The Curtiss XB-2 (26-211) was a direct development of the Curtiss-built Martin MB-2 (NBS-1) through the two Curtiss XNBS-4s. The primary differences were that steel tubing was used instead of wood for fuselage construction, Curtiss Conqueror liquid-cooled engines were used in place of the war-surplus Liberty engines, and the thicker Curtiss C-72 airfoil was used.
A single XB-2 prototype was ordered by the Army in 1926. The serial number was 26-211. First flight of the XB-2 took place in September 1927. The Conqueror engines were housed inside nacelles mounted on top of the lower wing. The engines were cooled by rather angular radiators which jutted up vertically from each nacelle. Like the NBS from which it had evolved, the XB-2 had twin rudders with twin horizontal stabilizers, which was a rather old-fashioned arrangement even by the standards of 1927.
One of the more unusual innovations introduced by the XB-2 was the addition of a defensive gunner position in the rear of each nacelle. It was hoped that this arrangement would offer a clearer field of fire for the gunners than the more conventional fuselage-situated positions. An additional gunner position was provided in the nose. Each position was provided with a pair of Lewis machine guns. A similar arrangement was fitted to the competing Keystone XB-1B.
The XB-2 found itself in competition against the Keystone XB-1B, the Keystone XLB-6, the Sikorsky S-37B, and the Atlantic-Fokker XLB-2. When an Army board of review met in February of 1928 to decide which design was to be awarded a contract, they immediately ruled out the XB-1B, the XLB-2, and the S-37. However, the Board was unable to decide between the XB-2 and the XLB-6. The XB-2 had the better performance, but the XLB-6 was only $24,750 per unit. The per unit cost of the B-2 was $76,373, more than three times the cost of a Keystone bomber. In a split decision, the Board opted for the Keystone design, but on June 23, 1928 Curtiss was given a contract for two B-2s (28-398/399). A further ten examples were ordered in 1929 (serials were 29-28/37).
The twelve production B-2s were delivered from May 1929 to January 1930. Notable differences from the XB-2 included the use of three-bladed propellers and somewhat shorter and wider radiators mounted on top of the engine nacelles.
One B-2 (serial number 29-30) became B-2A when fitted with full dual controls.
During the early 1930s, the advances in bomber design were so rapid that canvas-covered biplanes such as the B-2 rapidly became obsolete. Consequently, the B-2 served only briefly with the Army, being taken out of service in 1934. The last B-2 was surveyed in July of 1936. So far as I am aware, none survive today.
Serials of Curtiss B-2 Condor
28-398/399 Curtiss B-2 Condor 28-398 DELIVERED 6/10/29, SURVEYED 10/3/34, MARCH FIELD 28-399 DELIVERED 8/10/29, SURVEYED 8/15/34, MARCH FIELD 29-028/037 Curtiss B-2 Condor 29-028 DELIVERED 10/10/29, WRECKED 12/4/29 (TWO KILLED), LANGLEY FIELD 29-029 DELIVERED 11/2/29, SURVEYED 10/3/34, MARCH FIELD 29-030 DELIVERED 10/17/29, CONVERTED TO B-2A 10/6/31, SURVEYED 12/22/33, MARCH FIELD 29-031 DELIVERED 11/28/29, SURVEYED 8/6/34, MARCH FIELD 29-032 DELIVERED 12/9/29, SURVEYED 8/6/34, MARCH FIELD 29-033 DELIVERED 12/14/29, SURVEYED 8/6/34, MARCH FIELD 29-034 DELIVERED 12/22/29, SURVEYED 6/17/35, MARCH FIELD 29-035 DELIVERED 12/26/29, SURVEYED 5/23/33, MARCH FIELD 29-036 DELIVERED 1/4/30, SURVEYED 7/22/36, ABERDEEN PROVING GROUNDS 29-037 DELIVERED 1/16/30, SURVEYED 9/29/34, ABERDEEN PROVING GROUNDSSpecification of the Curtiss B-2 Condor:
Two 633 hp Curtiss V-1570-7 Conqueror liquid-cooled engines. Maximum speed 132 mph at sea level, 128 mph at 5000 feet. Cruising speed 114 mph, landing speed 53 mph. Service ceiling 17,100 feet, absolute ceiling 16,400 feet. Initial climb rate 850 feet per minute. An altitude of 5000 feet could be attained in 6.8 minutes. Range was 780 miles with 2508 pounds of bombs. Empty weight 9039 pounds, gross weight 16,516 pounds. Wingspan 90 feet, length 47 feet 6 inches, height 16 feet 3 inches, wing area 1499 square feet. Armed with two Lewis machine guns in each of the gunner positions at the rear of the engine nacelles, plus an additional pair of Lewis guns in the nose position. Bombload was normally 2508 pounds, but could be increased to 4000 pounds on short flights.