01040200

Ministry of DefenceDefence Standard 00-970 Part 1 Section 4

Issue 2 Publication Date 1 December1999

Design and Airworthiness Requirementsfor

Service Aircraft

Design and Construction

DSTANA list of the leaflets to this section is contained in Section 4 Supplements. A full list of leaflets is contained in Annex G Part 0.Page 388 of this document is intentionally missing.See last pages for the Guidance Notes accompanying this document.

DEF STAN 00-970 PART 1/2SECTION 4

Page 2

AMENDMENTS ISSUED SINCE PUBLICATION

AMENDMENTNUMBER

DATE OFISSUE

TEXT AFFECTED SIGNATURE & DATE

REVISION NOTEThis standard is raised to Issue 2 to update its content and introduce a new structure for thedocument.

HISTORICAL RECORD

This standard supersedes the following:Defence Standard (Def Stan) 00-970 Issue 1 dated 12 December 1983Design Requirements for Service Aircraft

Aviation Publication (AvP) 970 dated 1959Design Requirements for Service Aircraft

Air Publication (AP) 970 2nd Edition dated 1924Handbook of Strength Calculations

Handbook (HB) 806 1st Edition dated 1918Handbook of Strength Calculations.


Page 3

CONTENTSDescription Page No

Content 3Preface 4Main Text 5

SECTION 4 - DESIGN AND CONSTRUCTION4. Introduction 54.1 General Detail Design 74.2 Marking of Aeroplane Parts 194.3 Protection of Structure 314.4 Accessibility, Maintenance and Servicing 694.5 Material Strength Properties and Values 934.6 Processes and Working of Materials 1014.7 Castings 1094.8 Aero-Elasticity, Flutter and Vibration 1134.9 Birdstrike Damage 1184.10 Control Systems 1254.11 Design of Undercarriages 1354.12 Wheels, Tyres and Brakes 1704.13 Operation from Rough Ground/Ground Clearance 1864.14 Nose Wheel Steering 1914.15 Crew Stations - General Requirements 1954.16 Pilots Station - Layout 2204.17 View and Clear Vision 2264.18 Optically Transparent Components 2364.19 Cockpit Controls 2514.20 Doors 2714.21 Seats, berths, safety belts and harnesses 2774.22 Crash Landing & Ditching 2834.23 Emergency Provisions 3014.24 Ventilation & Heating 3204.25 Pressurised Air Ducts 3394.26 Fire Precautions 3434.27 Electrical Bonding 378Tables 389Diagrams 454


Page 4

DESIGN AND AIRWORTHINESS REQUIREMENTSFOR SERVICE AIRCRAFT

PART 1, SECTION

PREFACE

This document provides requirements and guidance for the design of aircraft to meet theairworthiness requirements for UK military operation. The requirements stated herein shall beapplied by the Ministry of Defence (MoD) and the contractor as agreed and defined in thecontract.

This document has been produced on behalf of the Defence Aviation Safety Board (DASB) byAirworthiness Design Requirements and Procedures (ADRP), Air/Land Technology Group(A/LTG), MoD Abbey Wood.

The appropriate Parts of this document are to be used, when called up in the Contract, for allfuture designs, and whenever practicable for amendments to existing designs. If any difficultyarises which prevents application of this document, ADRP shall be informed so that a remedymay be sought.

Any enquiries regarding this document in relation to an invitation to tender or a contract inwhich it is incorporated are to be addressed to the relevant MoD Project Director/ProjectManager named in the invitation to tender or contract.

This document has been devised solely for the use of the MoD and its contractors in theexecution of contracts for the MoD. To the extent permitted by law, the MoD herebyexcludes all liability whatsoever and howsoever arising (including, but without limitation,liability resulting from negligence) for any loss or damage howsoever caused where theDocument is used for any other purpose.

DEF STAN 00-970 PART 1/2SECTION 4 Page 5 Dec 99

SECTION 4 - DESIGN AND CONSTRUCTION

4.0 INTRODUCTION

4.0.1 This section specifies the requirements covering the design and construction of the aircraft. These requirements should be implemented with the aimthat no design features or details of the aircraft should be known to be hazardous or unreliable and that areas of doubt concerning design details and partsshould be confirmed by test and analysis.

4.0.2 Requirements are provided to cover the following aspects:

4.1 General Detail Design4.2 Marking of Aeroplane Parts4.3 Protection of Structure4.4 Accessibility, Maintenance and Servicing4.5 Material Strength Properties and Values4.6 Processes and Working of Materials4.7 Castings4.8 Aero-Elasticity, Flutter and Vibration4.9 Birdstrike Damage4.10 Control Systems4.11 Design of Undercarriages4.12 Wheels, Tyres and Brakes4.13 Operation from Rough Ground/Ground Clearance4.14 Nose Wheel Steering4.15 Crew Stations - General Requirements4.16 Pilots Station - Layout4.17 View and Clear Vision4.18 Optically Transparent Components4.19 Cockpit Controls


4.20 Doors4.21 Seats, berths, safety belts and harnesses4.22 Crash Landing & Ditching4.23 Emergency Provisions4.24 Ventilation & Heating4.25 Pressurised Air Ducts4.26 Fire Precautions4.27 Electrical Bonding

4.0.3 This section comprises the content of DEF STAN 00-970 Issue 1 Chapters 102, 104, 105, 106, 107, 108, 109, 111, 201, 209, 301, 302, 303, 304, 305,306, 307, 310, 311, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 500, 709, 713, 717, 720, 721, 733, 737, 740, 800, 801, 802, 803, 804, 805, 1007,1008, 1010 and 1016. It is intended to provide information similar to that contained in JAR 25 Section D.

4.0.4 In the electronic version of this document, this line provide a link to Part 0.


4.1 GENERAL DETAIL DESIGN

4.1.1 THIS INFORMATION WAS PREVIOUSLY PUBLISHED AS CHAPTER 400 OF DEF STAN 00-970 ISSUE 1 AND IS SIMILAR TO JAR 25.601 -607.

REQUIREMENT COMPLIANCE GUIDANCE

GENERAL4.1.2 In the detailed design of the aeroplane thevariety of materials and parts shall be kept to aminimum consistent with structural efficiency andwithout unduly sacrificing structure weight.

The design of parts and fittings shall be such as tofacilitate their manufacture in quantity.

4.1.3 Components and items of equipment shallhave at least the same factor as the main structure inall the appropriate stressing cases. Local loads atparts of attachment to the main structure shall becarefully considered to ensure that the mainstructure is not unduly weakened thereby.GRADING OF PARTS AND ASSEMBLIESINTRODUCTION4.1.4 In order to ensure that the material andprocesses used in the manufacture of a part are ofsuitable quality and that the part is satisfactory,quality control and testing, must be appropriate tothe design requirements and the application of thepart. To this end all parts, except standard parts asdefined in 4.1.10 - 12 shall be designated Grade Aor Grade B, taking cognizance of strength andstiffness requirements as promulgated in thispublication, quality requirements, maintainability

The grading requirements apply whether the part isdesigned to Damage Tolerance Requirements ornot.

The term "parts" relates to all parts of theaeroplane except missiles (DEF STAN 08-5)engines (DEF STAN 00-971) and propellers(Spec DERD 2006). The grading requirementsalso apply to the structural and mechanical partsof all systems and equipment in the aeroplane.



and inspectability requirements, and also suchfactors as failure by leakage, malfunction, or otherdefect.4.1.5 STANDARD PARTS SHALL NOT BEGRADED BUT SHALL BE SELECTEDACCORDING TO THE GRADE OF THEIRAPPLICATION.GRADING REQUIREMENTS4.1.6 Grade A A part shall be Grade A if thedeformation or failure of the part would result inone or more of the following:

(a) structural collapse at loads up to andincluding, the design ultimate load,

(b) loss of control,

(c) failure of motive power,

(d) unintentional operation of, or inability tooperate, any systems or equipment essential to thesafety or operational function of the aeroplane,

(e) incapacitating injury to any occupant,

(F) UNACCEPTABLEUNSERVICEABILITY OR MAINTAINABILITY.

Advice on the interpretation of these definitionsand requirements is given in Leaflet 1.

4.1.7 GRADE B. A PART MAY BE GRADE BAT THE DESIGNERS DISCRETION IF NONEOF THE PROVISIONS OF 4.1.6 APPLY.



DRAWINGS AND QUALITY CONTROL4.1.8 All drawings shall state the quality controlrequirements applicable to the grade of the part orassembly and the reference number of thespecification or design designation of the material orprocess.4.1.9 WHERE PARTS, OR DESIGNATEDAREAS OF PARTS IRRESPECTIVE OF THEIRGRADE, REQUIRE QUALITY CONTROL INADDITION TO VISUAL AND DIMENSIONALEXAMINATION (EG NON-DESTRUCTIVETESTS) THE ADDITIONAL INSPECTIONREQUIREMENTS SHALL BE DETAILED ORREFERENCED ON THE DRAWING.STANDARD PARTS4.1.10 THE REQUIREMENT OF THEAPPROPRIATE DEFENCE STANDARDS ANDOTHER STANDARDS LISTED IN CHAPTERS 1AND 2 OF DEFENCE STANDARD 00-00 (PART3) SECTION 1 SHALL BE MET.

Where these requirements standardize a givenitem, no other items shall be used to performfunctions for which this standard item is suitable,unless the use of an alternative item is:

(a) authorised by the Aeroplane Specification,

(b) permitted by the requirements of thispublication, or

(c) approved by the appropriate AeroplaneProjector Director - see also the Introduction toDEF STAN 00-00 (Part 3) Section 1.

4.1.11 When a suitable item is not covered byDefence Standards but is available in one of the



following series:

(a) AGS parts,

(b) SBAC standard parts,

(c) BSI standard parts,

(d) AECMA standard parts,

SUCH ITEM SHALL BE USED.4.1.12 ALL STANDARD ITEMSINCORPORATED IN THE AEROPLANESHALL BE IN ACCORDANCE WITH THELATEST APPROVED ISSUE OF THERELEVANT DRAWINGS, BUT THE ISSUENUMBER OF SUCH DRAWINGS SHALL NOTAPPEAR ON THE AEROPLANE DRAWINGS.MATERIALS AND PROCESSES4.1.13 FOR GRADE A PARTS THE MATERIALAND PROCESS OF MANUFACTURE SHALLNORMALLY CONFORM TO AN APPROVEDAEROSPACE SPECIFICATION IN THE SERIESLISTED IN DEF STAN 00-00 PART 3, INDEXOF STANDARDS FOR DEFENCEPROCUREMENT, SECTION 1: PREFERREDSTANDARDS FOR THE DESIGN ANDPROCUREMENT OF AEROSPACE VEHICLESAND EQUIPMENT.

For ease of reference the situation on somenational and international standards is as follows:

Approved Aerospace Specification

(a) British Standards: Aerospace Series,including ISO and EN Standards published by BSIin the Aerospace Series.

(b) pr EN Standard Specifications issued byAECMA.

SEE 4.3.10 - 11 FOR MATERIALS ANDPROCESSES USED FOR PROTECTIVETREATMENT.



(c) DTD Specifications, including DTD 900approvals.

Unapproved

(a) British Standards: General EngineeringSeries. These will require to be covered by aContractors' Specification.

4.1.14 WHERE IT IS PROPOSED TO USE ANUNAPPROVED MATERIAL OR PROCESSSPECIFICATION FOR A GRADE A PART, ACONTRACTORS' SPECIFICATION SHALL BEUSED.4.1.15 GRADE B PARTS MAY BEMANUFACTURED FROM MATERIALSSPECIFIED IN 4.1.13, OR FROM LESSCLOSELY CONTROLLED MATERIALS (EGGENERAL ENGINEERING MATERIALS) ATTHE DESIGNER'S DISCRETION.STRENGTH OF MATERIALS4.1.16 See Clause 4.5.USE OF WOOD4.1.17 NO PART OF AN AEROPLANE SHALLBE MADE OF WOOD, UNLESS AUTHORISEDEITHER IN THE AEROPLANESPECIFICATION OR BY THE AEROPLANEPROJECT DIRECTOR IN WRITING AFTERAPPLICATION HAS BEEN MADE WITHEVIDENCE THAT IT WILL BE

SEE ALSO 4.3.87 - 93



SATISFACTORY IN TROPICAL AND SEA-GOING CONDITIONS.LOCKING OF THREADED FASTENERS4.1.18 THE STANDARD OF LOCKING OF ATHREADED FASTENER SHALL BEDETERMINED BY THE GRADE OF THEAPPLICATION OF THE FASTENER WITHINTHE JOINT OR ASSEMBLY.

Where the preferred method of locking conflictswith an operational requirement (eg where quickrelease of parts is required), or where valueengineering assessment clearly indicates anadvantage, other methods may be used providedthat it can be shown to the satisfaction of theAeroplane Project Director, by tests, that they aresatisfactory for the environment they will have towithstand.

4.1.19 THREADED FASTENERS IN GRADE AAPPLICATIONS SHALL HAVE STANDARD ALOCKING. ADDITIONALLY, THOSE NUTAND BOLT FASTENERS IN GRADE AAPPLICATIONS AT 4.1.6 (B) AND (C) SHALLBE PROVIDED WITH A SECONDARY MEANSOF RETENTION SUCH THAT, ONCE THEFASTENER IS PLACED IN POSITION, THESECONDARY RETAINING DEVICE BECOMESAUTOMATICALLY EFFECTIVE INPREVENTING IT FROM DROPPING OUT OFPOSITION EVEN THOUGH THE USUALRETAINING DEVICE MAY HAVE BEENOMITTED.

(a) Acceptable means of locking to Standard Aare given in Leaflet 4 Para. 2.

(b) This secondary device should be automatic inoperation and should not depend uponmaintenance personnel remembering to carry out aseparate action such as the bending of locking tabsor the fitting of locking wire. Secondary means ofretention which depend upon friction or springs areusually acceptable.

4.1.20 THREADED FASTENERS IN GRADE BAPPLICATIONS SHALL HAVE STANDARD AOR B LOCKING.

Acceptable means of locking to Standard B aregiven in Leaflet 4, Para. 3.

4.1.21 LOCKING WIRE SHALL NOT BE USED



IN PURE SHEAR OR WHERE MOVEMENT OFTHE JOINT COULD RESULT IN ROTATIONOF THE FASTENER.4.1.22 Centre-popping shall not be used.4.1.23 Peening shall not be used to lock:

(a) titanium fasteners or titanium alloy fasteners,

(b) high tensile strength (over 1100 MPaspecification minimum) steel fasteners,

(C) BOLTS IN JOINTS WHICH HAVE TOBE DISMANTLED REGULARLY IN SERVICE.4.1.24 LOCKING ADHESIVES SHALL NOT BEUSED IN TAPPED HOLES AND OTHERLOCATIONS WHERE THE MATING PARTSCOULD BE DAMAGED OR ARE NOTREADILY REPLACEABLE.4.1.25 IN ALL CASES WHERE THE METHODOF LOCKING, WHETHER BY STANDARD AOR B, DOES NOT DEMAND MORE, THE ENDOF THE BOLT OR STUD SHALL PROTRUDEBEYOND THE NUT BY A DIMENSION EQUALTO AT LEAST 1.5 THREAD PITCHES.4.1.26 Any damage to protective treatment appliedto the structure caused by locking shall beadequately repaired.USE OF LEAD SEALS ON LOCKING WIRE4.1.27The use of lead seals on locking wire isprohibited on aeroplanes and aeroplane equipment,

Where equipment is supplied with lead seals theyshall be removed, unless they form part of the

*ORDER NO. 6470 IS NOT AVAILABLE FORGENERAL CIRCULATION, BUT IS



except where permitted by AP 100B-01 Order6470*.

equipment's warranty. When the lead seals formpart of the equipment's warranty the aeroplanedesigner/manufacturer shall inform the AeroplaneProject Director who will decide whether the leadseals are to be retained, bearing in mind thepossible danger to flight safety.

CONCERNED WITH SPECIALCIRCUMSTANCES RELATING TOAEROPLANE ARMAMENT SYSTEMS.

USE OF COLD FORGED STEEL BOLTS4.1.28 Where cold forged steel bolts are used inGrade A applications and are:

(a) likely to be subjected to any conditionsconducive to fatigue failure, or

(b) used in positions where no relaxation of theinitially applied torque is permissible,

the bolts shall be to Specification DTD 5162 or tosuch other specification which has been approved bythe Director, RAE.USE OF MAGNESIUM ALLOYS4.1.29 Magnesium alloy skins or parts made frommagnesium alloy sheet shall not be used in militaryaeroplane structures.

(a) Magnesium based alloys in cast or wroughtforms may be acceptable subject to appropriateprecautions.

(b) Where the Aeroplane Design Authorityconsiders it necessary to use magnesium alloy tomeet the draft specification for the aeroplane thisshall be made known during the pre-contractnegotiations, so that the implications can beassessed. Where magnesium alloy is permitted to

See Leaflet 2



be used the Aeroplane Specification will identifythe parts, and conditions for use includingprotective treatment.

4.1.30 MAGNESIUM ALLOYS SHALL NOT BEUSED IN THE CONSTRUCTION OF CREWSEATS.4.1.31 Magnesium alloy parts shall not be used inplaces where they are liable to continuous exposureto corrosive fluids, for example:

(a) for enclosed systems where water maycollect, such as fuel systems (See Clause 5.2),

(b) for structure in areas where water maycollect, such as bilge areas, gaps in control surfacesor folding joints in aeroplanes,

(C) FOR TOILET, WASHROOM ANDGALLEY COMPARTMENTS AND OTHERUNDERFLOOR SUPPORTING STRUCTURE.USE OF ASBESTOS4.1.32 Asbestos shall not be included in thecomposition of materials, products or equipmentunless:

(a) It is essential for the satisfactoryperformance of the materials, products orequipment.

(B) THE USE OF ANY ALTERNATIVE

If the requirement conditions apply, asbestos shallonly be used when the Design Authority hasobtained prior written agreement for the use of thematerial from the Aeroplane Project Director.



MATERIAL WOULD BE EQUALLY OR MOREHAZARDOUS.4.1.33 ANY MATERIAL, PRODUCT OREQUIPMENT WHICH CONTAINS ASBESTOSSHALL BE MARKED IN ACCORDANCE WITHTHE SYMBOL AND WORDING OFPACKAGING FORM FPKG 770, REPRODUCEDIN DEF STAN 81-41 PART 6.CONTROLLED TIGHTENING OF BOLTSOPERATIONAL REQUIREMENTS4.1.34The application of controlled tightening tothose bolts in joints which may require dismantlingduring servicing shall be limited to those jointswhere the loss of tightness could result inunacceptable degradation of structural integrity, orfailure of the part to perform its function.

See Leaflet 3

4.1.35 The bolt elongation technique shall not beused in such applications.

See Leaflet 3

4.1.36 WHEN THE TORQUE LOADINGTECHNIQUE IS TO BE USED, ADEQUATEACCESS SHALL BE AVAILABLE FOR THEUSE OF STANDARD SERVICE TOOLS.SAFETY REQUIREMENTS4.1.37 THE DRAWING SHALL SHOW THETYPE OF PRE-LOADING TO BE USED, THENECESSARY DATA TO ACHIEVE THECORRECT PRETENSION AND THELUBRICANT REQUIRED.

Consideration shall be given to controlling the pre-load of bolts in the following applications:

(a) heavily loaded tension joints,

(b) heavily loaded shear joints,

See Leaflet 3



(c) joints with a group of bolts sharing theload,

(d) joints subject to thermal strain (see 4.1.39),

(e) joints where the manner of carrying load inthe joint is affected by the pre-load of a bolt,

(F) JOINTS SUBJECTED TO CYCLICLOADING

4.1.38 THE LUBRICANT SHALL BECOMPATIBLE WITH ANY SEALS OR NON-METALLIC MATERIALS IN THE VICINITY.4.1.39 Where a joint is subject to sufficient heat toaffect the torque values on re-assembly of threadeditems this shall be identified on the drawings,together with instructions on:

(a) Whether items can be re-used if the appropriaterun-down maximum and minimum torque valuesand the final tightening torque value can be achievedwhen the used items are re-assembled.

(b) Whether the items are to be replaced on re-assembly.

(C) THE EXTENT TO WHICHRECONDITIONING, RE-COATING/RE-LUBRICATION OR RE-PLATING (WHERE



APPROPRIATE) IS PERMITTED.REDUCTION OF VULNERABILITY TO BATTLE DAMAGE4.1.40 Cockpit furnishings, paints, finishings andplastic materials having good repairability andresistance to the nuclear, biological and chemicaleffects of Defined and Specified Threats shall beused in preference to any alternative whereverpossible.

See Clause 9.9

4.1.41 PREFERENCE SHOULD BE GIVEN TOSTRUCTURAL MATERIALS WHICH AREEASILY REPAIRABLE.4.1.42 THE RESPONSE OF STRUCTURALADHESIVES TO NUCLEAR, BIOLOGICALAND CHEMICAL EFFECT SHALL BECONSIDERED BEFORE THEY AREINCORPORATED IN THE DESIGN.


4.2 MARKING OF AEROPLANE PARTS

4.2.1 This information was previously published as Chapter 404 of DEF STAN 00-970 Issue 1. This Clause defines requirements for the marking of aeroplaneparts to make them easily identifiable. The requirements of this Clause shall apply to all aeroplane parts.

4.2.2 Definitions of terms used in this clause are contained in Part 0


GENERAL4.2.3 The design authority shall be responsible forthe selection of the types of marking to be used andthe method(s) by which such markings are appliedto a particular part.

In addition to the markings required by thisClause, the contractor shall apply such permanentand/or temporary markings as may be called for bythe Aeroplane Project Director.

4.2.4 No method of marking shall be used in such amanner or in such a place that it would reduce thestrength or the life or affect the performance of thepart or the aeroplane in any other way.4.2.5 The method of marking adopted shall notincrease the risk of corrosion. In particular, where aplate made from a different material to thecomponent is affixed to it for marking purposes,precautions shall be taken so that no risk ofcorrosion is introduced.4.2.6 Details of identification markings used, themethods by which they are applied and theirlocation shall be stated on the drawing of the part

See DEF STAN 05-10.

4.2.7 The number of markings on any one part shallbe kept to a minimum



4.2.8 Parts shall be marked so that they can beeasily identified for maintenance purposes whenassembled on the aeroplane4.2.9 Identification symbols which can be mistakenas representing a direction of movement or flowshall not be usedMARKINGPARTS4.2.10 Each part shall be marked with:

(a) the detail drawing number for the part or acode number for the part or a code numbercorresponding thereto; the latter beingrecommended in all cases where the drawingnumber consists of more than 5 characters,

(b) the 13-digit NATO Stock Number (NSN),wherever possible prefixed by the relevant ServiceDomestic Management Code (DMC). If the spaceavailable is inadequate for the full NSN to be used,then the last 7 digits may be shown.

The contractor may impose such private markingsas necessary to facilitate the assembly of partsprovided that they are not located in a positionwhere they will confuse other identification marks.

Note:Items which are too small or fragile tocarry the required marking, will be identified bythe marking required to be put on the packagingby DEF STAN 81-41 Part 6.

4.2.11 Where 2 or more parts are identical andtherefore strictly interchangeable but are used ondifferent types of aeroplanes, the same numbersshall be used. For parts which differ from eachother as regards 'hand' (though otherwise identical),different numbers shall be allotted.4.2.12 Non-standard hexagon headed bolts havinga feature significantly different from the basicstandard but which is visually indistinguishable shall



have a raised disc on the head in addition to the partnumber.4.2.13 The following parts are, however, (subjectto 4.2.3) excluded from all forms of marking:

(i) hardened steel springs,

(ii) standard bolts and screws of any diameternot greater than 5.6 mm (7/32in), nuts of anydiameter not greater than 9.5 mm (3/8 in), ordinaryand spring washers of any diameter,

(iii) split pins, taper pins and parts similar inrespect of size.ASSEMBLIES4.2.14 Elements of assembled parts as defined inPart 0 under (i) shall be marked in accordance withthe requirements of 4.2.10.4.2.15 The fabricated parts as defined in Part 0under (ii) shall be marked in with the number of theassembly drawing. The elements shall be marked inaccordance with the requirements of 4.2.10 if theseelements are stocked separately or if so required bythe Aeroplane Project Director.COMPONENTS4.2.16 Components or complete units includingthose assemblies that are regarded as complete unitsfor service storage shall be marked with thefollowings:



(a) The name and mark or type number of the item.

(b) The 13 digit NATO Stock Number (NSN) andwherever possible prefixed by the Service DomesticManagement Code (DMC).

(c) The manufacturer's name, or NATOmanufacturer's 5-character code (if allotted).

(d) The serial number (where required). Contractors' symbols shall precede all serialnumbers. The symbol/serial number combinationfor any part shall not have been used previously forany other part or component on the same aeroplane.

(e) Any additional identification marking requiredby the contract or particular specificationAIRFRAME COMPONENTS4.2.17Components such as fuselages, mainplanes,control surfaces, alighting gears, etc, shall bear aSerial Number Plate and a Modification Record Plate. Where the fuselage, wing, etc, is built insections to comply with the requirement of Clause4.4 similar plates shall be fixed to each section. Themethod of fixing the plate shall not increase the riskof corrosion, stress corrosion or fatigue.

(a) The Serial Number and Modification RecordPlates shall be manufactured of approvedcorrosion-resistant material. Their dimensions andinscriptions shall be in accordance with Figs. 1and 2 where practical and the plates whencompleted may be protected with clear varnish asnecessary.

(b) The Serial Number Plate shall contain theNATO Stock Number and wherever possibleprefixed by the Service Domestic ManagementCode, the contractor's symbol/serial number for the

See DEF STAN 05-123 for details of themodification recording procedure.



component, drawing number and issuenumber/letter to which manufactured and thestamp of the approved member of the contractor'squality/inspection department accepting thecomponent. It shall be permanently fixed to themain structure of the component to which it relatesand so positioned that it is possible to read thedetails on the plate without resort to dismantling. It is permissible to provide special removablepanels if necessary for examination and such panelsneed not be of the quickly detachable type.

(c) The Modification Record Plate shall bear theNATO Stock Number and the contractor'ssymbol/serial number of the component to which itrelates and shall be located adjacent to itscompanion serial number plate but may bedetachable for the endorsement of modificatingnumbers provided that, when fitted, it is positivelylocked in position. When it is not detachable itshall be mounted in a position where stamping ofnumbers on the plate will not damage thesurrounding structure.

OIL TANKS4.2.18All oil tanks whether they are covered orotherwise shall have the NATO Stock Number, theserial number, drawing number, issue number andinspector's stamp applied in white colouring bystencil. Such markings shall be reproduced in asimilar manner on the outside of the self-sealing or



crash-proof cover, where fitted, in a positionadjacent to the inspection access panel.FUEL TANKS4.2.19 The marking of fuel tanks shall be inaccordance with the requirements of SpecificationNo. DTD 1101.REPAIRABLE PARTS4.2.20 During system development andprocurement phases the MOD, in conjunction withthe manufacturer and in accordance with theprocedures of DEF STAN 05-123, will identifythose items perceived to require regular repair inService or Industry. During initial manufacture themanufacturer shall allocate to each item a'Repairable Component Tracking Serial Number'(but see guidance) to enable them to be trackedduring Repair and throughout their Service life.

This Repairable Component Tracking SerialNumber shall be confined to 13 alpha-numericcharacters in accordance with AECMASpecification 2000M 'International Specificationfor Materiel Management - Integrated DataProcessing for Military Equipment: Appendix 1'.

Where the contractor has allocated a serialnumber already, for identification or otherpurposes, this serial number will be utilised byMOD for repair control purposes, and there willbe no need to allocate an additional RepairableComponent Tracking Serial Number.

RECONDITIONED PARTS4.2.21 Components which have been reconditionedshall have a new Serial Number Plate affixed eitheralongside the existing one or, if this is notpracticable, on top of it. The new plate shall showthe original markings with the original serial numberprefixed by the reconditioning contractor's symbolfollowed by the letter 'R'. In no circumstances arethe old markings to be removed.

Where used the Repairable Component TrackingSerial Number is to be retained unaltered.

TYRESPROTOTYPE TYRES4.2.22 Each new type of tyre shall be defined by aThe tyre drawing will give the dimensions of the



drawing prepared by the tyre firm and prototypetyres will be known by this drawing number.

tyre and wheel rim, its load deflectioncharacteristics over the permissible range ofinflation pressures, and particulars of the tyreconstruction in general terms

PRODUCTION TYRES4.2.23For production tyres, the stores referencenumber shall be added to the drawing. When a tyredesign is altered in such a way as to affect itsapplication, the drawing number and storesreference shall be changed.

Tyres intended for the same, application will bearthe same stores reference number.

SIZE OF MARKINGS4.2.24 The markings shall be in accordance withthe requirements of Specification No. DTD 1097.TRANSPARENT COMPONENTS4.2.25 All markings shall (as signified on thedrawing) be in a readily visible position wheninstalled in the aeroplane, and the lettering shall belarge enough for all serial and part numbers to beeasily readable.

A preferable standard serial number code wouldinclude; the manufacturer's code number,manufacturer's plant number, the date (eg 01June 83), followed by a serial number taken froma series of numbers which start from one eachday.

AS-CAST ACRYLIC SHEET4.2.26Transparent components such as windows,windscreens, panels and canopies made from as-castacrylic sheet to DTD 5592, shall be marked by oneof the following methods:

(a) A marked metal label attached to the, metalframe.



(b) An engraved acrylic label attached with anapproved cement to the fibre-glass or terylenereinforced edge member.

(c) Written in a suitable marking ink direct on tothe fibre-glass or terylene reinforced edge member,and covered with a thin layer of an approved acryliccement.

(d) Written direct on the transparency itself witha suitable marking ink PRIOR TO ANNEALING.STRETCHED OR PRESSED ACRYLIC SHEET4.2.27 Transparent components made fromstretched or pressed acrylic sheet shall be marked byone of the following methods:

(a) Any of the methods mentioned in 4.2.26provided subsequent annealing as mentioned in4.2.26 (d) is not used.

(b) By abrasive blasting through a stencil using400 mesh white alumina. The depth of markingshall not exceed 0.005 mm.GLASS4.2.28 Transparent components made from glassshall be marked by one of the following methods:

(a) Assemblies may have a small metal part numberor serial number label laminated within the, paneland near the panel edge, or in the case of an air



space design, the part number or serial number labelmay be attached within the air space with anapproved silicone or polysulphide adhesive.

(b) Single piece thermally toughened glasscomponents may be marked by an approvedabrasive blasting process through a suitable stencilor alternatively.

(c) Thermally toughened glass may be markedwith a ceramic paste subsequently fired duringtoughening.

(d) Chemically toughened glass shall be markedusing an air drying ceramic paste or paint.LOCATION OF IDENTIFICATION MARKINGS4.2.29Markings shall not be placed in thefollowing positions:

(a) On bearing surfaces or areas subject to wear.

(b) On mating surfaces or where bolts etc., mayobscure the markings.

(c) On areas subsequently removed or obscured bymechanical or chemical processing, except fortemporary marking.

(d) In areas where there may be a stressconcentration, such as near holes, on fillets, bends,

Note: It is permissible to mark stressed areasusing the Marking Ink Method



radii, lug faces or edges of parts.METHODS OF IDENTIFICATION MARKINGPHYSICAL IDENTIFICATION METHODS4.2.30 Physical identification methods shall not beused as follows:

(a) On steels of maximum specified tensile strengthexceeding 1450 MPa.

(b) In regions of high stress or where fatigue maybe critical.

(c) On areas of high grade surface finish.

(d) On surface hardened or nitrided areas.

(e) On materials thinner than 0.9 mm.

(f) On welded containers.

(g) On any surface that has been painted, plated,anodised or conversion coated.

(h) On hydraulic pipes or on the pressurisedwalls of ducts.

However, physical identification may be usedunder requirements (b) at the designers discretionif all the safeguards contained in this Clause andLeaflet 5 are followed.

For example: metal die stamping, engraving,vibro-percussion engraving.

Leaflet 5 provides details of recommendedmethods of identification marking and shall betaken into consideration when selecting methodsfor the marking of aeroplane parts.

4.2.31 Sharp cornered borders, sharp angles andcuts shall be avoided and the depth of markingshall be kept to a minimum consistent with legibilityMARKING INK4.2.32 Marking inks, paints and lacquers shall be



compatible with the applied paint scheme or thebase material or protective treatment, if not painted. The colour of the marking shall be a distinctcontrast with the background. For titanium alloysinks shall be halogen free.LABELS4.2.33Where transparent labels are used the paintand adhesive shall be compatible with the part andlabel.4.2.34 The method to be used to attach metallabels to the part shall be specified on the drawing. The label shall not foul moving parts or causedamage if it becomes detached4.2.35 Identification by marking ink, transparentplastic labels or metal labels and self-adhesive labelsshall not be used to identify parts that will be incontact with powerful oxidants such as hydrogenperoxide, liquid oxygenELECTROCHEMICAL MARKING4.2.36 Electrochemical Marking shall not be usedon:

(a) anodised aluminium parts,

(b) magnesium parts,

(c) non-metallic parts,

(d) steels of maximum tensile strength exceeding1550 MPa.


4.3 PROTECTION OF STRUCTURE

4.3.1 This information was previously published as Chapters 405, 406 and 409 of DEF STAN 00-970 Issue 1 and is similar to JAR 25.609. The clausecontains the requirements for the protection of aeroplanes and their equipment against corrosion and environmental deterioration including exfoliationcorrosion of aluminium alloys and stress corrosion cracking. General protective materials and processes are referred to in Table 1.

REQUIREMENT COMPLIANCE GUIDANCEBASIC OPERATIONAL REQUIREMENTS4.3.2 THE AIM SHALL BE THAT ALL PARTSOF THE AEROPLANE, BOTH INSIDE ANDOUTSIDE, SHALL BE SO DESIGNED,PROTECTED, DRAINED AND VENTED THAT,WHEN THE AEROPLANE IS MAINTAINED INACCORDANCE WITH THE SERVICINGSCHEDULE, THERE WILL BE NOUNACCEPTABLE LOSS OF AIRWORTHINESSAS A RESULT OF WEATHERING,CORROSION, ABRASION, UNAVOIDABLEMECHANICAL DAMAGE TO PROTECTIVETREATMENT DURING NOMINALMAINTENANCE OR OTHER CAUSES.

The aeroplane should therefore be able towithstand satisfactorily:

(a) the effects of standing for long periods inthe open in all weathers, including the corrosiveeffects of contamination by an industrialatmosphere,

(b) the corrosive effects of operating from salt-laden runways and of flying low over the sea, and

(c) on Naval aeroplanes, the corrosive effectsof salt spray and funnel gases, when stowed in theopen or operating from the deck of a ship.

Notes: 1 Requirements relating to theextremes of temperature and humidity that maybe experienced on the ground and in flight aregiven in Clause 7.1.

2 Requirements on operational,camouflage and identification markings are givenin Clause 7.3.

EXCLUSION OF CONTAMINATING LIQUIDSGENERAL4.3.3 ALL STATIC JOINTS SHALL BE SEALEDTO PREVENT THE INGRESS OF LIQUIDS.

(a) Unless otherwise excepted in 4.3.110 - 114sealing shall be effected by wet assembly with asuitable sealant, or jointing compound (4.3.108 -109).

Particular care shall be taken to prevent thewetting of equipment and heat and soundproofing material.


REQUIREMENT COMPLIANCE GUIDANCE(b) As a supplement to the sealant within the lapjoints, the application of sealing or caulkingcompounds to exposed edges of the lap to preventthe ingress of liquids shall be considered.

RAIN AND AIRBORNE SPRAY4.3.4 PARTICULAR CARE SHALL BE TAKENTO PREVENT WATER LEAKING INTO, ORBEING DRIVEN INTO, ANY PART OF THEAEROPLANE EITHER ON THE GROUND ORIN FLIGHT. ALL WINDOWS, DOORS,PANELS, CANOPIES ETC SHALL BEPROVIDED WITH SEALINGARRANGEMENTS SUCH THAT THE ENTRYOF WATER IS PREVENTED WHEN THESEITEMS ARE CORRECTLY CLOSED.

Where sealing is not practicable, precautions shallbe taken to ensure that any water that does gainaccess to the interior of the aeroplane does notconstitute a direct or indirect danger.

See also 7.1.16 - 21 and 7.1.26.

OTHER FLUIDS4.3.5 THE DESIGN OF THE AEROPLANESHALL BE SUCH AS TO MINIMISE THEPOSSIBILITY THAT ANY FLUID - WHICHMAY LEAK FROM A SYSTEM, ENTER THEAEROPLANE FROM THE OUTSIDE,CONDENSE ON COLD SURFACES (EGPRESSURE CABIN WALLS) OR MAY BESPILT WITHIN THE AEROPLANE - WILLCAUSE CORROSION.

(a) The following fluids shall be taken intoaccount:

(i)Water, cleaning fluid, ground and airbornede-icing fluids, fuel, oil, hydraulic fluid,battery electrolytes, and fluids associated withgalley and toilets.

(ii) Slush (including grit, salt or other runwayde-icing chemicals) which will impinge on, orpossibly enter, parts of the aeroplane duringtaxying, take-off or landing on precipitation-covered runways.


REQUIREMENT COMPLIANCE GUIDANCE(b) The use of corrosive fluids should be avoidedin aeroplane systems (eg in toilets). Adequateaccess, to the satisfaction of the CSDE or NATECProject Team, shall be provided for themaintenance of all joints and unions in pipe lines.

4.3.6 Particular attention shall be given to thedesign of those compartments where liquids arelikely to be spilt. Sealed floors with suitabledrainage shall be provided in battery areas, galleysand toilets. Urinals, sick basins, lead-away pipes,and collector boxes shall be manufactured fromurine-resistant material.

See also Leaflet 12.

4.3.7 Heat and sound proofing materials shall notcause corrosion either by direct contact or as aresult of leachants if wetted. Precautions shall betaken against the possibility of corrosion caused bymaterials acting as a wick .

Suitable provision shall be made so that it ispracticable to inspect for any signs of corrosiondue to these causes.

DRAINAGE AND VENTING4.3.8 All compartments in the structure, includingthose in control surfaces, cockpits and cabins, shallbe completely sealed or adequately drained andvented, both on the ground and in flight. Thedesign of each drainage system shall be such that itwill still be effective with any one drain or drain-hole blocked. Pockets in the structure which cannotbe drained shall be filled with inert, non-absorbent,caulking or filling material.

(a) Particular attention shall be given to thelocation and size of internal drain-holes tominimise the possibility of fluids being trapped inthe structure and being prevented from running toa drain. Care shall be taken to avoid undrainedpockets especially where liquids could freeze andso jam mechanisms.

(b) The position of drain-holes shall be shown oncomponent drawings and a complete key shall begiven in the Aeroplane Servicing Manual.

(a) In pressurised compartments, automaticdrains, that open when pressure is released, arepreferred.

(b)Honeycomb structure is dealt with in 4.3.58.

ACCESS FOR EXAMINATION


REQUIREMENT COMPLIANCE GUIDANCE4.3.9 The aim shall be to provide, access to everypart of the structure to facilitate visual examinationfor corrosion or deterioration at a reasonablemanhour cost.

The Contractor shall demonstrate compliancewith the requirement to the satisfaction of theCSDE or NATEC Project Team.

Although visual aids (eg endoprobes) may beused to meet this requirement, it is desirable to beable to examine the majority of the structurewithout visual aids. Ideally, it should be possibleto gain access simply by removing access panels.

DEHUMIDIFICATION OF AIRCRAFT STRUCTURE AND SYSTEMS4.3.10 The Aircraft Specification will identify:

(i) Whether dehumidification is required onindividual aircraft, or whether areadehumidification is to be used. If dehumidificationis required on individual aircraft it must beprovided for in the aircraft design.

(ii) For on-aircraft dehumidification, to whatextent standard Service equipment is to be used.

(iii) Whether specific air flow and air changerates are required.

(a) Dehumidification of aircraft whilst on theground, to reduce metal corrosion and improvethe reliability of electrical and avionics systems,may be a requirement for aircraft.

(b) Trials have shown that there are significantbenefits to be achieved by providing a supply ofdry air, from a commercial dehumidifier, to theaircraft structure and systems whilst the aircraft ison the ground. These benefits are; a reduction inmetal corrosion in the structure and enginecomponents, and an increase in reliability of theelectrical and avionic systems.

(c) Dry air may be introduced to the aircraftstructure; through the Environmental ControlSystem, through the engine intakes and/orspecifically designed intakes, or by using blanksand trunking if this is called up in the AircraftSpecification.

(d) Dehumidification may be applied toindividual aircraft in the open air or bydehumidifying the hangar or Aircraft Hardened


REQUIREMENT COMPLIANCE GUIDANCEShelter during long term storage. Either methodrequires the structure and systems to allow forthe free passage of air.

(e) Dehumidification is not to be assumed as ameans of preventing corrosion to meet thestructural life requirement or to meet thereliability requirement of the AircraftSpecification.

This guidance was previously issued as Leaflet409/7.

CHOICE OF MATERIALS IN RELATION TO THE AVOIDANCE OF CORROSION4.3.11 Materials for each given use are chosen inthe first place for their appropriate mechanical andother physical properties but their corrosion withinthe environment of the given use shall also beconsidered.

Materials with lower susceptibilities to corrosion,corrosion fatigue, stress corrosion or hydrogenembrittlement should be chosen where possible,and unnecessarily strong but susceptible materialsshall be avoided.

Joints between dissimilar electrically conductivemetals or other electrically conductive materialsare often unavoidable, but the advice in Leaflet10 shall be considered in relation to the serviceenvironment of each use. In the later paragraphsof this Chapter, methods are laid down forconverting C and D contacts (Leaflet 10 para2.3) into B contacts by the application ofelectroplated coatings to the more noble metal(eg the cadmium or tin plating of copper basematerials in contact with aluminium alloys,4.3.64) but it must be realised that in the morecorrosive environments the interposed protectivemetal coating will have only a limited life.

4.3.12 IF CORROSION CAN BE CAUSED BYTHE DECOMPOSITION PRODUCTS FROM A

DEF STAN 03-13


REQUIREMENT COMPLIANCE GUIDANCEMATERIAL, SUCH MATERIAL SHALL NOTBE USED UNLESS PRECAUTIONS ARETAKEN TO ENSURE THAT DECOMPOSITIONDOES NOT OCCUR DURING THE NORMALOPERATION OF THE AEROPLANE.DESIGNATION OF THE REQUIREMENTS FOR THE PROTECTION OF PARTS AND ASSEMBLIES4.3.13 The treatments appropriate to a detail itemshall be indicated on the drawing of the item andany to be applied during and after assembly, on theappropriate assembly drawing.

(a) This may be by direct reference to theappropriate material or specification number ormay be by coded reference to such information,which has been set down as a comprehensiveschedule included in the master drawings.

(b) Treatment requirements shall be sufficientlyspecific that they permit only those processingoptions that are acceptable, (eg, 'anodise to DEFSTAN 03-24, Type 2, chromic acid').

The requirements for the protection of parts andassemblies used in the construction of aeroplanesare given in the subsequent paragraphs of thisclause.

TREATMENT OF METAL PARTS, GENERALGENERAL REQUIREMENTS4.3.14 All metal parts shall be given an appropriateprotective treatment as set out in subsequentparagraphs unless otherwise excepted (4.3.25 - 32).

In the case of fasteners see Para. 4.3.18.

CLEANING4.3.15 All metal parts shall be cleaned in accordancewith DEF STAN 03-2.SURFACE TREATMENT4.3.16 All metal parts shall be given a surfacetreatment or plating treatment as specified in theappropriate clauses 4.3.33 - 75 below.

Components shall not be treated in the assembledcondition unless danger of corrosion by trappedtreatment chemicals can be completely avoided andthere is no danger of removal or degradation of


REQUIREMENT COMPLIANCE GUIDANCEsealants, jointing compounds etc.

PAINTING4.3.17 Where called for in the clauses (4.3.33 - 75below), metal parts shall be painted.

Painting shall be in accordance with DEF STAN 03-7 and with the aeroplane specification.

Note: In the chapter, the meanings of the terms'paint', 'primer', 'etch primer', 'finish' (in relation topainting), 'finishing coat' etc., are as defined inBS 2015 'Glossary of paint terms'.

4.3.18 Fasteners shall not be painted prior to use,but shall where required, be painted after assembly.

See 4.3.24

STANDARD PAINT SCHEMES FOR ALL AEROPLANESGENERAL4.3.19 Etch primer is regarded as pretreatment, notas a full part of the paint scheme-itself. It is notacceptable where high resistance to aggressivefluids (eg phosphate-ester hydraulic fluids, castor oiland synthetic lubricants) is required.

(Excluding areas made of doped fabric)

EXTERIOR SURFACES4.3.20 All surfaces of an aeroplane that are exposedto the external environment either permanently, aspart of the exterior construction, or transitorily to asignificant extent, and are made of metals requiredto be painted in accordance with the requirementsof this chapter, or that are to be painted for the sakeof appearance or to meet operational requirements,shall be given a full paint scheme of at least primerand finish to give, when dry, a minimum filmthickness of 50m.

Note: External surfaces include wheel-wells,undercarriages, wing-folds, air brakes, wing flaps,fairings or other areas which may be occasionallyexposed to the external environment or intowhich water may be driven or collect.

INTERIOR SURFACES (HEAVY DUTY)4.3.21 Interior surfaces subject to heavycondensation, aggressive hydraulic fluids, or otherpotentially corrosive fluids noted 4.3.4 - 7, shall


REQUIREMENT COMPLIANCE GUIDANCEcoated with a full scheme of at least primer andfinish, or two full coats of primer, resistant to thesefluids. In all cases interior finishing schemes forheavy duty protection shall have, when dry, aminimum film thickness of 40m.INTERIOR SURFACES (NORMAL)4.3.22 Interior surfaces, not subject to heavycondensation or severe contamination withaggressive fluids or special requirements for colour,shall be coated with epoxy primer to DTD 5567unless otherwise specified, to give a minimum filmthickness when dry of 20m.

Interior surfaces of integral fuel tanks. This isdealt with in detail in 4.3.77 - 79.

OTHER PAINT SCHEMES4.3.23 Steel parts forming part of mechanisms, maybe painted with stoving enamel (DTD 56, BS X 31). Other paint schemes and other organic coatingschemes, eg plastic coatings and anti-frettingcoatings, may be used for the purposes for whichthey are approved.PAINTING IN RELATION TO ASSEMBLY4.3.24 Components shall be given at least a coat ofprimer and preferably painted to the requirements of4.3.19 - 4.3.23 before assembly.

(a) Components which have only been primedbefore assembly, and which require a finishing coatafter assembly, should preferably be primed againoverall.

(b) After assembly, where required, all fastenersshall be painted according to 4.3.19 - 23, (See also4.3.53 - 54) and all damaged areas shall be paintedaccording to 4.3.118 - 121.

Excluding the specific cases covered by 4.3.25 -32.

For wet assembly see 4.3.104 - 116 and fortouch-up after assembly see 4.3.117 - 121

EXCEPTIONS AND SPECIAL CASES


REQUIREMENT COMPLIANCE GUIDANCE4.3.25 Bushes. Bushes shall be wet-assembled(4.3.104 - 116) even though the greater part of thejointing compound is exuded from the fit. Busheswith flanges shall be similarly wet-assembled so thata fillet is formed around the flange (4.3.105).

(a) Where bushes are inserted into aluminium ormagnesium alloys, especially those exposed to theatmosphere, (eg in undercarriage assemblies),particular care shall be taken in the application ofprotective surface treatments and in the preventionof ingress of water to the mating surfaces. Wherea plating treatment is required to prevent galvaniccorrosion, eg the cadmium or tin plating of copper-alloy bushes (4.3.64), the maximum thickness ofplate shall be applied consistent with satisfactoryassembly.

(b) As a supplement to sealing within the joint, theapplication of sealing or caulking compoundsalong the lap shall be considered

4.3.26 Metallic shims. Both sides of the shim shallbe coated with sufficient wet assembly material sothat a fillet is formed covering the edge of the shim.

(a) When shims are used during assembly, specialattention shall be paid to wet assembly.

(b) As a supplement to sealing within the joint, theapplication of sealing or caulking compoundsalong the edges of the lap shall be considered.

4.3.27 Lubricated parts. Surfaces that run in amaintained environment of oil or grease generallyrequire no protective treatment Magnesium alloyparts shall, however, be protected to therequirements of DTD 911.

See also 4.3.42 and 4.3.57.

4.3.28 Tube and pipes. Tubes and pipes carryingoperating fluids need not be painted internally. Ifthey are painted, the paint scheme chosen shall beresistant to the fluid and shall be suitable for


REQUIREMENT COMPLIANCE GUIDANCEcontinuous immersion in the fluid.4.3.29 Contact with fabric dope. To preventsoftening of the finishing coat by dope solvents, allsurfaces liable to come into contact with fabricduring doping operations shall be treated so as to becompatible with dope.

This requirement does not apply to surfaces towhich fabric is attached by an adhesive.

4.3.30 Rubbing surfaces. These may requirecoatings or treatments to prevent galling or wear.

In making a choice the Contractor shall take intoaccount their adequacy in protecting againstcorrosion in the environment in which the partswill operate, and their effects upon fatigue life.

See also 4.3.40 and 4.3.57.

4.3.31 Electrical bonding. To achieve satisfactoryelectrical bonding to the aeroplane structure, it issometimes necessary to re-move, or to omit locally,any surface protection. At such bonding pointsprecautions shall be taken to prevent the ingress ofany corrodent or operating fluid by suitable use ofjointing compounds, sealants and caulking materials,followed where possible by painting.4.3.32 Holes machined after painting. Except in thecase of magnesium alloys, holes and countersinksmachined in parts which have been painted need notbe given any protective treatment prior to wetassembly (4.3.105 - 116) with fasteners (4.3.106-107), or insertion of bushes (4.3.25). Afterassembly the parts shall be further protectedaccording to 4.3.24 or 4.3.25.TREATMENT OF NON-CORROSION-RESISTING STEELS4.3.33 These requirements apply to all parts, including

fasteners, made of steel containing less than 9%chromium.


REQUIREMENT COMPLIANCE GUIDANCEGENERAL REQUIREMENTS4.3.34 Cleaning. All steels shall be cleaned (DEFSTAN 03-2) and, unless otherwise excepted, givenone of the treatments in 4.3.34.4.3.35 Standard treatment for all parts for usebelow 235C Cadmium plating (DEF STAN 03-19)followed by painting.

(a) Prior to painting the cadmium shall be eitherpassivated (DEF-130) or etch primed (DEF STAN80-15 and proprietary alternatives covered byapproved specification for paint schemes) if etchprimer is acceptable, (see 4.3.19). Fasteners shallbe passivated (DEF-130) after cadmium plating,and painted only after assembly (4.3.18 and4.3.24).

(b) Alternatives to cadmium plating in specialcases:

(i)Aluminium coatings. Coating withaluminium by an approved process followedby painting, and for large parts and parts withwide tolerances, spraying with aluminium (BS2569: Part 1) and then painting. Unpaintedaluminium coatings may be suitable for use atelevated temperatures

(ii) Zinc coatings. Parts subject inservice to temperatures between 235C and350C may be zinc plated (DEF STAN 03-20), chromate passivated (DEF-130) andpainted with a suitable heat-resisting paintscheme. Except on Naval aeroplanes, other


REQUIREMENT COMPLIANCE GUIDANCEaeroplanes designed to operate in a marineenvironment, and on fasteners, zinc platingmay be used in place of cadmium plating onnormal interior surfaces (as defined in 4.3.22)of parts subject to service at any temperaturebelow 350C.

(iii) Phosphate coatings. Phosphatetreatment to Class I or II of DEF STAN 03-11 followed either by painting or othersuitable approved coating schemes, eg plasticcoatings and anti-fret coatings (para 8.5.6),may be used when cadmium plating is nottechnically feasible or desirable.

(iv) Grade B parts only. These may bezinc coated by electroplating (DEF STAN 03-20) or any other suitable process, nickel ornickel/chromium plated (DEF STAN 03-10),tin plated (DEF STAN 03-8), tin-lead alloyplated or made from tinned steel (BS 2920). Tin coated parts shall not, however, be usedin contact with cadmium plated parts wherethe temperature in service may exceed 120C. The protective metal coating shall befollowed by etch priming and painting. Alternatively Grade B parts may be phosphatetreated (DEF STAN 03-11), followed bypainting or other suitable approved coatingschemes.



(v) Vacuum cadmium coatings: Cadmium coating by vacuum evaporation maybe employed (DTD 940) instead of cadmiumplating to DEF STAN 03-19.

HIGH STRENGTH STEELS4.3.36 Parts made of steel of maximum specifiedtensile strength exceeding 1450 MPa shall besubject to the special requirements of DEF STAN03-4.STRUCTURAL TUBING4.3.37 It shall be assumed that the inside of tubularstructures will breathe and that water will condenseand cause rusting from the inside unless substantialprotection is given. Prior to welding or otherassembly procedures, any manufacturing or heat-treatment scale shall be removed, (eg by pickling). Phosphate treatment plus slushing with an inhibitiveprimer is desirable, but if aqueous treatments areimpossible, (eg in a complicated welded structure),then insides shall be thoroughly slushed with asupplementary protective, eg PX-28, suitablythinned. Access holes shall be provided if neededand, whenever possible, shall be securely sealedafter the organic protective has been introduced. Where secure sealing is not possible drainage holesshall be provided.

Outer surfaces should be sprayed with aluminiumor plated with cadmium if possible but phosphatetreatment plus a full paint scheme is acceptable.

EXCEPTIONS AND SPECIAL CASES4.3.38 Springs. The advice in Defence Guide DG-10 shall be followed.

Where protection is required, cadmium plating andpaint is the preferred protective.


REQUIREMENT COMPLIANCE GUIDANCE4.3.39 Gun parts. Steel gun parts classified asairframe components (eg deflector chutes,ammunition belt feeds and guides) shall be treatedby Sherardising (BS 4921), hard chromium plating(DEF STAN 03-14) or electroless nickel plating(DEF STAN 03-5).4.3.40 Parts subject to wear. Where increased wear resistance is required, hard

chromium plating (DEF STAN 03-14) is in manycases an acceptable process. Electroless nickel(DEF STAN 03-5) or nickel plating (DTD 905)may be used in some cases. A number of otherapproved hard surfacing treatments are availablefor special application (DTD 941, DTD 943 andDTD 900). In making a choice, the Contractorshall take into account the adequacy of thetreatment in protecting against corrosion in theenvironment in which the parts will operate, and itseffect upon fatigue life.

4.3.41 Wire Ropes. Zinc coated wire ropes whichhave been treated with a lubricant duringmanufacture shall be used, and shall be installed assupplied.4.3.42 Lubricated parts. Surfaces that run in a maintained environment of

oil or grease need not be protected againstcorrosion. Phosphate (DEF STAN 03-11, Class 1)or black oxide (DTD 900) treatment may be givenif desired.

Note: Black oxide treatments should be avoidedwherever possible, and shall not be used on steelsof maximum specified strength exceeding 1450MPa. This restriction does not apply to surfacehardened parts or to parts made from 1% C 1 %Cr bearing steel.

4.3.43 Safety Harness Components. When Safety Harness Components are made fromnon-corrosion resisting steels and particles of paint

For design of Safety Harness Components seeClause 4.21.


REQUIREMENT COMPLIANCE GUIDANCEproduced in use by abrasion/wear could causedetriment to the operation/function of amechanism, then cadmium plating and passivationwithout further painting is the preferred protection.

TREATMENT OF CORROSION RESISTING STEELS4.3.44 These requirements apply to all parts, including

fasteners, made of steel containing not less than9% chromium.

GENERAL REQUIREMENTS4.3.45 Designs embodying corrosion resisting steelsshall avoid crevices wherever practicable. Wherecrevices are unavoidable these shall be sealedwherever possible with an approved sealant(4.3.105 - 109).

Where sealing is not practicable, (eg on movingparts), specialist advice shall be sought on theselection of a corrosion resisting steel with theoptimum combination of required properties andresistance to crevice corrosion).

In certain environments, especially maritime,corrosion resisting steels can suffer severe pittingcorrosion and advice shall be taken on the choiceof alloy and suitable protective schemes (Leaflet13).

4.3.46 All parts made from corrosion resisting steelsshall be cleaned by appropriate methods inaccordance with DEF STAN 03-2 to ensurefreedom from surface contamination.

In particular, the surfaces of forgings, castings,welds, "black" bars, heat treated parts etc, shallhave sufficient surface material removed to ensurefreedom from contamination caused bymanufacturing operations, where these surfaces areto be present on the finished parts.

4.3.47 Corrosion resisting steel wire ropes shall beinstalled as supplied.4.3.48 Parts for use above 235C shall not becoated with cadmium.PARTS IN CONTACT WITH ALUMINIUM ALLOY4.3.49 These parts shall be treated by one of thefollowing procedures:

(a) Cadmium plated (DEF STAN 03-19),optionally followed by painting, and then wet

See also 4.3.11 Guidance


REQUIREMENT COMPLIANCE GUIDANCEassembled (4.3.105 - 116).

(b) Zinc plated (DEF STAN 03-20), optionallyfollowed by painting, and then wet assembled (para24).

(c) Zinc sprayed (BS 2569, Part 1) optionallyfollowed by painting and then wet assembled (para24).

(d) Coated with aluminium by any approvedmethod (DTD 900) optionally followed by paintingand then wet assembled (4.3.105 - 116).

(e) Painted, and then wet assembled (4.3.105 -116) using, optionally, a sacrificial metal shim.

(f) Painted and assembled with a non-metallicseparator.

(g) Painted and assembled using an elastomericsealant.PARTS IN CONTACT WITH MAGNESIUM ALLOY4.3.50 Surfaces that will be assembled to contactmagnesium alloy shall be treated by one of thefollowing procedures and painted where this isfeasible prior to wet assembly (4.3.105 - 116).

(a) Cadmium plated (DEF STAN 03-19) andchromate passivated to the requirements of DEF-

See also 4.3.11 Guidance


REQUIREMENT COMPLIANCE GUIDANCE130,

(b) Zinc plated (DEF STAN 03-20) and chromatepassivated to the requirements of DEF-30,

(c) Zinc sprayed (BS 2569, Parts 1 and 2) andchromate passivated to the requirements of DEF-130,

(d) Shimmed with zinc which has been chromatepassivated to the requirements of DEF-130,chromate conversion coated 5000 and 6000aluminium series washers to DEF STAN 03-18,anodised aluminium washers, or with insulatingmaterial, eg, Nylon. The shim shall extend from thearea of contact to an extent sufficient to break anyelectrolytic path.TREATMENT OF ALUMINIUM AND ALUMINIUM ALLOYSGENERAL REQUIREMENTS4.3.51 ALL PARTS SHALL BE CLEANED (DEFSTAN 03-2) AND, WITH THE EXCEPTION OFTHOSE LISTED IN 4.3.53 - 60, SHALL BEGIVEN ONE OF THE FOLLOWINGTREATMENTS FOLLOWED BY PAINTING:

(a) Anodised (DEF STAN 03-24 or 03-25),

(b) Chromate filmed (DEF STAN 03-18),

(c) Etch primed (DEF STAN 80-15 and proprietary

Selection of Treatment. The considerationsaffecting the choice of the treatment from thoselisted shall include the following:

(a) The suitability of a casting for anodising, andto some extent the type of process used, willdepend on the alloy (DEF STAN 03-24, 03-25 and03-26).

(b) Sprayed metal coatings are not suitable forclose tolerance parts or for thin sheet.


REQUIREMENT COMPLIANCE GUIDANCEalternatives covered by approved specifications forpaint schemes) when treatments (i) or (ii) are nottechnically feasible or desirable and when etchprimer is acceptable (4.3.19),

(d) Sprayed with aluminium, aluminium-zinc alloy,or zinc (DEF STAN 03-3), followed by etch primerif etch primer is acceptable (4.3.19) or, in the caseof aluminium or aluminium-zinc alloy, by chromatefilming (DEF STAN 03-18).

(c) Some alloys containing a high proportion of alloying elements do not give good coatings byanodising or chromate filming. The treatment shallbe chosen that gives a film of good appearance andproperties.

(d) Where anodising is required as an aid toinspection for cracks, laps etc, or of gain flow, thechromic acid process (DEF STAN 03-24) shall beused.

(e) Selection of the treatment to be used will beaffected if parts are to be adhesive bonded.

(f) While sulphuric acid anodising processes (DEFSTAN 03-25 and 03-26) may reduce fatiguestrength, the chromic acid process (DEF STAN03-24) has comparatively little effect on fatigueproperties.

(g) Where fatigue is a major design considerationholes should not be anodised.

4.3.52 Parts that cannot be painted: These parts shall be anodised (DEF STAN 03-24 and 03-25).

Thin anodic films with relatively poor resistanceto corrosion can result when overagedaluminium-zinc alloys (eg BS L160, BS L161,BS L162) are anodised by the standard chromicacid process (DEF STAN 03-24).

EXCEPTIONS AND SPECIAL CASES4.3.53 Aluminium alloy fasteners other than rivets.


REQUIREMENT COMPLIANCE GUIDANCEExcept where used in electrical circuits, these shallbe anodised (DEF STAN 03-24, 03-25 and 03-26) before wet assembly. All fasteners shall be paintedwith a complete scheme after assembly.4.3.54 Solid rivets. Solid rivets used as suppliedneed not be given any surface protective treatmentprior to wet assembly (4.3.105 - 116). In the caseof rivets placed in the freshly solution treatedcondition care shall be taken to remove completelyall salt residues from the heat-treatment process. After assembly, exposed areas of all rivets shall bepainted with the paint scheme as specified in 4.3.24.4.3.55 Structural and other tubing. Tubing shallbe treated externally as in 4.3.51. Structural tubingshall be treated internally as in 4.3.51.

For the interior of tubes carrying operating fluids,see 4.3.28.

4.3.56 Welded parts. When welded parts are to beanodised, the chromic acid process shall be used(DEF STAN 03-24).4.3.57 Part subject to wear. Where the standard anodising processes (DEF

STAN 03-24 and 03-25) give insufficientresistance to wear, parts may be hard anodised(DEF STAN 03-26), chromium plated (DEFSTAN 03-14) or coated with hard facing material(DTD 900). Anodic films may be impregnatedwith approved solid film lubricants (DTD 900). Inselecting a process, the Contractor shall considerthe effect which the coating may have upon fatiguelife and corrosion resistance of the aluminiumalloy.

4.3.58 Honeycomb core. Core materials made ofAlternatively, the core material may be given an


REQUIREMENT COMPLIANCE GUIDANCEaluminium alloys shall, at the foil stage ofmanufacture, be given a chromate filming treatment(DEF STAN 03-18), or be chromic acid anodised(DEF STAN 03-24) if this is practicable. At theexpanded honeycomb stage of manufacture, an inertorganic coating shall be applied whereverpracticable to ensure good corrosion resistance ofthe honeycomb core material and good durability ofadhesive bonds.

etching treatment (DTD 900) but only if an inertorganic coating is to be applied subsequently.

4.3.59 Items adhesively bonded to honeycombcore.

The treatment of skins, etc. bonded to the coreshall be selected so that a good bond is obtainedand so that external surfaces are suitable forsubsequent protection (4.3.60).

4.3.60 Completed honeycomb structure. Theexternal surfaces of the completed honeycombstructure shall be protected by the appropriate paintscheme (4.3.19 - 23).INFLUENCE OF PROCESSING TEMPERATURE ON ALUMINIUM ALLOYS4.3.61 Temperatures used in processing (eg curingof organic coatings or adhesives) parts made fromaluminium alloy shall be such that there is nodeleterious effect upon the alloy properties.TREATMENT OF MAGNESIUM ALLOYS4.3.62 All parts shall be given the completetreatment specified in DTD 911.

Other protective schemes such as plastic coatings(eg Nylon) and anodic treatments (eg the HAE orDOW 17 processes) may be used subject tocompliance with the requirements of DEF STAN05-123, Chapter 107.

TREATMENT OF COPPER AND COPPER BASE ALLOYSGENERAL REQUIREMENTS


REQUIREMENT COMPLIANCE GUIDANCE4.3.63 All parts shall be cleaned (DEF STAN 03-2).Except as required by para 13.2, no furthertreatment is needed.

Parts may be painted if desired, in which case thecopper base material should be given a mildabrasive blasting, or be etched (DEF STAN 03-2)or etch primed (4.3.19).

PARTS IN CONTACT WITH OTHER METALS4.3.64 Aluminium alloys. The copper base materialshall be cadmium plated (DEF STAN 03-19) or tinplated (DEF STAN 03-8) and optionally paintedprior to wet assembly (4.3.105 - 107).4.3.65 Magnesium alloys. The copper base materialshall be cadmium plated (DEF STAN 03-19),chromate passivated to the requirements of DEF-130, and optionally painted prior to wet assembly (4.3.105 - 107).4.3.66 Non-corrosion resisting steels. A cadmiumcoating shall be interposed between the two metalsby plating (DEF STAN 03-19), optionally followedby painting, at least the steel surface and preferablyalso that of the copper base part prior to wetassembly (4.3.105 - 107).PARTS SUBJECT TO CONDENSATION4.3.67 Surfaces from which condensation can dripon to other metals shall be coated to preventdissolution of traces of copper.

Suitable coatings are: cadmium plate (DEF STAN03-19) preferably painted, tin plate (DEF STAN03-8), or paint (4.3.63).

4.3.68TREATMENT OF TITANIUM AND TITANIUM BASE ALLOYS4.3.69 These requirements apply to all parts including

fasteners.GENERAL REQUIREMENT4.3.70 All parts shall be cleaned (DEF STAN 03-Parts may be painted if desired, in which case the


REQUIREMENT COMPLIANCE GUIDANCE2). Except as required by 4.3.71 - 73, no furthertreatment is needed.

metal shall be pretreated by one of the followingprocesses:

(a) mild wet abrasive cleaning (DEF STAN 03-2,Methods D2 and D3),

(b) etch primer (4.3.19),

(c) pickling (DEF STAN 03-2, Method S),

(d) anodising (DTD 942).PARTS IN CONTACT WITH OTHER METALS4.3.71 Magnesium alloys. Contact with magnesiumalloy shall be avoided wherever possible.

Surfaces that will be assembled to contactmagnesium alloy shall be treated by one of thefollowing procedures and then painted where it isfeasible prior to wet assembly (4.3.105 - 116):

(a) zinc plated (DEF STAN 03-20) and chromatepassivated to the requirements of DEF-130,

(b) zinc sprayed (BS 2569 Parts 1 and 2) andchromate passivated to the requirements of DEF-130,

(c) coated with aluminium or an aluminium richcoating by an approved method and conversioncoated to the requirements of DEF STAN 03-18,

(d) shimmed with zinc which has been chromatepassivated to the requirements of DEF-130,


REQUIREMENT COMPLIANCE GUIDANCEchromate conversion coated 5000 and 6000aluminium series washers to DEF STAN 03-18,anodised aluminium washers, or with insulatingmaterial, eg, Nylon. The shim shall extend fromthe area of contact to an extent sufficient to breakany electrolytic path.

(e) anodised (DTD 942) and coated with a resincontaining molybdenum disulphide (DEF STAN91-19).

4.3.72 Aluminium alloy. Surfaces that will be assembled to contactaluminium alloy should first be painted but wherepainting is omitted, special attention shall be paidto wet assembly (4.3.105 - 107). Alternatively, thetitanium base material may be plated with zinc(DEF STAN 03-20), metallised with zinc (BS2569 Parts 1 and 2) or coated with aluminium oran aluminium-rich coating by an approved method. Titanium based materials may be anodised (DTD942) and where required coated with a resincontaining molybdenum disulphide (DEF STAN91-19).

4.3.73 Non-corrosion-resisting steel. No treatmentof the titanium is required. The steel may be coatedwith aluminium or an aluminium-rich coating orcoated with cadmium before wet assembly. It shallbe noted that cadmium can penetrate and embrittletitanium alloys under certain circumstances

See Leaflet 8.

PARTS IN CONTACT WITH NON-METALLIC MATERIALS4.3.74 Fluorinated organic polymers. The possibility ofSee Leaflet 9.


REQUIREMENT COMPLIANCE GUIDANCEcorrosion or stress corrosion of titanium alloys bycontact with fluorinated sealants shall beconsidered in the choice of materials

4.3.75 Phosphate ester hydraulic fluids. Titaniumalloys shall not be used in situations wherecontamination with phosphate ester hydraulic fluidcan occur at temperatures (eg, over 120C) atwhich the fluid can cause corrosion of the alloy.TREATMENT OF METAL TANKS (INCLUDING INTEGRAL TANKS)GENERAL REQUIREMENTS4.3.76 THE EXTERIOR SURFACES OF TANKSSHALL BE PROTECTED BY A TREATMENTAPPROPRIATE TO THE METAL FROMWHICH THEY ARE MADE. INTERIORSURFACES SHALL BE TREATED ASDESCRIBED BELOW.TANKS FOR AVIATION FUEL (INCLUDING INTEGRAL TANKS)4.3.77 ALUMINIUM AL LOY TANKS. THEINSIDE SURFACES SHALL BE ANODISED INCHROMIC ACID (DEF STAN 03-24) ORCHROMATE FILMED (DEF STAN 03-18) ANDSHALL THEN BE PAINTED WITH ACHROMATED EPOXY PRIMER (DTD 5567,SCHEME 1) OR WITH AN APPROVED (DTD900) ALTERNATIVE SCHEME RESISTANT TOFUEL CORROSION AND TO MICRO-BIOLOGICAL ATTACK. IN ADDITION TOTHE SURFACE TREATMENT AN INHIBITORCARTRIDGE OR BAG CONTAININGCALCIUM CHROMATE TO SPECIFICATION

The cartridge shall be installed in a position wherefree water present in the tank will come intocontact with it when the aeroplane is in thestanding position. There shall be no risk of thecartridge or its contents getting into other parts ofthe system.


REQUIREMENT COMPLIANCE GUIDANCEDTD 495 OR STRONTIUM CHROMATE IN ANAPPROVED CARTRIDGE, BAG OR TABLETFORM SHALL BE PROVIDED IN TANKS NOTHAVING SUMPS, EG SHALLOW WINGTANKS OR INTEGRAL TANKS. 4.3.78 Titanium alloy tanks. The inside surfacesneed no protective treatment.4.3.79 Use of copper-base materials. Consideration shall be given to the possibility of

adverse effects due to attack by aviation fuel oncopper-base materials with consequent degradationof fuel.

TANKS FOR WATER-METHANOL AND FOR DE-ICING FLUIDS4.3.80 Tanks made from corrosion resisting steel ortitanium need no protection inside. Tanks made ofaluminium base material shall be anodised (DEFSTAN 03-24, 03-25 and 03-26) and the presence ofother metallic components may necessitate furtherinternal protection with a suitable paint scheme.TANKS FOR DRINKING WATER4.3.81 Tanks made of corrosion resisting steel andtitanium need no protective treatment inside. Thosemade of aluminium alloy shall be anodised (DEFSTAN 03-24, 03-25 and 03-26) and painted withclear varnish to DTD 5562, the material used beingsuitable for contact with drinking water.TANKS FOR HIGH TEST PEROXIDE (HTP)4.3.82 The internal surfaces of HTP tanks shall betreated as described in DEF-60 and 61 asappropriate.TANKS FOR AVPIN


REQUIREMENT COMPLIANCE GUIDANCE4.3.83 Tanks for Avpin shall be made of corrosion-resisting steel containing not less than 5% nickel. They shall be treated only as in 4.3.46; paint shallnot be applied internally.EXFOLIATION CORROSION OF ALUMINIUM ALLOYS4.3.84 The aim shall be that all aluminium alloyparts of the aeroplane are so designed that when theaeroplane is maintained according to the servicingschedule there shall be no unacceptable loss ofairworthiness as a result of exfoliation corrosion.

(a) Necessary precautions shall be taken in thechoice of alloy, heat treatment, degree of working,grain structure, manufacturing methods, protectivetreatments, etc, to minimize the chance ofexfoliation corrosion occurring

(b) Wrought aluminium alloys categorised C inTable 1 of Leaflet 6, because of their highsusceptibility to exfoliation corrosion, shall not beused without the prior approval of the AeroplaneProject Director. In the case of aluminium alloysnot included in the Table application shall be madeto the Aeroplane Project Director forCategorisation.

(c) Aluminium alloys categorised C in Table 1 ofLeaflet 6, which have occasionally sufferedexfoliation corrosion in service, shall be used onlyafter consultation with materials specialists.

Leaflet 6 gives advice on means of complyingwith this para. Advice on testing procedures toestablish the susceptibility of aluminium alloycomponents is given in Leaflet 6.

STRESS CORROSION CRACKING4.3.85 THE AIM SHALL BE THAT ALL PARTSOF THE AEROPLANE ARE SO DESIGNED,PROTECTED, ASSEMBLED, DRAINED ANDVENTED THAT WHEN IT IS MAINTAINED INACCORDANCE WITH THE SERVICING


REQUIREMENT COMPLIANCE GUIDANCESCHEDULE THERE WILL BE NOUNACCEPTABLE LOSS OF AIRWORTHINESSAS A RESULT OF SPONTANEOUS,PROGRESSIVE OR DELAYED CRACKINGINDUCED BY STRESS CORROSION AND/ORASSOCIATED HYDROGENEMBRITTLEMENT.GENERAL REQUIREMENTS4.3.86 The Designer shall take the necessaryprecautions by controlling such aspects as thestrength of material, heat treatment, grain direction,stress concentrators, manufacturing methods,surface condition, residual and assembly stress, andprotective treatment to minimise the chance offailure due to such cracking.

(a) Because of their high susceptibility to stresscorrosion cracking, those materials (aluminiumalloys and steels) categorized D in Table 1,2 or 3of Leaflet 7 shall not be used without the approvalof the Aeroplane Project Director. When it isproposed to use an aluminium alloy or steel whichis not included in the tables, application shall bemade to the Aeroplane Project Director forcategorization. (The materials considered inLeaflet 7 are based on the SBAC's currentrationalized list).

(B) MATERIALS CATEGORIZED C INTABLES 1, 2 AND 2 OF LEAFLET 7 HAVEOCCASIONALLY BEEN SUBJECT TOSTRESS CORROSION FAILURE IN SERVICEAND SHALL THEREFORE ONLY BE USEDAFTER CONSULTATION WITH MATERIALSSPECIALISTS, PREFERABLY WITHIN THECONTRACTORS ORGANISATION ORALTERNATIVELY WITHIN MOD. PARTSMADE FROM THESE MATERIALS SHALL BE

Leaflet 7 gives advice on acceptable means ofcompliance with this clause.


REQUIREMENT COMPLIANCE GUIDANCEDESIGNED AND MANUFACTUREDOBSERVING ALL OF THE PRECAUTIONSLISTED IN 4.3.2.

TREATMENT OF WOOD4.3.87 SEE ALSO 4.1.17.EXTERNAL PLYWOOD SURFACES4.3.88 The surfaces shall be covered with a suitablefabric (BS-F series) applied with an approvedadhesive (DTD 900). They shall then be paintedwith the standard paint scheme appropriate to theadjacent structure.INTERNAL SURFACES4.3.89 After any adhesive bonding is complete,surfaces shall be either painted with the standardinterior paint scheme, or varnished (BS 4Xl7).FLOORS4.3.90 Wooden parts in floors shall be treated withwood preservative chosen by reference to BS 1282.Types OS or WB 1, 2 or 3 are preferred to TypeTO. Type WB4 shall not be used. Surfaces shallthen be either varnished (BS 4Xl7) or painted withthe standard interior paint scheme.ASSEMBLY OF WOOD TO METAL4.3.91 Except where adhesive bonding is used, alljoints between wood and metal shall be wetassembled (as described in 4.3.104 - 116) after themetal surfaces have been painted.

Note: The impregnants used to preserve and toimprove the flame resistance of wood mayseriously increase the corrosion of metals withwhich the wood is in contact.

4.3.92 Fasteners used in contact with timber shouldpreferably be made of brass or corrosion-resistingsteel. If made of non-corrosion-resisting steel, they


REQUIREMENT COMPLIANCE GUIDANCEshall be coated with cadmium (DEF STAN 03-19)or zinc (DEF STAN 03-20).4.3.93 Magnesium base alloys shall not be used indirect contact with wood, but shall be separated bya shim of zinc, aluminium or a suitable non-metallicmaterial.TREATMENT OF FABRIC COVERING OPEN STRUCTURES4.3.94 The external fabric covering open structuresshall be tautened and protected with dope to BSX26. Any paint scheme used over the doped areashall not significantly affect the tauteningcharacteristics of the dope.NATURAL FIBRES4.3.95 Natural fibres, whether in the form of fabrics,tapes, webbing, cordage or threads, shall beprotected against rot.

Parachute materials shall be treated in accordancewith Specification DTD 928. Other materials shallbe treated in accordance with BS 2087 by one ofthe following processes:

(a) Pentachlorophenyl laurate process (aqueousemulsion type) - this is generally applicable and iscolourless and odourless.

(b) Chrome copper process (with stitch finish) -this is applicable to cellulose threads but shouldnot be used where there is contact with rubber oraluminium or magnesium alloys. It is light green incolour and odourless.

(c) Mineral khaki process followed by (a) (normalprocess with stitch finish) - this is applicable to

Note: Information is given in Leaflet 11 on thedeleterious effects of light and heat on fibreproperties.


REQUIREMENT COMPLIANCE GUIDANCEcellulose fabrics, tapes and webbing. It is khaki incolour and odourless.

4.3.96 Polymer coated fabrics. Where appropriate to the end use the coating shallcontain additives which provide the material withresistance to degradation to the satisfaction of theAeroplane Project Director

SYNTHETIC FIBRE MATERIALS4.3.97 WHEN SYNTHETIC FIBRE MATERIALSARE INTENDED FOR APPLICATIONS INWHICH THEY MAY RECEIVE MUCHEXPOSURE TO LIGHT, FIBRE OF THE'BRIGHT' TYPE SHALL BE USED, IE FIBREWHICH IS SUBSTANTIALLY FREE FROMDELUSTERING PIGMENT.

Synthetic fibre materials are resistant to rotting butdressings added in course of manufacture shouldbe removed.

(Information is given in Leaflet 11 on avoidanceof degradation due to light, heat and abrasion).

PLASTIC MOULDED MATERIALS4.3.98 NO ADDITIONAL FINISH ISNORMALLY REQUIRED.TREATMENT OF SYNTHETIC RESIN COMPOSITES4.3.99 Internal surfaces may be left untreated, except

where painting is required to attain a desiredcolour.

Note: The fire retardant properties of thin gaugelaminates may be compromised by theapplication of some paint schemes.

4.3.100 EXTERNAL SURFACES SHALLNORMALLY BE PAINTED WITH ANAPPROPRIATE APPROVED SCHEMEPRECEDED BY AN APPROPRIATEPRETREATMENT.

Note: Some methods of surface abrasion andchemical paint removers may cause severedamage to some types of composite materials,particularly those containing carbon fibres. Forthis reason expert guidance should be sought onsuitable surface treatments and paint schemes.

4.3.101 Where surfaces of composites containing carbonfibres are in contact with metals, special attentionshall be given to design (para 6) and to assembly

Note: Carbon fibre behaves as a noble metal inits galvanic corrosion effects on metals, that is,its effect will be similar to that of gold etc. in


REQUIREMENT COMPLIANCE GUIDANCE(para 24), to prevent galvanic corrosion. Inparticular, direct contact of carbon fibre compositewith magnesium alloy, aluminium alloy, non-corrosion resisting steel, cadmium and zincsurfaces shall be avoided either by using adhesivebonding techniques to electrically insulate thecomposite and metallic components or by paintingthe carbon fibre composite component before it iswet assembled (4.3.104 - 116) to the metalliccomponent which should be protected to thenormal preassembly requirements (4.3.33 - 43,4.3.51 - 61, 4.3.62).

column 1 of Table 1 of Leaflet 10. In particular,it will give D class contacts when in contact withaluminium base and magnesium base alloys.

TREATMENT OF RADOMES4.3.102 THE GENERAL CONSIDERATIONS OF4.3.99 - 101 APPLY BUT DUE ATTENTIONSHALL BE PAID TO THE POSSIBILITY OFCERTAIN MATERIALS, EG PIGMENTS,AFFECTING RADAR TRANSPARENCY (DTD926, BS 2076).BATTERY STOWAGES4.3.103 Surfaces that may be affected by batteryelectrolyte, including by spray, shall be given theappropriate surface treatment and then painted toDTD 5567 or DTD 5580.

If mechanical damage to the paint coating isexpected, consideration should be given toproviding suitable supplementary non-metallicprotection

PRECAUTIONS AND TREATMENTS DURING ASSEMBLYFIELD OF APPLICATION4.3.104 These requirements apply to all static joints and

interfaces; that is, all contacting surfaces whetherbetween similar or dissimilar materials (one orboth of which is a metal) that are not intended to


REQUIREMENT COMPLIANCE GUIDANCEmove relative to one another in service. Therequirements apply also to static joints that willbe parted from time to time, eg inspection covers.

WET ASSEMBLY4.3.105 Except as detailed in 4.3.110 - 114 all staticjoints shall be wet assembled with an approvedsealant or an approved jointing compound (4.3.108-109).4.3.106 Sealants. These shall be applied to themating surfaces so as to completely fill any creviceand produce at the edge of the joint a specific filletwhich shall not, be subsequently removed Wherefasteners form part of the assembly, the sealant shallbe present down the shank and under the head andtail.4.3.107 Jointing compounds. These shall be appliedto the mating surfaces so as to completely fill anycrevice but excess material at the edge of the jointshould be largely removed by wiping prior topainting. Where fasteners form part of theassembly, compounds shall be applied to the holeand/or the shank and thread so that in the assembledjoint the compound completely fills any space underthe head and tail of the fastener.MATERIALS APPROVED FOR WET ASSEMBLY4.3.108 Sealants curing to produce an elastomerwhich adheres to one, or preferably both, surfaces(DTD 900). This type of crevice filler should beused for fuel tanks, cabin skins and pressurecapsules.

Note: Possible dangers to titanium alloys fromfluorinated sealants when at elevatedtemperatures are described in Leaflet 9, and it isrecommended that the Aeroplane ServicingManual calls for titanium parts in contact with


REQUIREMENT COMPLIANCE GUIDANCEViton sealants at temperatures of 200C andabove to be subject to spot inspection forincipient cracking after every 1000 hours attemperature.

4.3.109 Jointing compounds

(a) Pigmented jointing compound non-hardeningtype (DTD 5604, DTD 900),

(b) Pigmented varnish jointing compound, (DTD369),

(C) ALTERNATIVES TO (B) ABOVE (DTD900). EXCEPTIONS AND SPECIAL CASES4.3.110 SPOT AND SEAM WELDED JOINTS. ALL SPOT AND SEAM WELDS SHALL BEMADE THROUGH A COATING OF APPROVED(DTD 900) WELD-THROUGH PRIMER,SEALANT, OR ADHESIVE. THE COATINGSHALL BE APPLIED TO ONE OR BOTH OFTHE SURFACES, AFTER SUITABLECLEANING IN SUCH A WAY AS TO FILL THECREVICE OF THE WELDED JOINTCOMPLETELY.4.3.111 Joints made with an adhesive. Jointingcompound shall be omitted from adhesively bondedareas.4.3.112 Screwed unions in liquid and gaseoussystems. Jointing compound other than those


REQUIREMENT COMPLIANCE GUIDANCEspecifically designed for the purpose shall beomitted from unions in oxygen systems and may beomitted from unions in oth

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