Douglas Skystreak

The Douglas Skystreak, also known as D-558-1 or D-558-I, was a research aircraft with a single engine that originated in the United States in the 1940s.

Its design was commissioned by the U.S. Navy Bureau of Aeronautics in collaboration with the National Advisory Committee for Aeronautics (NACA) and was developed by the Douglas Aircraft Company in 1945.

The Skystreaks were equipped with turbojet engines and were capable of taking off from the ground independently.

Additionally, they featured unswept flying surfaces.

The D558 program was initially conceived as a collaborative research effort between the National Advisory Committee for Aeronautics (NACA) and the United States Navy, to explore transonic and supersonic flight.

The program was designed to consist of three phases, namely a jet-powered aeroplane, a mixed rocket/jet-powered configuration, and a combat aircraft design and mock-up.

On 22 June 1945, a contract was issued for the design and construction of six D558-1 aircraft for the first phase.

The original plan called for six aircraft with a combination of nose and side air inlets and varying wing airfoil sections.

However, this plan was quickly revised to three aircraft of a single configuration with a nose inlet.

Plans for the second phase with mixed rocket/jet propulsion were also abandoned, and a new aircraft, the D558-2, was developed with mixed rocket and jet propulsion for supersonic flight.

Construction of the first D558-1 began in 1946 and was completed in January 1947.

The fuselage extensively utilized magnesium alloys, while the wings were fabricated from more conventional aluminium alloys.

The airframe was constructed using HK31, which is composed of 3% thorium 1% zirconium, and the remainder magnesium.

This material is much lighter than Inconel and has a 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 to be jettisoned from the aircraft in an emergency, including the cockpit.

The aircraft was configured to carry over 500 pounds (230 kg) of test equipment, including sensors such as strain gauges and accelerometers, located in 400 locations throughout the aircraft.

One wing was pierced by 400 small holes to enable the collection of aerodynamic pressure data.

The Skystreaks were equipped with a single Allison J-35-A-11 engine, which was developed by General Electric under the designation TG-180.
This engine was one of the earliest examples of axial-flow turbojets originating from the United States.

Additionally, the aircraft had a fuel capacity of 230 US gallons (equivalent to 871 L) of kerosene-based jet fuel.
Specifications
D-558-1 Skystreak
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 take-off 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.
Performance
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.
Sources
Air Mobility Command Museum.
McDonnell Douglas aircraft since 1920: Volume I-René J Francillon.
San Diego Air and Space Museum Archive.
The National Museum of the U.S. Air Force.
X-Planes, Douglas D-558-D-558-1 Skystreak & D-558-2 Skyrocket-Peter E Davies, Adam Tooby.
Naval Fighters No.56, Douglas D-558-1 Skystreak-Scott Libis.

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