No, the Assessor's examination I'm referring to has nothing to do with the CAA but is the test for accreditation as an Interlocutor and Rater using the British Council approved Test of English for Aviation.
The candidate, following the training course, has to correctly rate a number of recordings of interlocution.
Not only must the overall grading in each case be correct but each individual area, i.e. Pronunciation, Structure, Vocabulary, Fluency, Interaction, Comprehension, in each interlocution must also be correctly graded.
It's undoubtedly the hardest exam I've ever taken.