| D-558-1 Skystreak | |
|---|---|
 | |
| General information | |
| Type | Experimental aircraft |
| National origin | United States |
| Manufacturer | Douglas Aircraft Company |
| Status | Retired |
| Primary user | United States Navy National Advisory Committee for Aeronautics |
| Number built | 3 |
| History | |
| First flight | 14 April 1947 |
| Developed into | Douglas D-558-2 Skyrocket |
TheDouglas Skystreak (D-558-1 or D-558-I) is an American single-engine jetresearch aircraft of the 1940s. It was designed in1945 by theDouglas Aircraft Company for theU.S. Navy Bureau of Aeronautics, in conjunction with theNational Advisory Committee for Aeronautics (NACA). The Skystreak was aturbojet-powered aircraft that took off from the ground under its own power and had unswept flying surfaces.
The D558 program was conceived as a joint NACA/U.S. Navy research program fortransonic andsupersonic 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.[1] 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 sideair inlets and varying wingairfoil 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, theD558-2, 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 lightweight, high strengthHK31 magnesium alloy extensively, while the wings were fabricated from more conventional aluminum alloys. The airframe was designed to withstand unusually high loads of up to 18times gravity due to the uncertainties of transonic flight. The forward fuselage, including the cockpit, could be jettisoned from the aircraft in an emergency.[2] The aircraft was configured to carry more than 500 pounds (230 kg) of test equipment, including sensors (such as strain gauges and accelerometers) in 400 locations throughout the aircraft. One wing was pierced by 400 small holes for the pressure measurements required for calculating airloads.[3]
The Skystreaks were powered by oneAllison J-35-A-11 engine (developed by General Electric as the TG-180) — one of the firstaxial-flow turbojets of American origin — and carried 230 US gallons (871 L) ofjet fuel (kerosene).
All the Skystreaks were initially painted scarlet, which led to the nicknamecrimson test tube. NACA later had the color of the Skystreaks changed to white to improve optical tracking and photography. The first of three D-558-1 Skystreaks, BuNo37970, made its maiden flight on 14 April 1947, at Muroc Army Air Field (later namedEdwards AFB). Less than 4 months later, on August 20, this aircraft with CommanderTurner Caldwell, USN, reached 640.744 mph (1,031.178 km/h; 556.791 kn) flying D-558-1 #1. This was recognised as an official worldair speed record, as the World War II GermanMe 163B V18Komet rocket fighter prototype that was claimed to have reached 1,130 km/h (702 mph; 610 kn) in July 1944[4][5] did so in secrecy and not under the strict conditions that regulate official records (presence of FIA officials as observers, timed runs in two directions to cancel out wind speed, etc). The D-558-1 #1 Skystreak's record lasted 5 days, and was broken by then-Lieutenant ColonelMarion Carl, USMC, going 10 mph (16 km/h; 8.7 kn) faster in D-558-1 #2, BuNo37971. 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 theNational Naval Aviation Museum atNaval 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 pilotHoward C. Lilly. The third D-558-I, BuNo37972, 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 in1949 through1953 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 atCarolinas Aviation Museum located at theCharlotte-Douglas International Airport (CLT) inCharlotte, North Carolina.
The Skystreak reached Mach 0.99 in level flight, but only flew supersonic in a dive.[3] In the public mind, much of the research performed by the D-558-1 Skystreaks was quickly overshadowed byChuck Yeager and the supersonicBell 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.
Data fromMcDonnell Douglas aircraft since 1920 : Volume I,[1] Jane's all the World's Aircraft 1949-50[6]
General characteristics
Performance
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