Some B-29s were converted to carrier aircraft and used to air-launch experimental aircraft in the years following World War II. The bomb bay was modified to accept the experimental aircraft, which was mated to the B-29 "mother ship" on the ground and flown to a specified altitude where the test aircraft was released.
“Air-launch” is defined as two or more air-vehicles joined and working together, that eventually separate in flight, and that have a combined performance greater than the sum of the individual parts. The use of the air-launch concept has taken many forms across civil, commercial, and military contexts throughout the history of aviation.
From the very beginning of heavier-than-air flight, air-launch has been envisioned as a means of enhancing the performance of an air-vehicle. In 1892, the United States Patent Office, responding to Louis Mouillard’s patent application for a rigid-wing glider, explains: “Examining the project presented we believe that the described invention as a whole is not practical, since the machine cannot rise without a balloon”. The patent office was not convinced that a glider, by itself, could take flight. A glider needed another air-vehicle to join with it to enhance its performance.
By the time WWII ended on September 2, 1945, the war had sparked a myriad of advances in guided munitions. Many, if not most of those advances were enabled by or even fundamentally built around air-launch. Air-launch in WWII helped established a foundation for guided weapons systems, a legacy that continues today.
One B-29 aircraft was converted to carry the Bell X-1 series test aircraft and was used until replaced by a more modern Boeing B-50. Initially designated the XS-1, (the S, which stood for Supersonic, was dropped early in the program), the X-1 was the first aircraft given an “X” designation, and became the first aircraft to exceed the speed of sound in controlled level flight on 14 October 1947. On this flight, the first X-1 (nicknamed Glamorous Glennis) was piloted by Captain Charles E. “Chuck” Yeager, who achieved 700 mph (Mach 1.06) at approximately 45,000 feet.
Beginning a precedent that survives to this day, the X-1 was air-launched—in this case carried under a Boeing B-29 Superfortress to an altitude of approximately 20,000 feet. The X-1 was not designed to take off under its own power, but was instead taken aloft attached to the bomb bay of a modified B-29 bomber. This fuel saving measure allowed for more flight time at test altitudes. Unpowered glide flights began early in 1946.
NACA test pilot Joseph Walker made a familiarization flight on July 20, 1955 followed by another scheduled flight on August 8, 1955. Shortly before launch the X-1A suffered an explosion. The extent of the damage prohibited landing the crippled aircraft. The X-1A was jettisoned into the desert, exploding and burning on impact. Walker and the B-29 crew returned to base in satisfactory condition. Four pilots had completed 29 (including aborts) flights.
The X-1 program was extremely productive, proving much of the technology necessary to produce the first-generation of supersonic combat aircraft. Many structural and aerodynamic advances were pioneered by the first generation X-1s, including extremely thin yet exceptionally strong wing sections, supersonic fuselage configurations, and advanced control system designs. The other launch aircraft was EB-50A (46-006).
Another EB-29 was used carry the XF-85 and test the parasite fighter concept. The XF-85 Goblin parasite aircraft was developed to protect B-36 bombers flying beyond the range of conventional escort fighters. In theory, a B-36 penetrating enemy territory would carry its protecting fighter in the bomb bay. If attacked by enemy aircraft, the bomber would lower the Goblin on a trapeze and release it to combat the attackers. After the enemy had been driven away, the parasite fighter would return to the bomber, hook onto the trapeze, fold its wings and be lifted back into the bomb bay.
Two test aircraft were ordered in October 1945, and flight testing with a modified B-29 began in 1948. Test pilots could successfully launch the XF-85, but the turbulent air under the B-29 made recovery difficult and hazardous. About half of the Goblin flights ended with emergency ground landings after the test pilot could not hook up to the B-29. Although the XF-85 was successfully launched and retrieved from an EB-29B on several test flights, it was never flown from a B-36. The test program was canceled in late 1949 when mid-air refueling of fighter aircraft for range extension began to show greater promise.
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