Aircraft type rating training must have been started and be completed within the 3 years preceding the application for a type rating endorsement (Part-66, Appendix III, paragraph 1 refers).
It does not make sense to attend in the first instance a TRT course with the intent of getting this TRT later endorsed on the maintenance licence for two main reasons:
- at the time the TRT is gained, the holder has no licence and it may take more than 3 years before the applicant is compliant with the basic knowledge (66.A.25) as well as the experience requirements (66.A.30). Therefore the applicant runs the risk to get its TRT certificate expired at the time he applies for the licence and the TRT endorsement; and
- From an intellectual point of view, this is not logical to demonstrate maintenance competence on a specific aircraft type without having acquired the basic knowledge, skills and attitude related to the maintenance and the technologies used in aviation in general.
Legally speaking the situation is not forbidden. However be sure that you get your licence within the 3-years’ timeframe from the date you passed the TRT course.