Northrop BT: American Dive Bomber

The Northrop BT was an American 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. While unsuccessful in its own right, the BT was subsequently redesigned into the Douglas SBD Dauntless, which would form the backbone of the Navy's dive bomber force.

Design and Development

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 (dive brakes), and main 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.

Operational History

The U.S. Navy placed an order for 54 BT-1s in 1936 with the aircraft entering service during 1938. BT-1s served on USS Yorktown and Enterprise. The type was not a success in service due to poor handling characteristics, especially at low speeds, "a fatal flaw in a carrier based aircraft." It was also prone to unexpected rolls and a number of aircraft were lost in crashes.

Variants

XBT-1: Prototype, one built.

BT-1: Production variant, 54 built.

Type: Dive bomber

National origin: United States

Manufacturer: Northrop Corporation

Primary user: United States Navy

Number built: 55

First flight: 19 August 1935

Developed into: Douglas SBD Dauntless

Crew: two (pilot and gunner)

Length: 31 ft 8 in (9.65 m)

Wingspan: 41 ft 6 in (12.65 m)

Height: 9 ft 11 in (3.02 m)

Wing area: 319 sq ft (29.6 m2)

Empty weight: 4,606 lb (2,094 kg)

Maximum takeoff weight: 7,197 lb (3,271 kg)

Powerplant: 1 × Pratt & Whitney R-1535-94 Twin Wasp Jr. double row radial air-cooled engine, 825 hp (615 kW)

Maximum speed: 193 kn (222 mph, 357 km/h) at 9,500 ft (2,900 m)

Cruise speed: 167 kn (192 mph, 309 km/h)

Range: 1,000 nmi (1,150 mi, 1,852 km)

Service ceiling: 25,300 ft (7,710 m)

Rate of climb: 1,270 ft/min (6.5 m/s)

Armament:

Guns:

1 × forward firing 0.50 in (12.7 mm) Browning machine gun

1 × 0.30 in (7.62 mm) machine gun in rear cockpit

Bombs: 1,000 lb (454 kg) bomb under fuselage

BT-1S: A BT-1 (c/n346, BuNo 0643) was fitted with a fixed tri-cycle undercarriage. This aircraft was damaged in a crash on 6 February 1939, returned to Douglas and repaired to BT-1 standard.

XBT-2: One BT-1 modified with fully retractable landing gear and other modifications.

BT-2: Production variant of the XBT-2, 144 on order completed as SBD-1 and SBD-2.

Douglas DB-19: One BT-1 (c/n346, BuNo 0643), the former BT-1S, was modified as the DB-19 which was tested by the Imperial Japanese Navy as the Douglas DXD1 (long designation - Douglas Navy Experimental Type D Attack Aircraft)

Operators

United States

United States Navy

Notable Mentions in Media

Northrop BT-1s appeared in pre-war yellow wing paint schemes in the Technicolor film Dive Bomber (1941) starring Errol Flynn.

Bibliography

Bowers, Peter M. United States Navy Aircraft since 1911. Annapolis, MD: Naval Institute Press, 1990.

Brazelton, David. The Douglas SBD Dauntless, Aircraft in Profile 196. Leatherhead, Surrey, UK: Profile Publications Ltd., 1967.

Drendel, Lou. U.S. Navy Carrier Bombers of World War II. Carrollton, TX: Squadron/Signal Publications, Inc., 1987.

Gunston, Bill. The Illustrated History of McDonnell Douglas Aircraft: From Cloudster to Boeing. London: Osprey Publishing, 1999.

Kinzey, Bert. SBD Dauntless in Detail & Scale, D&S Vol.48. Carrollton, TX: Squadron/Signal Publications, Inc., 1996.

Listemann, Phil. Northrop BT-1 (Allied Wings No.3). France: www.raf-in-combat.com, 2008.

Swanborough, Gordon and Peter M. Bowers. United States Navy Aircraft since 1911. London: Putnam, Second edition, 1976.

Northrop BT-1, aircraft number 18 of Bombing Five off USS Yorktown pictured in flight on 9 April 1938.

Northrop BT-1, aircraft number 2 of Bombing Five off USS Yorktown, Oakland, March 1940.

Northrop BT-1 of Bombing Five off the USS Yorktown.

Northrop BT-1 of dive bomber squadron VB-5, assigned to the U.S. aircraft carrier USS Yorktown (CV-5). Deliveries to VB-5 began in April 1938.

Aircraft number 10 of Bombing Squadron Five (VB-5) assigned to the Yorktown Air Group in the aircraft carrier USS Yorktown (CV-5). Struck off charge October 31, 1944.

U.S. Navy Northrop BT-1 (BuNo 0815) of dive bombing squadron VB-6, circa 1939/40.

U.S. Navy Northrop BT-1 pictured sitting on flight line outside of a hangar at El Segundo, California.

Eleven U.S. Navy Northrop BT-1s of Bombing Squadron Five (VB-5) pictured sitting lined up. In the background are three Vought SBUs and a USAAC North American O-47. Note the sign at the right: "Notice! Photographing Military Airplanes is Forbidden by U.S. Government!"

Northrop BT-1 modified to test tricycle landing gear, circa 1936-37.

U.S. Navy Northrop BT-1 dive bombers flying over Miami, Florida, October 1939.

Northrop BT-1, landing at Oakland, California.

U.S. Navy Northrop BT-1 (BuNo 0614) of Bombing Squadron 5 (VB-5) goes into the starboard catwalk during a landing accident aboard the aircraft carrier USS Yorktown (CV-5), circa 1940. Note man in asbestos suit and other members of the flight deck crew running to assist.

A U.S. Navy Northrop BT-1 (BuNo 0631) of Bombing Squadron 6 (VB-6) aboard the aircraft carrier USS Enterprise (CV-6), circa 1940. The yellow color of its wings visible and 'true blue' color of vertical and horizontal stabilizers were assigned to the Enterprise Air Group. The BT-1s were removed from fleet service by 20 April 1941. The BT-1 0631 then served as a training plane and was finally retired on 31 October 1944.

U.S. Navy Northrop BT-1 of bombing squadron VB-6 in flight. VB-6 was assigned to the aircraft carrier USS Enterprise (CV-6).

Northrop BT-1 of VJ-3.

Northrop XBT-1 (BuNo 9745) on 4 December 1936.

XBT-2 (BuNo 0627) prototype on 23 July 1938. This was to be the prototype of the later Douglas SBD Dauntless, although canopy and tail would differ from the XBT-2.

Northrop (Douglas) XBT-2 undergoing handling and drag reduction tests in the Langley 30 x 60 Full Scale Tunnel. This is the revision of the Northrop BT-1 that eventually became the Douglas SBD prototype. At the time this aircraft was produced, Northrop became the El Segundo Division of Douglas.

U.S. Navy Northrop XBT-1 prototype (BuNo 9745) which made its first flight in August 1935.

View taken on the flight deck of the aircraft carrier USS Enterprise (CV-6) showing U.S. Secretary of the Navy Frank Knox inspecting aircraft (Northrop BT-1s). Knox is followed by Admiral James O. Richardson, USN (center). Commander Milton L. Deyo, USN (Aide to SecNav), also is visible, at far right.

Northrop BT-1, aircraft 13 of Bombing Five off USS Yorktown.

Douglas XBT-2, El Segundo, circa 1939.