Army Pursuits the Biplane Period, 1920-1932
Boeing XPW-8, XPW-9, Pw-9, PW-9C, & TM-24, 24
Additional weight such as wheel brakes, reduced performance below that of earlier models and required a balanced rudder, but still the Boeing fighters were usually considered a bit more maneuverable than the Curtiss types. Total PW-9 production, after the three prototypes, was 111, most of them serving with the overseas squadrons, and Boeing sold the similar FB series to the Navy.
Curtiss responded to Boeing’s challenge by rebuilding the third XPW-8 prototype by August 1924 as the XPW-8A with shorter single-bay wings like those of the PW-9. At first the radiator was put in the XPW-8A wing’s center section, but then a tunnel radiator under the engine, again like the Boeing’s, was fitted for competitive flight tests in October. Top speed was greatly improved, but the Boeing’s maneuverability advantage remained.
In December 1924, the same prototype was ordered converted to the XPW-8B with new tapered wings. Designed by George Page, Jr., the new Clark Y airfoil wings and tail became standard on future Curtiss Hawks from the P-l to P-23. The P-ls ordered into production parallel with the Boeing PW-9 in March 1925 were nearly identical to the XPW-8B prototype.
While Boeing and Curtiss had profitable results from their fighter initiatives, the Thomas-Morse company at Ithaca, New York, would lose money on its efforts. All-metal construction was boldly tried on the TM-23 single-seat biplane with the same Curtiss D-12, a short corrugated aluminum fuselage, and small wings joined by “I” struts. But many difficulties interrupted company tests in 1924.
The same construction was used by the Thomas-Morse TM-24 two-seat fighter tested at McCook Field in February 1925 with a 440-hp Curtiss D-12 cooled by radiators in the wing roots. This biplane’s upper wing was smaller than the lower wing, and was supported by an ugly arrangement of “V” and “N” struts.
Since the first version of the single-seat TM-23 was unsuccessful, it was rebuilt with a new strut system and the radiator under the fuselage, but official performance tests in March 1926, brought complaints that the TM-23 flew badly and had too high a landing speed. No Army contract or designation was given either effort, so the company lost over $77,000 on the TM-23 and $46,000 on the TM-24, showing how risky expensive technical innovation was for a small company competing against large ones. The day of the all-metal fighter waited for better aluminum technology.