Bell X-1

First Flight: December 9, 1946
Mission: Determine feasibility of supersonic flight.
Major Accomplishments: First human controlled aircraft to exceed the speed of sound in controlled level flight.
Power Source: One (1) Reaction Motors E6000-C4 (Thiokol XLR-11) rocket. 6,000 lbs thrust (2,722 kg) Fuel by ethyl alcohol/water mix and liquid oxygen.
Wing Span: 28 ft (8.53m)
Length: 31 ft (9.45 m)
Weight (Loaded): 13,400 lb (6,078 kg)
Maximum Achieved Speed: 957 mph (1,540 km/h)

Additional Information: 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 the `X' designation. 3 X-1's were built, and carried USAF serial numbers 46-062, 46-063 and 46-064.

The X-1 became the first human controlled aircraft to exceed the speed of sound in controlled level flight. This historic event occurred on October 14, 1947, while the X-1 #1 (nicknamed "Glamorous Glennis") was piloted by Captain Charles (Chuck) Yeager. Top speed achieved on this flight was 670 mph (1,078 km/h, or Mach 1.015). Altitude at the time the sound barrier was broken was approximately 45,000 ft.

The X-1 was carried under a Boeing B-29 Superfortress to an altitude of 20,000 ft, where it was drop-launched. The Reaction Motors E6000-C4 rocket engine was not throttleable, but had 4 combustion chambers which could be operated individually or simultaneously.

Though the X-1 was built with straight wings, it was able to achieve controlled flight through the "sonic barrier" due to its variable pitch horizontal stabilizer. Initially, this surface was designed to be adjusted before flight and would remain in a fixed position.

This design was changed before power flights commenced. The design change permitted the pilot to adjust the pitch of the horizontal stabilizer during flight, via an electric motor. General Chuck Yeager has often credited the success of the X-1 with the pilot adjustable variable pitch horizontal stabilizer. It was years before other nations' design teams were able to duplicate this concept (see The Tale of the Tail, below ).

The second X-1 differed from the first and third in that it had a thicker wing (10% thickness/cord ratio vs. 8%).

The third X-1 was over 3 years late in delivery and successfully completed only 1 drop-glide flight. Following its second flight, in which it remained attached to the B-29 for fuel system testing, the fully loaded fuel tanks were about to be emptied when an explosion destroyed the X-1. Fortunately, no one was killed as a result of this accident.

Though several significant modification were considered for the X-1 (replacing the straight wings with swept wings, and a V-tail configuration), the most significant modification was the improved windscreen on the third X-1. This windscreen was stronger than provided on the first 2 X-1's and did not require straps to hold it in place. This greatly improved visibility for the pilot.

The X-1E
After the loss of the 3rd X-1 and the X-1D. The need remained for a higher performance performance X-1 for the NACA to conduct testing in.

The 2nd X-1 (46-063) was almost completely rebuilt and redesignated as the X-1E. Significant modifications include and updated canopy, ultra-thin wings (4% thickness/cord ratio) and a rocket assisted ejection seat.

The maximum altitude achieved by the X-1E was 75,000 ft, and the top speed was Mach 2.24 (1,450 mph). The plane was retired from service in November of 1956 after 26 flights.

The first X-1 is on permanent display at the Smithsonian Air & Space museum. The second X-1, which was reconfigured as the X-1E, is on permanent display at the NASA's Dryden Flight Research Facility.

The Tale of the Tail:
In 1942 the British Air Ministry and the Ministry of Aviation approached Miles Aircraft with a top-secret contract for a turbojet research plane designed to reach supersonic speeds. This plane, the Miles M.52 was designed for a speed of 1000mph at 36,000 feet to be reached in 1.5 minutes.

The functional model of the M.52 included a fully moveable tail surface. Though not officially documented by British or American agencies, many believe that the X-1's moveable tail surface was "borrowed" from the M.52 design, which were initially tested on the Miles Falcon-Six racer.

The M.52 program never went past the test model stage and test models were not flown until 1947, well after the X-1 had broken the "sound barrier". While it is possible that the X-1's movable tail surface was the result of the M.52's design, it was the X-1 that proved the concept in flight.