12/30/2025
A Flight Test Museum History Moment: The Douglas D-558-1 Skystreak was an single-engine jet research aircraft designed in 1945 by the famous Ed Heinamann of the Douglas Aircraft Company for the U.S. Navy Bureau of Aeronautics, in conjunction with the National Advisory Committee for Aeronautics (NACA).
Unlike most of our early jet aircraft, the Skystreak was equipped with an axial-flow turbojet, not a centrifugal flow as was equipped in our early jets of the period such as the P-59, P-80 and P-84. It was designed to take off from the ground under its own power, but like the early jets and the Bell X-1, still had unswept, or straight wings. The mission of the Skystreak was to fly for extended periods of time at transonic speeds, which freed up the Bell X-1, a pure rocket powered research aircraft, to fly for very limited periods at supersonic speeds.
The D-558-1 program was conceived as a joint NACA/U.S. Navy research program to explore transonic flight and then supersonic flight with the second phase of the program, which became the D-558-2. 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 as they soon realized the limitations of the straight wing configuration. Instead, a new aircraft, the D-558-2, was designed with both mixed rocket and jet propulsion for supersonic flight exploration and swept wings for supersonic flight.
Like the Bell X-1 program, construction of the first Douglas D-558-1 began in 1946 and was completed in January 1947. The fuselage used lightweight, high strength HK31 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 18 times gravity due to the uncertainties of transonic flight. The forward fuselage, including the cockpit, could be jettisoned from the aircraft in an emergency. The aircraft was configured to carry more than 500 pounds 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.
The Skystreaks were powered by a first generation Allison J-35 turbojet engine — one of the first axial-flow turbojets of American origin — and carried 230 US gallons of jet fuel (kerosene).
All the Skystreaks were initially painted scarlet, which led to the nickname "Crimson Test Tube". The 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, BuNo 37970, made its maiden flight on 14 April 1947, at Muroc Army Air Field (later named Edwards AFB). Less than 4 months later, on 20 August, this aircraft flown by Commander Turner Caldwell, USN, reached a speed of 640.7 mph. This was recognized as an official world air speed record. That record lasted only 5 days, as it was again broken by Lt. Colonel Marion Carl, USMC, going 10 mph faster in D-558-1 #2, BuNo 37971.
Following 27 flights by the Navy, Marine and Douglas Test Pilots, the second D-558-1 aircraft was delivered to the NACA in November of 1947. The D-558-1 #2 underwent extensive instrumentation upgrades by the NACA Muroc instrumentation section. The number 2 Skystreak went on to made a total of 19 flights with the NACA before it crashed on takeoff due to compressor disintegration on 3 May 1948, killing NACA pilot Howard C. Lilly.
Howard C. “Tick” Lilly was the first NACA engineering pilot assigned to the Muroc Flight Test Unit, today known as NASA Armstrong. Lilly had trained as a Naval Aviator and joined the NACA’s Langley Memorial Aeronautical Laboratory in Virginia, now known as Langley Research Center in 1942. In 1943 he transferred to the NACA’s Lewis Flight Propulsion Laboratory in Cleveland, Ohio, (today's Glenn Research Center) and then to Muroc in 1947.
At Muroc he flew the Douglas D-558-1 transonic research aircraft and the Bell X-1. Lilly was the fourth person to exceed the speed of sound. He died 3 May 1948, when components of the D-558-1’s J-35 engine compressor failed, severing control cables and the airplane crashed during takeoff. He was the first NACA pilot to die in the line of duty. Story Credit: NASA
Additional Note: The compressor section was located on the Rogers Dry Lake Bed off the North End of the original South Base runway about two-thirds of the way to the Lilly crash site. It was spotted by members of the 412TW Airfield Management team and given to the Museum. Visit: https://flighttestmuseum.org
