Part-21: design (DOA) and production (POA) approvals, the architecture of initial airworthiness

The regulatory framework

Initial airworthiness of civil aircraft in Europe rests on Commission Regulation (EU) No 748/2012 of 3 August 2012, a recast of the rules for airworthiness and environmental certification of aircraft and related products, parts and appliances, and for the certification of design and production organisations. Its Annex I, Part-21, is divided into subparts, each corresponding to a type of certificate or approval.

Among the most significant for industry:

• Subpart D: changes to type-certificates;
• Subpart F: production without production organisation approval;
• Subpart G: production organisation approval (POA);
• Subpart J: design organisation approval (DOA);
• Subpart M: repairs.

DOA: responsibility for design

EASA defines a design organisation approval as recognition that an organisation complies with the requirements of Subpart J. The terms of approval set out its scope, product categories, products covered and privileges granted. For organisations established in the Union, EASA is the competent authority.

A DOA is built on a design assurance system: an independent function verifying compliance, an airworthiness office handling relations with the authority, procedures for classifying changes and repairs, and management of continuing airworthiness data. Depending on its privileges, the organisation can classify changes and repairs as "minor" or "major" and approve some of them itself, which considerably shortens lead times.

For simpler projects, EASA offers Alternative Procedures to Design Organisation Approval (ADOA), which recognise that an organisation meets certain Part-21 criteria without requiring the full DOA set-up.

POA: ensuring every unit conforms

The production organisation approval under Subpart G certifies that a manufacturer can produce aircraft, engines, propellers, parts or appliances that conform to approved design data. It is issued by the national authority of the state where the principal place of business is located; in France, oversight takes place within the framework organised by the DGAC.

The core of a POA is a production quality system: supplier control, inspection and testing, non-conformity management and traceability. The holder can issue an EASA Form 1 for the new parts it produces, a document that then accompanies the part throughout its life. Subpart F offers an alternative, case-by-case route for limited production without an organisation approval.

An essential interface

DOA and POA do not operate in silos. A production approval holder must demonstrate that it has an arrangement with the design organisation ensuring satisfactory coordination: transmission of up-to-date design data, reporting of production deviations and handling of concession requests. In large groups, both approvals often coexist within the same entity; in the supply chain, the arrangement links separate companies.

Oversight and continued validity of approvals

A Part-21 approval is not granted once and for all. The competent authority continuously oversees holders through planned audits and investigations on specific projects or products. Findings must be closed within the set deadlines, failing which the approval may be limited, suspended or revoked. Any significant change to the organisation, its premises or its scope of work must also be notified and, where required, approved before implementation.

Why MRO is concerned

The boundary between initial and continuing airworthiness is less watertight than it seems. A Part-145 shop can only carry out a repair or modification using approved data, issued by the manufacturer, a DOA holder or the authority. Developing its own repairs, or supplemental type certificates for cabin or avionics modifications, requires holding a DOA or working with a partner that does.

This is why many MRO players have, over the years, built an approved design office alongside their maintenance activities. The combination lets them offer repair solutions that are faster and cheaper than part replacement, and capture a greater share of value over the aircraft's life cycle.