HAA Discussion Paper 1Vintage Aircraft and The Acceptance of Spares1 IntroductionIndustry has highlighted increasing problems with obtaining spares for vintage aircraft. Obviously, with the demise of the manufacturers many years ago, there is no longer new manufacture of spares for these aircraft. It is also known, as reported by the HAA members, that there are decreasing amounts of ‘new old stock’ manufactured many years ago but still in circulation. With replacement components in such short supply, attention had to turn to the use of ‘used’ stock items or the possible use of alternatives.These issues need to be reviewed by the CAA to see if alternative arrangements or processes can be agreed in lieu of a rigid adherence to the requirements that presently apply. It should be noted that these discussions relate to vintage aircraft under Annex II. The basic problems regarding vintage aircraft are outlined below and apply whether the aircraft is operated on a Permit to Fly or a Certificate of Airworthiness.Note: This does not apply to ex-military aircraft, which will be covered by a separate discussion paper.2 ‘New Old Stock’In the majority of cases, the manufacture of new stock for these vintage aircraft ceased with the demise of the manufacturer. There are however limited numbers of original spares in circulation and available for use. These are satisfactory for use although the paperwork that is likely to accompany them probably bears little relationship to the release requirements that currently exist. There may also be issues of provenance for some of these parts. This needs to be considered in a flexible manner, provided there is some assurance that the parts are genuine.Discussion/Action point 1.1 – Review the release paperwork requirements to accept vintage aircraft parts.The existence of a military stockpile of spares for some aircraft, e.g. the Chipmunk, may be a boon as these are released into the civil market place. Most, if not all of these spares were equally applicable to the civil variants of the aircraft and therefore can readily be used, subject to the proper release. These are often accompanied by manufacturer’s releases but not necessarily against a civil requirement. In some instances dual releases were made but even these do not conform to current requirements. Discussion/Action point 1.2 – Review the process for acceptance of military spares for vintage aircraft.3 ‘New New Stock’It is possible for new items of stock to be manufactured by an approved organisation, e.g. BCAR A8-2 Supplier Approval, providing the production can be derived from manufacturer’s drawings. In many cases, these drawings are available and can be used as the basis for new manufacture. The part number remains the same although the manufacturer will obviously now be the company making the part providing all the drawing requirements are met. Industry however highlighted a number of concerns with regard to the application of the new BCAR A8-21 approval to cover simple supplier issues. In certain instances, and the absence of a suitably approved company that wishes to undertake the work, the CAA has considered an authorisation to manufacture the part, e.g. Tiger Moth spars. This however is not the preferred option due to the cost of CAA involvement. There are possible issues with regard to the need to have a substitute material. In such cases, the alternative material will have to be agreed as a suitable substitution and the drawings updated to allow manufacture to proceed. In most cases the part number will have to change to reflect this alteration in specification. Discussion/Action point 1.3 – Review the manufacturing approval requirements under A8-2 and A8-21 for options to allow easier access to manufacturing capability.For some vintage aircraft of US manufacture, there is a ready market in PMA parts or newly manufactured stock from a variety of suppliers under an STC approval, e.g. for the Piper Cub. The PMA system accounts for the production of an alternative part, or indeed manufacture of the part using alternative materials. An STC addresses the same sort of issue with regard to parts availability but often offers a slightly different capability. These can be used on UK aircraft although there may be a need for UK modification action to approve the fitment. The CAA acknowledges that the cost of manufacture of spares for vintage aircraft in limited numbers can be high, simply due to the volumes involved. The same situation exists for vintage or collectors cars that are no longer in production. Newly manufactured spares are available but sometimes at a premium. This is something for the industry to consider carefully. Discussion/Action point 1.4 – Industry review the possibility of establishing a cost effective spares manufacturing capability. 4 ‘Used Recoverable Parts’ There are a large number of parts that are removed but which can be repaired or overhauled in accordance with the manufacturer’s instructions. These activities can be performed under a suitable CAA approval or, in some instances, by a BCAR Section L Category ‘B’ or ‘D’ Licensed engineer. However, it should be noted that no deviation from the manufacturer’s requirements are allowed. These principles were outlined in CAA Airworthiness Notices No.3 and 10. Discussion/Action point 1.5 – The CAA to review the previous contents of AWN 3 and 10 with regard to working practices.The difficulty in carrying out such work may be the availability of the constituent spares, for example sub-components and even things like seals. There may be modern equivalents but again if these are to be used then the agreement of the TC/TRA holder or the CAA should be obtained. Obviously if there is no alternative then new manufacture is possible as described in Section 3 above. 5 ‘Material Substitution’It is clear that the material specifications that were originally used in the construction of these vintage aircraft are no longer available in many cases. Modern equivalents can be used but adequate substantiation of the alternative material’s fitness for use in the particular circumstances must be shown. A separate paper will deal with this issue in greater depth. 6 ‘Modifications’Technically any change to the aircraft, whether the substitution of a material type, the use of a different (modern) seal in the aircraft systems, constitutes a modification and needs to be dealt with as such. However, the CAA does not wish to see each change as a unique event limited to only one aircraft, particularly when the generic approval of such modifications, often referred to as ‘series modifications’, allow some resolution of the spares issues noted above. Industry has also expressed a desire to have a simple modification approval process for vintage aircraft and simple changes necessitated by the unavailability of original spares. The CAA has recently decided to centralise the process for dealing with modifications due to the lack of applications with the move of many aircraft into the EASA system. Discussion/Action point 1.6 – The CAA should review the centralisation process for minor modification in particular to determine a streamlined process for addressing industry’s needs.7 ‘The Role of the TRA holder in relation to Spares’A TRA holder approved by the CAA is primarily there to provide a monitoring role in continuing airworthiness information. There is no obligation on the TRA holder to take over a responsibility for the supply of spare parts or to facilitate such supply. Quite clearly, there is a need for the aircraft owners to decide what to do about the supply of spares and this may require separate action to that expected of the TRA holder.HAA Discussion Paper 2Vintage Aircraft and Rebuild1 IntroductionDuring the HAA meeting, the issue of rebuilding vintage aircraft was raised. In the past, the majority of this work has been done under the oversight and auspices of a BCAR Section L Category ‘B’ licence holder. This is certainly the case for aircraft operating on a CofA but the principles can equally be applied to Permit to Fly types.CAA Airworthiness Notice No.11, now CAAIP Leaflet 11-45, addressed the subject of ‘The Rebuilding and Restoration of Aircraft’. This gave guidance on what was permitted and the level of control and interface with the CAA that was expected in such projects. It is worth noting that in some case, the CAA was not advised of the project and this led to delays and additional work being required to substantiate the extent of the repair and the oversight applied. 2 The Impact of European LegislationThe majority of vintage aircraft will fall under the exclusions to the EASA Basic Regulation and therefore these aircraft will remain under National control. This means that the process outlined under the CAAIP leaflet can be adopted. Discussion/Action point 2.1 – Review CAAIP Leaflet 11-45 to ensure that the process is robust but pragmatic in its application.However, for those aircraft that fall under the EASA Regulation there are potentially further restrictions on what can be done during rebuild or restoration. The biggest issue here, without doubt, is the need for the involvement of a suitable organisation if the work involves the performance of complex tasks. The other key issue is, of the course, the need for Part 21 approval of any repairs or modifications that may be applied.3 Facilities There is obviously a need to have suitable facilities to carry out this work but this need not mean the use of hangarage or workshops within a CAA approved organisation. The certifying engineer must satisfy himself or herself that the facilities are adequate for the level of work to be performed. This is a key element of any work as previously outlined in CAA Airworthiness Notice No.3, now CAAIP Leaflet 15-2. 4 Structural RepairsThe rebuild or restoration of vintage aircraft often requires the complete disassembly of the aircraft and the subsequent repair or replacement of structural components. The existing guidance is quite clear that the work must be performed to approved data, including where appropriate structural repair data or manuals. Whilst many manufacturers provide such data in a generic sense, the work actually required on the aircraft must be specifically defined to reflect the interpretation of the data in determining the repair scheme. It should be noted that where the work is not defined adequately by the available approved data then a specific repair scheme approval would need to be sought. It should also be noted that, whilst the FAA document AC43-13 can be used as a source of generic data for US certificated types the data cannot be applied to aircraft of non-US manufacture. Discussion/Action point 2.2 – Review the information available about repair data.The use of alternative materials in a repair also constitutes a modification and approval must be sought to have the substitution approved so that the work can be certified against approved data. (see separate discussion paper)5 Special SurveyThe CAA controlled its involvement in such projects by having a process that required the CAA to agree the arrangement and the extent of the work via a special survey. This allowed the CAA to determine whether the project was to be managed properly and offered opportunity to determine any subsequent CAA involvement. This provision still stands. Discussion/Action point 2.3 – Review the basis upon which the CAA will carry out a Special SurveyHAA Discussion Paper 3Ex-Military Restoration1 IntroductionThe restoration of ex-military aircraft varies considerably from the transition of a just out of service aircraft into the civil environment to a more substantial recovery of a severely damaged World War II aircraft, complete with bullet holes, fire damage and corrosion. Accordingly the aircraft will have different demands to ensure that airworthiness is achieved to allow a Permit to Fly to be issued.Each ex-military aircraft is regarded as being unique. Whilst a number of the type may have qualified for a Permit to Fly the circumstances surrounding the nature of the individual aircraft’s history requires separate consideration. Each aircraft therefore has its own Airworthiness Approval Note (AAN) covering the history, any work done on transition to the civil system and the conditions associated with the issue of the Permit. The CAA is content to continue to allow the scale of restoration of ex-military aircraft that has developed over the last fifty years or more. However, such restoration must be managed throughout the life of the project in an appropriate manner that ensures that an airworthy product results that is properly defined and compliant with the relevant requirements.2 Major Restoration ProjectsThe UK CAA has overseen and issued Permits to Fly to a number of aircraft that have been rebuilt virtually from first principles. The recovery of a severely corroded airframe, or part of one, can often act as the initiation point for such a restoration. This is therefore taken as the worst-case scenario. It is recognised that the restoration will often be performed within a BCAR A8-20 approved organisation. This means that the organisation will have demonstrated an overall competence in ex-military aircraft maintenance that will allow the CAA to take a degree of confidence that the project will be managed appropriately.In many cases, the availability of replacement parts is severely restricted, particularly with regard to structural components. The solution often therefore requires manufacture of replacement parts to drawings that may be available or by reverse engineering. This introduces also issues of material substitution, as many of the original specification materials may no longer be available. It is important therefore that the restoration is managed around a defined progressive programme of decisions and activities such that the work can be substantiated and the decisions on alternative manufacture or materials can be seen and demonstrated. Where necessary, if the approval is not held in house, the support of an appropriately approved design organisation (BCAR A8-8 class E1 or E2 etc) will be needed to substantiate the decisions. This is important, as material substitutions will often require careful consideration with regards to all aspects of the intended use of the material (see also the discussion paper on material substitution). The cataloguing of changes is also required to allow a proper aircraft design standard to be determined for Permit issue. This means that the work has to result in a progressive picture of what is being done, why and how it is substantiated as the project proceeds. It is most practical to develop communication pathways with the CAA during such extensive rebuilds to ensure that agreement on the actions being taken is given. Too often, the CAA is presented fait accompli with aircraft where the substantiation for the changes performed is not available, leading to repetition of the work and disputes. The lack of CAA involvement at the appropriate time can also lead to the aircraft having to be dismantled to some extent to allow structural surveys of modifications or repairs to be reviewed. Keeping the CAA informed periodically, or consulting on key decisions will help ensure that there is no ambiguity over the project’s status.3 BCAR A8-20 ApprovalTo avoid any confusion over what the BCAR A8-20 approval can cover it is worth reiterating that there are two aspects to the potential scope of approval that can be granted. The approval covers an E4 element which allows the organisation to compile a substantiation report on the aircraft, its history, build standard, modifications, equipment fit to help the CAA draft the AAN that will eventually clear the aircraft for Permit issue. This is not, as some think, a design approval and confers no privileges in respect of the approval of modifications or changes at any level. The HAA meeting asked for consideration of some design capability but the paths available for design approval under BCAR A8-8 appears to be satisfactory although the current BCAR notes that the approval is not available other than for microlights. Discussion/Action point 3.1 – Review the availability of BCAR A8-8 for the design functions associated with the support of ex-military and permit to fly aircraft. Discussion/Action point 3.2 – Review the current requirements for E4 approval with regard to the clarity of purpose.The other aspect of the approval is the M5 element. This provides for maintenance of the aircraft and the scope of approval will normally relate to specific aircraft types. The approval does not provide any commercial manufacturing capability and therefore the manufacture of parts or components to support ex-military restoration in other organisations requires a further approval, such as that available under BCAR A8-2 or A8-21. The current version of BCAR Section A notes that, again with the exception of microlights, the A8-2 approval is no longer issued.Discussion/Action point 3.3 – Review the availability of BCAR A8-2 for the manufacture and supply of parts and/or components for ex-military and permit to fly aircraft. There is no reason why BCAR A8-20 cannot be used for the purposes of performing maintenance on engines, propellers or equipment for ex-military aircraft. It is relatively straightforward to build in a capability to cover these ancillary tasks to allow these to be covered separately from a complete aircraft approval. This provides for a greater degree of flexibility (see also HAA discussion paper 5)4 Modification ClearancesAt present, the aircraft are dealt with as complete entities. This means that the final AAN for Permit issue provides a consolidated clearance of the various modifications that have been embodied on that aircraft. This does not make it easy to understand whether a series modification, i.e. one which can be applied in a more generic sense to aircraft of the same or similar type, is approved for other aircraft.It would be beneficial if, when a modification is the same as that previously approved in every respect, it could be used on other aircraft without further approval. This saves unnecessary investigation on the part of the CAA and cost to the industry. However, the limiting factor is that the modification has to be the same in every respect. Any change invalidates the modification approval, however insignificant it may appear.Discussion/Action point 3.4 – Review the way in which AANs are used to provide for modification clearance for ex-military and permit to fly aircraft and whether this constitutes a basis upon which the can be regarded as series modifications.The applicant for the AAN has normally owned the data approved under the modification. This clearly imposes restrictions on who can use the data as it clearly becomes propriety data and its use by others is subject to the ‘owner’s agreement’. The availability of data as to what modifications are approved or not also leads to a potential overlap in modification requests and clearances. This may be an issue for HAA to consider as it may be beneficial to have the ability to use certain modifications on vintage and ex-military aircraft on a series basis without re-investigation.It should be noted that confusion has arisen where an aircraft has previously had a configuration approved under an AAN when the aircraft was originally on the UK register. The aircraft then leaves the UK for another register before returning. The original configuration may no longer be reflective of the aircraft’s current condition. The receiving organisation, wishing to place the aircraft on the register, may wish to carry out modifications or re-embody modifications to re-establish compliance with the originally approved configuration. Due to the uniqueness of the AAN and Permit to Fly system, unless the aircraft can be restored to its previous UK standard by the application of the same modification standard, using the same materials, components or equipment the original configuration approval cannot be applied. A further modification approval will be required to address the changes, even though they may appear insignificant. This is predominantly an issue for aircraft returning to UK registration. Of course, if the aircraft has not been altered then the original AAN should suffice. Discussion/Action point 3.5 – Review the current provisions in BCAR A3-7 and A8-20 for the return of aircraft that were previously UK registered to the UK register and how this ties in to existing AANs.HAA Discussion Paper 4Material Substitution1 IntroductionAt the recent meeting with the Historic Aircraft Association (HAA) one of the key areas of concern surrounded the use of alternative materials. This is often necessary due to the simple fact that material to the original specification is no longer available. HAA members indicated that there are a number of material substitution lists that are believed to have been ‘approved’ by the CAA and that many BCAR A8-20 approved organisation had these embedded in their expositions.The CAA accepted that material substitution was inevitable and indicated that such substitution constituted a modification or change to the baseline certification of the aircraft, engine, propeller or equipment. There appeared to be a divergence of opinion between the CAA and the HAA members over this issue and this discussion paper seeks to redress those issues and establish a more common view. 2 Original versus New MaterialsMany ex-military aircraft are of such an age that the materials in use were fairly basic specifications compared to the more developed higher strength alloys that we use today. This often means that there are no direct equivalent materials that can be used and the alternatives often have significantly different characteristics when a detailed comparison is made.Substitution is not always about the ultimate strength of the material. Other factors come into play, the different alloying properties can also have a significant bearing on the flexibility or the ductility of the material. A simple comparison of specifications could be acceptable for historic aircraft designed with static strength requirements only. However, fatigue is a totally different issue, and will require the input of a suitably approved design organisation. 3 Casting and Forging versus MachiningMany original components were produced from castings or forgings, which were then partially machined to produce the finished article. The ability to manufacture new components probably no longer exists and therefore an alternative method of manufacture may well have to be considered. As an alternative manufacturing strategy, many believe that making a new component out of machined solid provides a suitable solution. However, the way in which the component is machined has a significant bearing upon whether it is suited for service or not. The casting often managed to carry the internal stresses in the component in a suitable manner to avoid the presence of areas of stress concentration. In machining a solution, care must be taken to make sure that the method does not lead to the production of a component that has stress points leading to in service weaknesses. 4 Considerations for Material SubstitutionsFinding a suitable material for substitution is not as easy as many may think. This is the current problem where organisations are not referring back to the specifications/standards. The industry is using documents often due to cost factors, such as ‘the properties of Al and Al Alloys’, that cannot be considered as design data. In any case, the way that the material design values is presented can vary and requires specialist knowledge to really make a determination of material comparability. A licensed engineer, or an authorised engineer capable of certifying work on permit aircraft, is not empowered to make decisions on alternative materials unless the substitution is covered by approved data for the type or specifically drawn up for that individual aircraft. Discussion/Action point 4.1 – Review the existing provisions of BCAR A8-20 and CAAIP leaflet 11-42 regarding the issue of material substitution and the role of the authorised/licensed engineer.The manufacturer may well specify alternative materials through their continuing airworthiness information or updates to documents such as structural repair manual data. Where the original manufacturer no longer exists, such as is the case for many ex-military types, the data may not have been amended for some time. However, just because one manufacturer specifies a material as being an alternative to an older specification for certain skin replacements this does not constitute an approval for that substitution to be used on other types, or in alternative applications.The same is true of military documents, e.g. alternative specification documents raised by the Integrated Project team for support of the BBMF aircraft. These documents may not have had any civil scrutiny with regard to the data that is presented and the basis upon which the comparison in made. This suggests quite clearly that whilst an alternative material may be identified fairly readily, say for example using BS. L163 to replace L72 aluminium alloy sheet, the actual way in which the material is to be used needs to be considered. What are the loads? What is the material heat treatment regime? The full evaluation of the application requires some form of design organisation to substantiate the change. Discussion/Action point 4.2 – Review the requirements of BCAR A8-20 and CAAIP Leaflet 11-42 with regard to the need to have design substantiation for material substitutions.5 An Alternative Materials ListingThe very existence of an alternative materials list in the expositions or manuals of BCAR A8-20 and other companies tends to confuse the situation and could lead to the use of the alternatives without proper consideration of the way in which the material is to be used. The way in which some materials react over time, and under dynamic loading, can vary significantly. Whilst it is recognised that in some instances there is no, or little, safety impact, this could potentially have longer-term implications.There is also some doubt, as the lists have not been compared against one another, as to whether the lists provide the same information and what they say regarding the circumstances under which the information may be used. From a regulator’s perspective, this situation is not tenable in today’s environment. It may be possible to provide some form of generic information that can be used only as a starting point to identify alternative materials that may, subject to appropriate design substantiation, be used as a substitute. To do so, the CAA would like to gather the existing lists and compile a composite document for the benefit of all. This would replace all of the existing lists. Discussion/Action point 4.2 – Request HAA members to supply copies of all alternative material lists to the CAA. Discussion/Action point 4.3 – CAA to review alternative material data from HAA members and consider the publication of a consolidated list of baseline alternative materials. HAA Discussion Paper 5The BCAR A8-20 Requirements1 IntroductionThe current requirements published under BCAR Section A, Chapter A8-20, cover the ‘Approval of Organisations Responsible for the Restoration, Airworthiness Control and Maintenance of Aeroplanes and Rotorcraft of military origin – Group E4 and M5’.Originally intended to capture aircraft above 2730 kgs, recent amendments to the BCAR have extended the potential scope of such approved organisations to ex-military aircraft of any weight. This followed requests from industry and allowed the organisation to apply their process and expertise to all ex-military aircraft that might fall under their area of responsibility. The recent meeting with the HAA highlighted a number of concerns regarding this approval, the associated CAA oversight and the link to the basic Permit to Fly requirements under BCAR A3-7.The CAA announced at the meeting that it was in the process of drafting amendments to BCAR A3-7 to formally introduce the concept of non-expiring Permit to Fly supported by Certificates of Validity. These had already been introduced in practice among some sectors of the industry and the Air Navigation Order had recently been changed to address the legal provision for this. The changes to BCAR A3-7 would close off the remaining actions in this area. 2 The E4 ApprovalThe concept of the E4 approval followed the rationale that had been used when the corresponding E3 approval was rolled out for CofA aircraft. The E4 approval permitted the approved organisation to take a more prominent role in reviewing the history of the aircraft and preparing a documented report. This report would assist in the drafting of the Airworthiness Approval Note that would be associated with the clearance of the aircraft for Permit issue. The E4 capability is not a design approval but is focused on drawing together the historical records, evaluating the configuration and modification status and the equipment fit. It confers no ability to alter the aircraft’s configuration or install new equipment, these activities requiring compliance with the normal requirements for the approval of modifications on Permit aircraft.If an organisation wishes to be considered for a design capability then it must apply for and obtain a suitable design approval, e.g. under BCAR A8-8 or the design elements of a BCAR A8-21 approval.3 CAA Oversight of the E4 ApprovalThe CAA carries out routine oversight of the E4 approval, at a minimum level of one visit per year. The oversight had originally been carried out by the CAA’s design surveyors due to the link to the drafting of the AAN. More recently, another look at the basis for the approval and its output has suggested that the Regional Office Surveyors can deal with this approval. This is based on the rationale that the work associated with the E4 approval is more specifically related to the review of historical data, which requires little application of design expertise in the compilation of the report. However, the report may well identify shortfalls that require a further, more detailed review by suitably qualified design staff in order to bring the aircraft into compliance with the requirements of BCAR A2-5.Discussion/Action point 5.1 – Review the provisions in BCAR A8-20 with regard to the explanation of the purpose of the E4 requirements and the associated criteria for staff qualification etc. The E4 approval also provides a good basis for looking at organisational competence to carry out the periodic airworthiness reviews of Permit to Fly aircraft in order that the organisation can issue a Certificate of Validity. 4 The M5 ApprovalThe M5 element associated with the BCAR A8-20 approval allows maintenance of ex-military aircraft. The current requirements talk about the organisations identifying the arrangement for support with regard to the maintenance of certain components. In fact, the question has been asked why an A8-20 organisation cannot hold approval under the M5 rating for these sub-contract activities. Discussion/Action point 5.2 – Review the scope of approval under BCAR A8-20 to provide capability for the maintenance of engines, propellers, parts and/or components for ex-military and permit to fly aircraft. During the meeting, the HAA stated that it had concerns that the CAA was applying regulation by looking at the maintenance aspects rather than specifically addressing the design, engineering and production elements. This is inevitable given the original premise upon which BCAR A8-20 was established. The activity of restoration is essentially a maintenance activity albeit there can be a high degree of component manufacture involved in the process. This is covered by recommendation 3.3 in HAA discussion paper 3, looking at BCAR A8-2.The BCAR A8-20 approval does not provide for any design related activity and therefore the surveyor focus has to be very much with regard to maintenance. However, the design aspects are addressed by surveyor involvement in the inspection and clearance of AANs. The recent queries over the standards applied in certain modifications and repairs arose out of CAA concerns over the adequacy of materials substitutions and their declaration during modification clearance procedures. It should be noted that this is the main subject of HAA Discussion paper 4. This brought into question the CAA’s role in revisiting histo