As the term implies they were the best performing students from each course. They weren't quite 'students one minute, instructors the next', as they had to complete the QFI course before they were let loose on real trainees. In my experience though as they had generally passed through their own training with relative ease they weren't particularly understanding of those that found it hard. I preferred the ex-truckies and similar who had grafted their way through to their wings and who could actually comprehend that what they were teaching was quite difficult for some and therefore why Bloggs was having trouble doing it.