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Douglas X-3 Stilleto

Designed and built by the Douglas Aircraft Company of Santa Monica, California. The X-3 was designed to explore high-speed aerodynamic phenomenon to speeds of up to Mach 2 for sustained periods upwards of 30 minutes in duration. Unlike the X-1 series and the X-2, the X-3 was designed for conventional ground takeoff operations. The X-3 would also explore the feasibility of using low-aspect-ratio wings.

 

 

 

 

 

 

 

 

 

 

 

Specifications

 

Length – 66’ 9”

Wingspan - 22’ 8”

Height – 12’ 6”

Gross Weight – 23840 lbs.

Dry Weight – 16120 lbs.

Powerplant – 2x Westinghouse J34 turbojets with after burner

Power output – 4850 lbs. thrust with re-heat (3370 lbs. thrust without)

Range – 500 miles

Endurance – approx. 1 hour

Maximum Speed (level flight) – Mach 0.95

Maximum speed (in 30° dive) – Mach 1.21

Maximum altitude – 35000’

 

Due to the aircraft’s high weight and relatively low power output, the X-3 would never come close to achieving its performance objectives. The aircraft’s first flight was made on October 20th 1952 in the hands of Douglas test pilot William “Bill” Bridgeman. The duration of the flight was approximately 20 minutes and was made from Rogers Dry Lake at Edwards AFB. After this flight, it was readily apparent to Bridgeman that the X-3 was drastically underpowered. Due to the low-lift provided by the very low-aspect-ratio wings and the low thrust generated by the J34 engines, the takeoff speed for the X-3 was an astounding 260mph!

 

Once the contractor flight-testing was complete, the aircraft was turned over to the USAF for testing. Lt. Col. Frank Everest was named as project pilot. There would be no extended Air Force flight testing of the X-3. The Air Force already knew how poor the aircraft performed from Bridgeman’s flights. All they wished to acquire was minimal flight experience in a low aspect ratio wing high performance aircraft. Everest completed only 3 flights and was then replaced at the controls by Maj. Charles E “Chuck” Yeager, Yeager also made only 3 flights.

 

The X-3 had a reputation fo being a “Hangar Queen”. This terminology given by pilots to an aircraft that no-one wanted to fly. Every so often the “Hangar Queen” would be washed/polished, wheeled out of the hangar into the sunlight for a few hours and then wheeled back inside again.

 

The NACA (National Advisory Committee for Aeronautics) took over the X-3 flight testing program on August 23rd 1954. Between that date and May 23rd 1956, the X-3 made only 20 flights, all in the hands of NACA test pilot Joseph “Joe” Walker. The X-3 is on display at the USAF museum at Wright-Patterson AFB, Ohio.

 

Northrop X-4 Bantam

 

Designed and built by the Northrop Aircraft Corporation of Hawthorne, California. The X-4 was designed to test the tailless or semi-tailless configuration at transonic speeds of Mach 0.85.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Northrop were exclusively contracted to explore this type of aircraft configuration (YB-39, B-2 Spirit!). The overall layout is not dissimilar to that of the British de Havilland D.H. 108 Swallow research aircraft built for the assault on the sound barrier. Two X-4’s were built and were allocated Air force serial numbers 46-676 and 46-677.

 

Specifications

 

Length – 23’3”

Wingspan - 26’ 10”

Wing Area – 300sq’

Height – 14’ 10”

Crew – 1

Gross Weight – 7820 lbs.

Dry Weight – 5507 lbs.

Powerplant – 2x Westinghouse J30 turbojets (non afterburning)

Power output – 1600 lbs. thrust each

Range – 420 miles

Maximum Speed – Mach 0.92 – 630mph

Maximum altitude – 42300’

 

The first flight of the X-4 was made in the hands of company test pilot Charles Tucker on December 16th 1948 (46-676). Contractor demonstrations of both aircraft continued until February 17th 1950, when Tucker made his 30th and last flight in the X-4 (46-677). Ten flights were made with the #1 X-4 (46-676) before the aircraft was grounded and used as a source of spare parts for the #2 (46-677) aircraft, twenty with the #2 X-4.

 

The next flight of the X-4 would be in the hands of Maj. Chuck Yeager of the USAF. The flight occurred on August 18th 1950 at Edwards AFB and was conducted by a joint co-operation between the NACA & AMC (Air Material Command, USAF). Yeager flew the X-4 another six times. Other pilots who flew the X-4 for the Air Force were Brigadier General Albert Boyd, Colonel Fred J Ascani, Colonel Frank Everest, Lt. Colonel Richard Johnson & Captain James S. Nash.

 

Pilots from the NACA completed the majority of testing. The X-4 achieved a maximum speed of Mach 0.92 in the hands of NACA pilot Scott Crossfield on January 24th 1951 and a maximum altitude of 42300 feet (also by Crossfield) on May 29th 1951. The last flight of the X-4 was on September 9th 1953.

 

The #1 X-4 is on static display at the USAF Academy, Colorado Springs; the #2 X-4 is on static display at the USAF museum at Wright-Patterson AFB, Ohio. It should be noted that both aircraft survived the flight test program (the first of the early X-planes to do so) and that there was not a single serious accident during nearly four years of continuous flight-testing.

 

 

Bell X-5

 

Designed and built by the Bell Aircraft Corporation of Buffalo, New York. The X-5 program was instigated to explore the facets of design & production of aircraft with variable sweep wings.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After WW2, a thorough study of a captured German Messerschmitt P.1101 fighter was carried out by the Bell engineering staff (Bob Woods, Richard Passman, Stanley Tracz and others), together, they presented a proposal to the Air Force calling for the design and construction of an aircraft that would incorporate wings whose sweep could be varied in flight. (The P.1101 did have variable sweep wings, but these could only be adjusted on the ground). Indeed the two aircraft were superficially very similar.

 

The X-5 program was initiated to investigate the aerodynamic results (in flight) of varying degrees of sweepback from 20º to 60º. Bell built two X-5’s; these aircraft were allocated Air Force serial numbers 50-1838 and 50-1839.

 

Specifications

 

Length – 33’4”

Wingspan - 20’ 9” (swept) 33’6” (unswept)

Wing Area – 175sq’

Height – 12’ 0”

Crew – 1

Gross Weight – 9875 lbs.

Dry Weight – 6350 lbs.

Powerplant – Allison J35-A-17A turbojet (non afterburning)

Power output – 4900 lbs. thrust

Range – 750 miles

Maximum Speed – 705mph

Maximum altitude – 42000’

 

The first flight of the X-5 (#1 aircraft 50-1838) was made in the hands of company test pilot, Jean “Skip” Ziegler on June 20th 1951. Ziegler climbed to an altitude of 15000ft with the landing gear fully extended throughout the duration of the 20-minute flight. It was July 26th (Ziegler’s 8th flight), that the variable sweep was activated in mid-air for the first time. The #1 X-5 was turned over to the Air Force for testing and evaluation on November 7th 1951. The testing continued with Ziegler, who made another 20 flights. Brigadier General Albert Boyd also made one flight in this aircraft before turning it over to the NACA for testing in late December 1951.

 

The NACA team of pilots (Joe Walker, Scott Crossfield, John Reeder, Walter Jones, Stan Butchart, Jack McKay & Neil Armstrong) made 133 flights between Walker’s first flight on January 9th 1952 & Neil Armstrong’s one and only flight on October 25th 1955. The #1 X-5 is on display at the USAF museum, Wright-Patterson AFB, Ohio.

 

The #2 X-5 (50-1839) was first flown by Jean Ziegler on October 10th 1951, it was accepted for testing by the Air Force 8 days later. Air Force pilots who flew this aircraft included Maj. Chuck Yeager & Col. Fred J. Ascani. This aircraft was lost on October 14th 1953 while undergoing stall tests with 60º sweepback. The pilot was Maj. Ray Popson of the USAF. During the stall tests, Popson entered a spin, from which he could not recover. Although emergency egress was attempted, it was unsuccessful and Ray Popson was killed when the X-5 hit the desert floor.