‘Translation is like a woman. If it is beautiful, it is not faithful, if it is faithful, it is most certainly not beautiful’
Using an interpreter is sometimes necessary but the limitations of teaching through a third party need to be understood and taken into account. It takes about one third longer to teach through an interpreter. If your lesson plans do not reflect this then the trainee is getting a rough deal.
Using an interpreter is a skill and you will almost certainly have to learn this yourself because no one I have come across is prepared to admit to the need for training to deliver this skill. A short course is all that is needed so that you are at least alerted to the tips and traps.
It is very important that the interpreter understands aviation and aviation terminology. I once told the Chinese crew I was training that I was going to change the wind for the next exercise. When they dissolved in laughter I found out that the interpreter had told them that the instructor was about to fart!
Listen-up, training via interpreters will never be as good as a lesson taught in the first language of the candidate. The common teaching language is English but if the candidates are not fluent in English then a similar problem exists. My advice to those commissioning training is to do everything possible to optimise the delivery of any licence related training course. Do not accept the standard course without suitable supplements to support this method of teaching.