• The Douglas Skystreak (D-558-1 or D-558-I) was an American single-engine jet research aircraft of the 1940s. It was designed in 1945 by the Douglas Aircraft Company for the U.S. Navy Bureau of Aeronautics, in conjunction with the National Advisory Committee for Aeronautics (NACA). The Skystreaks were turbojet-powered aircraft that took off from the ground under their own power and had unswept flying surfaces.
    The D558 program was conceived as a joint NACA/U.S. Navy research program for transonic and supersonic flight. As originally envisioned, there would be three phases to the D558 program: a jet-powered airplane, a mixed rocket/jet-powered configuration, and a design and mockup of a combat aircraft. A contract for design and construction of six D558-1 aircraft for the first phase was issued on 22 June 1945. The original plan had been for six aircraft with a mixture of nose and side air inlets and varying wing airfoil sections. That plan was quickly reduced to three aircraft of a single configuration with a nose inlet. Plans for the second phase with mixed rocket/jet propulsion were also dropped. Instead, a new aircraft, the D558-2, was designed with mixed rocket and jet propulsion for supersonic flight.

    Construction of the first 558-1 began in 1946 and was completed in January 1947. The fuselage used magnesium alloys extensively, while the wings were fabricated from more conventional aluminum alloys. It was made of HK31, which is 3% thorium and 1% zirconium and the rest magnesium, being much lighter than inconel and having a much higher heat capacity. The airframe was designed to withstand unusually high loads of up to 18 times gravity due to the uncertainties of transonic flight. The forward fuselage was designed so that it, including the cockpit, could be jettisoned from the aircraft in an emergency. The aircraft was configured to carry more than 500 pounds (230 kg) of test equipment, including sensors (primarily strain gauges and accelerometers) in 400 locations throughout the aircraft. One wing was pierced by 400 small holes to enable aerodynamic pressure data to be collected.

    The Skystreaks were powered by one Allison J-35-A-11 engine (developed by General Electric as the TG-180) — one of the first axial-flow turbojets of American origin — and carried 230 US gallons (871 L) of jet fuel (kerosene)
    Operational history
    On March 15, 1944, while Allied forces prepared for the invasion of Normandy in Europe and the assault on the Marianas in the Pacific, Army Air Forces and Navy officers looked to the future in a meeting at the National Advisory Committee for Aeronautics’ (NACA) Langley Laboratory. The subject was high-speed flight and by the end of the year a plan was in place for the development of research aircraft, with the Navy focusing on subsonic flight and the Army Air Forces (later U.S. Air Force) tasked with pushing beyond the sound barrier.

    The specifications for the Navy aircraft called for it to be a pure research design, capable of taking off and landing on its own power using existing engines. It also had to be able to carry 500 lb. of instruments to records data from the test flights.

    In developing their company’s proposal, Douglas Aircraft Company engineers designed a straight-wing airplane with a cylindrical fuselage to house the engine, which was the 5,000 lb. static thrust Allison J35-A-11. One unique aspect of the design was the escape system for the pilot. In the event of an emergency, the nose detached from the fuselage and when it reached a safe speed, the pilot would perform a bailout through the detached end of the nose section.

    With Douglas test pilot Eugene F. May at the controls, the D-558-1 Skystreak made its maiden flight at Muroc Army Air Field (later Edwards Air Force Base) on April 15, 1947. Landing gear problems revealed themselves on early test flights, but by August the airplane was ready for high-speed flights. Improving its aerodynamic qualities was a streamlined canopy replacing the original bubble canopy design.
    Below original canopy
    On August 20, 1947, Commander Turner F. Caldwell took off in the first D-558-1 (Bureau Number 37970) on an attempt to top the speed record of 623.738 M.P.H. established a month earlier by Army Air Forces Colonel Albert Boyd in a P-80R Shooting Star modified for the flight. In four passes over the 3-kilometer course, Caldwell averaged a speed of 640.743 M.P.H., shattering Boyd’s mark. According to newspaper accounts of the era, Caldwell made his turns at the end of his four runs as tightly as possible to conserve fuel, using a black stripe on the ground and two clouds of green smoke marking the beginning and end of the 3-kilometer distance. His altitude was 75 feet. It marked the first time the Navy held the world speed record since Lieutenant Al Williams attained 266.59 M.P.H. in 1923.

    Caldwell could rest on his laurels for just five days. On August 25, 1947, wearing the traditional cloth flight helmet because the height of a hard hat would preclude his tall frame from fitting in the cockpit, Marine Lieutenant Colonel Marion Carl climbed into the second Skystreak (Bureau Number 37971). Describing the airplane as the “blood-red Douglas Skystreak,” a newspaper article announced “Plane Zooms Ahead of Sun,” in describing Carl’s flight that day, reflecting the fact that with his average speed of 650.6 M.P.H., he would have had to set his watch back a few minutes if flying from Berlin to London. “The ship is a beautiful one to fly, and I had no trouble whatever,” Carl said after completing his four passes, sometimes at just 25 ft. off the ground. “I felt nothing like compressibility or turbulence.”

    The aircraft that the press nicknamed “The Crimson Test Tube,” held the mantel of fastest aircraft in the world for just a brief time. The X-1, flown by Captain Chuck Yeager, became the first airplane to break the sound barrier on October 14, 1947.
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    D-558-1 #2, BuNo 37971. This aircraft was delivered to the NACA Muroc Flight Test Unit in April 1949 after 101 flights had been completed by the Navy, Air Force, and Douglas. This aircraft was never flown by the NACA. The D-558-1 #1 is located at the National Naval Aviation Museum at Naval Air Station Pensacola, Florida.

    Following 27 flights by the Navy and Douglas the second D-558-1 aircraft was delivered to the NACA in November 1947. The D-558-1 #2 underwent extensive instrumentation by the NACA Muroc instrumentation section. The number 2 Skystreak made a total of 19 flights with the NACA before it crashed on takeoff due to compressor disintegration on May 3, 1948, killing NACA pilot Howard C. Lilly. The third D-558-I, BuNo 37972, aircraft was delivered to the NACA Muroc Flight Test Unit in 1949 after three Douglas test pilots and Howard Lilly had flown it. The number three aircraft took over the planned flight program of the D-558-1 #2. From the first flight in 1949 through 1953 the third Skystreak was flown in an intensive flight-research program by seven NACA test pilots, with a great deal of useful data collected on high-subsonic handling. The D-558-1 #3 made a total of 78 research flights with the NACA before being retired on June 10, 1953. The third Skystreak is on display at Carolinas Aviation Museum located at the Charlotte-Douglas International Airport (CLT) in Charlotte, North Carolina.

    The Skystreak reached Mach 0.99 in level flight, but only flew supersonic in a dive. In the public mind, much of the research performed by the D-558-1 Skystreaks was quickly overshadowed by Chuck Yeager and the supersonic Bell X-1 rocket plane. However, the Skystreak performed an important role in aeronautical research by flying for extended periods of time at transonic speeds, which freed the X-1 to fly for limited periods at supersonic speeds.
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    Specifications (D-558-1 Skystreak)
    General characteristics
    Crew: 1
    Capacity: 500 lb (230 kg) of instrumentation
    Length: 35 ft 8.5 in (10.884 m)
    Wingspan: 25 ft 0 in (7.62 m)
    Height: 12 ft 11.6875 in (3.954463 m)
    Wing area: 150.7 sq ft (14.00 m2)
    Airfoil: NACA 65-110
    Gross weight: 9,750 lb (4,423 kg)
    Max takeoff weight: 10,105 lb (4,584 kg)
    Fuel capacity: 230 US gal (190 imp gal; 870 l) + optional 50 US gal (42 imp gal; 190 l) jettisonable tip-tanks
    Powerplant: 1 × Allison J35-A-11 turbojet engine, 5,000 lbf (22 kN) thrust
    Maximum speed: 651 mph (1,048 km/h, 566 kn) at sea level
    g limits: +11 (ultimate)
    Wing loading: 64.7 lb/sq ft (316 kg/m2)
    Thrust/weight: 0.51

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