Test 118, which was conducted in January 1953, is listed in the tunnel log book as "MX 1964 Drag Test Model (Convair)". At some unknown date, the tunnel log book was corrected from MX 1964 to MX 1626. The MX numbering system was the (probably classified) USAF project designator system similar to today's code word system for classified projects. MX-1964 was the USAF project designation for the long-range supersonic bomber XB-58 Hustler aircraft and was a continuation of USAF MX-1626 project which was a Convair supersonic bomber/reconnaissance aircraft study (Convair Model W-4). MX-1626 was, in turn, a continuation of the USAF project MX-871, which was a Consolidated-Vultee generalized supersonic heavy bomber study. It is interesting to note that the weapons pod carried by the production B-58 aircraft was originally a strategic high-altitude air-to-surface missile designated MX-1964-A. Regardless of the correct project designation (probably MX-1626), the photographs below obviously show an early B-58 Hustler development model (note the mid-wing mounted, single engine-nacelle on each wing and the long weapon, or weapon pod, mounted under the fuselage). Based on the tunnel log description, the model (note faired-over nacelle inlets) was used to determine the subsonic/transonic drag characteristics of the aircraft configuration.
Tests in the 16-Foot Transonic Tunnel covered all three major development phases (see the first photograph below):
Test 118 (Current Test) - Convair MX-1626 Drag Test
Test 120 - Convair MX-1964 Trim Drag Test
Test 132 - Convair B-58 Aerodynamics Test
