The Bell contractor portion of the X-1 program was divided into two phases. The #1 aircraft made its first ten flights at Pinecastle Army Air Field between January 25, and March 6, 1945. The Bell team included Stan Smith as project engineer and P.V. "Jack" Woolams as test pilot and test site manager. The NACA team, led by Walter C. Williams as project manager and Joel R. Baker as NACA pilot observer, collected and analyzed the flight data.
The purpose of the ten glide flights by Woolams was to check out the aircraft's airworthiness and handling characteristics in the absence of the rocket engine. The achievements of the Pinecastle tests included demonstration of the mother-ship airlaunch procedures, proof of the data collection techniques, and the excellent general flight characteristics of the X-1. The X-1 #1 was first unveiled to the public at Wright Field on May 17, 1946, at a special open-house exhibition.
For the second phase, the X-1 #2 received its rocket engine in early September, 1946. About the same time, it was equipped with the 10-percent wing and 8-percent tail. The Bell contractor team was headed by Richard Frost as project engineer and Chalmers "Slick" Goodlin as prime pilot. The NACA team was headed by Walt Williams as project leader and Joel Baker as NACA pilot observer. The #2 aircraft made the next 16 contractor flights of the X-1 program at the AAF flight test facilities at Muroc Army Air Field in California. The first powered flight was on December 9, 1946. The X-1 #1 returned to flight operations at Muroc in April, 1947. It possessed the new thin wing/tail along with its RMI rocket engine. On April 10, 1947 the X-1 #1 made its first powered flight.
Controversy ensued over the cost of the Bell follow-on contract proposal. The AAF offered Bell a fixed price contract. Bell Aircraft declined to accept the AAF proposal. The AAF and NACA then agreed to assume program flight responsibilities in May 1947.
The 27 Bell contractor flights at Muroc exceeded AAF contractual obligations. The X-1 flew to a recorded speed of Mach 0.82 and demonstrated structural integrity of the plane at loads up to 8.7g of stress. Despite NACA reservations, the rocket engine had proven difficult, but generally safe and reliable. Data collection had confirmed previous NACA information.
By the time the X-1 aircraft were released to the AAF in June 1947, the X-1 #1 had made 19 flights with Woolams and Goodlin as pilots. The X-1 #2 had made 18 flights with Goodlin and Alvin "Tex" Johnston as pilots. Twenty-three were powered flights and 14 were glide flights.
The Air Force/NACA follow-on phase of the program coincided with the second part of the initial work plan for the X-1 aircraft. The follow-on contract was designed to take the X-1 program to supersonic speeds and into high-altitude research. The Air Force/NACA effort developed as a two-fold complimentary program.
The Air Force designed an accelerated program using the X-1 #1 airplane. Program intent was to rapidly exploit the speed potential of the aircraft consistent with safety considerations. Later work would focus on altitude capabilities. NACA would continue to plan the flights, supervise collection of the flight data, and analyze the results.
The Air Force Flight Test Division team from Wright Field included Major Roberto L. "Bob" Cardenas as project manager, Captain Jack L. Ridley as project engineer, Captain Charles E. "Chuck" Yeager as prime pilot and Lieutenant Robert A. Hoover as backup pilot. Richard Frost continued as civilian advisor for the program on loan from Bell Aircraft. This was the first time the Air Force had undertaken flight research (as opposed to development testing) since the 1920s.
The NACA developed a detailed program for the X-1 #2 airplane. The NACA program was to accumulate comprehensive flight data information in the transonic range for application by industry.
The NACA team was formally designated as the Muroc Flight Test Unit on September 7, 1947. It included Walt Williams as project manager and Herbert H. Hoover and Howard C. Lilly as agency pilots. Total NACA station personnel at that time consisted of 27 people. The #2 plane was turned over to NACA in October, 1947.
Yeager flew the #1 airplane on its first powered Air Force flight on August 29, 1947. He achieved a maximum speed of Mach 0.85. On October 14, 1947 the #1 airplane with Yeager as pilot reached a speed of Mach 1.06 and officially broke the sound barrier. It was the fiftieth flight of the X-1 program.
On October 21, 1947, NACA pilot Herb Hoover made his first glide flight in the #2 aircraft, which had actually been the first X-1 flown at Muroc on October 11, 1946, with Goodlin as pilot. On December 16, 1946, Hoover piloted the #2 aircraft on the first NACA powered flight to a speed of Mach 0.84. On March 10, 1948, Hoover became the first civilian pilot to break the sound barrier, achieving a speed of Mach 1.065. On May 26, 1950, the NACA #2 aircraft piloted by John H. Griffith achieved its highest speed at Mach 1.20.v
On March 26, 1948 and May 2, 1949, the #1 aircraft with Yeager as pilot achieved the fastest speed of the initial X-1 program at Mach 1.45. On January 5, 1949, the #1 aircraft with Yeager as pilot achieved the only ground takeoff of the X-1 program. He reached just over 23,000 feet before the limited propellant was exhausted.
On August 8, 1949, Air Force Major Frank K. Everest Jr. flew the #1 aircraft to a new unofficial altitude record of 71,902 feet. It was the 125th flight of the program. On the next flight on August 25, the #1 aircraft suffered a canopy crack and pressurization loss at approximately 69,000 feet resulting in the first deployment of the high-altitude pressure suit being worn by Everest.
During November, 1947, the AAF authorized studies that led to a contract (W-33-038-ac-20062) with Bell Aircraft to build four (later three) improved X-1 aircraft (the X-1C being cancelled). Designated X-1A (#48-1384), X-1B (#48-1385), and X-1D (#48-1386), the airplanes were ready by late 1950. The aircraft were about five feet longer and 2,500 lbs. heavier than the original X-craft planes. They used the 8-percent wing like the earlier X-craft. The D-model had a low-pressure turbo-pump and the B model was fitted with a prototype hydrogen peroxide reaction control system for later aircraft to use in exoatmospheric research flights. Access was through a lift-off canopy. The planes were finished in their bare metal color and white.
The X-1D was ready first, but on what was intended to be its second flight (August 22, 1951) it was jettisoned and crashed at Muroc after an aerial explosion while still mated to its mother (B-50A [#46-006A]) ship.
The long-delayed X-1 #3 airplane with the turbine pump was finally completed for the NACA in 1951. It made its first glide flight on July 20, 1951, with NACA pilot Joseph Cannon. Its second and final captive flight was on November 9, 1951. It was destroyed on the ground by an explosion and fire along with its B-50A mother ship while attempting to jettison fuel.
The X-1A arrived at Muroc in January, 1953 and had its first powered flight on February 21, 1953. On December 8, 1953 with Yeager as pilot, the aircraft investigated high-speed stability and control issues. During the flight, the plane achieved a speed of Mach 1.90. On December 12, Yeager flew the X-1A to Mach 2.44 (1,650 mph) at 75,000 feet. The plane experienced inertia coupling and fell 50,000 feet before Yeager could regain control. NACA wind tunnel testing had predicted this high-speed stability problem, and the flight testing had inadvertently verified the wind-tunnel data. Further Air Force testing established a new world altitude record of 90,440 feet. The X-1A was turned over to the NACA, but was lost to aerial explosion on August 8, 1955, shortly before it was to be launched on its second flight. It had to be jettisoned to the Muroc desert. Shop experiments soon determined that the deadly explosive culprit for the X-1D, the X-1 #3, and the X-1A was the ulmer leather gasket material used in contact with the liquid oxygen tanks.
The X-1B was delivered to Edwards AFB in June 1954 and turned over to NACA in December. After removal to NACA Langley for installation of its test instrumentation, it was returned to Edwards in August, 1955. Its first flight was August 14, with NACA pilot John B. "Jack" McKay, who would fly the first fourteen X-1B missions. NACA pilot Neil A. Armstrong would fly the last four missions concluding on January 23, 1958. Most of the flights were focused on thermal heating data. The last three flights, however, utilized extended wingtips and a very basic hydrogen peroxide-fueled reaction control system for use by manned aircraft in thin atmosphere flight control. During June, 1958, the plane was retired due to stress cracks in the liquid oxygen.
The loss of the X-1 #3 and the X-1D led the NACA to rebuild the X-1 #2 into a new aircraft. By December 1955, the redesignated X-1E was ready. It featured a new, very thin 4-percent wing along with the existing 8-percent tail, with an efficient low-pressure turbo-pump for the engine. It also contained an ejection seat for the pilot. On October 8, 1957, the aircraft with NACA pilot Joseph A. Walker achieved a speed of Mach 2.24 (1,478 mph). Significant engine improvements were added in fall 1958 that promised Mach 3.0. Ventral fins were also added to aid high-speed stability. The plane was forced to retire in December, 1958 due to stress cracks in its fuel tank.
During its second flight career, the new X-1E allowed NACA to gather significant data on high Mach flight and stability questions and to demonstrate improved engine and production technology for incorporation into new USAF aircraft. Likewise, the A and B models contributed valuable information, on high Mach flight and altitude issues for the planes, and on human factor questions or the pilots. The NACA stability data collected above Mach 2.0 confirmed previous NACA directional stability research. The B model flights provided some initial information to the NACA on aerodynamic heating problems. The research into aircraft control issues in thin atmospheric flight was useful, together with reaction-control research on simulators and the F-104, in developing the better systems for the later X-15 flights into outer space.