Examination is a written form of demonstration of a certain level of theoretical knowledge by the student based on achievement of the learning objectives, usually performed on completion of a theoretical training course or a portion of a course. The student shall demonstrate, to the levels identified in the table in Appendix III, the detailed theoretical knowledge of the aircraft’s applicable systems, structure, operations, maintenance, repair, and troubleshooting according to approved maintenance data, as well as the use of manuals and approved procedures, including the knowledge of relevant inspections and limitations. The standard, format, pass mark, etc. are defined in Appendix III, 4.1. The examination shall be performed by the appropriately trained and approved examiner.
Assessment is a practical form of measuring the competence of the student by evaluating three major factors associated to the learning objectives: knowledge, skills and attitude, usually performed on completion of a practical training course. The assessment should focus on the competencies relevant to the aircraft type and its maintenance. The principles on how to perform the competence assessments are given in the AMCs to Part-66, Appendix III. The assessment shall be performed by appropriately trained and approved assessors.
Regarding Part-66 Appendix III, point 5., “Type Examination Standard” does not apply to the examination performed as part of type training. This point only applies to those cases where type examination is performed as a substitute for type training, which means it is intended for the examinations conducted by (or on behalf of) the competent authority on those aircraft that do not require a type training (typically Group 2 and Group 3 aircraft according to Appendix I to the AMCs to Part-66). So, it is true that the examiners authorised by the competent authority shall not have been involved in the applicant's training. In all other cases AMC to Part-66 Appendix III applies, which means that the roles of the assessor and the instructor may be combined for the practical elements, depending on the size of the organisation.
Regarding the roles of examiners and assessors, these are different functions (which does not prevent that one person can’t be authorised both as examiner and assessor). Normally, these functions should not be confused. The expression “The examination shall be oral, written or practical assessment based, or a combination thereof, …” applies only for Section 5, i.e. “Type Examination Standard”.