Douglas D-558-1 Skystreak (Phase 1) - United States, 1947
Detailing the development and operational history of the Douglas D-558-1 Skystreak (Phase 1) Experimental Research Aircraft.
Entry last updated on 5/2/2016; Authored by Staff Writer; Content ©www.MilitaryFactory.com
Test aircraft such as the Douglas D-558-1 Skystreak paved the way for American aviation research in the post-World War 2 years.
World War 2 (1939-1945) sparked a research boom for American aviation - particularly concerning the realm of transonic/supersonic travel and rocket/jet-powered flight that would go on to influence both military and civilian markets for decades. One product of this period was the Douglas D-558-1 "Skystreak" which was developed between the United States Navy and the National Advisory Committee for Aeronautics ("NACA" - forerunner to our modern-day NASA establishment). The program delivered three of the six planned experimental aircraft designated simply (and sequentially) as D-558-1 #1, #2 and #3) - numbers 4, 5 and 6 were cancelled.
The Skystreak was intended from the beginning as a research-minded, data-collecting platform, the program to evolve along a three-phased route to include a dedicated turbojet-powered airframe, a hybrid jet/rocket-powered design and a combat-oriented interceptor/fighter for possible procurement by the US military. Between these designs were to be various changes such as relocated intakes and differing wing arrangements to finalized optimal qualities of a transonic airframe in future offerings. The joint venture was charged with development of six airframes on June 22, 1945 and the program was revised to reduce the total count to just three and these would all utilize the same intake position/wing arrangement for simplicity. Production of the initial test model was undertaken in 1946 and ended in January 1947. After her internals were installed, the aircraft recorded a first flight (in its early red-coatd guise) on April 14th, 1947 out of Muroc Army Air Field (Edwards Air Force Base). The vehicle was designated as a "Phase 1 D-558-1".
Externally, the D-558-1 was of a highly conventional design shape though aerodynamically refined through heavy use of curves and smooth contouring. The engine was buried within the tubular fuselage and aspirated at the front through a nose intake and exhausted at the rear through a conventional tapered ring. The pilot was situated in a forward-set cockpit under a vision-restrictive canopy along the fuselage spin. The tail unit included a single, tall vertical fin, mid-mounted horizontal planes and a support section emanating from the spine for added support and aerodynamics. The main wing appendages were low-mounted along the fuselage sides and straight in their general design. The aircraft was given a wholly retractable wheeled undercarriage with two main single-wheeled legs and a single wheeled nose leg. This was a unique quality as jet-powered research aircraft for the time go for the D-558-1 could take-off and land on its own without the need for an expensive "mothership/ host ship" launching platform. The "Skystreak" was given a running length of 35 feet, 8 inches with a wingspan of 25 feet and a height of 12 feet. It sported a Maximum Take-Off Weight (MTOW) of 10,100lbs that included an equipment payload of 500lbs.
Power for the D-558-1 series was served through a single Allison J35-A-11 axial-flow turbojet engine installation delivering 5,000lbs of thrust (one of the earliest wholly-American jet engine designs in fact). This provided the airframe with a maximum recorded speed of 650 miles per hour (at sea level) and service ceiling of up to 45,700 feet. Rate-of-climb was listed at 9,220 feet per minute. The D-558-1 (#1) set a new world speed record on August 20th, 1947 when it reached 640.7 miles per hour and this was then itself broken by D-558-1 (#2) less than a week later when the aircraft peaked at 650 miles per hour.
Continued evaluations of the D-558-1 family of research aircraft revealed the design to be largely sound, exhibiting some instability when approaching Mach 1 speeds. The first airframe managed a total of 101 flights before being retired and delivered to the National Naval Aviation Museum of Pensacola, Florida. The second airframe was lost to a crash (killing pilot Howard Lilly) and managed 46 flights during its shortened career. The cause of the crash was ruled as "compressor disintegration" and reaffirmed the life of a test pilot was not a glamorous one, a career fraught with daily inherent dangers. The third airframe continued in service into June of 1953 before netting 78 total flights. She now resides as a museum showpiece at the Carolinas Aviation Museum in Charlotte, North Carolina.
The D-558-1 "Phase 2" portion of the program evolved to become the D-558-2 "Skyrocket" with its hybrid jet/rocket propulsion system (detailed elsewhere on this site). Three of the type were built with the first vehicle flown on February 4th, 1948. These models were designed for high-speed flight research with swept wing assemblies unlike the transonic-minded, straight-winged Skystreaks. This aircraft was credited with becoming the first to exceed Mach 2 - twice the speed of sound.
D-558-1 "Phase 3" was a short-lived Douglas proposal for a high-speed, swept-wing military interceptor. The airframe would have carried either a General Electric TG-180 or Westinghouse 24C turbojet engine with rocket motor and featured swept-back wings, taking into account all of the data garnered from the D-558 family of research planes. The aircraft was to have been armed with 2 x 20mm cannons or aerial rockets in its finalized form. The initiative fell to naught.