Thought leadership from our experts

Aircraft Maintenance – The Regulatory Framework

This article is mainly targeted at aviation transaction lawyers, particularly those for whom their encounters with aircraft maintenance issues do not necessarily rank as a career high ("that's for the techies" being a typical refrain). Nevertheless, maintenance is such a vital feature of an airline's operation that at least a rudimentary knowledge of its regulatory environment is beneficial if not essential. It is not only relevant to some extent for the purposes of understanding and negotiating maintenance covenants and maintenance reserve provisions in lease agreements, but it is highly relevant for those involved in the negotiation of maintenance contracts, particularly as power-by-the-hour agreements are becoming ever more prevalent. These can be complex and challenging and can, depending on their scope and duration, run to billions of dollars.

Chicago Convention

The primary instrument regulating international civil aviation is the 1944 Convention on International Civil Aviation, usually referred to as the Chicago Convention, which came into effect in April 1947. It has 191 contracting States including all United Nations member States with the exception of Dominica and Tuvalu. One of Its principal objectives, reflected in its preamble was to agree "certain principles and arrangements in order that international civil aviation may be developed in a safe and orderly manner" and in that respect it has been resoundingly successful.

The International Civil Aviation Organisation (ICAO), a specialised U.N. agency, was established by Part II, Chapter VII of the Chicago Convention. Article 37 of the Convention obliges every contracting State to collaborate in attaining the highest degree of uniformity in civil aviation regulations, standards and procedures and to that end ICAO was charged with the responsibility for adopting international standards and recommended practices (commonly referred to as SARPS). These are embodied in Annexes to the Convention, of which there are currently 19. A "standard" is a prescribed practice the uniform application of which is considered necessary and which contracting States are therefore obliged to adopt, whereas a "recommended practice" is considered desirable rather than essential and contracting States are only obliged to endeavour to implement it.comply with it. Annex 8 (which deals with airworthiness and most of its requirements are standards.

Article 31 of the Convention provides that the State of Registration is responsible for issuing certificates of airworthiness in respect of those aircraft registered with it and Article 33 obliges all contracting States to recognise certificates of airworthiness issued by other contracting States provided they comply with or exceed the minimum prescribed standards. Annex 8 defines those minimum standards.

Annex 8

Part I of Annex 8 contains the following fairly unremarkable but nevertheless important definition of "maintenance":

"The performance of tasks required to ensure the continuing airworthiness of an aircraft, including any one or combination of overhaul, inspection, replacement, defect rectification, and the embodiment of a modification or repair."

Curiously, neither the Chicago Convention nor Annex 8 seems to contain a definition of "airworthy" or "airworthiness", presumably on the basis that their meanings are obvious and what matters is any prescribed level or standard of airworthiness.

The key provisions in Annex 8 dealing with the initial development of continuing airworthiness and maintenance information as part of the type certification process for large aircraft (i.e. those weighing more than 5,700 kg) are to be found in Chapter 10 of Part IIIA in the case of type certification applications submitted to the State of Design after 2 March 2004 and in Section 7.7 of Chapter 7 of Part IIIB in the case of post-2 March 2004 applications. Part IIIA, Chapter 10 and Part IIIB, Section 7.7 are virtually identical. Paragraph 7.7.2 requires that the "Maintenance Information shall include a description of the aeroplane and recommended methods for the accomplishment of maintenance tasks. Such information shall include guidance on defect diagnosis." Paragraph 7.7.3 then provides that the "Maintenance programme information shall include the maintenance tasks and recommended intervals at which these tasks are to be performed" and paragraph 7.7.4 stipulates that "Mandatory maintenance requirements that have been specified by the State of Design as part of the type design shall be identified as such and included in the maintenance information of 7.7.3."

ICAO's commentary on Annex 8 recognises that it is not intended to replace national codes of airworthiness and that each State is entitled to develop its own comprehensive airworthiness code or to adopt one established by another State. Annex 8, together with guidance material contained in ICAO's Airworthiness Technical Manual (Doc 9760), is simply intended to establish a basic airworthiness standard. However,

Regulatory oversight – the FAA and EASA regimes

Unless there has been a delegation, pursuant to Article 83 bis of the Chicago Convention, of its airworthiness responsibility under Article 31 by a State of Registry to the home State of an operator (which occasionally happens with leases and interchanges), that responsibility will reside with the aviation authority of the State of Registry of the aircraft in question. The two most developed and prominent airworthiness regimes are those administered by the FAA and EASA and many States follow one of those models.

Title 49 of the United States Code, § 44701 charges the FAA with responsibility for promoting the safe flight of civil aircraft in air commerce by prescribing regulations and standards in the interest of air safety. 49 U.S.C. § 44701 also obliges the FAA to regulate aircraft operations at different levels of safety, with air carrier operations requiring the highest level. The regulations are contained in Title 14 of the Code of Federal Regulations and are commonly known as the Federal Aviation Regulations or FARs. As far as the maintenance of large transport aircraft is concerned, the important regulations are in 14 C.F.R. Part 21,Subpart B and Part 25, Subpart G and Appendix H, dealing with initial airworthiness, and Part 121, Subparts G and L, dealing with continuing airworthiness.

EASA is the European Aviation Safety Agency and was created by Regulation (EC) No 1592/2002, since replaced by Regulation (EC) No 216/2008, known as the "Basic Regulation". EASA comprises the 28 European Union States, together with Iceland, Liechtenstein, Norway and Switzerland. The Basic Regulation is supplemented by a number of implementing regulations, the most important of which from a maintenance perspective are contained in Annex I (Part-21) to Commission Regulation (EU) No 748/2012, dealing with initial airworthiness, and Annex I (Part-M) to Commission Regulation (EU) No 1321/2014, as amended by Commission Regulation (EU) 2015/1536, dealing with continuing airworthiness.

The two regimes are very similar and in 2011 the U.S. and the European Union entered into an Agreement on Cooperation in the Regulation of Civil Aviation Safety, known as "BASA", which is designed to promote further regulatory harmonisation and is intended to improve efficiency in the transatlantic oversight of certification, continued airworthiness and maintenance. The current version of BASA is Revision 3, dated March 2016. There is a Technical Implementation Procedures document, entered into pursuant to BASA, which facilitates the co-ordination of the activities of the FAA and EASA. The U.S. and the EU have entered into other similar bilateral agreements with other States, but the BASA is the most significant.

The development of a maintenance programme

As part of the type certification process, the manufacturer is required to develop a set of Instructions for continued airworthiness. These take the form of manuals, which typically include an Aircraft Maintenance Manual and a Component Maintenance Manual, and which must be delivered to the first operator of each aircraft. They are mandated by 14 C.F.R. 21 § 50(b) and 14 C.F.R. 25 § 1529 and Appendix H, para H25.2 and by EASA Part 21, section 21.A.61 and CS-25.1529 and Appendix H, para H25.2. (Appendix H to 14 C.F.R. Part 25 and Appendix H to CS-25 are virtually identical – any differences between 14 C.F.R. Part 25 and CS-25, including their respective Appendices H, are identified in a list of "Significant Standards Differences" (known as an SSD list) produced pursuant to the Technical Implementation Procedures.)

Appendix H, para H25.3(b) to both 14 C.F.R. Part 25 and CS-25 provides that the manuals must include maintenance instructions. These must contain scheduling information setting out the recommended intervals at which the aircraft and its components, including engines, should be inspected and tested, the allowable wear tolerances, and the tasks recommended at each interval. They must also contain troubleshooting information. These maintenance instructions are developed in relation to each aircraft type by an Industry Steering Committee (commonly referred to as the ISC) comprising representatives of the airframe and engine manufacturers, other product vendors and expected airline operators. They report to a Maintenance Review Board (commonly referred to as the MRB) which comprises regulators appointed by the regulatory authority of the State of Design. The ISC formulates a draft MRB Report (referred to as the MRBR), using MSG-3 methodology. MSG-3 is an analytical process devised by Airlines for America (A4A, formerly known as the ATA). Basically, it comprises three main elements:

(a) the Aircraft Systems/Powerplant;

(b) the Aircraft Structure, meaning all load bearing members including wings, fuselage, empennage, engine mountings, landing gear and flight control surfaces; and

(c) a Zonal Inspection Programme, which divides the aircraft into zones, with a task listing work sheet for each zone and zonal task intervals.

When it has been approved by the MRB, the MRBR is submitted for approval by the regulatory authority of the State of Design, following which it will be adopted by the manufacturer as a Maintenance Planning Document (MPD) on which each operator of the aircraft will then base its own individual maintenance programme (usually referred to as the maintenance schedule in the U.S.) for approval by its own regulatory authority. 14 C.F.R. 121 § 135(b)(18) obliges a Part 121 air carrier to have a maintenance schedule and it is authorised by the FAA through the air carrier's OpSpecs (operations specifications). Under EASA Part M, para M.A.302(a) and (b), all maintenance must be undertaken in accordance with a maintenance programme approved by the operator's regulatory authority.

The MRBR/MPD is a dynamic document which is revised throughout the life of the aircraft, so that task intervals may be increased and maintenance periods extended as experience is gained and component reliability and durability improves. The maintenance programme or maintenance schedule may then need to be amended accordingly.

Maintenance Performance

14 C.F.R. 121 § 363(a) makes a Part 121 air carrier responsible for the airworthiness of its aircraft and the performance of all necessary maintenance, even if that maintenance is contracted to a third party. EASA Part M, para M.A.201(e) provides that an air carrier licensed in accordance with Regulation (EC) No.1008/2008 (the broad equivalent of a Part 121 air carrier in the U.S.) is similarly responsible.

Pursuant to 14 C.F.R. 121 § 379, a Part 121 air carrier is, by virtue of its air carrier certificate, a maintenance entity and is thereby authorised to undertake maintenance on its own aircraft. Any individual who is in charge of the performance of any such maintenance must hold an "appropriate airman certificate". That means a mechanic, duly certificated under 14 C.F.R. Part 65, Subpart D. Any third party maintenance organisation contracted by the air carrier to undertake the maintenance need not necessarily be 14 C.F.R. Part 145 certificated (although it typically would be) – its obligation is to comply with the applicable Part 121 requirements and the maintenance programme, and not with the requirements of Part 145.

Under EASA Part M, para M.A.201(e), a licensed air carrier is approved, as part of its AOC (air operator certificate), as a continuing airworthiness management organisation (a CAMO) for all aircraft covered by its AOC (para M.A.703(b)) and must also either be approved as a maintenance organisation under EASA Part 145 (Annex II to Commission Regulation (EU) No 1321/2014, as amended by Commission Regulation (EU) 2015/1536) or must contract with such an organisation pursuant to para M.A.708(c). The role of the CAMO is to determine what maintenance is required, when it has to be performed, by whom and to what standard in order to ensure the continued airworthiness of the aircraft. The actual maintenance has to be performed by a Part 145 organisation and the work needs to be signed of by an engineer holding a category B1 or B2 aircraft maintenance licence issued under EASA Part 66 (Annex III to Commission Regulation (EU) No 1321/2014, as amended by Commission Regulation (EU) 2015/1536) with an appropriate type rating.

Release to Service

Upon completion of any maintenance an aircraft or a component (including an engine) needs to be released to service. Under the FAA regime, 14 C.F.R. 121 § 379(b) authorises an air carrier to approve an aircraft its engines or other components for release to service. This is accomplished, in the case of a component, by the issuing of an FAA 8130-3 airworthiness approval tag. FAA Order 8130-21H, para 1.7.c. provides that an FAA 8130-3 cannot be used for the release to service of an aircraft. 14 C.F.R. 121 § 709 provides that an aircraft is released to service by either an airworthiness release form or an entry in the aircraft log. In practice, the log entry is the method used.

Under the EASA regime, a component is released to service after maintenance by the issuing of an EASA Form 1. In the case of maintenance carried out by a Part 145 organisation, the EASA Form 1 is issued pursuant to EASA Part 145, para A.50(d). The EASA Form 1 cannot be used for the release to service of an aircraft, a certificate of release to service is required and in the case of maintenance carried out by a Part 145 organisation this is issued pursuant to EASA Part 145, para 145.A.50(a).

Record Keeping

Under the FAA regime, 14 C.F.R. 121 § 369(c) requires an air carrier to establish a record keeping system for the preservation of all work performed on its aircraft. The system must be documented in the maintenance manual. 14 C.F.R. 121 § 59(b)(1)(ii)) requires the air carrier to maintain a listing which identifies the location of each record, document and report which it is required to make and retain.

14 C.F.R. 121 § 380(a)(2) sets out the record keeping requirements, which may be summarised as follows:

(a) the total time in service since new or rebuilt of the airframe and engines;

(b) the current status of each life-limited part (LLP);

(c) the time since the last overhaul in respect of those components requiring overhaul;

(d) the current inspection status of the aircraft (including the time in service since the last accomplishment of each scheduled maintenance task and the time remaining until the next scheduled task becomes due); and

(e) the current status of all applicable airworthiness directives (ADs).

14 C.F.R. 121 § 380(c)(2) requires that the records of the last complete overhaul of each airframe, engine and component are retained until the work is superseded by work of equivalent scope and detail and 14 C.F.R. 121 § 380(c)(3) provides that the records required to be kept pursuant to § 380(c)(2) must be transferred with the aircraft when it is sold.

Under the EASA regime, EASA Part M, para M.A.305(b) requires a air carrier to maintain a continuing airworthiness record system comprising aircraft and engine logbooks, life limited part log cards and a technical log. Para M.A.305(d) provides that the records must contain the current status of the following:

(a) ADs and other such mandatory requirements;

(b) modifications and repairs;

(c) maintenance programme compliance; and

(d) service life limited components, together with a mass and balance report and a list of deferred maintenance.

AMC M.A.305(d)4 and AMC M.A.305(h) explain the concept of "service life-limited components". It embraces components which are subject to a certified life limit after which the component should be discarded and components which are subject to a service life limit after which their serviceability has to be restored by appropriate maintenance. The current status of components having a certified life limit must indicate that life limit, the number of accumulated hours and cycles and the calendar time and the hours, cycles and calendar time remaining. Similarly, the current status of components having a service life limit must indicate the service life limit, the number of accumulated hours and cycles and the total calendar time since the service life was restored and the hours, cycles and calendar time remaining until the next required removal.

EASA Part M, para M.A.305(h) specifies the periods for which the records must be retained. All detailed maintenance records in respect of the aircraft and its installed service life limited components must be kept "until such time as the information contained therein is superseded by new information equivalent in scope and detail but not less than 36 months after the aircraft or component has been released to service". The records of total time in service (i.e. hours, cycles and calendar time) of the aircraft and all service life limited components must be retained for at least 12 months after the aircraft or component has been permanently withdrawn from service and the records of the time in service since the last scheduled maintenance in respect of those components having a service life limit must be retained at least until the next scheduled maintenance of equivalent work scope.

As can be seen, neither the FAA nor EASA requires the indefinite preservation of complete back-to-birth traceability of life limited parts. This is made clear in the case of the FAA by its Advisory Circular AC No. 120-16F, para 8-12 ("Records such as the in-service history of life-limited parts (traceability back-to-birth)……..do not need to be kept indefinitely"). Nevertheless, it is the invariable practice of operating lessors to require such full back-to-birth traceability.

Hopefully, for those who have made it to the end of this article, it has provided some insight, or enhanced insight, into the regulatory aspects of the aircraft maintenance environment.