Structural Repair Manual

The SRM revisions—incorporating DC-10, Md-11, MD-fourscore, Medico-90 and 717 aircraft—take the course of a await-up table that allows users to lucifer flaw blazon/size with either a metal repair or the equivalent composite doubler repair.

From: Aircraft Sustainment and Repair , 2018

Development and Validation of Bonded Composite Doubler Repairs for Commercial Shipping

Dennis Roach , Kirk Rackow , in Aircraft Sustainment and Repair, 2022

8.3 Revision of Structural Repair Manual

Afterwards successful completion of the Pilot Plan, the Structural Repair Manuals were modified to include this set of 3 composite doubler designs. This allows for more than routine use of composite doubler repairs within the allowable awarding government specified in the manuals. The SRM revisions—incorporating DC-x, MD-11, MD-eighty, MD-90 and 717 aircraft—accept the form of a await-upwards table that allows users to match flaw type/size with either a metallic repair or the equivalent composite doubler repair. Using these look-up tables, maintenance facilities can accept the option of choosing the traditional metallic repair or the 'equivalent' blended doubler repair. The engineering drawing for the composite repairs was integrated into the SRM. The NDT procedure for bonded composite doublers (ultrasonic resonance technique) was besides included in the Boeing NDT Standard Practices Transmission. Finally, a set of training classes are beingness adult to safely integrate composite doubler technology into the commercial maintenance depots. The classes volition cover all aspects of pattern, analysis, installation, quality control and in-service inspection. They volition depict the infrastructure and personnel capabilities/training that must be nowadays at an aircraft maintenance depot in order to safely utilise the technology.

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Nondestructive Inspection and Repair: Considering Things Practise Non Always Become As Planned

F.C. Campbell , in Manufacturing Processes for Advanced Composites, 2004

xiii.vii Repair

All repairs of composite or bonded assemblies should exist conducted per the specific instructions outlined in the Structural Repair Manual (SRM) or Technical Order (TO) for the aircraft. These manuals are prepared by the shipping manufacturer and canonical by the appropriate governing bureau, such as the Federal Aviation Agency (FAA) for commercial aircraft or the Air Force/Navy/Army bureau for war machine shipping. If the damage exceeds the limits specified in the transmission, information technology is imperative that a qualified stress engineer approves the repair process. All personnel conducting structural repairs should be trained and certified in the repair procedure. The instructions in the repair transmission must be followed to the letter of the alphabet. A repair that is done incorrectly tin can oft result in a second more extensive and complicated repair.

Repairs can be categorized every bit fill, injection, bolted or bonded repairs. Elementary fill repairs (Fig. 17) are conducted with paste adhesives to repair non-structural damage such as modest scratches, gouges, nicks and dings. Injection repairs use depression-viscosity adhesives that are injected into composite delaminations or adhesive unbonds. Bolted repairs are commonly done on thick highly loaded blended laminates while bonded repairs are often required for thin skin honeycomb assemblies. Similar NDI, the literature on composite repair is quite all-encompassing. An excellent in-depth treatment of repair technology tin be found in Ref. half-dozen.

Fig. 17. Typical Composite Repairs

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Repairing composites

F. Collombet , ... R. Thévenin , in Advances in Composites Manufacturing and Process Pattern, 2022

10.ane Introduction

"In-field" repair of composite primary main structures is a very strategic result for the aeronautical manufacture. Evidently, whatever the material (metal or composite), the Structural Repair Manual (SRM) does non cover all repairs. As far as a blended solution is concerned, the fuselage and fly cannot be dismantled (and fifty-fifty if it could be it would not be in accordance with schedule and cost for airline companies; encounter Figure 10.ane). Structural damage needs a "case-by-instance" solution including pattern, adding phases, damaged zone removal, patch construction, set up-up, and finishing.

Effigy ten.1. Views of big repairs with (left) A340-541 after a tail strike (http://world wide web.atsb.gov.au/media/3532364/ao2009012.pdf) and (correct) B787-eight after a fire under the crown in front end of the vertical tail fin (http://airwaysnews.com/web log/category/aircraft-manufacturing-and-applied science/page/11/).

A view of A340-541 after a tail strike (MSN 608) of Emirate Company for Flying EK-407 is shown in Effigy 10.1 (left) with no injuries and no fatalities. The incident occurred on March xx, 2009. The render to flight (RTF) was on December 22, 2009, after a end of 277 days for a repair toll of virtually eighty million USD, which is an amount higher than 33% of the shipping cost (A/C cost). Even if a structural repair had been defined and validated by Airbus experts, Emirate Company decided to supercede all damaged parts.

A view of B787-viii afterward a fire under the crown in front of the vertical tail fin of an Ethiopian Airlines aircraft in Heathrow Drome (UK) is shown in Figure 10.one (correct) with no injuries and no fatalities. The RTF was July 12, 2022 after a cease of 160 days for a repair cost of nearly 5 million USD, which is a few percent compared to the A/C toll. These two costs do not include grounding costs, which are really huge. An club of magnitude of cost to airlines of an unscheduled aircraft on the footing is, on boilerplate, $100,000 per day (Source: Boeing, http://www.compositesworld.com/articles/in-situ-blended-repair-builds-on-basics).

Everything needs to be controlled and approved by certification government. The requirements must be accustomed worldwide by companies and certified by airworthiness regime, which include the US Federal Aviation Administration (FAA) also as the European Aviation Rubber Agency (EASA).

Repair of primary chief blended structures involves complex patches including thickness variations, stiffeners and/or frames' parts, and opening frames. Plain, the evolution and production of unitary complex primary composite construction as quickly equally possible is a great challenge! Composite solutions need to be considered with real "industrial" variabilities and with a continuous link betwixt all scales (from microscale to structure scale). A definition of the country of the field is mandatory for "in-field" repairs of composite principal principal structures.

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Repair of damaged aerospace composite structures

Due east. Archer , A. McIlhagger , in Polymer Composites in the Aerospace Manufacture, 2022

fourteen.six Decision and future trends

Regarding the current composite airframes, Boeing claim their rapid composite repair technique for the 787 offers temporary repair capability to become an airplane flight once more quickly, despite minor damage that might ground an aluminium airplane. The 787 SRM specifies iii types of blended repair: traditional vacuum debulked bonded scarfed repair, the company's patented quick composite repair technique and conventional bolted repair [29]. Looking to the futurity, EADS Innovation has been working on automation that might somewhen behave out an unabridged repair bicycle encompassing impairment detection, surface preparation, repair patch cosmos, patch application and finally quality assurance checking. Meanwhile, the German Aerospace Research Middle DLR has been investigating the automation of resin-infused repairs. The aim is to develop scarf repair capability including damage removal by computer-controlled milling, impregnation of a dry preform laid into an excised site, and subsequent cure. DLR claims the method is particularly appropriate for curved areas, reducing complexity and fugitive the demand to produce special tooling. Laser specialists cleanLASER and SLCR, also in Germany, are separately working on systems to gear up repair sites. GKN Aerospace (Isle of Wight, U.M.) and SLCR Lasertechnik (Düren, Germany) have agreed to develop automated laser repair for composite structures on aircraft [30]. Looking beyond country of the art, enquiry on structural health monitors using techniques such equally embedded fibre optic strain sensing and cocky-healing composites using microvascular systems of repair networks accept been demonstrated. Whatever the future holds, the arroyo for the blended construction design teams needs to be based upon input and knowledge gained from a working relationship established with the airline maintenance personnel. This can be accomplished through repair workshops, or inquiries, involving airline and OEM customer support personnel, engineering personnel and involvement with the Commercial Aircraft Composite Repair Committee (CACRC). CACRC meets twice per year, under the auspices of the SAE International, alternating between Europe and Northward America. The remit is to accost issues experienced by aircraft operators when maintaining composite components on commercial shipping. Delegates are drawn from airlines, OEMs, regulatory regime, material suppliers and maintenance and repair organisations.

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Repair of metallic airframe components using fibre-reinforced polymer (FRP) composites

A.A. Baker , in Rehabilitation of Metallic Ceremonious Infrastructure Using Fiber Reinforced Polymer (FRP) Composites, 2022

2.one Introduction

Airframe structures must exist repaired or replaced when service damage results, or has the potential to result, in the residual force being reduced below an acceptable level for flying safe. The nigh prevalent forms of service damage in aging metal airframe components are cracks and corrosion. The availability of efficient, rapid and cost-effective means of making repairs is a very important economic requirement for both military and civil aircraft. Repairs to significant harm more often than not involve the attachment of a reinforcing metal patch or doubler over the damaged region. The aim is to restore mechanical properties to the original pattern specifications, including: residual strength, stiffness, fatigue resistance and damage tolerance. 1 The method of attaching the repair patch prescribed in the Structural Repair Manual (SRM) for the aircraft uses bolts or rivets. Figure 2.1a is a schematic of a typical mechanically fastened repair, for case to a wing skin. Generally, prior to application of the reinforcement, the defect – typically a cleft – is removed leaving a circular or elliptical shaped shine-edged cut-out.

2.1. Comparison of typical repair involving mechanically fastened patches (a) with 1 involving adhesively bonded fibre composite patches (b).

Although these SRM repair procedures are generally effective, they can have limited fatigue lives, especially for repairs to relatively thick, highly loaded primary structure; they are also dissentious in that they require a big number of extra fastener holes. The purpose of this chapter is to show that application of a fibre composite patch by structural adhesive bonding over the defective region, as illustrated in Fig. two.1b, can provide a far more than efficient and cost-effective repair as well as beingness much less damaging, fatigue prone and intrusive to the structure.

This chapter discusses the repair of metallic aircraft structure with adhesively bonded fibre-reinforced composites, mainly from an Australian perspective. Firstly, a brief background is provided on the advantages and scope of bonded composite repairs for aircraft construction – including fabric choices. Details are so provided on the engineering for applying the reinforcing patches to the construction, especially the disquisitional outcome of surface treatment for durable agglutinative bonding. The design of patch repairs is then discussed, mainly from the perspective of estimation of stress intensity in the patched crack, including some experimental confirmation of an belittling model.

The futurity claiming in the certification of bonded repairs for flight-critical applications is discussed, and a proposal is made on how to run into this challenge. This is based on the testing of representative joints to obtain material allowables for the patch system and the use of proof testing or structural-health monitoring to validate the through-life integrity of the applied patch. Finally, two applications, i USAF and the other Australian, are briefly described followed by a conclusion on limitations and lessons learned.

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Continuing1 Airworthiness and Air Operator'southward Certification

Filippo De Florio , in Airworthiness (Third Edition), 2022

10.ii.five.2 Standard repair

According to point 21.A.431B

Standard repairs are repairs:

(ane)

in relation to:

•

aeroplanes of 5700   kg Maximum Take-Off Mass (MTOM) or less;

•

rotorcraft of 3175   kg MTOM or less;

•

sailplanes and powered sailplanes, balloons, and airships as divers in ELA1 or ELA2.

(2)

that follow design data included in certification specifications issued past the Agency, containing adequate methods, techniques, and practices for carrying out and identifying standard repairs, including the associated instructions for continuing airworthiness; and

(three)

that are not in conflict with TC holders data.

There are types of impairment that can be predictable, and so that the repair of this impairment can be studied in accelerate. Manual and other Instructions for Continued Airworthiness (such as Manufacturer Structural Repair Transmission ) are provided by the TCH for the aircraft operators and incorporate useful data for the development and approval of repairs.

When these data are explicitly identified and approved, they may be used past the operators without further approval to cope with anticipated in-service bug arising from normal usage provided that they are used strictly for the purpose for which they have been developed. Of course, damages that cannot be predictable take to be approved on a case-past-instance ground.

21.A.433 Repair Blueprint

(a)

The applicant for approval of a repair design shall:

1.

demonstrate compliance with the type-certification basis and environmental protection requirements incorporated by reference in the type-certificate or supplemental type-document or APU ETSO authorisation, equally applicable, or those in result on the date of application (for repair design blessing), plus any amendments to those certification specifications or special conditions the Agency finds necessary to constitute a level of safety equal to that established past the type-certification basis incorporated by reference in the blazon-document, supplemental blazon-certificate or APU ETSO authorisation;

2.

submit all necessary substantiation information, when requested by the Agency;

3.

declare compliance with the certification specifications and environmental protection requirements of point (a)(1)

(b)

Where the applicant is not the type-certificate or supplemental blazon-certificate or APU ETSO authorisation holder, as applicable, the applicant may comply with the requirements of point (a) through the employ of its own resources or through an organisation with the blazon-certificate or supplemental type-certificate or APU ETSO dominance holder as applicable.

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Adhesively Bonded Repair/Reinforcement of Metal Airframe Components: Materials, Processes, Pattern and Proposed Through-Life Direction

Alan A. Baker , John Wang , in Aircraft Sustainment and Repair, 2022

one Introduction

The objective of this chapter is to highlight the fundamental topics for bonded composite repairs and to suggest approaches to repairs and reinforcement that contribute to extending the lifespan and/or the inspection interval when applied to chief airframe structures.

This affiliate lists the scope of bonded repairs and reinforcements—some applications are listed in the appendix. Important materials, processes and design issues are presented, based on Australian approaches. Finally, key bug are addressed with the focus on agglutinative bond structural integrity for through-life direction of repairs.

Structural modifications to airframe structures are oft made either to repair regions damaged by fatigue cracking or to extend fatigue life by reducing stresses in prospective regions of smashing.

With traditional repairs a metallic patch or doubler is attached to the parent structure using bolts or rivets after removal of the croaky region. The aim is to restore mechanical properties, including: residual strength, stiffness, fatigue resistance and damage tolerance to an acceptable level.

Structural reinforcements utilize a like arroyo, only in this case the objective may be to reduce strain at a known 'hot-spot', where futurity nifty is anticipated due to a local stress concentration, or just to restore force and stiffness to replace material lost by corrosion following a grind out.

When repairing cracks, the method for attaching the repair patch generally prescribed in the aircraft's structural repair manual (SRM) uses bolts or rivets. Fig. 1A shows a schematic of a typical mechanically attached repair recommended, for example, for a wing skin suffering fatigue cracks. Prior to application of the reinforcement the defect—typically a scissure—is removed to get out circular or elliptical shaped shine-edged cut-out.

Fig. 1

Fig. 1. Comparison between (A) mechanically fastened and (B) bonded repairs.

Well designed and correctly implemented these SRM repair procedures are constructive in the short term, even so, they may accept express fatigue life due to the development of loftier stresses at the new fastener holes. Some problems associated with mechanical repairs are listed in Fig. 1A include the danger of inadvertent damage to the internal structure, wiring and hydraulic lines.

An alternative approach is to utilise the repair patch over the defective region using structural agglutinative bonding every bit illustrated in Fig. 1B. This approach is far more efficient in transferring loads from the parent structure into the patch or reinforcement, and does non cause damage to the parent structure considering there is no requirement for fastener holes. This arroyo does not require removal of the crack; this is an important advantage because in many cases removal of the cleft is hard or non feasible.

The use of composites, particularly boron/epoxy and carbon/epoxy, have many advantages [1] over metals for the patches and reinforcements. These include high strength and stiffness, fatigue and corrosion resistance, formability and the ability to be 'tailored' to match stress and stiffness requirements precisely. Low electrical conductivity is an important advantage of boron/epoxy because information technology avoids galvanic corrosion problems with the parent structure and enables use of eddy-current nondestructive inspection (NDI) to detect cracking in the parent structure.

To demonstrate the advantages of using bonded repairs for crack repair, fatigue tests were performed on patched edge-notched 2024 T3 aluminium blend panels, shown inset with details in Fig. 2A and B . The full thickness of the aluminium patches, on both sides, was equal to the thickness of the metallic. The plotted points show scissure growth. Unidirectional boron/epoxy was chosen for the bonded patch. As unidirectional boron/epoxy in the fibre direction has three times the elastic modulus of aluminium, the thickness used was 1/three the thickness of the panel.

Fig. 2

Fig. ii. Comparison of patching efficiency between a mechanically fastened mechanical repair (A) and an adhesively bonded composite repair (B).

Another very of import reward of using boron/epoxy is its nonconductivity. Therefore, inspection techniques (NDI) using eddy currents can be used to detect crack growth—as shown past the plotted points in Fig. 2.

Fig. 2A shows that the mechanically attached metallic patch provides poor reinforcing efficiency since there is only a very slight reduction in fissure growth rate. Also, as seen in Fig. 2, once the fissure emerges from under the patch it grows very chop-chop. The metallic patch can appear to exist effective in some cases if the scissure arrests temporarily in a fastener hole. In contrast, the adhesively bonded boron/epoxy patch is shown to reduce the rate of crack growth significantly, even when it emerges from nether the patch. The growth rate of the emerging crack with the boron/epoxy patch is like to the rate expected for a crack of the emerged length, indicating that the patch is nevertheless finer restraining crack opening.

A summary of the advantages of bonded repairs compared with mechanical repairs is provided in Fig. ane.

Equally stated earlier, aim of this chapter is to highlight some of the fundamental issues with bonded composite repairs and to propose approaches where credit may exist given to the repair or reinforcement for extending life and/or the inspection interval when applied to primary airframe structures.

In this chapter the telescopic of bonded repairs and reinforcements, with examples of applications, is first discussed very briefly. So key materials and process and design issues are discussed, focusing on Australian approaches. Finally, the word focuses on the key issue of how to admission adhesive bond structural integrity, particularly in relation to the through-life direction of repairs.

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Polymer Matrix Composites: Applications

John Tomblin , ... Cindy Ashforth , in Comprehensive Blended Materials Two, 2022

3.9.4 Conclusions and Recommendations

three.nine.4.1 Critical Bonded Repair Processing Parameters

Critical processing parameters were identified from this research work. These parameters must exist advisedly evaluated during the process development and validation

•

Repair station environs.

•

Timeframe for repair operation and execution.

•

Repair material out time and storage life.

•

Batches of materials used.

•

Quality of the repair scarf.

•

Time lag betwixt drying and concluding cure.

•

Pre-bond moisture.

•

Surface preparation.

•

Number of filler plies.

•

Resin mixing ratios (wet lay-upwardly repairs).

•

Resin piece of work life (pot life, moisture lay-up repairs).

•

Repair bagging scheme and materials.

•

Heat blanket and thermocouple installation (hot bonder calibration).

•

Repair cure cycle ramp up rate.

•

Repair cure dwell fourth dimension.

•

Vacuum level achieved during repair cure.

3.9.4.ii CACRC Standards

The results also showed that when properly followed, the procedures following the CACRC standards yielded strong durable repairs. CACRC standards cannot be used as a sole document to repair a blended part. These standards represent best practices/techniques for repair and therefore a part specific document is required. The CACRC standards tin all the same exist used along with an SRM or other part specific repair document.

3.nine.4.3 Bonded Repair Variability

Inquiry work showed variability in the repair remainder forcefulness results betwixt depots and mechanics and underscored that repair technician experience alone is not a predictor of repair functioning and that some of the procedure deviations may have been avoided with more than stringent quality control oversight.

3.9.4.four Repair Procedure Development, Substantiation, and Knowledge Transfer (Records Keeping)

Results of the study besides demonstrate the importance of repair procedure evolution, substantiation and proper execution. Process substantiation should include agreement of the critical process steps and parameters affecting the repair functioning and the consequences of bad process implementation. Considering of the chemical characteristics of the diverse systems used for bonding and repair, information technology is very important to understand the capabilities and limitations of the specific systems peculiarly when they are shut to the stop of their storage and/or work lives. The use of adequate processes specific to the materials used is key to the structural integrity of the repaired part. Caution should be exercised when applying results from 1 material system to the next.

This should be used to demonstrate that the substrate will yield durable bonds in service, and must exist conducted in the about aggressive environments the construction volition be subjected to.

Knowledge transfer in the grade of training, validated repair instructions and repair records and documentation is an integral function in ensuring repair process repeatability, stability and thus structural integrity of the repaired component. Procedure documentation is necessary to ensure strict adherence to the procedure. QA oversight is strongly advocated.

3.9.4.v Repair Curing Process Simulation

The simulation of cure procedure for bonded repairs can be used for procedure development, to sympathise the evolution of cure as well as the development of residue stresses. For large repair areas on complex structures with multiple components, this can be used to identify the optimal layout for rut blankets and thermocouples.

3.9.4.6 Workforce Education and Training

The report demonstrates the importance of workforce teaching and preparation for the proper execution of bonded repairs to composite substrates. Part specific training of the composite repair workforce, taking into account the process learning curve, is strongly advocated. At this point, due to the potential for understrength bonded repairs, and limitations in inspection methods, repair sizes should exist limited such that the repair failure will not crusade the aircraft to lose its adequacy for continued safety flight and landing.

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Surface Treatment and Repair Bonding

Andrew Due north. Rider , ... James J. Mazza , in Shipping Sustainment and Repair, 2022

1.4 Standards and Environments for Adhesive Bonding

The facilities, environment, weather, skills and techniques available for adhesive bonding vary widely. However, it must be emphasised that the quality and long-term performance of an adhesive bond relies on attention to standards and the skill of the technician, together with controls over processes and procedures for all bonding situations.

one.4.one Bond Integrity and Standards

Adhesively bonded components are manufactured, and bonded repairs are conducted, without the benefit of a comprehensive gear up of effective nondestructive procedure control tests or techniques to fully assess the through-life integrity of the bonded product. Standard nondestructive inspection (NDI) techniques may be able to discover physical defects leading to voids or airgaps in bondlines, but they cannot detect weak bonds or bonds that may potentially weaken in service. Recently, however, at that place has been a proof test developed based on shock waves generated past a loftier-peak power, curt-pulse light amplification by stimulated emission of radiation, which provides some hope that a localised measurement technique with the ability to consistently verify bail strength will exist available in the future [20,21]. In the meantime, the quality and integrity of the bonded component volition rely on a fully qualified bonding procedure, together with the assurance that the procedure was carried out correctly. The Aloha Airlines Boeing 737 incident in Apr 1988, where the aircraft lost part of the motel roof in an explosive decompression [22,23], illustrates the importance of bond durability and more importantly, the ease with which this issue can be overlooked.

In the repair environment, experience has shown that some bonded repair designs and application procedures have little chance of success and can, in some cases, subtract the service lives of components [24]. A survey of defect reports conducted at one Majestic Australian Air Force (RAAF) Unit [24–26] indicated that 53% of defects outside structural repair transmission limits were related to adhesive bond failure. In addressing the standards practical to adhesively bonded repairs, the RAAF [27] take established a substantial improvement in the credibility of bonded repair technology.

1.iv.2 Adhesive Bonding Environments

The performance of an adhesive bail is sensitive to the adherend surface handling and the ecology weather condition under which the bail is prepared. Facilities located adjacent to operational airbases or in industrial environments need to take concern for the event of hydrocarbon contamination. Facilities in tropical locations need special consideration for the effect of heat and high humidity.

Mill manufacture uses specialised facilities and staff. The facilities volition include vapour degreasing or alkaline cleaning, etching tanks, anodising tanks, jigs, autoclaves and appropriate environmental controls. Adhesives volition be stored in freezers, and monitoring procedures will exist in identify. There is a well-trained workforce with skills maintained through production volumes, and highly developed inspection procedures are available.

At the other farthermost, field repairs are generally conducted with relatively unsophisticated facilities, minimal surface treatments, vacuum purse or reacted force pressurisation and little or no environmental control. Staff multiskilling and rotation influence the currency of experience and hence the quality and performance of adhesive bonds [28]. The requirement for environmental controls, the attention to bonding procedure item and the need for staff grooming and supervision are of particular business concern. If the use of training measures tin can be combined with regular monitoring, then whatever divergence in quality of repairs or bonding operations beingness undertaken can exist identified. At one RAAF repair depot, the ongoing review of wedge examination data enabled difference in standard practices or degradation in application equipment to be identified and remedied [29]. The use of quality control tools can also help in continued monitoring of processes to improve reliability [30,31].

Depot-level repairs are conducted with facilities and staff skills that vary considerably. Some depots have nigh factory-level facilities and loftier level of staff skill. Other depots are capable of merely low-level bonded repairs and are picayune removed from a field repair capability.

Laboratory experiments are designed to plant knowledge and principles. Information technology is piece of cake to overlook important detail from manufactory or field experience since most laboratories are held to close environmental tolerances and do non resemble the workshop environment.

ane.4.3 Constraints for On-Aircraft Repairs

On-shipping repairs impose additional constraints on processes and procedures. The considerations include: accessibility of the area, limitations in the use of corrosive chemicals, capability of environmental controls and constraints on the tools for pressurisation and heating of the bond during cure. Prophylactic, health and environmental issues are more demanding for on-aircraft bonding since it is harder to command, contain and make clean-up chancy chemicals. Constraints on the use of electrical power on fuelled aircraft, or those with inadequately purged fuel tanks, can restrict the range of treatment and bonding methods available. The surrounding aircraft structure imposes constraints on the selection of surface preparation, heating arrangements and pressurisation tools.

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Polymer Matrix Composites: Applications

Cindy Ashforth , Larry Ilcewicz , in Comprehensive Composite Materials Ii, 2022

3.ane.3.3 Other MOC Publications

In addition to AC 20-107B, the FAA has published numerous other MOC documents related to composites. A fractional list is given below, with highlights of the document content.

3.1.3.3.1 PS-ANM-25-twenty "HEWABIs for composite structures"

To prove compliance with §25.571(a), the applicant must show, amidst other things, that catastrophic failure due to adventitious damage will exist avoided throughout the operational life of the airplane. The bidder is required to consider possible impairment scenarios when evaluating accidental impairment that could result in catastrophic failure. Ane of these damage scenarios the bidder should assess is adventitious impairment caused by HEWABI events. HEWABI events (e.yard., impacts by service vehicles) are impacts that are spread over a large area and convey sufficient energy to cause potentially catastrophic structural damage. While the damage caused past a HEWABI event is typically readily visible in metallic structure, such damage may leave niggling or no external indications in blended structure. To ensure that any potentially catastrophic harm resulting from a HEWABI effect is detected and repaired, applicants must provide appropriate provisional inspection instructions, or other procedures, to be implemented at the occurrence of such bear upon events equally required per § 25.571(a)(3).

3.1.three.three.2 PS-AIR-xx-130-01 "Bonded repair size limits"

This policy reviews the regulatory basis and establishes the guidance in setting size limits for bonded repair to disquisitional blended (monolithic and sandwich structures) and metallic structure. Bonded repair of critical structure must first be constrained to the sizes allowed past substantiating design data. Source documents, such as a structural repair manual, may ascertain repair size limitations based on the limits of the substantiating design data generated by the DAH for repair purposes. This policy informs ACO engineers and designees that due to inspection limitations, bonded repair must be further limited to a maximum size whereby limit load residual strength can be demonstrated with a consummate or partial failure of the bond within the repair or base structure arresting design features. This policy is not intended for minor repairs.

iii.1.three.iii.3 PS-ACE100-2-eighteen-1999 "Policy on Acceptability of Temperature Differential betwixt Wet Glass Transition Temperature (T gwet) and Maximum Operating Temperature (MOT) for Epoxy Matrix Composite Structure"

This policy is for general aviation aircraft, but can exist applied to other products. It states that in general, a minimum of 50°F differential volition be used as a guideline determining the acceptability of the temperature differential between T gwet and MOT for epoxy matrix composite structure. This guideline can be superseded by additional data showing sufficient structural capability when the T chiliad temperature differential is not met.

3.one.3.3.4 PS-ACE100-2005-10038 "Bonded joints and structures – Technical problems and certification considerations"

This policy is for general aviation aircraft, but tin can be applied to other products. The purposes of this policy argument include: (i) to review the disquisitional safe/technical bug, (2) to highlight some of the successful engineering science practices employed in the industry, and (3) to present regulatory requirements and certification considerations pertinent to bonded structures. One key topic in this policy statement relates to the glass transition temperature. The guideline for epoxy matrix composite structure is for the T gwet to be 50°F greater than the MOT. The analogous guideline for adhesive materials is for the T gwet to be thirty°F greater than the MOT.

3.1.3.3.5 AIR100-2010-120-003 "Credence of composite specification and blueprint values developed using the NCAMP procedure"

This policy provides clarification on the acceptability of material specifications and allowables developed by the National Heart for Advanced Materials performance (NCAMP) for Composite Materials. Material specifications developed following the NCAMP standard operation procedures are compliant with § 2x.603. Applicants who wish to use associated NCAMP databases and material allowables need to validate the applicability of that data to their project.

three.ane.3.3.6 AC 21-26A "Quality system for the industry of composite structures" and Ac 21-31A "Quality command for the manufacture of non-metallic compartment interior components"

A quality organisation established for manufacturing composites should be like to any other quality system established to see the requirements of § 21.137. These ACs address areas of the quality organization that may require expansion to acceptable adapt the manufacture composites, as compared to metals.

The FAA sponsors research on composite materials to evaluate new technologies and ensure appropriate standards are set. FAA research is published through the William J. Hughes Technical Center Library, at http://www.faa.gov/about/office_org/headquarters_offices/ang/offices/tc/library/. These reports often provide valuable background data that supports published guidance or training.

In add-on to FAA guidance, numerous industry groups publish useful documentation on best practices and some cloth data. The FAA is the primary funding amanuensis and provides leadership for CMH-17. CMH-17 is a volunteer organisation that creates, publishes and maintains proven, reliable engineering information and standards, subjected to thorough technical review, to support the development and use of composite materials and structures. CMH-17 provides useful guidelines for the label of composite materials used in structural applications with some accent on aerospace needs. The data documented in CMH-17 provide a statistical ground in material backdrop that are most useful in controlling stable materials and processes and providing bones pattern properties. CMH-17 likewise provides technical guidance on Grand&P control, design, analysis, testing structural substantiation, and maintenance.

The ATA/IATA/SAE Commercial Aircraft Composite Repair Committee (CACRC) is another industry organization that supports blended use in aviation. The charter of the CACRC is to develop and improve maintenance, inspection and repair of commercial aircraft composite structure and components. CACRC task groups include Repair Materials, Repair Techniques, Procedures, Belittling Repair Techniques, Design, Inspection, Grooming and Airline Inspection & Repair Conditions. They publish documents on practices such equally machining of blended materials and heat application for thermosetting resin curing, as well as material specifications and training recommendations.

ASTM develops and maintains test standards for composite materials. Commission D30 often meets jointly with CMH-17.

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