I'm afraid you and a few others betray your slight lack of knowledge on the subject. The T6C is not intended to replace the Hawk T1. Students currently move from Tucano straight to Hawk T2. IV Sqn is 208 and 19 Sqns in old money. There never has been a Hawk T1 transition to Hawk T2.
The T6C will replace the Tucano with a shorter course.
I hope I have now spelt it out in obvious enough terms.
Whether the numbers of airframes are sufficient is for the bean counters to work out. I'm just the pilot!
BV
