The Skystreak was a joint United States Navy/National Advisory Committee for Aeronautics (NACA) research aircraft designed to explore flight at high subsonic speed. The Phase I Skystreak was designed by a team led by Douglas Chief Engineer Edward Henry Heinemann. Flight testing was conducted at the NACA High Speed Flight Station at Muroc Army Airfield (later known as Edwards Air Force Base). Three D-558-Is were built, followed by the Phase II, swept-wing Mach 2 D-558-II Skyrocket rocketplane.
The D-558-I carried extensive flight test instrumentation for its time. The wings had 400 orifices for air pressure sensors. During the test series, aircraft stability in the range of 0.82–0.99 Mach was investigated. One of the Skystreaks may have briefly exceeded Mach 1 as it came out of a dive.
Unlike some of the other experimental high speed aircraft of the time, the Skystreak took off from the ground under its own power rather than being carried aloft by a mother ship. While those other aircraft could briefly reach much higher speeds, the D-558-I was able to fly for extended periods in the high-subsonic range, providing scientists and engineers with a tremendous amount of data.
The research airplane was a single-place, single-engine, low-wing monoplane with retractable tricycle landing gear. The fuselage of the D-558-I was constructed of an aluminum framework covered with sheet magnesium. It was designed for an ultimate load factor of 18 gs. The wings and tail surfaces were aluminum. The airplane was painted scarlet (not orange, like its contemporary, the Bell X-1) and was known as “the crimson test tube.”
The D-558-I was 35 feet, 1.5 inches (10.706 meters) long with a wingspan of 25 feet, 0 inches (7.620 meters) and overall height of 12 feet, 1.6 inches (3.698 meters). Gross weight 10,105 pounds (4,584 kilograms). It carried 230 gallons (871 liters) of kerosene in its wings.
Bu. No. 37970 made 101 of the 228 Phase I flights. It set a world speed record 1,031.178 kilometers per hour (640.744 miles per hour), flown by Commander Turner F. Caldwell Jr., U.S. Navy, 20 August 1947.² (Major Marion E. Carl, U.S. Marine Corps, flew the second Skystreak, Bu. No. 37971, to 1,047.356 kilometers per hour (650.797 miles per hour),³ breaking Caldwell’s record.)
After Douglas completed the contractor’s test series, the Number 1 Skystreak was turned over to the NACA High Speed Flight Station and designated NACA 140. It was not as highly instrumented as the Number 2 and Number 3 Skystreaks and was not flown, but was used as a source for spare parts for the other D-558-Is.
Douglas D-558-I Skystreak Bu. No. 37970 is on display at the National Naval Aviation Museum, NAS Pensacola, Florida.
¹ Determining the actual dates of historic events is sometimes difficult. In the case of the first flight of the Douglas D-558-I Skystreak, NASA sources cite 14 April 1947. The Naval History and Heritage Command National Naval Aviation Museum says it took place 15 April. Dozens of contemporary newspapers articles published on 15 April indicate that “flight testing will begin this week,” suggesting that the first flight had not yet taken place.
² FAI Record File Number 9864
³ FAI Record File Number 9865
© 2019, Bryan R. Swopes
minor typo-should be plural
providing scientists and engineer with
Thanks, Eric. Fixed it.
Great blog, Bryan. I read it every day! Thanks for the hard work.
Thank you very much. I appreciate it.
Hi Bryan,
Wonderful article on a great plane. Do you have any knowledge of why this aircraft was designed to withstand such high g loads? 18 g’s is way beyond the ability of any human. I’m curious what the rational was. Thanks!
Thank you, Pete. As to the g-limit, I don’t know, but assume that as these were all experimental aircraft, engineers did not know what extremes would be encountered. I did find this statement in an Air Force Flight Test Center report regarding the Bell X-1: “In order to insure that the airplane
would not break apart during its turbulent transition
from subsonic to supersonic flight, both the AAF
and the NACA insisted that it be designed for an
ultimate load factor of 18 g’s. That represented a
figure about 50 percent higher than for any existing
fighter aircraft. Ben Hamlin later recalled that this
load factor was nothing more than an ‘ignorance
factor.’ ‘I protested in vain,’ he noted, ‘and lost
another battle. It proved to be loads and loads of
ignorance, that factor did.’ ”
That makes sense. Better safe than sorry. Thanks for researching Bryan!