Northrop BT-1

BT
Northrop BT-1s over Miami in October 1939
Role	Dive bomber
Manufacturer	Northrop
First flight	19 August 1935
Primary user	United States Navy
Number built	55
Variants	SBD Dauntless

The Northrop BT was a two-seat, single-engine monoplane dive bomber built by the Northrop Corporation for the United States Navy. At the time, Northrop was a subsidiary of the Douglas Aircraft Company.

The design of the initial version began in 1935. It was powered by a 700 hp (520 kW; 710 PS) Pratt and Whitney XR-1535-66 double row air-cooled radial engine and had hydraulically actuated perforated split flaps or "dive-brakes" and a landing gear that retracted backwards into fairing "trousers" beneath the wings. The perforated flaps were invented to eliminate tail buffeting during diving maneuvers.

The next iteration of the BT, the XBT-1, was equipped with a 750 hp (560 kW; 760 PS) R-1535. This aircraft was followed in 1936 by the BT-1, powered by an 825 hp (615 kW; 836 PS) R-1535-94 engine. One BT-1 was modified with a fixed tricycle landing gear and was the first such aircraft to land on an aircraft carrier.

The final variant, the XBT-2, was a BT-1 modified to incorporate landing gear which folded laterally into recessed wheel wells, leading edge slots, a redesigned canopy, and was powered by an 800 hp (600 kW; 810 PS) Wright XR-1820-32 radial. The XBT-2 first flew on 25 April 1938 and after successful testing the Navy placed an order for 144 aircraft. In 1939 the aircraft designation was changed to the Douglas SBD-1 with the last 87 on order completed as SBD-2s. By this point, Northrop had become the El Segundo division of Douglas aircraft, hence the change.

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