pulsations shall be controlled to aietielwhich does not adversely affect ~he-aircraft system tubing, components,and supports installation. The contractor shall determine by test the effectof pump pulsations (pump ripple) on the hydraulic system. Initial tests shallbe conducted on the functional mockup and simulator, with suitable recordingequipment; and shall cover the complete speed range from zero revolution perminute (rPm) to the maximum speed, pressures, and flows that the pump will besubjected to when installed in the aircraft. Adverse effects including inducedresonant vibrations shall be eliminated. Results of tbe functional mockup/simulator.tests for pump ripple effects shall be documented, forwarded to theprocuring activity, and shall be verified on the first aircraft, and any addi-tional corrections required shall be made prior to the first flight.

* 3.6.10.4 Pump rotation reversal. For ~q”ipment not designed to withstand

reverse rotation, the system and components shall be designed so that no singlefailure will permit reverse rotation.

3.6.11 Pump supply shutoff valves. Pump supply (suction) shutoff valvesshall be provided if the fire protection requirements of the particular modelaircraft specify the need for such equipment in other systems, such as fuel orlubricating oil systems, or both. These valves, when required, shall not belocated on the engine side of firewalls or flametight diaphragms but shall be

14


MIL-H-5440G

located as close as practicable to these members. However, the valves shallbe so removed from the engine that the loss of the engine from the attachingstructure will not impair the operation of the valve. These valves shall beoperable from tbe cockpit, to both the closed and open positions.

3.6.12 Special tools. Hydraulic syst,emsshall be so designed that specialtools will not be required for installation or removal of components unlessit can be shown that use of special tools is unavoidable.

3.6.13 System pressure indication. Pressure-indicating equipment acceptable

to the procuring activity shall be provided to indicate the system pressure inhydraulic systems or subsystems. on engine-driven multi-pump systems, pressure-indicating equipment shall be provided for each pump to enable the flight crewto check for proper operation of each pump without shutdown of any engine. Thepressure indicators shall be so located as to be readily visible by the flightcrew.

3.6.13.1 System low-pressure warning light. In addition, but not as asubstitute for the requirement of 3.6.13, a suitable warning light shall beinstalled in the cockpit in a conspicuous location to warn the pilot of lowhydraulic system pressure. The light shall be actuated by a pressure switchin the system. For Navy aircraft, there shal1 be a separate warning light foreach hydraulic system. The warning light, or lights, shall not be actuated byany combination of flight-control operations under normal operations. A momen-tary flicker of the warning Iigbt during ground checkout only is permissible,provided such condition is adequately described in the appropriate aircraftoperation and maintenan~e manuals and provided such condition does not occurduring flight unless a system malfunction exists.

3.6.13.2 Maintenance check gages and indicators. Pressure gages/indicators

that require a preflight, postflight, or daily check shal1 not require work-stands or platforms in order to read the gages or indicators.

3.6.14 Fluid sampling valves (Navy) A fluid sampling valve; conforming toMIL-V-81940, shall be provided i? tbe system return line that is common to allactuating circuits and shall be located upstream of tbe main return line filter.The sampling valve (s) shall be located in a readily accessible area and shallallow convenient use of sampling containers. Fluld sampling valves shall also

be provided in other portions of the system if considered necessary by the pro-curing activity. The sampling valve shall allow representative fluid samplesto be taken while the system is fully pressurized. Centamination generated bytbe operation of the valve shall not be sufficient to adversely affect the fluidsample. ?he valve nozzle shall be designed so that penetration of a thin plasticmembrane cover on the sampling container neck, when so provided, can be readi1yaccomplished. The valve.nozzle shall include a protective cap, and the cap shallalso prevent external leakage in the event of valve malfunction. The cap shall

be provided with a security chain, or equivalent, to prevent loss of the cap.

15


I

MIL-H-5440G

3.7 Utility system design. All hydraulically operated services (excludingflight controls covered by 3.2) that are essential to the accomplishment of thebasic aircraft mission (bomb-bay doors, in-flight refueling, etc) or essentialto land and stop the aircraft (landing gear, brakes (excluding types I and IVbrakes, etc)) shall have provisions for emergency actuation. No single failureof the utility system shall result in loss of the aircraft.

3.7.1 Definition. The utility system ‘shall include all systems used for thenormal operation of any service on the aircraft, excluding the systems used forthe operation of the aircraft primary control surfaces.

3.7.2 Application. The general requirements of 3.6 and subparagraphs thereto

aPPIY tO the utility system.

3.7.3 Wheel brake systems. Wheel brake systems shall be in accordance withMIL-B-8584.

3.8 Flight-control system design. F1ight-control systems which requirehydraulic power for operation shall conform to MIL-F-949o for Air Force orMIL-F-18372 for Navy, as applicable. In dual flight-control systems, botbsystems shall be so designed that a ground test stand may be connected to eitherone of the flight-control systems and that system may be operated without adverseeffect on the dead system, such as overflow of the system or failure of any partthereof. In order to accomplish this objection, automatic bypass of the fluidin the dead system from one side of the actuator to the other side shall beprovided.

3.8.1 Definitions. Primary flight controls include those control systems usedto actuate such surfaces as ailerons, rudders, elevators, stabilizers, or com-bined function surfaces.

3.8.1.1 Power-boosted flight-control system. A power-boosted flight-controlsystem is a reversible control system wberei” the pilot effort, which is exertedthrough a set of mechanical linkages, is at some point in these linkages boostedby a.hydraulic power source.

3.8.1.2 Power-operated flight-control system. A power-operated flight-controlsystem is an irreversible control system wherein the pilot either electricallyor mechanical y, actuates a power control servomechanism. ‘Ibismechanism actuatesthe primary ‘control surface or corresponding device.

3.8.1.3 Combined flight-control[utility system. A combined flight-control/utility system (combined system) is a system that supplies a portion of thepower required to operate the flight-control system and also supplies power tothe utility system.

16


1.

MIL-H-5440G

* 3.8.2 System isolation. Whenever hydraulic power is required for primaryflight controls, a completely separate, integral, and adequate hydraulic systemshal1 be provided to supply only the primary flight controls. This hydraulicsystem shall not be used to supply any other system or component in the aircraft,unless approval is obtained from the procuring activity. This hydraulic systemshall be as simple as practicable and shall contain a minimum number of com-ponents. Dual actuator systems may employ the combined flight-control/utilitysystem for one-half of the power, in which case the flight-control system shallbe given pressure priority. In addition, the combined flight-control/utilitysystem shall be so designed that the portions of,the system required for opera-tion only during the takeoff and landing phases of flight [e.g., landing gearor wing flaps) may be isolated from the rest of the system by means of a suitableshutoff valve in the pressure line, controllable from the cockpit, and checkvalves in the return lines so located that a rupture in any portion of theutility system will not cause loss of fluid from the reservoir when the systemisolation valve is closed. Wlen isolation valves are used in a combined flight-control/utility system to isolate nonessential flight functions, the systemshall be designed to preclude inadvertent isolation, during taxi or groundoperation, that would result in loss of wheel braking, nose-gear steering, orother critical functions.

3.8.3 Hydraulic power failure. In aircraft where direct mechanical controlsufficient to obtain aircraft controllability to pass the emergency require-ments of MIL-F-8785 cannot be accomplished following hydraulic power failure,an emergency power source shall be provided, supplying controllabilityrequirements.

3.8.3.1 Emergency system application. The means of engaging the emergencypower system shall be either manual or automatic; however, they shall be of thesimplest and most reliable nature possible consistent with the requirements ofthe aircraft. Manual engagement is preferred, when suitable. Automatic en-gagement of the emergency power system shall not be used unless specifically

approved by the procuring activity. If the aircraft has a single engine, theemergency power source shall be independent of the operation of this engine.Dn multiple-engine aircraft, the emergency source of power shall be on adifferent engine than the primary source of power. In some cases, it is per-missible to utilize the utility hydraulic system as the emergency source ofpower, if it is accomplished in such a way that there is no interconnection withthe flight-control power system and no single failure can cause loss .ofbotbsystems. Consideration shall be given to the possibility of out-of-fuel landingswherein “one of the engines are operating. Inasmuch a5 some turbojet engines willnot windmi11 enough to provide adequate flight-control power supp1y duringlanding, it may be necessary to provide emergency power sources not dependentupon engine operation. In aircraft which are capable of being landed withoutengine power, this condition shall not be considered an emergency, and pro-visions shall be made for landings with one of the power systems failed while

17


MIL-H-5440G

out of fuel. When designing for this condition, extreme care must be exercisednot to reduce the reliability of the power systems. It shall always be possibleto reengage the flight controls or return them to normil following operation ofthe emergency hydraulic system, and where a ram-air turbine is used as the sourceOf emergency power, it shall be capable of extension, Operation, and retractionunder any flight conditions.

3.8.3.2 Disengagement and bypassing. Where direct mechanical control isutilized following primary hydraulic system failure, or as made ,necessary byother system design conditions, provisions shall be made for automatic, directbypassing of the fluid from one side of the primary flight-control actuator tothe other. Where the actuator can be disengaged from the system, bypassingwill not be required. For dual actuator systems, where necessary, both systemsshall provide automatic bypass.

* 3.8.4 System separation. Where duplicate hydraulic systems are provided,these systems shall be separated as far as possible to obtain the maximumadvantage of the dual system with regard to vulnerability from gunfire orengine fires. Where practicable, dual systems should be on opposite sides ofthe fuselage, the wing spar, or similarly separated. In any case the systemsnecessary for safety of flight shall be separated a minimum of 18 inches, pre-ferably in a plane perpendicular to ground fire. Where it is deemed necessary,in a particular aircraft model, for these systems to come together, as in a

dual tandem surface actuator, that actuator shall be protected from the threatto a degree specified by the procuring activity. Adequate consideration shouldbe,given to the clearance between moving flight-control-system components andstructure or other components to insure that no possible combination of tempera-ture effects, airloads, or structural deflections can cause binding, rubbing,or jamming or any portion of the primary flight-control system.

3.8.5 System pressure. Systems which use a pressure lower than the ful1system pressure shall be designed to withstand and operate under the full pres-sure or shall have an adequate relief valve installed downstream of the pressurereducing valve if tbe full pressure would be detrimental or dangerous. Thisrelief valve may be incorporateed into the same housing as the pressure reducer,provided that the relief valve mechanism is independcmt of the mechanism ofthe pressure reducer.

* 3.8.6 Power sources. Aircraft primary flight-control hydraulic systems shallhave engine-driven.pumps as their source of power, unless sufficient justifica-tion exists for using other power sources and is specifically approved by theprocuring activity. Helicopter primary flight-control systems shall havetransmission-driven pumps as a source of power so that power will be availableduring the auto rotation.

18

./.


MIL-H-5440G

* 3.8.7 System temperature. The hydraulic flight control actuators shall providethe required actuation rates under minimum and maximum in-f1izht fluid and ambi&t-. -.temperatures. ‘Thetlight critical components shall not hind or jam under anycombination of in-flight fluid and ambient conditions including single failures,such as relief valves, worn pump, failed valves and other heat generating failures.The effects of differential fluid temperature in tandem units shall also bedemonstrated.

3.9 Emergency system aesign for utility system

3.9.1 - Where emergency devices are required in hydraulic systems, theemergency systems shall be completely independent of the main system up to, butnot necessarily including, tbe shuttle valve, the actuating cylinder, or motor.The system shall be so designed that failure of an actuator in one subsystemshall not prevent the operation of or cause the failure of both normal andemergency actuation of another subsystem. These emergency systems shal1 uti-lize hydraulic fluid, compressed gas, gas-generating devices, direct mechanicalconnection, or gravity. Mechanical connections may include electromechanicalunits. Use of other types of emergency systems shall require specific approvalof the.procuring activity.

3.9.1.1 High-lift devices. Wlere safe operational landings cannot be accom-plished without the use of hydraulically operated high-lift devices, they shallbe powered by dual actuator hydraulic systems or be provided with a suitableemergency system.

3.9.2 Emergency-line venting. ‘theemergency line from the shuttle valves shallbe vented to the reservoir or to a low-pressure (15 psi gage maximum, abovereservoir pressurization) nonsurging return line when the emergency system is notin use, except as authorized by the procuring activity. When shuttle valveleakage is not critical, the line may be vented to the atmosphere. After use ofa compressed-gas emergency system, the system shall be bled directly to theatmosphere rather than to the reservoir.

3.10 Component design. All component% used in the system shall conform toMIL-H-8775 and applicable detail specifications.

3.10.1 Standard components. Standard components shall be used in preferenceto nonstandard components wherever they wi11 perform the function required bythe system operating needs. Where no applicable AN or MS standard componentexists, a minimum size envelope compatible with the performance, installation,inspection, and maintenance requirements shall be used.

19


I

*.,

*

*

MIL-H-5440G

3.10.2 Orifices. Orifices larger than 0.012 inch but smaller than 0.070 inch@ diameter shall be protected by adjacent strainer elements having screenopenings O.008 to O.012 inch in diameter. Orifices smaller than the aboverange shall be protected by adjscent elemen<s having openings smaller than theorifices and shall be subject to approval of the procuring activity. Orificesand strainer elements shall be strong enough to absorb system design flow andpressure “itho”t rupture or pe~anent defo~ation.

3.10.3 Actuators essential to safe ope=ation of the aircraft. where t“. ~=more independent hydraulic ‘systemsare utilized to power services essential forsafe flight (e.g., primary flight controls), the actuation and control devicesshall be designed and constructed (either parallel or series configuration) sothat no single structural or hydraulic failure will cause loss of more than onehydraulic system or allow transfer of fluid from one s~stem to another. Alwninu”shall not be used as a barrel material for actuators essential to safe operation(flight control and landing gear) in Navy aircraft.

3.11 Component installation. If a fluid such as MIL-H-6083, which is differentfrom the specified fIuid, is used for component testing and shipping, it shal1be drained prior to the installation of the coiponent in tbe aircraft.

3.11.1 Design practice and installation. The hydraulic system component

installation requirements specified in the following subparagraphs are con-sidered to be representative of good design practice; however, it is recognizedthat variations from these practices will, in many cases, be necessary due to

specific installation exigencies. All installation of standard parts or com-

ponents shal1 be designed to accommodatee the worst dimensional and operationalconditions permitted in the applicable part or component specification or AN orMS standard. All components shall be installed and mounted to satisfactorilywithstand all expected acceleration loads. wrench loads, vibration effects, etc.

3.11.1.1 Reverse installation. All system components shall be designed so

I that reverse installation cannot occur. Nonstandard components may be used,

I if necessary, to conform to these requirements.

3.11.2 Accumulators. Accumulators shall be installed with the utmost con-sideration given to the protection of crewmembers in the case of rupture dueto gunfire. For type I systems, hydraulic accumulators shall be in accordancewith either MIL-A-5498 or MIL-A-8897 and the standard drawings listed therein.For type II systems, accumulators shall be in accordance with MIL-A-8897.

3.11.2.1 Measurement of accumulator gas pressure. When accumulator gas charge

is critical to the functioning of the hydraulic system or subsystem, a permanentpressure gage shall be attached to the gas side of the accumulator. In non-critical installations, the use of the pressure gage shall be at tbe discretionof the procuring activity. A gage indicating accumulator gas pressure shall

20


MIL-H-5440G

never be used to indicate equivalent hydraulic pressure to the crewmembers.AN or MS standard hydraulic gages shal1 be used and shall be attached withthe shortest practicable length of line and minimum number of fittings.

3.11.2.2 Accumulator accessibility. In all accumulator installations space

shall be provided around the gas charging valve for use of a MIL-G-8348 high--pressure,gas-testing gage assembly and for standard fitting connections tocharge accumulators.

3.11.2.3 Accumulator instructions. Instructions for servicing the accumu-lator with gas pressure with tbe accumulator oil chamber discharged shall beprovided immediately adjscent to the accumulator. Adequate information shallbe included to indicate the proper gas preload pressure throughout the tempera-ture range fcr which the accumulator will be serviced.

3.11.2.4 Gas requirements. For type I systems, accumulators may be chargedwith air or inert gas (nitrogen) For type II systems, accumulators shall becharged with inert gas only. For Army use only, all rotary-wing aircrafthydraulic system accumulators shall be charged with either air or inert gas(nitrogen).

3.11.3 Actuating cylinders. Hydraulic actuating cylinders shall be so in-stalled that they do not interfere with the adjacent structure and are readilyaccessible for maintenance and inspection. If possible, the cylinder should beinstalled in a protected area, or if exposed, be protected from flying debrisduring landing and takeoff. Actuating CY1inders other than those used forprimary f1ight control shall conform to MIL-C-5503.

* 3.11.4 Bleeder valves. Where required, bleeder valves shall conform to MIL-v-B1940and shall be so located that they can be operated without necessitating removal ofother aircraft components. Such installations shall permit attachment of a flexiblehose so that fluid bled off may be directed into a container.

3.11.5 Brake valves. Brake valves shall be installed in accordanceMIL-B-B584.

3.11.6 Check valves. Check valves shall conform to MIL-V-25675.

3.11.7 Directional control valves. The installation of directionalvalves shall be compatible with the control valve performance such that thesystem operation will not be affected by back pressure, interflow, or pressuresurges which might tend to cause the valves to open or move from their settingor cause them to bypass fluid in other than the intended manner. No hydrauliccontrol valves shall be installed in the pilot Is cockpit or compartment withoutthe approval of the procuring activity.

with

control

21


MIL-H-5440G

3.11.7.1 Directional control valve handle installation. All installations ofdirectional control valve handles shall conform to AFSC DH 2-2 for the Air Forceand the Army, and for the Navy as approved by the Cockpit Board of the Naval AirSystems Command. Wlen the effective handle length exceeds 0.8 inch, limitingstops, external to the valve, shall be provided. These stops shall be capableof withstanding 75r pound-inches limit load (where, r, equals tbe effectivehandle length) and shall be so positioned that no load will be applied to theinternal valve stops, unless the valve has been specifically designed to handlesubject loads.

3.11.7.2 ktultiplecontrol valve systems. In systems which incorporate two ormore directional control valves, provision shal1 be made -to prevent fluid frombeing transferred inadvertently, at any possible valve setting, from the cylinderports of one valve into the cylinder ports of another valve.

,.3.11.7.3 Control valve actuation. Control valve operation may be direct,such as push-pull rods or cable control, or indirect, such as electricallY

I operated controls. Push-pull rods shall require a minimum or no adjustment.Sheathed flexible controls shall not be used without specific approval of the

procuring activity. Cable control shaII be designed to provide minimum adjust-ment and positive control. All controls shall be designed to prevent overtravelor undertravel of the valve control handle by use of external or internal stops.Electrically operated valves shall be provided with mechanical override controlmechanisms wherever practicable and at the option of the procuring activity.

3.11.7.4 Control valve wiring. Electrically operated control valves shall bewired in accordance with MIL-w-5088.

3.11.8 Other valves. Other valves shall conform to MIL-V-5525, MIL-V-5527,MIL-V-5528, MIL-v-8566, MIL-V-19067, or MIL-V-27162, as applicable.

3.11.9 Filter requirements. All vent openings or fluid exposed to breathingaction through vents shall be protected by filters. Line filters, when in-stalled in the aircraft system in close proximity to an accumulator, shall beinstalled upstream of the accumulator. Where pressure-drop indicators areprovided on the filter assembly, the indicator shall be easily visible toservicing personnel. Wlen a screen or filter is provided either internally orin close proximity to a component, suitable provisions shill be made for removalof the screen or filter for cleaning or replacement. Sintered-t~e elementsshall not be used.

22


*

*

*

MIL-H-5440G

3.11.9.1 Navy aircraft fiIters. All filters installed.in the hydraulic system(s)shall be in general accordance with the requirements of MIL-F-8815/4, MIL-F-8815/5and MIL-F-8815/6 as applicable. These filters shall be used to filter all of thecirculating fluid in the system. Filtration design shall be capable of maintain-ing the particulate contamination level of the normally operating system at alevel not to exceed Class 8 of NAS 1638 or Navy Standard Class V as determinedin accordance with Method 3009 of FED-STD-791 or by use of automatic particlecouiitingequipment approved by the procuring activity. Fluid samples for con-tamination tests shall be obtained from sample valve specified in 3.6.14 and anacceptable level assured at aircraft delivery.

3.11.9.2 Air Force and Army aircraft filters. Filters in accordance withMIL-F-8815/1, MIL-F-8815/2 and MIL-F-8815/3 shall be provided in all hydraulicsystems. Filters incorporating elements having absolute ratings lower (finer)than 15 microns may be used, subject to approval of the procuring activity.These filters shall be used to filter all circulating fluid in the system. Theacceptable contamination level for aircraft delivery shall be specified by theprocuring activity.

3.11.9.3 Filter locations. Filters shall be provided in the following loca-tions as a minimum requirement. Other filter locations shall be provided atthe option of the procuring activity.

3.11.9.3.1 Pressure line installation. A no-bypass-type line filter(s) shallbe installed in the system pressure line and shall be so located that all fluidfrom the aircraft pump (s) and the ground test equipment pressure connection willbe filtered prior to entering any major equipment or components of the system.In multi-pump systems, each pump shall have a separate filter installation.

3.11.9.3.2 Return line installation. A bypass-type line filter shall beinstalled in the return line. All fluid entering the return circuit shall becirculated through the filter prior to entering the return line to the pump (s)and reservoir.

3.11.9.3.3 Reservoir fill line installation. A no-bypass-type line filtershall be installed to filter all fluid entering the system through the reservoirfi11 connection.

3.11.9.3.4 Pump-case drain line installation. Each pump-case drain (bypass)line shall have a bypass-type filter installed.

3.11.9.3.5 Pump suction line. Filters shall not be installed between thesystem reservoir and the pump suction port unless specifically authorized bythe procuring activity.

3.11.9.4 Hydraulic sequencing. Where hydraulic sequencing is critical, andwhere contamination can prevent proper sequencing, each sequence valve shallbe protected from contamination in each direction of flow by a suitable screen-type filter element. This element may be included as a part of the sequencevalve assembly.

23


MIL-H-5440G

* 3.11.10 Fittings. Al1 tube fittings (other than connections at production breakpoints, to removable components, and where needed to faci1itate maintenance)shall be permanently joined employing no screw threads or similar mechanicalmeans and shall require approval by the procuring activity prior to installationin the applicable aircraft. In addition, suitable repair and replacement methodsinvolving failed tubing and fittings shall be established for each aircraft modeland shall be included in the applicable aircraft publications Removable compo-nents shall accept fittings conforming to MIL-F-5509 or MIL-F-18280. ‘heirselection shall be subject to the approval of the procuring activity. Theyshall be connected and assembled in accordance with MS21344 or MS33566. The useof fittings in remwable components other than those conforming to MIL-F-S509or MIL-F-18280 shall require approval of the procuring activity, No threadlubricant other than hydraulic fluid specified in 3.3 shall be used on hydraulicfittings unless specifically authorized by the procuri?g activity.

* 3.11.10.1 Universal fittings. Universal fittings conforming with MS33515 and ~MS33657 shall not be used in boss applications in hydraulic systems unless writ-ten approval is obtained from the procuring activity.

3.11.11 Flow dividers. Flow dividers shall not be used if the effect of amalfunction of tbe flow divider would result in an unsafe flight condition.

3.11.12 Flow regulators. Flow regulators may be installed in the hydraulicsystem to limit the rate of fluid flow. The direction and rate of fluid flowshall be clearly indicated on the flow regulator and the adjacent structure.Regulators used under continuous dynamic conditions shall not adversely affectthe operation of the hydraulic system.

3.11.13 Protective devices. Hydraulic fuses, circuit breakers, reservoirlevel sensors, or other similar devices may be used to meet survivability re-quirements established by the procuring activity. The specific application ofsuch devices shall be subject to the approval of the procuring activity. Pre-mature or inadvertent shutoff or any other malfunction of such devices shall notoccur during any flow or pressure variations or any conditions of system opera.tion. The function and reliability of such devices shall be demonstrated in thefunctional mockup and simulator. Fuses used i“ type 1 systems shall conform toMIL-F-5508.

3.11.14 Snubbers. Pressm’e smbbers shall be used with all hydraulic pressuretransmitters, hydraulic pressure switches, and hydraulic pressure gages. Pneu-matic pressure gages are excluded from this requirement.

3.11.15 Manually operated pumps. Where a manuaI1y operated pump is required,either a hand-actuated or foot-actuated pump shall be selected, based on trade-off studies. In installations where the pump can be operated by personnel in astanding position, strong consideration shal1 be given to a foot pump to minimizephysical exertion.

24


MIL-H-5440G

3.11.15.1 Manually OpeTatedPump suction line. No screen or filter shall beused in the suction line of the pump. The sucticm line shall be of suitable

I diameter and length to insure pr~mi~g a dry pump and obtaining full-rated flowat -54°C (-65”F) temperature with 12 complete cycles at a rate of 20 cycles

Iper minute. The pump circuit shall be capable of full priming and rated flowin flight at the highest altitude at which DUmD o~eration is essential and. . .intended.

3.11.15.2 Manually operated pump check valve. A standard check valve shall beprovided in the pump pressure line.

3.11.15.3 Hand pump handle length. The effective operating handle length ofhand pumps shall be such that the handle load shall not exceed 67 pounds. ?helength of this handle travel at the handgrip shall not exceed 18 inches.

* 3.11.16 Flexible connections. Whenever relative motion exists between twopoints, metal coiled tubing in accordance with ARP 584 is preferred.

* 3.11.16.1 Hose assemblies. Hose assemblies shall not be subjected to torsionaldeflection (twisting) when installed, or during system actuation. No hose clamp

*

*

type installation shall be used in hydraulic systems. Medium pressure tetra-fluoroethylene hose assemblies shall conform to MIL-H-25579. These hose assem-blies (using permanently attached fittings) may be used, with adequate spaceprovided to permit replacement with spares made of MIL-H-27267 hose and

MIL-F-27272 fittings. High pressure tetrafluoroethylene hose assemblies shal1conform to MIL-H-38360. Adequate space shall also be provided to permit re-placement with spares made of NIL-H-83298 hose and MI L-F-83296 fittings. Hose

selections shall be made from MS3362O.

3.11.16.2 Hose support. The support of a flexible line shall be such that itwill never tend to cause deflection of the rigid lines under a“y possible rela-tive motion that may occur. Flexible hose between two rigid connections mayhave excessive motion restrained where necessary but shall never be rigidlysupported .as by a tight rigid clamp around the outside diameter of the flexiblehose. Extreme care should be used in the selection and placement of the supportsto assure the flexible line is not restricted and does not rub on structure OTadjace”t members during any portion of its excw-sion.

3.11.16.3 Hose bend radii. The minimum radius of bend of hose assembliesshall be a function of hose size and flexing range to which the hose installa-tion will be subjected. The minimum bend radii for hoses shall be as listedin the applicable hose specification.

25


MIL-H-5440G

3.11.16.4 Hose protection. Hose shall be suitably protected against chafingwhere necessary to preclude damage to the hose and to the adjoining structure,tubing, wiring, and other equipment Hose assemblies (including end fittings)of amphibicms aircraft which are s“bject to salt water immersion shall becovered with three coats of type II rubber conforming to 1.U41.-A-1617.If type11 is “ot available, type 111 may be wed.

3.11.16.5 Provisions for hose elongation and contraction. Hose assembliesshall be so selected and installed that elongation and contraction under pres-sure, within the hose specification limits, will not be detrime”’talto theinstallation either by causing strains on the end fittings or excessive bindingor chafing of the hose.

3.11.17 Lock valves. Use of lock valves to hydraulically lock actuatingcylinders shall require approval of the procuring activity. Where lock valvesare used, provisions shall be made for fluid expansion and contraction through-out the temperature range. Where several actuating cylinders are mechanicallytied together, only one lock valve shall be used to hydraulically lock allactuators so tied together.

3.11.18 Motors. All constant-displacement motors shall be in accordance withMIL-M-7997. All motors shall be accessible for maintenance and inspection andshall be located in an appropriately cool or warm space depending upon theirservice. Proper case overflow connections to the reservoir shall be provided.Shaft seal drains shall be vented overboard.

3.11.19 Power pumps, variable-delivery a“d fixed-displacement, Variable- -,

delivery pumps shall be in accordance with MIL-P-19692. For variable-delivery f*

pumps, the pressure differential between the pump-case cooling port and thereservoir shall be such as to permit the pump to maintain ‘adequate cooling flow

/. “

in any pump flow condition. Fixed-displacement pumps shall be in accordance .~~.

with MIL-P-7858. -.

3.11.19.1 Electric-motor-driven pumps. Electric-motor-driven hydraulic pumpsin accordance with MIL-P-5954 or MIL-P-5994 may be used, as necessary, foreither normal, emergency, or auxiliary operation of hydraulic systems.

3.11.20 Pressure regulators (unloading valves) Pressure regulators, orunloading valves in accordance With MIL-V-5519 (type 1 systems only), arenormally used in conjunction with an e“gi”e-drive”, fixed-displacement-t~epump and an accumulator. Since this type of power circuit is considered in-ferior to the variable-displacement-type pump, specific written approval of tbeprocuring activity nmst be obtained prior to “se thereof. Wen an unloadingvalve is used, the return line to the reservoir shall be as short as possibleand shall not be s“bjected to back pressure or pressure surges in excess ofallowable values stated herein without specific approval of the procuring

26


MIL-H-5440G

,—

activity. The unloading valve shall have the drain port piped directly to thereservoir or routed to some return line in which the maximum pressure does mtexceed the reservoir pressurization and is not subjected to pressure surges.The tubing connecting the unloading valve,shall be so designed and installedthat the pressure surges in the system will not affect the operation of theunloading valve at any flow rate of the system. In addition, provisions shallbe made in the system to eliminate any harmful shocks caused by pressure surgesdue to the operation of the unloading valve.

3.11.21 Relief valves, system and thermal expansion. Relief valves shallconform to MIL-V-8813. With specific approval of the procuring activity,celief valves may be incorporated as part of another unit, provided they complywith applicable relief valve requirements. Relief valves are designed to beused as a safety device to prevent bursting of, or damage to, tbe system in theevent the normal pressure regulation device i“ the system malfunctions; or, in ablocked line condition, to relieve excessive pressure due to either thermal?xpansion of the fluid or overload forces on actuating units. Therefore, reliefvalves shall not be used as the sole means of limiting pressure in a po”er cir-cuit but shall function only as a safety valve.

* 3.11.21.1 System relief valves. Provisions shall be made to insure that pres-sure in any part of the power system will not exceed a safe limit above thecutout pressure of the hydraulic system. Pressure relief valves, as specifiedherein, shall be located in the hydraulic system wherever necessary to accomplishthis pressure relief (see table I). The system relief valve shall have a capacityegu?l to or greater than tbe combined rate of flow of pumps where fixed-displacement

PUMPS with common cutout regulators are used, or equal to or greater than tberated flow of the largest pump when variable-volume pumps with a common pressurelink are used. The systems shall be designed so that excessive temperature (over71°C (160°F) for type I; over 135°C (27.5”F)for type II) does not occur due to‘fluid flowing through a relief valve. AS an alternative, a temperature warningand indication system may be used if approved by the procuring activity.

3.11.21.2 Thermal expansion relief valves. Relief valves shall .be installedas necessary to prevent excessive pressure rise and system damage resultingfrom thermal expansion of hydraulic fluid. Internal valve leakage shall not beconsidered an acceptable method of providing thermal relief. (For relief valvesetting, see table I..)

3.11.22 Reservoirs. Hydraulic reservoirs shall be in accordance with MIL-R-5520 or MIL-R-8931, as applicable. When a hydraulic emergency system is usedin any military aircraft except trainer types, a separate emergency reservoirshall be provided. The emergency reservoir shall be located as remote aspracticable from the main reservoir to minimize gunfire damage. It shall bepossible to fill the main and emergency reservoirs through a common filler port,

27

;—_


MIL-H-5440G

unless the two reservoirs are so far distant as to make this requirement imprac-ticable. The feed and vent lines in the two reservoirs shall be so located thatrupture of either of the reservoirs or the feedlines will not cause loss Of suf-ficient fluid from the other reservoir to impair the system operation. Reservoirsshall be suitably protected (i.e., return line relief valve) to prevent failureor damage when rapid discharge of the main or emergency system into the reservoirsis encountered. Installations of pressurized reservoirs shall include a suitabledepressurization valve for maintenance purposes.

3.11.22.1 Reservoir location. It is desired that the reservoir should be solocated that the following conditions will be obtained.

a. A static head of fluid will be supplied to the hand pump and the power-driven pump or pumps in all normal flight attitudes of ,theaircraft

b. The length of suction line to the pump is a minimum

c. The best available temperature and pressure is utilized, but must not beinstalled in engine compartments

d. Protection from combat damage

e. If practicable, suction lines shall be so routed as to prevent breakingof the fluid column caused by gravity after engine shutdowm and during theparking period. Where such routing is not possible, or “here the reservoircannot be located above the pump, suitable provisions.shall be installed tomaintain the fluid column to the pump after-engine shutdown. A swing typecheck valve in the suction port of the reservoir should normally maintainthe fluid column to the pwnp.

f. If routing of the pump bypass cannot be accomplished so that breaking ofthe fluid column by gravity after engine shutdown is prevented, check valvesshall be incorporated in the lines.

3.11.22.2 Reservoir venting. If a vent is provided in the reservoir, itshall be so at-rangedthat loss of fluid will not occur through the vent duringflight maneuvers or ground operations of the aircraft. A filter in accordancewith AN6240 shall be incorporated into the vent line if the temperature require-ment is suitable. If a filler cap is used, the act of removing the filler cap

shall automatically vent the reservoir in such manner that the energy containedin the pressurizing air is not dissipated by imparting kinetic energy to eitherthe filler cap or the fluid contained in the reservoir or elsewhere in thesystem.

I 3.11.22.3 Gas-pressurized reservoirs. The air (or inert gas) pressure shallbe controlled by an externally nonadjustable pressure-regulating device to con-trol the gas pressure in the reservoir. A relief valve shall also be connectedto the airspace to protect the reservoir and pump from excessive pressure. If

28


MIL-H-5440G

the air pressure regulator and relief valve are combined into one housing, a

single failure in that unit shall not permit overpressurization of the reservoir.Devices, such as aspirators, that introduce air into the hydraulic fluid shallnot be used. When the air is separated from the fluid by a piston or otherdevice, operation of the ,system shall not introduce air into the hydraulicfluid. Provision shal1 be made to remove entrained air which may have enteredthe system during servicing or operation.

3.11.22.4 Reservoir air pressurization moisture removal equipment. Whenengine bleed air is used for reservoir pressurization, a suitable moistureremoval unit shall be so located as to protect the pressure regulation linesand equipment. An adequate filter shall be provided.

3.11.22.5 Reservoir fluid level indication. Reservoir fluid level indicationshall be provided in the cockpit. Indicator fluid level markings shall corre-spond with the direct-reading fluid level indicator markings provided on thereservoir and shall be lighted in accordance with applicable cockpit lightingrequirements. A suitable warning light shall also be provided to advise thepilot of a low fluid level condition. The cockpit fluid level indicator shallnot eliminate the requirement for the direct-reading fluid level indicator onthe reservoir itself, as this is required for reservoir servicing with powerOFF.

3.11.23 Restrictor valves. Adjustable orifice restrictor valves may be usedin experimental aircraft, but only fixed orifice restrictor valves shall be usedin service test and production aircraft. For one-way restrictors, the directionof restricted and unrestricted flow shall be indicated on the restrictor valves

\ and adjacent structure. (For orifice filtration requirements, see 3.10.2.)

3.11.24 Self-sealing cOuplingS. Hydraulic systems shall be provided withself-sealing couplings for each engine-driven pump and so located that thepowerplant section can be readily removed for servicing. A suitable couplingshall be used in each line going to each pump. Self-sealing couplings shall

also be provided on all hydraulically operated brake installations where it isnecessary to disconnect the brake line in order to remove the wheel. ‘I%eself-

sealing coupling shall be attached to the brake, and it shall be possible toremove the wheel without damaging the CQUP1ing. Self-sealing couplings shall

also be provided at all other points in the hydraulic system which requirefrequent disassembly or, where convenient, to isolate parts of the system as injacking and servicing one landing gear only. Sufficient clearance shall be

provided around the coupling to permit connection and disconnection. Self-sealing couplings installed adjacent to each other shall be of different sizeor be otherwise designed that inadvertent cross connection of the lines cannot

occur. Couplings shall conform to MI L-C-2 S427,

29

I


MIL-H-S440G

*

*

3.11.24.1 Airframe break points. When self-sealing couplings are provided ,]at airframe break points, especially in flight-control systems, and where dis- 4connection of such a coupling or couplings will adversely affect the operationof any of the systems, adequate means shall be provided to prevent the in-advertent disconnection of the couplings. Such means shall also provide adequateindication when a coupling connection is incomplete. If the means of preventinginadvertent disconnection are not absolutely pos:tive, the system shall be sodesigned that a hydraulic lock resulting from an inadvertent coupling disconnec-tion will not be the cause of an aircraft accident.

3.11.25 Shuttle valves. Shuttle valves shall conform to MIL-v-5530 for typeI ‘andMIL-V-19068 for type II systems. Shuttle valves shall not be used ininstallations in which a force balance can be obtained ‘on both inlet portssimultaneously which may cause the shuttle valve to restrict flow from the outletport. Where sbuttle valves are necessary to connect a“ actuating cylinder “iththe nonna] and emergency systems, the shuttle valve unit shall be built into the

appropriate cylinder bead, using component parts of applicable m. or MS-

apprO~ed shuttle valves in a suitable cartridge, unless specifically approvedotherwise by the procuring activity. Ivlerethe above installation cannot bemade, a standard shuttle valve may be located at the actuator port. In theevent neither of the above installations is possible, a length of rigid line ispermissible between tbe cylinder port and the sb”ttle valve, provided that therigid line and sb”ttle valve are firmly attached to the act”ati”g cylinder.Flexible hose shall not be used between tbe actuating cylinder port and theshuttle valve.

3.11.26 Pressure switches. Pressure switches may be installed in hydraulicsystems where the regulation of hydraulic pressure is required by controlling anelectric-motor-driven pump or other applications approved by the procuring activity.Adequate precautions shall be taken to prevent chatter or cutoff. Pressure switchesshall conform to the applicable requirements of MIL-s-9395.

3.11.27 Swivel joints. Swivel jpints shall be designed in accordance withMIL-J-5513. Life test data shalllbe submitted to the procuring activity for

(approval. WheTe lines or fittings are used to drive swivel joints, they shallbe adequately supported and shall’be of sufficient strength to insure a satis-factory operating installation.

3.11.28 =

3.11.28.1 Tubing materials. Tubing shall be either corrosion-resistant steelconforming to MIL-T-6845 or MIL-T-8504 or ClaSs T6 aluminum alloy conforming toMIL-T-7081. Higher strength-to-weight ratio steel or titanium tubing may beused with the approval of the procuring activity. Tubing mounted on shockstruts shall be corrosion-resistant steel. For Navy aircraft, aluminum alloytubing shall not be w,ed in any pressure or actuating circuit lines. The mini-mum wall thickness in any alloy or tube size shall be not less than .020 inch.

30


*

3.11.28.2 Tubing bends.with MS33611.

MIL-H-5440G

Bends shall be uniform and shall be in accordance

3.11.28.3 Installation of small size tubing. If t“bi.ngin sizes smaller than

l/4-inch outside diameter (-4 size) is used in hydraulic systems, particularcare shall be taken to properly install, support, and protect it, and it mustbe shown that proper operation of the service in which such tubing is used wil1be possible at -54°C (-65”F) temperature.

3.11.28.4 Designed motion in tubing. Looped or straight aluminum-alloy tubingshall not be used between two connections where there is designed relative motion.Coiled tube and torsion tube installations shall be designed and installed inaccordance with the data given in ARP 584.

3.11.28.5 Straight tube lines. Straight tube lines between two rigid tubingend connections shall not be used.

3.11.28.6 Tubing in fire hazard areas. Aluminum tubing shall not be usedwithin powerplant compartments and at other locations where fires are likelyto occur. Where separable tube fittings are required, they shall be corrosion-resistant or carbon steel.

3.11.28.7 Tubing and fitting identification. “All hydraulic fluid lines shall

be permanently marked in accordance with MIL-STD-1247. A sufficient number of

I hydraulic lines shall be marked in conspicuous locations throughout the alrcratt! in order that each run of line may be tTaced. This markinz shal1 indicate the1...

unit operated and the direction of flow, such as LANDING GEAR UP _ orFLAPS DOWN ~ These markings shall be repeated as often as necessary,particular y on 1ines entering and emerging from closed compartments, tofacilitate maintenance work. Wlterefittings are located in members, such asbulkheads and webs, each fitting location shall be identified (placarded) asto system function, using the same terminology as on its connecting line.

3.11.28.8 TUbing supports. All hydraulic tubing shall be supported from rigidstructure by MS21105 (MIL-C-8956, type III, class B) cushioned steel clamps orby suitable multiple-tube block-type clamps. Supports shall be placed as nearas practicable to bends to minimize overhang of the tube. Recommended spacingsbetween supports are specified in table II, except that where tubes support fit-tings such as unions and tees, spacings should be reduced approximate lY 20 percent.Where tubes of different diameters are connected together, an average spacingdistance may be used. In any event, the installation shall be in compliancewith 3.11.29.6 and 3.11.29.7. Provisions shall be made in support locations toacconunodate change in tubing length caused by expansion and centraction. Inorder to facilitate inspection and repair, tubing shall not be bundled together.


MIL-H-5440G

TABLE II. Hydraulic Line Support Spacings

‘omi’:’;oo~Maximum Length Between Support Centers

1/8 9-1/2 11-1/23/16 12 141/4 13-1/2 165/16 15 183/8 16-1/2 201/2 195/8 22 ;:-1/23/4 24 27-1/2

1 26-1/2 301-1/4 28-1/2 31-1/2

1-1/2 29-1/2 32-1[2

3.11.28.9 Location of hydraulic tubing. Hydraulic lines shall not be installedin the cockpit or cabin and shall be remote from personnel stations. Inaddition, hydraulic lines shall be located remotely from exhaust stacks andmanifolds; electrical, radio, oxygen, and equipment 1ines; and insulatingmaterials. In all cases, the hydraulic lines shall be below the aforementionedto prevent fire from line leakage. Hydraulic lines shall not be grouped with

lines carrying other flammable fluids in order to prevent inadvertent crossconnection of different systems. Hydraulic drain and vent lines shall exhaustin areas where the fluid will not be blown into the aircraft, collect in poolsin the structure, or be blownonto or “ear e’xha”st stacks, manifolds, OT other

sources of heat. Tubing shall be located so that damage will not occur d“e to

being stepped on, used as handholds, or by manipulation of tools during main-tenance. Components and lines shall be so located that easy accessibility forinspection, adjustment, and repair is possible. Hydraulic tubing shall n& beused to provide support of other aircraft installations, such as “iri”g, otheraircraft tubing, or similar installations. Attachment of so-called marriageclamps for spacing of such installations is likewise prohibited.

3.11.28.10 Tubing flares and assembly. Tubing flares shall conform to NS33583or MS33584. When installing tube connections, care should be exercised to keepthe wrench torque used to assemble each joint within the limits specified onMS21344. Male threaded aluminum-alloy flared fittings shall not be used withstainless-steel lines below size -8.

I 32


* ., MIL-H-5440G..,,.....

.3.11.28.11 Tubing Pre-stress. Each titanium tube assembly shall be pre-stressedby the application of pressure to approximately 5 percent of the minimum yieldstrength. This test may be performed,on the bench or in the aircraft.

3.11.29 Design of system installations

3.11.29.1 Component lines. Two or more lines attached to a hydraulic componentshall be sufficiently different to prevent incorrect connection to the component.

3.11.29.2 Drain lines. Drain or vent lines coming from the pump, reservoir,or other hydraulic components shal1 not be connected to any other line or anyother fluid system in the aircraft in such manner as to permit mixture of thefluids at any of the components being drained or vented.

3.11.29.3 Mounting lightweight components. Lightweight components that donot have mounting provisions may be supported by the tubing installation, prO-vided that the comuonent is rieidlv installed and does not result in destrtlctive-.vibration or cause other adverse conditions and the tubing installation. Clampsor similar devices may be used to support such units to structure, providedthat nameplates, flow-direction arrows or markings, or other data is not obscuredand that the supporting member(s) do not affect the operation of the unit.

3.11.29.4 8onding. The aircraft hydraulic system components and lines shallbe bonded to the aircraft in accordance with MIL-B-5087.

3.11.29.5 Vibration. The complete hydraulic system, including lines andcomponents, shall be designed to withstand the effect of vibration, pump pul-sation, and shock loads encountered during service operation of the aircraft.

3.11.29.6 Tubing clearance. Where tubing is supported to structure or otherrigid members, a minimum clearance of 1/16 inch shall be maintained with suchmember. A minimum clearance of 1/4 inch shall be maintained with adjscentstructure, tubing, or other installations. In areas where relative motion ofadjoining components exists, a minimum clearance of 1/4 inch shall be main-tained under the most adverse conditions that will be encountered.

3.11.29.7 Corrosion protection. All tubing in exposed areas, such as wheelwells, weapons bays, and cove areas, shall be adequately protected againstcorrosion,

MIL-F-7179

3.11.29.B

particularly under the sleeve at the fittings, in accordance withor procedures approved by the procuring activity.

Suction line to power-driven pumps

33

---

., .*.


MIL-H-5440G

~

3.11.29.8.1 Suction-line flow. The supply line to the power-driven pump (s)shal1 be desi~ to provide adequate flow and pressure at the pump inlet port.This requirement shall include operating the pump at the maximwn output flowrequired of the pump and shall i“cl”de all ground and flight conditions theaircraft will encounter. Zero g and negative g coriditionsand low-temperaturestart and operation shal1 also be included in the above requirement.

I

3.12 Workmanship. Workmanship shall be high grade throughout to insure properoperation and service life.

4. QUALITV ASSURANCE PROVISIONS

4.1 Responsibility for inspection. Unless otherwise specified in the contract,the contractor is responsible for the performance of al1 inspection requirementsas specified herein. Except as otherwise specified in the contract, the con-tractor may use his own or any other facilities suitable for the performance ofthe inspection requirements specified herein, unless disapproved by the Govern-ment. The Government reserves the right to perform any of the inspectionsset forth in the specification where such inspections are deemed necessary toassure supplies and services conform to prescribed requirements.

4.2 Inspection. The hydraulic system installation of one of the first com-plete experimental and production aircraft shall be subject to inspection forconformance to the requirements of this specification by engineering represen-tatives of tbe procuring activity. It is expected that this inspection willbe performed at the co”tractorvs plant concurrently with similar engineeringinspections of other systems of the aircraft. Detailed arrangements for theinspection will be the subject of correspondence between the procuring activityand the contractor.

4.2.1 Vibration. The hydraulic system of the first flight aircraft shall betested prior to first flight to determine if any destructive vibration occursas the result of any and all combinations of engine and hydraulic pump speed,and hydraulic pump flows and pressures. Hydraulic lines, hoses and theirsupports, fittings, and all components shall be checked. Corrective actionshall be taken on any discrepancies.

4.2.2 Ground and flight tests. Ground and flight tests shall be conductedin accordance with MIL-T-5522.

34


MIL-H-5440G

4.3 Cleaning of parts and systems. To assure that the hydraulic system isfree of contamination, al1 parts of the hydraulic system shall be thoroughlycleaned prior to installation, and each “ew hydraulic system shall be ODeratedat least-10 times in order to insure filtrati& of all ~irculati”g flui~.Ground equipment which is ,usedfor this cleaning process shall be provided withfilters with the same, or finer degree, of filtration used in the aircraftsystem. Dead-end lines in the system shall be properly connected with jumpersto completely clean such lines. If the filter element in the hydraulic systemis used during this operation, it shall be replaced.

* 4.3.I System contamination level for production aircraft. For Navy aircraftonly, a minimum of two contamination tests (see requirements 3.11.9.1) shallbe performed on each major system, separated by a minimum of 2 flight hoursand a determination made that a stable or decreasing particulate level hasbeen achieved.

5. PREPAPATION FOR DELIVERY

?his section is not applicable to this specification.

6. NOTES

6.1 Intended use. The design and installation requirements covered by thisspecification are intended for use in aircraft hydraulic systems, such as theutility system, the flight-control system, various subsystems, and componentinstallation procedures for types 1 a“d 11 aircraft hydraulic systems.

6,.1.1 Type III -54° to +232°C (-65” to +450°F) systems are covered by MIL-H-8891.

6.2 Typical submittal data. TO obtain approval of the hydraulic system,

applicable data in the fOllOwing subparagraphs should be included in compliancewith 3.5.

6.2.1 Hydrauiic system analysis and design study. Tbe data listed in thisparagraph should be submitted for eval”atio” of design studies of a proposednew aircraft during the preliminary design and defini,tio”phases of a research,experimental, or prototype aircraft. The contractor should submit a reportcovering such design studies and analysis as are required to establish thedesign parameters of the hydraulic system of the proposed aircraft. The designanalysis should show that the hydraulic system fulfills the needs imposed bythe weapon system requirements. This report should include tbe following in-formation and data:

a. Hydraulic system schematic or block diagram

b. Pressure and flow rates versus time for each mission profile along withtbe load analysis

35


I MIL-H-5440G

* c. A thermal analysis with temperature versus time curves for fluid tempera-ture for typical missions and for ground operations. This analysis shallinclude the highest and lowest temperatures expected to flight including themaximum temperatures due to single failures such as worn pumps, relief valvebypass etc.

d. Nonflammable (or less flammable) hydraulic fluids should be considered inthe interest of reducing the potential fire hazard in a combat environment.The fluid selection should be based on a trade study to insure that specificimprovements i“ safety and survivability are realized without excessive penaltyin hydraulic system performance, operational capability, or cost of the air-craft. The trade study should consider reliability and all logistic aspectsover the expected life of the aircraft including supply and maintenance aswell as impact o“ support and service equipment on the flight line, in repairshops, and overhaul facilities.

e. Analyses or trade studies should include the following:

(1) Gptimum approach to permanent tube joining

(2) Dptimum separable tube fitting design

(3) Whether tubing materials having a strength-to-weight rzt<o higher thanthat of MIL-T-6845 can be used successfully, consistent with (1) and (2) alone,and be available within the time constraints of the program schedule.

6.2.2 Developmental and preproduction data. The following data should be sub-mitted during the development phase of the hydraulic system and should be suitablefor use as production procurement data:

a. Hydraulic systems schematic diagram in accordance with 6.2.3.2 should besubmitted for approval.

b. Hydraulic system design report in accordance with 6.2.4 should be submittedfor approval.

c. Hydraulic system ground and flight test report in accordance with MIL-T-5522should be submitted for approval.

d. Detail specifications and test reports for the following components shouldbe submitted for technical review and approval :

(1) Pumps and motors

(2) Flight-control actuators and servos

(3) Valves and switches

(4) Flexible connectors

36

(Army)

including hoses (if nonstandard)


MIL-H-5440G

(5)

(6)

(7)

Packings and packing installations(if nonstandard)

Fluids (if nonstandard)

Fittings (if nonstandard)

NOTE: Other components that may require surveillance, in view of the critical-ness of the particular item to the proper functioning of the weapon system, maybe specified after the hydraulic system schematic diagrams have been reviewed.The list of surveillance items will be established during the service-contractorconference (see 3.5.1).

e. Cross-sectional assembly drawings, in accordance with 6.2.5, of all non-standard hydraulic components should be submitted for information.

f. Analysis of failures and malfunctions affecting performance and safety

Ishould be submitted.

I 6.2.2.1 The following procedure should be adapted by the contractor forcomponents not listed under 6.2.2 (d):

a. The contractor should certify, upon completion of validating tests, thatthe hydraulic component conforms to the applicable military or contractor-prepared specifications approved by the procuring activity and is satisfactoryfor use in the particular aircraft weapon system hydraulic system.

b. The test reports, as well as the specifications and other applicableengineering data covering the hydraulic system components, other than thosespecified in 6.2.2(d), should be retained by the contractor and should beavailable to tbe procuring activity upon request, with the exception that allthe cross-sectional assembly drawings should be submitted for information.

c. The contractor should list in a status of equipment list those componentsthat are contractor certified for data availability and compliance with tbe

applicable Government-approved specifications.

6.2.3 Production data. Where changes have been made in tbe hydraulic systemover the developmental hydraulic system, the developmental data required in6.2.2 should be submitted.

6.2.3.1 Functional test specification. A specification incorporating the

necessary functional tests of the hydraulic system of production aircraft shouldbe submitted to the procuring activity for approval.

6.2.3.2 Schematic diagram. me schematic diagram should consist of one copyof tbe conventional size and one copy approximately 11 inches in height. The

arrangement of the schematic diagram should be such as to present tbe system in

37


MIL-H-5440G

I

a clear and easily readable form, with complete subsystems grouped and labeledaccordingly. Emphasis should be placed on simplicity and clarity of presenta-tion, with location in the aircraft being of secondary importance. Nomenclatureof each unit should be made adjacent to or in the vicinity of each unit. Inaddition, the schematic diagram should contain the following information:

a. Operating pressure of all systems and subsystems

b. All relief valve reseat and full flow pressures

c. Initial gas pressure of accumulators and their “o’%nalcapacities

d. Pressure range of pressure regulators

e. Diameter, wall thickness, and material of tubing

f. Total and reserve fluid capacities of reservoir, or reservoirs, and thesystem; reservoir pressure; and method of pressurization

g. Displacement of fluid in cubic inches of each actuating cylinder for bothextension and retraction

h. Actuating cylinder pistonhead diameter, rod diameter, effective pistonarea, and total and working stroke of each cylinder.

1. Displacement per revolution and number of required revolutions ofhydraulic motors for each half-cycle of operation and the torque load requiredfor each unit

j. Type of power-driven pump and displacement, including flow rate curveshowing engine and pump rpm, for all phases of flight such as takeoff, climb,cruise, and landing

k. Indicated fluid flow direction through al1 hydraulic lines

1. Reservoir pressurizing system source, operating pressure, and schematicdiagram of plumbing

m. Simple schematic diagram of linkage showing mechanical disconnects, down-locks, and uplocks, and other data to tie the mechanical system to the hydraulicsystem for analysis

n. A simple schematic wiring diagram of the electrical portion of thehydraulic system giving current loads and describing functions. (This diagramand data may be on a separate drawing.)

38


MIL-H-5440G

o. Name and part number of all units. Standard part numbers should be indi-cated where applicable. Nonstandard units should also include name of manufac-turer and the manufacturer’s part number.

p. Connections for testing with auxiliary or ground test power system shouldbe indicated.

‘q. Tubing and hose lines should be identified in accordance with AS 1290.

* r. Hydraulic components should be shown in simple schematic form. Multipleposition units, such as selector valves, should clearly indicate internal fluidporting. Flow path of selector valves should be shown for each position of tbevalves. Hydraulic components should be shown in accordance with AS 1290.

s. Maximum and normal system temperature (estimated) In estimating maximumand normal system temperatures, the following conditions should be specified:

(1)

(2)

(3)

(4)

(5)

(6)tion at

Location of temperature

Altitude

Ambient temperature

Compartment temperature

Engine power setting

Time duration of flight and time duration limitations for ground opera-maximum system temperature

t. Pressure and temperature pickup locations to be installed for instrumen-tation purposes in accordance with MIL-T-5522 should be indicated on the copiesof the schematic diagrams submitted to the procuring activity.

u. Hydraulic system block diagram. (This may be a seParate sheet Of theschematic diagram.)

6.2.4 Hydraulic system design report. The hydraulic system design reportshould be submitted prior to or with the final schematic diagram. The reportshould incorporate sufficient design calculations and data to verify that thehydraulic system design complies with all design requirements. A hydraulicsystem temperature survey (minimum through maximum) should be included consider-ing the location of the hydraulic system in the aircraft. kbe time of flightat maximum system temperature and conditions under which this temperature occursshould be included. Compartment temperatures should be estimated. For primaryflight-control systems, peak and average flow rates and the power spectrumshould be indicated. Duration of peak flow rates should also be indicated. Theminimum temperature at which full performance occurs should be determined by tbecontractor and submitted for approval.

39


MIL-H-5440G

6.2.5 Hydraulic system nonstandard component cross-sectional assembly drawings.The cross-sectional assembly drawings for each nonstandard hydraulic componentshould contain sufficient information in order that an evaluation of the unitcan be made. Such information should include the applicable specification, thematerial protective finish of each part, and bearing data. This informationmay appear as a written addition to tbe drawing. Reason for the use of a non-standard component, where a standard,exists, should be submitted with thecomponent drawing.

6.2.6 Functionalmockup design report and ,testprogram. A.report describingthe general design of the functional mockup and the anticipated test programshould be submitted to the procuring activity for ap@roval not later than 30days prior to beginning construction of the mockup, in order that any modifi-cation of the mockup or revision of the test program recommended by the pro-curing activity may be included.

6.2.7 Vibration test plan. A test plan for the vibration test in 4.2.1 shouldbe submitted to tbe procuring activity for approval not later than 30 days priorto start of the test.

6.3 Marginal indicia. The outside margins of this specification are markedwith an asteri-dicate where changes (additions, modifications, correc-tions, deletions) from the previous issue were made. This was done as aconvenience only and tbe Government assumes no 1iabi1ity whatsoever for anyinaccuracies in these notations. Bidders and contractors are cantioned toevaluate the requirements of this document based on the entire content irre-spective of the marginal notations and relationship to the last previous issue.

Custodians:Army - AVNavy - ASAir Force - 11

Review activity:Air Force - 71

User activity:

Army - MI

40

Preparing activity:Air Force - 11

Project No. 1650-0269


MIL-H-5440G

ALPHABETICAL INDEX

A Paragraph

Accelerated loadsAcceleration effectsAccumulator accessibilityAccumulator instructionsAccumulatorsActuating CY1indersActuators essential to safe operation of the

aircraftAdditional loadsAPPLICABLE DOCUhIINTSApplicationAir Force and Army aircraft filtersAirframe break points

Back pressureBackup ringsBleeder valvesBondingBrakesBrake valves

c

Check valvesClassificationCleaning of parts and systemsClimatic extremes

Combined flight-control/utility systemComponent designComponent installation

Component 1inesConferences, service-contractorControl valve actuationControl valve wiringCorrosion protection

3.6.3.23.6.6.23.11.2.23.11.2.33.11.23.11.3

3.10.33.6.3.1

;.7.23.11.9.23.11.24.1

3.6.4.23.4.33.11.43.11.29.43..6.4.33.11.5

3.11.61.24.33.6.1.1

3.8.1.33.103.113.11.29.13.5.13.11.7.33.11.7.43.11.29.7

Page

81121212021

2081

162330

862133821

1“358161920337222233

,

41


ALPHABETICAL INDEX (Cent’d)

MIL-H-5440G

D Paragraph

DefinitionDefinitionsDesignDesigned motion in tubingDesign of system installationsDesign practice and installationDevelopmental and preproduction dataDirectional control valve handle installation

Directional control valvesDisengagement snd bypassingDrain lines

E

Electric-motor-driven pumpsEmergency line ventingEmergency power pumpsEmergent y system applicationEmergency system design for utility system

Filter locationsFilter requirementsFire hazardsFittingsFlexible connectionsFlight-control system designFlow dividersFlow regulatorsFluidFluid flow effectsFluid sampling valvesFluid temperature limitationsFluid velocity limitationsFor maximum fluid temperature between

107° and 135°C (225° snd 275”F)For maximum fluid temperature of 107”C (225”F)Functional mockup and simulatorFunctional mockup design report snd

test programFunctional test

F

specification

3.7.13.8.13.23.11.28.43.11.293.n.l6.2.23.11.7.13.11.73.8.3.23.11.29.2

3.11.19.13.9.23.6.10.13.8.3.13.9

3.11.9.33.11.93.6.23.11.103.11.163.83.11.113.11.123.33.6.6.13.6.143.6.13.6.6

3.4.2.23.4.2.13.5.2

6.2.66.2.3.1

Page

1616

s313320362221

1833

2619141719

23228

2425162424

6111s7

11

667

4037

42


Gas-pressurized reservoirsGas requirementsGeneral system designGround and flight testsGround test connectionsGround test dataGround test provisions

MIL-H-5440G


G Paragraph

H

Hand pump handle lengthHigh- lift devicesHose assembliesHose bend radiiHose protectionHose supportHydraulic power failureHydraulic sequencingHydraulic system analysis and desiszn studyHydraulic‘systemdata-submittal antiappro~alHydraulic system design reportHydraulic system nonstandard component

InspectionInstallation of small size tubingIntended use

Location of hydraulic tubingLock valves

Maintenance checkManual 1y operatedManually operatedManually operatedMarginal indiciaMaterials

gages and indicatorspump check valvepumpspump suction line

I

L

M

3.11.22.33.11.2.43.64.2.23.6.8.13.6.8.23.6.8

3.11.15.33.9.1.13.11.16.13.11.16.33.11.16.43.11.16.23.8.33.11.9.46.2.13.56.2.46.2.5

4.23.11.28.36.1

3.11.28.9‘3.11.17

3.6.13.23.11.15.23.11.153.11.15.16.33.1

Page

28217

34121312

2519252526251723356

3940

343135

3226

15252425405

43


MIL-H-5440G


Measurement of accumulator gas pressureMotorsMount ing lightweight componentsMultiple control valve systemsMultiple pumps, engine driven

N

Navy aircraft filtersNOTES

OrificesOther valves

P

PackingsPower-boosted flight-control systemPower-operated flight-control systemPower pumpsPower pumps, variable-delivery and fixed

displacementPower sourcesPP.EPARATIONFOR DELIVERYPressure limitationsPressure line installationPressure regulationPressure regularots (unloading valves)Pressure switchesProduction dataProtective devicesProvisions for hose elongation

and contract ionPump-case drain line installationPump pulsationPump rotation reversalPump suction linePump supp1y shutoff

Paragraph

3.11.2.13.11.lB3.11.29.33.11.7.23.6.10.2

3.11.9.16

0

3.11.9.13.10.2

3.43.8.1.13.8.1.23.6.10

3.11.193.8.653.6.43.11.9.3.43.6.4.43.11.203.11.266.2.33.11.13

3.11.16.53.11.9.3.43.6.10.33.6.10.43.11.9.3.53.6.11

Page

2026332214

2320

6161614

2618358231126303724

262314142614

44


MIL-H-5440G


Q

QUALITY ASSURANCE PROVISIONS

R

Relief valves, system and thermal expansionRemoval of entrapped airREQUIRENENTSReservoirReservoirReservoir

ReservoirReservoirReservoirReservoirReservoir

air pressurization moisture removalbootstrap pressurizationfilling connectionfill line installationfluid Ievel indicationlocationpressurizationsupercharging connect ioo

ReservoirsReservoir ventingResponsibility for inspectionRestrictor valvesReturn line iristallationReverse installation

s

Schematic diagramSCOPEScopeSelf-sealing couplingsService-contractor conferenceShuttle valvesSnubbersSpecial toolsStandard componentsStraight tube linesStrengthSubsystem isolationSuction-1ine flowSuetion line to power-driven pumpsSystem air toleranceSystem contamination level production

aircraftSystem isolationSystem low-pressure warning lightSystem pressure

Paragraph

4

3.11.213.6.933.11.22.43.6.5.13.6.8 .1.2

3.11.9 .3.33.11.22.53.11.22.13.6.53.6.8.1.13.11.223.11.22.24.13.11.233.11.9 .3.23.11. 1.1

6.2.3.211.13.11.243.5.13.11.253.11.143.6.123.10.13.11.28.53.6.33.6.73.11.29 .8’.13.11.29.83.6.9.1

4.3.13.8.23.6.13.13.8.5

Page

34

27135

2911132329281113272834292320

3711

297

3024151931811343313

35171518

45


I MIL-H-5440G -1System pressuresSystem pressure indicationSystem relief valveSystem separationSystem temperatureSwivel joints


Paragraph

Thermal expansion relief valvesTubing -Tubing and fitting identificationTubing bendsTubing c1earanceTubing in fire hazard areasTubing materialsTubing pre- stressTubing supportsType I systemType II systemType IIITypesTypical submittal data

Universal fittingsUtility system design

VibrationVibrationVibration test plan

Wheel brake systemsWorkmanship

46

T

u

3.6.4.1,3.6.133.11.21.13.8.43.8.73.11.27

3.11.21.23.11.283.11.28.73.11.28.23.11.29.63.11.28.63.11.28.13.11.28.113.11.28.83.4.13.4.26.1.13.9.16.2

3.11.10.13.7

v

3.11.29.54.2.16.2.7

3.7.33.12

Page

91527181920

27303131333130333166

351935

2416

333440

1634

L


MIL-H-5440G


Page

TABLES

Table I System Pressures

Table II Hydraulic Line Support Spacking

9&lo

32

47


STANDARDIZATION ~tJMENT IMPROVEMENT PROPOSAL(ScEIIulndiau- R fwne Side)

.00CUMENTNUM6Ell 2. DOCUMENT TITLE

1a NAME OF SUBMITTING OROANIZATION 4, TVPE OF ORGANIZATION (Mark .JIU)

❑ VENDOR

❑ USEI?

AOOFli&(.TbWt, CItv, .5Wti. ZIPC*)

•1 MANUFACTURER

1PROBLEM AREAS

. P.,o#mPII Nu.bor m.d WordlW

b. RdmmnnndalWoww

c.Ruao”/Ratlo”ala farnocornnmndation:

REMARKS

.,”<

I. NAME OF SU8M1TTER ht. Flint, MI) - Omlond b. WORK TELEPHONE NuMEER (lIIclud# A maCo&) - OIMION1

MAIL!NG ADDREEE (Stir, CltY. StatG ZIPCod8)- “otlond 8,DATEOFSUBMISSIONO’YMMDD)

●REV1OIJS EDITION IS O@SOLETE.


. . . . . . . . .... . ,.,

I lNsTRucllOMs

NOTS: W formmay notb wed torequestcopiesof documents, ❑ or to requ=t waivers, deviaticuu, or WG=atkn of@fication mquiremeati on -t comtmcb. Camwnk mibmltted on tbk form do notcomstitubor impEy .uthobuon

to wairo any pwtkm of the mfemnceddocument(s) or to umad contractual mquirementi.

I

(Mid dmu EM! tttu)

0EP4NTMENT OF THE AIR FORCE

111111r%R31“II II I I IF MAILEO

IN THE

P!R!!IuOFFICIAL •ttSIN~●ENAL7V Fon ● RIvATE USE s30u BUcS~NESS~REPL~~HMAJ&c

FO%AGE WILL BE PAID wf THE DEPAIWMEN7 OF 7HE AIR FOFfCE

ASD?EWYESS

Wright-Patterson AFB, OH 45433

~.._ .


,5.- ..,- .$ MIL-H-5440G .,. 28November1975 SUPERSEDING ...

Documents

Transcript of ,5.- ..,- .$ MIL-H-5440G .,. 28November1975 SUPERSEDING ...