The fourth V-force bomber
In late 1961 it was recognised that the TSR.2 was unlikely to be in full squadron service before 1968, and Soviet air defences in Eastern Europe were improving rapidly and reducing the probability of a successful strike on certain high value targets by the existing subsonic strike aircraft operated by the RAF. A requirement was therefore drawn up for an interim supersonic nuclear strike aircraft, the requirement stating that an existing aircraft should be utilised if possible to meet an in service date in 1963, with multi-role capability also being sacrificed to meet the in-service date.
Coincidentally the requirement was issued at the same time as the US Navy reassigned its nuclear strike capability to its submarine fleet, leaving the recently developed A-5B Vigilante without a role whilst the USN and Congress wrangled over funding for the RA-5C programme. This funding hiatus had left North American with 18 partially completed A-5B airframes littering their shopfloor with no certainty about an order from the Navy, so the company was glad to be able to sell them to the UK.
To meet the in-service date the aircraft was taken virtually as is with American avionics and engines, the only major modification being to fit conventional bomb bay doors to the forward two thirds of the weapons bay, a modification originally offered to the USN but not taken up by that service. This change was carried out due to problems encountered with the A-5A in weapons delivery using the rearward ejection of stores, where the ejected store tended to be pulled along by the aircrafts slipstream to the detriment of delivery accuracy. The rearmost third of the weapons bay was converted to fuel tankage, and the arrestor hook was removed to reduce weight.
The Vigilante proved a good match to the RAF requirement, with even its name falling in line with the other V-force aircraft, though its relatively large wing made for a bumpy ride at low level, and all 18 A-5B airframes originally ordered by the USN were purchased. Resplendent in their white anti-flash finish ( until a more muted colour scheme was applied in 1967 ) these aircraft became a familiar sight in their QRA shelters until withdrawn in late 1969. Throughout its service only the Red Beard nuclear store was carried, it being felt that adapting the limited number of aircraft to carry other stores would not be cost effective given the intended short term of its service, and would affect its availability in its primary role of nuclear deterrent.