Boeing Model 42 (CO-7)

The DH-4B and DH-4M modifications extended the DH-4’s service life until the mid-1920s, but by then, the model was completely obsolete. However, considering the large number of engines and spare parts for these aircraft in storage, the U.S. Army decided on a “final” extension of the DH-4’s operational life. As part of the approved program, Boeing was tasked with developing a modernized DH-4, designated Boeing Model 42.

This design combined the powerplant, fuselage, and vertical empennage of the DH-4M-1 with new horizontal empennage, wing, and landing gear. The U.S. Army provided Boeing with three DH-4M-1 aircraft for conversion into CO-7 prototypes, which were intended as observation aircraft. One aircraft, the XCO-7, was allocated for static tests.

Development and Prototypes

The other two, the XCO-7A and XCO-7B, were designated for flight tests. The XCO-7B featured a new tail assembly and powerplant. Notably, the XCO-7B differed from the XCO-7A only in its elevators, which included mass balances, and an inverted version of the Liberty 12A engine with a high shaft line.

After assembly, both aircraft, the XCO-7A and XCO-7B, were transported by rail to McCook Field, Ohio. There, on February 6, 1925, the XCO-7A performed its maiden flight. Tests indicated that the aircraft was quite adequate in terms of flight performance and handling, demonstrating better characteristics than the DH-4M-1.

Flight Tests and Final Decision

Despite these positive results, a decision for serial production was not pursued. The U.S. Army ultimately opted to develop an aircraft of an entirely new design. Furthermore, Boeing also created a similar aircraft based on the DH-4M-1 for the Navy, which was designated O2B and produced in O2B-1 and O2B-2 modifications.

Technical Specifications

Modification	Model 42 (XCO-7A)
Wingspan, m	13.72
Length, m	8.89
Height, m	3.25
Wing area, m2	40.88
Empty weight	1409
Maximum takeoff weight	2116
Engine type	1 Piston engine Liberty 12A
Power, hp	1 x 420
Maximum speed, km/h	196
Cruising speed, km/h	177
Practical range, km	676
Practical ceiling, m	3980
Crew, crew members	2
Armament	two fixed forward-firing 7.62-mm Browning machine guns in the forward fuselage and two turret-mounted 7.62-mm Browning machine guns in the rear cockpit.

Image and diagram gallery of the Boeing Model 42 (CO-7)

Boeing Model 42 (CO-7)	Boeing Model 42 (CO-7)
Boeing Model 42 (CO-7)	Boeing Model 42 (CO-7)
Boeing Model 42 (CO-7)	Boeing Model 42 (CO-7)
Boeing Model 42 (CO-7)	Boeing Model 42 (CO-7)