The answer is, as has been aluded to already, that the last 2 miles of the approach must be conducted viusally, i.e. if you don't get the runway in sight when the SRA terminates, you must go around.
The same applies to an SRA anywhere else in the UK.
Sadly, runway 04/22 at Norwich is closed due to subsidence on the north side of the intersection with 27/09, and it's unlikely ever to re open due the cost of the repair work.
Crying shame cos it's a very useful option, not only for us, but the operators as well.
Anyone got £2.50?
