It is little known that the famous Dauntless dive bomber from the Unites States started its life at the Northrop works as the Northrop XBT-2. In fact this was a further improved version of Northrop’s BT-1, based on the famous series of Northrop Gamma all-metal multi-purpose plane. The XBT-2 was produced for the U.S. Navy as BT-2, but when Douglas took over Northrop’s plant at El Segundo it was further produced as the SBD-1. It was built in large numbers with the SBD-5 as the major production version.
The SBD-5 was fitted with a more powerful 1200 hp Wright R-1820 engine. For better performances it had a redesigned low-drag engine cowling. With its increased engine power it could carry a heavier offensive load of up to 1021 kg. As defensive armament it featured a double rearward firing machine guns for the second crew member. The first production model was supplied on 21 February 1943. Total production of this version was 2964 aircraft.
A further improved model with a even more powerful engine was the SBD-6. With the war coming to an end only 450 were built; the remaining orders were canceled. The Dauntless played a major role in the defeat and destruction of the Japanese fleet.
Source: R.J. Francillon, McDonnell Douglas aircraft since 1920 Volume I, Putnam UK (1988)