Would it not be more useful if it was a lozenge?
PPL students are taught to calculate MSAs 5 miles beyond destination just in case they overshoot. Should the NRB not also do the same.
I generally want to know the area between Biggin and Rochester out to 20 miles either side. 20 miles beyond both airfield would reduce the risk of hitting a tra or other restriction if you accidentally go beyond destination. To do this I need to put in heathrow to manston.
I also could not find an explanation of a narrow route briefing in the AIs help text, hence the question.