Operational Use
Small numbers of SABS became available in early 1943 and were initially sent to No. 8 Group RAF, the "Pathfinder Force". They used them only briefly before turning their examples over to No. 617 Squadron RAF, who were in the process of converting to the earthquake bomb and required higher accuracy that the Mk. XIV could provide.
SABS was used operationally for the first time by No. 617 on the night of 11/12 November 1943 for their attack on the Anthéor railway viaduct at Saint-Raphaël, Var in southern France. No hits on the viaduct were recorded by any of the ten 12,000 lb (5,400 kg) Blockbuster bombs.
SABS was used both for direct aiming during daylight missions, as well as referencing on target indicators dropped by other aircraft flying at much lower levels. In these cases the accuracy of the drops was dependant on the accuracy of the marking, which varied. For instance, during attacks on the V weapon launch site at Abbeville on 16/17 December 1943, Tallboys were dropped with a circular error probable of only 94 yd (86 m), a superb result, but the markers were 350 yd (320 m) from the target. Better results followed; on the night of 8/9 February 1944, Wing Commander Leonard Cheshire visually dropped markers on the Gnome et Rhône factory in downtown Limoges, 11 Lancasters then dropped 10 Tallboys directly on the factory with the last falling in the river beside it. The factory was knocked out of the war, with few or no civilian casualties.
General accuracy improved dramatically as the crews gained proficiency with the system. Between June and August 1944, 617 recorded an average accuracy of 170 yd (160 m) from 16,000 ft (4,900 m), a typical bombing altitude, down to 130 yd (120 m) at 10,000 ft (3,000 m). Between February and March 1945 this had further improved to 125 yd (114 m), while Air Marshal Harris puts it at only 80 yd (73 m) from 20,000 feet (6,100 m). Two other precision bombing squadrons formed up during this period, but used the Mk. XIV. These squadrons were able to achieve 195 yd (178 m), an excellent result that offered performance roughly equal to the early SABS attempts, and far outperformed the average by the more famous Norden.
The SABS' best known role was in the sinking of the German battleship Tirpitz on 12 November 1944, by a combined force from 617 and No. 9 Squadron RAF. Known officially as Operation Catechism, 30 Lancasters attacked the Tirpitz at altitudes from 12,000 to 16,000 feet (3,700 to 4,900 m). At least two bombs from 617 hit the Tirpitz, causing it to capsize in the fjord it was hiding in. Another celebrated attack was made during daylight on 14 June 1944 against the E-boat pens at Le Havre. One bomb penetrated the roof of the heavily guarded base, knocking it out of the war.
Read more about this topic: Stabilized Automatic Bomb Sight, Development