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145.A.20 establishes that a Part 145 approval is granted based on a defined scope of work, and the organisation may only perform maintenance within the terms and limitations specified on its approval certificate.
What it means in practice
The terms of approval define exactly what maintenance an organisation is authorised to carry out. This is specified using a class and rating system. For aircraft maintenance, the ratings define which aircraft types and categories are covered. For component maintenance, the ratings cover specific component types or categories. An organisation may hold multiple ratings across different classes.
The approval certificate, EASA Form 3, is the official document that states the approved scope. Any maintenance performed outside the terms stated on that certificate is unauthorised. The terms of approval also set any specific limitations, such as restrictions to a particular location or type of work.
Key requirements
The organisation must ensure that all maintenance is performed strictly within the scope of its approval. The class and rating system provides the framework: Class A covers aircraft maintenance (line and base), Class B covers engine maintenance, Class C covers component maintenance other than engines, and Class D covers specialised services. Each class is further divided into ratings that specify exact aircraft types, engine types, or component categories.
Any change to the terms of approval, such as adding a new aircraft type or component rating, must be applied for and approved by the competent authority before the work commences.
Common compliance gaps
A common gap is performing maintenance tasks that subtly exceed the approved scope, for example, carrying out a component repair when the organisation only holds a rating for component overhaul, or performing work on a sub-variant of an aircraft type that is not explicitly covered by the rating. Organisations should regularly review their approval certificate against actual work being performed.
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