Aerotechnical Consulting & Coaching - Fachwissen in Aviation und Maintenance

Aviation Glossary

Revolving around Maintenance Training and Consulting

Here we provide you with the definition of some terms used in our special field. In case you cannot find the word or abbreviation you are looking for, please contact us.

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Aircraft Maintenance Licence. An AML is a requirement for obtaining a qualification for release after maintenance work. The licence is subdivided into the Categories A, B1 (Mechanics), B2 (Avionics), and C.


Condition of an aircraft that permits safe operation.

Airworthiness Directive (AD)

Work on the aviation device in accordance with the binding directive issued by the public authorities. In case of a failure to comply with an Airworthiness Directive, the airworthiness expires. The required time for carrying out the work and its nature is stated in the Airworthiness Directive (AD).

Appropriate Public Authorities

The appropriate public authority for companies with their headquarters within the territorial area of an EASA member country is the public authority of the same member country. For other companies, EASA is the appropriate public authority.


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Big Training Facility

A training facility offering the possibility of training 50 or more applicants simultaneously.


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Certifying Staff

Maintenance and test work on commercially used aircraft is only to be certified by persons who hold an Aircraft Maintenance Licence (AML), in accordance with EASA Annex III (Part-66). Only staff with a qualification for release (Certifying Staff) are allowed to issue a release to service - the Certificate of Release to Service (CRS).

Continuation Training

Corresponding to the regulations stipulated in EASA Annex II (Part-145), a maintenance facility has to establish proof of Continuation Training for its Certifying Staff every two years.


Certificate of Release to Service - Release of aircraft after maintenance work


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The European Aviation Safety Agency defines uniform quality standards for airlines in the countries of the European Union.  The EASA regulations emerge from the JAR requirements and are decisive for the aviation maintenance facilities as well as for the training of their staff.  [The EASA regulations] are enforced by the national public authorities of their member countries; in Germany by the Luftfahrt-Bundesamt (German Federal Aviation Authority)

EASA Annex 1


Defines the term airworthiness, thus the operational safety of aircraft.  It describes, e.g., who has to ensure airworthiness and which organizations are allowed to carry out maintenance measures.  The operator is allowed to carry out the necessary maintenance work itself, if it is an authorized maintenance facility in accordance with Part-145.  Otherwise it has to entrust an authorized facility with the maintenance that issues Certificates of Release to Service for the work carried out. Also JAR OPS 1 Subpart M.

EASA Annex 2 (Part-145)

Maintenance Organization Approvals - requirements for maintenance facilites.  Stipulates, e.g., the requirements that a maintenance facility has to meet in order to be granted the maintenance license for aircraft and aircraft components.  Maintenance work on an aircraft or on an aircraft component are only to be carried out by a facility that is authorized in accordance with EASA Annex II (Part-145) or that uses the quality assurance system of an authorized maintenance facility.  A Certificate of Release to Service after work on an aircraft or on an aircraft component is only to be issued by a maintenance facility.  Maintenance work and test functions on an aircraft can only be carried out by specifically qualified staff in a facility that has a license in accordance with EASA Annex II (Part-145).  The Certificate of Release to Service has to be issued by Certifying Staff. Also JAR 145 / Part-145.

EASA Annex 3 (Part-66)

Describes the requirements for Certifying Staff in approved maintenance facilities, as well as the requirements for obtaining and retaining this qualification.  Required is an Aircraft Maintenance Licence (AML) issued by the Aviation Authority after successful training with ATCC.  The different AML categories represent the areas of operation and responsibilities.  In addition, an operational qualification is required after an internal briefing.  [This qualification] is only valid for the issuing company. Also JAR 66 / Part-66.

EASA Annex 4 (Part-147)

Describes the requirements for approved training organizations that conduct the training and examinations for Certifying Staff.  The training is only to be provided by qualified training organizations that guarantee a minimum standard in theoretical and practical training.  The training courses provide a definite minimum of knowledge. Also JAR 147 / Part-147.


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Joint Aviation Authorities JAA

Special partnership of the European Aviation Authorities in Hoofddorp, the Netherlands.

Joint Aviation Requirements JAR

Aviation regulations developed in Europe and maintained under the JAA umbrella.


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Luftfahrt-Bundesamt (LBA) German Federal Aviation Authority

The higher German Aviation Authority (compare LBA Act), headquartered in Braunschweig, responsible for model and transportation licensing of aviation devices, licensing and monitoring of aviation companies, issuing and developing aviation regulations, and a great deal more.


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Maintenance Training Organization Exposition (MTOE)

Each approved training organization has to have a MTOE (handbook) authorized by the Aviation Authority (Luftfahrt-Bundesamt - German Federal Aviation Authority), in accordance with EASA Annex IV (Part-147). The MTOE ensures that at any time all training courses meet the standards stipulated in EASA Annex IV. This MTOE embodies precise descriptions of the training, examinations, teaching staff, quality assurance, and training facilities.

Maintenance, Repair and Overhaul Facility

Describes a facility that carries out maintenance, repair, and overhaul of aircraft.

Maintenance Work

One or a combination of the following assignments: overhaul, repair, inspection, replacement, modification or fault corrective action on an aircraft or on a component, with the exception of the pre-flight check.


Defined condition of an aircraft (possibly the prototype).

Model Test

Examination of the proof that the construction regulations have been fulfilled, as well as one/more prototypes to have fulfilled the construction regulations. At the close of the model test a model licence is issued by issuing a licence certificate, the identification sheet.

Model Licence

A positive result of the model test. Afterwards parts of the aircraft can be mass-produced according to the model.


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Overhaul Facility

A facility authorized to carry out aircraft overhaul.  Work within the framework of operational approval.  Newly introduced by the regulation (EG) 2042/2003 under the name Part-145.


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Quality assurance.


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Small Training Facility

A training facility that does not fall within the ambit of the category "Big Training Facility"