Tag Archives: Prototype

26 April 1948

Aviation, , , , , , , , , , , , ,
est Pilot George Welch flying the prototype North American Aviation XP-86 Sabre, 45-59597. (U.S. Air Force)
North American Aviation test pilot George S. Welch, flying the first of three XP-86 prototypes, serial number 45-59597. (North American Aviation, Inc.)

26 April 1948: At Muroc Field (now known as Edwards Air Force Base), in the high desert of southern California, North American Aviation test pilot George Welch put the prototype XP-86 Sabre, 45-59597, into a 40° dive and broke the Sound Barrier. It is only the second U.S. aircraft to fly supersonic. The first was the Bell X-1, piloted by Chuck Yeager, only a few months earlier.

Or, maybe not.

In his book, Aces Wild: The Race For Mach 1, fellow North American Aviation test pilot Albert W. Blackburn makes the case that George Welch had taken the prototype XP-86 Sabre supersonic on its first flight, 1 October 1947, and that he had done so three times before Chuck Yeager first broke the Sound Barrier with the Bell X-1 rocketplane, 14 October 1947. Blackburn described two runs through the NACA radar theodolite with speeds of Mach 1.02 and 1.04 on 13 November 1947.

Mr. Blackburn speculates—convincingly, in my opinion—that Secretary of the Air Force W. Stuart Symington, Jr., ordered that Welch’s excursions beyond Mach 1 were to remain secret. However, during a radio interview, British test pilot Wing Commander Roland Prosper (“Bee”) Beamont, C.B.E, D.S.O. and Bar, D.F.C. and Bar, stated that he had flown through the Sound Barrier in the number two XP-86 Sabre prototype (45-59598). Once that news became public, the U.S. Air Force released a statement that George Welch had flown beyond Mach 1 earlier, but gave the date as 26 April 1948.

Test pilot George S. Welch, wearing his distinctive orange helmet, in the cockpit of the prototype XP-86. This photograph was taken 14 October 1947. (U.S. Air Force)
Test pilot George S. Welch, wearing his distinctive orange helmet, in the cockpit of the prototype XP-86. This photograph was taken 14 October 1947. (U.S. Air Force)

It wasn’t long after the first flight of the XP-86 on October 1, 1947, that Welch dropped into Horkey’s [Edward J. Horkey, an aerodynamicist at North American Aviation] office at the Inglewood plant. He wanted to talk about his recent flight and some “funny” readings in the airspeed indicator. He had made a straight-out climb to more than 35,000 feet. Then, turning back toward Muroc Dry Lake, he began a full-power, fairly steep descent.

“I started at about 290 knots,” Welch was explaining to Horkey. “In no time I’m at 350. I’m still going down, and I’m still accelerating but the airspeed indicator seems stuck like there’s some kind of obstruction in the pitot tube. I push over a little steeper and by this time I’m through 30,000 feet. All of a sudden, the airspeed indicator flips to 410 knots. The aircraft feels fine, no funny noises, no vibration. Wanted to roll off to the left, but no big deal. Still, I leveled out at about 25,000 and came back on the power. The airspeed flicked back to 390. What do you think?”

“. . . You may be running into some Mach effects. . . .”

— Aces Wild: The Race For Mach 1, by Al Blackburn, Scholarly Resources Inc., Wilmington, Delaware, 1999, at Pages 147–148.

The “funny” reading of the airspeed indicator became known as the “Mach jump.” George Welch was the first to describe it.

The Sabre became a legendary jet fighter during the Korean War. 9,860 were built by North American, as well as by licensees in Canada, Australia and Japan.

George Welch had been recommended for the Medal of Honor for his actions as a P-40 Warhawk fighter pilot in Hawaii, December 7, 1941. He was killed while testing a North American Aviation F-100A Super Sabre, 12 October 1954.

Test pilot George S. Welch with a North American Aviation F-86 Sabre. (San Diego Air and Space Museum Archives)

© 2018, Bryan R. Swopes

19 April 1960

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Grumman YA2F-1 Inruder Bu. No. 147864 (San Diego Air and Space Museum Archives)
Grumman YA2F-1 Intruder Bu. No. 147864 with landing gear extended during the first flight, 19 April 1960. (San Diego Air and Space Museum Archives)

19 April 1960: Grumman Aircraft Engineering Corporation test pilot Robert K. Smyth made the first flight of the prototype YA2F-1 Intruder, Bu. No. 147864, at the Grumman Peconic River Airport (CTO), Calverton, Long Island, New York. During the flight, Smyth climbed to 15,000 feet (4,572 meters). The landing gear remained extended during the flight. At one point, Smyth attempted to retract it, but a malfunction was indicated, so they remained down and locked. The first flight lasted one hour.

During follow-on flights, Bob Smyth and project test pilot Ernie von der Heyden (who flew the photo-chase plane during the first flight) alternated left and right seats.

Bu. No. 147864 was painted gray with U.S. Navy markings before being accepted by the Navy on 29 April 1960. The airplane was lost 31 May 1960.

Grumman test pilot Robert K. Smyth in the cockpit of the YA2F-1 prototype, Bu. No. 147864, 29 April 1960. With Program manager Bruce Tuttle and VP Larry Mead. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Grumman test pilot Robert K. Smyth in the cockpit of the YA2F-1 prototype, Bu. No. 147864, 29 April 1960. With Program manager Bruce Tuttle and VP Larry Mead. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

Eight Grumman YA2F-1 Intruders were built for the test program.  They were redesignated A-6A Intruder in 1962.

The Grumman A-6A Intruder was a carrier-based, all-weather attack bomber powered by two turbojet engines. It was operated by a pilot and a bombardier/navigator, or “b/n,” in a side-by-side cockpit. The wings were slightly swept.

The A2F-1 was 53 feet, 3 inches (16.231 meters) long with a wing span of 53 feet, 0 inches (16.154 meters) and overall height of 15 feet, 2 inches (4.623 meters). The wings had a total area of 528.9 square feet (49.14 square meters) and were swept aft to 25° at 25% chord. The aircraft had an empty weight of 23,412 pounds (10,620 kilograms) and maximum takeoff weight of 53,278 pounds (24,166 kilograms).

Grumman YA2F-1 Intruder, Bu. No. 147864, in Navy markings. (San Diego Air and Space Museum Archives)
Grumman YA2F-1 Intruder, Bu. No. 147864, in Navy markings. (San Diego Air & Space Museum Archives)
Grumman A2F-1 Intruder (A-6A) three-view illustration with dimensions. (U.S. Navy)

The prototypes were powered by two Pratt & Whitney J52-P-6 turbojet engines which had previously been used on the North American Aviation AGM-28 Hound Dog cruise missile. The J52 was a two-spool, axial-flow turbojet with a 12-stage compressor section (5 low- and 7 high-pressure stages) and 2-stage (1 high- and 1-low pressure stages). The engines had a normal power rating of 7,500 pounds of thrust (33.36 kilonewtons) at 11,400 r.p.m., and a maximum of 8,500 pounds (37.81 kilonewtons) at 11,650 r.p.m. The J52-P-6 was 31 inches (0.787 meters) in diameter, 127 inches (3.226 meters) long, and weighed 2,056 pounds (933 kilograms) The engine incorporated an exhaust nozzle that could be swiveled downward 23° to assist in short field takeoffs.

The A-6A had a cruise speed of 429 knots (493 miles per hour/795 kilometers per hour) at 44,450 feet (13,548 meters) and a maximum speed of 566 knots (651 miles per hour/1,048 kilometers per hour) at Sea Level. The service ceiling was 48,250 feet (14,707 meters), and the maximum range was 2,061 nautical miles (2,372 statute miles/3,817 kilometers).

The initial production Intruders could carry 18,000 pounds ( kilograms) of bombs on hardpoints under the wings. It could also carry AIM-9 Sidewinder air to air, or AGM-12 Bullpup air to ground missiles. “Special Weapons” that could be carried included Mk. 28 or Mk. 43 thermonuclear bombs.

The Intruder was a very successful combat aircraft with 693 built in attack, tanker and electronic warfare variants. They remained in service with the United States Navy until 1997.

Grumman YA2F-1 (A-6A) Intruder Bu. No. 147867, the third prototype, carrying thirty Mk. 82 low-drag bombs on multiple ejector racks under the wings and fuselage. (U.S. Navy)
Grumman YA2F-1 (A-6A) Intruder Bu. No. 147867, the third prototype, carrying thirty Mk. 82 low-drag 500-pound bombs on multiple ejector racks under the wings and fuselage. (U.S. Navy)

© 2019 Bryan R. Swopes

18 April 1952

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Convair YB-60-1-CF 49-2676 takes off on a test flight. (U.S. Air Force)

18 April 1952: Piloted by Chief Test Pilot Beryl A. Erickson, and Arthur S. Witchell, the prototype Consolidated-Vultee YB-60-1-CF, serial number 49-2676, made its first takeoff at Carswell Air Force Base, Fort Worth, Texas.

As a proposed competitor to Boeing’s B-52 Stratofortress, the YB-60 (originally designated B-36G) was developed from a B-36F fuselage by adding swept wings and tail surfaces and powered by eight turbojet engines. Its bomb load was expected to be nearly double that of the B-52 and it would have been much cheaper to produce since it was based on an existing operational bomber.

Test pilot Beryl A. Erickson waves from the cockpit of the YB-60. (Convair, via Jet Pilot Overseas.)
Test pilot Beryl A. Erickson waves from the cockpit of the YB-60. (Jet Pilot Overseas.)

The Associated Press reported:

New Jet ‘Rides Like Cadillac’, Crew Says After Test Flight

     FORT WORTH, April 18 (AP)—The all-jet YB-60 bomber “rides like a Cadillac” and “touched at fighter speed,” crew members said Friday after the ultra-secret global bomber completed its first test flight.

   “I came back with very little perspiration, B.A. Erickson, chief test pilot for Consolidated Vultee Aircraft Corp. said. “That’s the answer to any pilot.”

  Erickson tried the YB-60’s performance and capabilities only “modestly,” he said. The flight was made at a moderate altitude—”a couple of Texas miles,” Erickson said.

Rides Like Cadillac

     “The YB-60 rode like a Cadillac with no noise like a B-36—no prop noise or vibration,” Arthur S. Witchell Jr., the co-pilot, said.

“This is the Queen Mary coming in gracefully,” Erickson said.

     The YB-60, an eight-jet bomber sometimes called a jet version of the B-36, was in the air one hour and six minutes. Erickson said it “touched at fighter speed.”

The plane is about the same size as the B-36, Erickson said. “Most any B-36 pilot would feel right at home,” he said.

Higher Speed Tests

     Witchell said tests would probably be made soon at higher speeds and higher altitudes.

The plane took off with a deep roar, with a shrill, whining overtone. Several thousand spectators, including Air Force personnel from Carswell Air Force Base, home of the B-36, lined the left side of the Carswell runway and stood on rooftops.

     The spectators were able to distinguish little more than the YB-60’s extreme, almost-triangular swept-back shape.

     The YB-60 made a rendezvous in the air with a B-25 Air Force camera plane from which highly secret photographs were taken.

—Valley Morning Star, Volume XLII, No. 271, Saturday 19 April 1952, Page 1 at Columns 3 and 4.

Consolidated-Vultee YB-60 (Jet Pilot Overseas)
Consolidated-Vultee YB-60 49-2676. (Jet Pilot Overseas)

The YB-60’s first flight was three days after that of the Boeing YB-52 Stratofortress. In testing, it was 100 miles per hour (161 kilometers) slower than the B-52 prototype, despite using the same engines. A second B-60 prototype was cancelled before completion, and after 66 flight hours the YB-60 test program was cancelled. Both airframes were scrapped in 1954, with the second prototype never having flown.

The Convair YB-60 was 171 feet (52.121 meters) long with a wingspan of 206 feet (62.789 meters) and overall height of 60 feet, 6 inches (18.440 meters). The wings were swept at a 37° angle. It had an empty weight of 153,016 pounds (69,407 kilograms) and gross weight of 300,000 pounds (136,078 kilograms).

Consolidated-Vultee YB-60-1-CF 49-2676. (U.S. Air Force)

The prototype jet bomber was powered by eight Pratt & Whitney Turbo Wasp YJ57-P-3 turbojet engines. The J57 was a two-spool, axial-flow turbojet developed from an experimental turboprop engine. It had 16-stage compressor section (9 low- and 7-high-pressure stages), 8 combustors and a 3-stage turbine section (1 high- and 2 low-pressure stages). The YJ57-P-3s were rated at 8,700 pounds of thrust (38.70 kilonewtons), each. The YJ57-P-3 was 183.5 inches (4.661 meters) long, 41.0 inches (1.041 meters) in diameter and weighed 4,390 pounds (1,991 kilograms). These were the same engines used in the YB-52, and were similarly mounted in four 2-engine nacelles below the wings.

Right profile of the first prototype YB-60. Note the tail landing gear strut. (Jet Pilot Overseas)
Right profile of the first prototype YB-60. Note the tail landing gear strut. (Jet Pilot Overseas)

Maximum speed was 0.77 Mach (508 miles per hour, 818 kilometers per hour) at 39,250 feet (11,963 meters) and the combat ceiling was 44,650 feet (13,609 meters). The YB-60 could reach 30,000 feet (9,144 meters) in just over 28 minutes. Takeoff required 6,710 feet (2,045 meters) and 8,131 feet (2478 meters) were required to clear a 50-foot (15.24 meters) obstacle. Maximum range was 8,000 miles (12,875 kilometers) but the combat radius was 2,920 miles (4,699 kilometers) with a 10,000 pound (4,536 kilograms) bomb load.

The maximum bomb load was 72,000 pounds (32,659 kilograms). Defensive armament consisted of two M24A1 20 mm autocannon in a remote-controlled tail turret. The second YB-60 retained the upper forward and lower aft retractable gun turrets of the B-36, adding eight more 20 mm cannon.

Chief Test Pilot Beryl Arthur Erickson. (Convair)
Chief Test Pilot Beryl Arthur Erickson. (Convair)

© 2017, Bryan R. Swopes

16 April 1949

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Tony Levier and  Glenn Fulkerson in the prototype Lockheed YF-94. (Lockheed Martin)

16 April 1949: At Van Nuys Airport, California, test pilot Tony LeVier and flight test engineer Glenn Fulkerson made the first flight of the Lockheed YF-94 prototype, serial number 48-356. The aircraft was the first jet-powered all-weather interceptor in service with the United States Air Force and was the first production aircraft powered by an afterburning engine.

Prototype Lockheed YF-94 48-356, first flight, 16 April 1949. (U.S. Air Force)

Two prototypes were built at Lockheed Plant B-9, located on the east side of Van Nuys Airport. Two TF-80C-1-LO (later redesignated T-33A) Shooting Star two-place trainers, 48-356 and 48-373, were modified with the installation of air intercept radar, an electronic fire control system, radar gun sight, four Browning AN-M3 .50-caliber (12.7 × 99 NATO) aircraft machine guns and a more powerful Allison J33-A-33 turbojet engine with water-alcohol injection and afterburner. The rear cockpit was equipped as a radar intercept officer’s station.

The prototype Lockheed YF-94 test fires its four .50-caliber guns at Van Nuys, California. (Lockheed Martin)

It was initially thought that the project would be a very simple, straightforward modification. However, the increased weight of guns and electronics required the installation of a more powerful engine than used in the T-33A. The new engine required that the aft fuselage be lengthened and deepened. Still, early models used approximately 80% of the parts for the F-80C fighter and T-33A trainer. The Air Force ordered the aircraft as the F-94A. Improvements resulted in an F-94B version, but the definitive model was the all-rocket-armed F-94C Starfire.

The prototype Lockheed YF-94, 48-356. (U.S. Air Force)

The Allison J33-A-33 was a single-shaft turbojet engine with a single-stage centrifugal-flow compressor, 14 combustion chambers and, a single-stage axial flow turbine. The engine was rated at 4,600 pounds of thrust (20.46 kilonewtons) and 6,000 pounds (26.69 kilonewtons) with afterburner. The J33-A-33 was 17 feet, 11.0 inches (5.461 meters) long, 4 feet, 1.3 inches (1.252 meters) in diameter and weighed 2,390 pounds (1,084 kilograms).

Originally a P-80C Shooting Star single-place fighter, 48-356 had been modified at Lockheed Plant B-9 in Van Nuys to become the prototype TF-80C two-place jet trainer (the designation was soon changed to T-33A), which first flew 22 March 1948. It was then modified as the prototype YF-94. 48-356 was later modified as the prototype F-94B. It is in the collection of the Air Force Flight Test Museum, Edwards Air Force Base, and is in storage awaiting restoration.

Probably the best-known Lockheed F-94 variant is the all-rocket-armed F-94C Starfire. (Lockheed Martin)

© 2019, Bryan R. Swopes

15 April 1952

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The Boeing YB-52 Stratofortress, 49-231, takes off from Boeing Field at 11:09 a.m., 15 April 1952. (Robert F. Dorr Collection)
The Boeing YB-52 Stratofortress, 49-231, takes off from Boeing Field at 11:08 a.m., 15 April 1952. (Robert F. Dorr Collection)

15 April 1952: At 11:08 a.m., Boeing’s Chief of Flight Test, Alvin M. “Tex” Johnston, and Lieutenant Colonel Guy M. Townsend, U.S. Air Force, ran all eight turbojet engines to full power and released the brakes on the YB-52 Stratofortress prototype, 49-231.

With an awesome eight-engine roar, the YB-52 sprang forward, accelerating rapidly, wings curving upward as they accepted the 235,000-pound initial flight gross weight. At V2 (takeoff speed) the airplane lifted off the runway, because of the 6-degree angle of incidence of the wing, and at 11:08 a.m. we were airborne. The initial flight of the YB-52 had begun.

—Tex Johnston: Jet-Age Test Pilot, by A.M. “Tex” Johnston with Charles Barton, Smithsonian Books, Washington, D.C., 1992, Chapter 13 at Pages 397–398.

Alvin M. "Tex" Johnston, test pilot, after the first flight of the Boeing XB-52 Stratofortress prototype, 2 October 1952. (LIFE via Jet Pilot Overseas)
Alvin M. “Tex” Johnston, Boeing Chief of Flight Test, after the first flight of the Boeing XB-52 Stratofortress prototype, 2 October 1952. (LIFE via Jet Pilot Overseas)

The YB-52 remained over the Seattle area for approximately 40 minutes while Johnson and Townsend ran through a series of systems checks. When completed, they climbed to 25,000 feet (7,620 meters) and flew the new bomber to Larson Air Force Base at Moses Lake, Washington, where they stayed airborne for continued testing. The Stratofortress finally touched down after 3 hours, 8 minutes—the longest first flight in Boeing’s history up to that time. Johnston radioed that the airplane performed exactly as the engineers had predicted.

Boeing YB-52 Stratofortress 49-231. (Boeing)

The YB-52 had actually been ordered as the second of two XB-52s, but modifications and additional equipment installed during building resulted in enough differences to warrant a designation change. The first XB-52, 49-230, should have been the first to fly, but it was damaged during ground testing.

Boeing XB-52 Stratofortress 49-230. (U. S. Air Force)

The Boeing XB-52 and YB-52 were prototypes for a very long range strategic bomber. Both were built with a tandem cockpit for the pilot and co-pilot, similar to the earlier B-47 Stratojet. The wings were swept and mounted high on the fuselage (“shoulder-mounted”). The eight turbojet engines were in in two-engine nacelles mounted on pylons, below and forward of the wings. This had the effect of preventing the airplane’s center of gravity from being too far aft, and also provided cleaner air flow across the wings. The B-52’s landing gear has four main struts with two wheels, each. They can turn to allow the airplane to face directly into the wind while the landing gear remain aligned with the runway for takeoff and landing. With the landing gear under the fuselage, the wings could be constructed with greater flexibility.

Boeing YB-52 Stratofortress 49-231. (U.S. Air Force)
Boeing YB-52 Stratofortress 49-231. (U.S. Air Force)

The YB-52 was 152 feet, 8 inches (46.533 meters) long with a wingspan of 185 feet, 0 inches (56.388 meters). The prototype’s overall height was 48 feet, 3.6 inches (14.722 meters). The vertical fin could be folded over to the right so that the B-52 could fit into a hangar. The total wing area was 4,000 square feet (371.6 square meters). The wings’ leading edges were swept aft to 36° 54′. Their angle of incidence was 6° and there was 2° 30′ dihedral. The YB-52 had an empty weight of 155,200 pounds (70,398 kilograms) and gross weight of 405,000 pounds (183,705 kilograms).

The YB-52 was powered by eight Pratt & Whitney Turbo Wasp YJ57-P-3 turbojet engines. The J57 was a two-spool, axial-flow turbojet developed from an experimental turboprop engine. It had 16-stage compressor section (9 low- and 7-high-pressure stages), 8 combustors and a 3-stage turbine section (1 high- and 2 low-pressure stages). The YJ57-P-3s had a continuous power rating of 8,700 pounds of thrust (38.70 kilonewtons). The YJ57-P-3 was 183.5 inches (4.661 meters) long, 41.0 inches (1.041 meters) in diameter and weighed 4,390 pounds (1,991 kilograms).

The YB-52 had a cruise speed of 519 miles per hour (835 kilometers per hour) and maximum speed of 611 miles per hour (983 kilometers per hour) at 20,000 feet (6,096 meters). Its range was 7,015 miles (11,290 kilometers).

The two prototypes were unarmed.

Boeing YB-52 Stratofortress 49-231. (U.S. Air Force)

The B-52 was produced by Boeing at its plants in Seattle and Wichita from 1952 to 1962, with a total of 744 Stratofortresses built. The last version, the B-52H, entered service with the Strategic Air Command in 1960. The final B-52, B-52H-175-BW Stratofortress 61-0040, was rolled out at Wichita, Kansas, 26 October 1962. This airplane remains in service with the United States Air Force. The newest B-52 in service, 61-0040 is 62 years old and has flown more than 21,000 hours.

The Boeing YB-52 Stratofortress, 49-231, lands on Rogers Dry Lake, circa 1953. (U.S. Air Force 071204-F-9999J-039)

All previous versions, B-52A through B-52G, have long been retired to The Boneyard and scrapped. Of the 102 Boeing B-52H Stratofortress bombers, 76 are still in the active inventory. One, 61-007, known as Ghost Rider, was recently taken from Davis-Monthan and after an extensive restoration and update, returned to service.

The YB-52 prototype was retired to the National Museum of the United States Air Force in the late 1950s. By the mid-60s it was determined to be excess and was scrapped.

Captain William Magruder (standing) Boeing Chief Test Pilot Alvin M. Johnston (center) and Lieutenant Colonel Guy M. Townsend with the Boeing YB-52 Stratofortress 49-231. (Boeing)
Left to right: Captain William Magruder, USAF; Boeing Chief Test Pilot Alvin M. Johnston; and Lieutenant Colonel Guy M. Townsend, USAF, with the Boeing YB-52 Stratofortress, 49-231. (Boeing)

© 2019, Bryan R. Swopes