2 down refers to the MOD's acknowlegement that failings in the airworthiness system caused (or contributed to, depending on your interpretation) the fatal accidents to a Hercules and a Nimrod.
Whether the CDP's acknowledgement of the failings in the RTS of the Chinook Mk2 referred to in Tecumseh's post #5533 above means that three are now down will not be true until Wratten and Day's refusal to comply with the AP is recognised and overturned.