THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF  S. A. C.

 

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The YB-36G / YB-60 Jet Bomber

 

The following is the text of the photo release for this picture.

It is printed on a letterhead titled:

                  

"CONVAIR A DIVISION OF GENERAL DYNAMICS CORPORATION".

 

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YB-60 in flight

FIRST FLIGHT VIEW OF CONVAIR YB-60 -- A Convair YB-60 swept-wing, eight-jet bomber is shown here in the first flight view of the U.S. Air Force's latest addition to its air arsenal.  Equipped with eight Pratt & Whitney turbojet engines, most powerful of their type now in use, the YB-60 was rolled out of the factory at Consolidated Vultee Aircraft Corporation's Fort Worth, Texas, Division on April 6, 1952, for engine run-ups and ground tests.  First flight, on April 18, 1952, occurred just 14 days after installation of its final engine.  Planes needle-nose appearance originates from a slender boom used for test purposes.  Wingspan of the YB-60 is 206 feet; its length, 171 feet; its height, 50 feet.  The new sky giant is nine feet longer and three feet three inches higher than the Convair B-36, now the largest airplane operational in the Air Force.  Wingspan of the B-36 is 230 feet; the shorter wingspan of the YB-60 is occasioned by the sweep of the YB-60's wings which reduce the span from tip to tip.  The YB-60 was built in record time.  A contract for two swept-wing jet bombers was awarded Convair by the Air Force on March 15, 1951.  Eight months later the first of the two airplanes was ready for engines.

 

The YB-60 was the all-jet competitor the Boeing B-52 Stratofortress.

                     

The Convair YB-60

By Joe Baugher

 

The B-36G was the designation initially applied to a swept-wing, jet-powered version of the B-36F. Two B-36Fs (49-2676 and 49-2684) were ordered as B-36Gs, but the designation was changed to YB-60 before they were built.

 

The Convair YB-60 Photo Gallery

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Note the 3 B-36's in the background.
First flight of Convair YB-60, 49-2676. Beryl Erickson was the pilot on the first flight of the YB-60 on April 18, 1952, three days after the first flight of the Boeing YB-52 Stratofortress.
YB-60 on Edwards Air Force Base old south base flightline. It was assigned to Edwards Air Force Base in January 1953 for the Phase II tests of the type. Lt. Col. Boyd L. Grubaugh was the flight test pilot and Frederick N. Stoliker was the flight test engineer.
YB-60 in flight. Only four flights of the Phase II test series had been completed when the Air Research and Development Command cancelled the test program on January 20, 1953. The YB-60 was flown for fifteen hours and forty-five minutes in the course of the four flights.
Convair made 20 test flights of the YB-60 and accumulated 66 hours of flight time. The Air Force cancelled the B-60 production program on August 14, 1952.
Night shot of YB-60 on south base ramp
There's a new sheriff in town. The cowboy in the foreground is Bill Whiteside, the son of Walter W. Whiteside, the chief maintenance officer at Edwards in the early 50's. The photo appeared on the front page of the Edwards Air Force Base paper and possibly on the front page of the Air Force Times. Note the enormous hydrogen bomb test shape just to the left of the access stand.

On August 25, 1950, Convair issued a formal proposal for an all-jet swept-winged version of the B-36, initially designated XB-36G. The Air Force was sufficiently interested that on March 15, 1951 the USAF authorized Convair to convert two B-36Fs (49-2676 and 49-2684) as B-36Gs. Since the aircraft was so radically different from the existing B-36, the designation was soon changed to YB-60.

In the interest of economy, as many components as possible of the existing B-36F were used to build the YB-60. The fuselage from aft of the cabin to near the end of the tail remained essentially the same as that of the B-36F. However, the nose was lengthened to accommodate more equipment, and was tapered to a needle-like instrument probe. The conversion to a swept wing had moved the center of gravity farther aft, which necessitated the addition of a retractable tail wheel underneath the rear fuselage. The plan was to leave the tail wheel still extended during the takeoff run, retracting it just prior to rotation. During landing, the tail wheel remained retracted until both the main and nose gears were firmly on the ground. Because of the higher landings speeds that were inherent with a swept-wing design, the design team included provisions for a drag chute in the tail cone, although it is unclear if it was actually fitted to either prototype. The fuselage was a bit longer than that of the B-36F, having a length of 171 feet.

The most readily-noticeable difference between the YB-60 and the B-36F was the swept wing. A wing sweep of 37 degrees was accomplished by inserting a wedge-shaped structure at the extremity of the center portion of the center wing. A cuff was added to the leading edge of the center wing to continue to sweep line to the fuselage. The net result was an increase of wing area to 5239 square feet. The wing span was 206 feet, about 24 feet less than that of the B-36F. The aircraft was also fitted with a new swept vertical tail and a set of swept horizontal elevators. The new swept vertical tail made the YB-60 somewhat taller than the B-36F, the tip of the new swept vertical fin reaching 60 feet 6 inches from the ground.

The YB-60 was to be powered by eight 8700 lb.s.t. J57-P-3 turbojets, housed in pairs on four pods that were suspended below and forward of the wing leading edge, similar to the B-52, but turboprop engines were still considered as a possible option if the jet engines did not work out.

The YB-60 also differed from the B-36F in its crew allocation and in its armament fit. The original YB-60 concept had only five crew members-pilot, copilot, navigator, bombardier/radio operator and radio operator/tail gunner. All were seated in the pressurized and heated forward compartment. All of the defensive armament of the B-36F was omitted, save the twin 20-mm tail cannon that were remotely directed by the radio operator/tail gunner seated in the forward fuselage via an AN/APG-32 radar in the extreme tail. The K-3A bombing/navigation system, with Y-3A optical and radar bombing sight was retained. The maximum bomb load capacity was the same as that of the B-36F, namely 72,000 pounds.

 The YB-60, 49-2676 was Convair's alternative to the Boeing B-52 Stratofortress. It is seen here in flight over Texas.
YB-60 and B-36F-5, 49-2683 on Edwards Air Force Base south base flightline.
YB-60 in flight over Kramers Junction at the intersection of Highways 58 and 395 northeast of Edwards Air Force Base
YB-60 takes off from the old main runway of Edwards Air Force Base.
Rare color photo of the YB-60 over Rogers Dry Lake on the approach to the old main runway

The second YB-60 and any production aircraft were to have the crew increased to nine. Early in the design process, the Air Force asked Convair to add back some of the retractable turrets that had been omitted from the initial design. The upper forward and lower aft turrets were to be identical to those of the standard B-36F, but the upper aft turret was still to be omitted.

The conversion of 49-2676 to YB-60 configuration began in the spring of 1951. The work was completed in only 8 months, since almost 72 percent of the parts of the YB-60 were common with those of the B-36F. However, the project was delayed by the late delivery of the J57 turbojets, which did not arrive at Convair until April of 1952. The aircraft was rolled out on April 6, 1952. It was the largest jet aircraft in the world at the time.

The first flight of YB-60 49-2676 took place on April 18, 1952, with Convair chief test pilot Beryl A. Erikson at the controls. The Boeing YB-52 took to the air for the first time only three days later. Although there was never any formal competition between the YB-60 and the B-52, the B-52 quickly exhibited a clear superiority. Although the YB-60 had a clear cost advantage over the B-52 (the YB-60 had a 72 percent parts commonality with the B-36 and used much already-proven equipment), the B-52 clearly had a superior performance. The top speed of the YB-60 was only 508 mph at 39,250 feet, more than 100 mph slower than the B-52. In addition, flight tests of the YB-60 turned up a number of deficiencies--engine surge, control system buffeting, rudder flutter, and electrical engine-control system problems. The stability was rather poor because of the high aerodynamic forces acting on the control surfaces acting in concert with fairly low aileron effectiveness. Consequently, the Air Force concluded that there was no future for the YB-60 and canceled the flight testing program on January 20, 1953. At that time, 66 hours of flight time had been accumulated.

The second prototype was never flown at all. Although it was 95 percent complete, it was never provided with any engines and was not fitted with any government-supplied equipment.

After flight test cancellation, Convair vainly attempted to convince the Air Force to continue interest in the YB-60. Convair even offered to complete the remaining B-36s on the production line as B-60s without charging the Air Force any more money. This proposal was turned down. Convair then tried to convince the Air Force that the YB-60 could be used as an experimental test bed for turboprop engines. This proposal was also rejected. Convair even considered trying to adapt the YB-60 as a commercial jet airliner. Nothing came of this idea either. There was even some consideration of using the YB-60 as a test vehicle for the proposed nuclear-powered X-6. This idea went nowhere as well.

Although the Air Force formally accepted both YB-60s in mid 1954, flight testing was already over and the two aircraft had been permanently grounded. The two YB-60s were shunted off to the side of the runway at Fort Worth, where they sat out in the weather for several months. By the end of July 1954, they had both been scrapped, with some of the components that were common with the B-36F being scavenged for spare parts.

 

Specification of Convair YB-60

Engines: Eight 8700 lb.s.t. Pratt & Whitney J57-P-3 turbojets. Performance: Maximum speed 508 mph at 39,250 feet. Combat ceiling 44,650 feet. Maximum range 8000 miles. Combat radius 2920 miles with 10,000 pound bomb load. Initial climb rate 1570 feet per minute. An altitude of 30,000 feet could be attained in 28.3 minutes. Ground run 6710 feet, takeoff to clear a 50 feet obstacle 8131 feet. Normal cruising altitude 37,000 feet. Maximum cruising altitude 53,300 feet. Dimensions: wingspan 206 feet 0 inches, length 171 feet 0 inches, height 60 feet 6 inches, wing area 5239 square feet Weights: 153,016 pounds empty, 300,000 pounds gross Armament: Two 20-mm cannon in the extreme tail. Maximum bomb load  of 72,000 pounds.


Joe Baugher

Sources:

  1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.
     

  2. Post World War II Bombers, Marcelle Size Knaack, Office of Air Force History, 1988.
     

  3. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
     

  4. General Dynamics Aircraft and their Predecessors, John Wegg, Naval Institute Press, 1990.
     

  5. Convair B-36-A Comprehensive History of America's "Big Stick", Meyers K. Jacobsen, Schiffer Military History, 1998.
     

  6. Eight-Engined Giant, Dennis R. Jenkins, Wings, Feb 2005.

 

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One of two YB-60's built at the Fort Worth Convair plant. (Air Force plant 4).  One was completed and was flown, the other was never finished and both were scrapped after losing the competition for an all-jet heavy bomber to the B-52.   The YB-60 was 72% B-36.  The long boom on the nose was for gathering flight test data, and would not be installed on production models.  The engine strut design was salvaged for use on the B-58 and the B-58 struts were essentially identical to those shown here.

 

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This photograph was taken while the craft was aligned with the main runway prior to take-off for its' first flight from the Fort Worth plant.

YB-60 ready for its first flight.

YB-60 first take-off

YB-60

The problem of increasing B-36 speed had led Convair engineers to develop a swept-wing configuration in 1950.  At first six turbo-prop engines were considered but before long it became apparent that eight jet engines of the same J-57 type to be used on the B-52 were the most promising powerplants.  On March 5, 1951, Air Force authorized two prototypes to be modified from production aircraft numbers 151 and 165.  Originally these B-36Fs were to be renamed B-36Gs, but eventually the designation YB-60 was applied to this very different airframe.  With 72% parts commonality with the B-36, Convair finished the first YB-60 (49-2676) quickly.  It made its first flight on April 18,1952.

A wider center chord on the new wing increased the wing area to 5,239 sq. ft., but the sweepback reduced span to 206'S".  Including the instrument probe at the end of the streamlined nose, the YB-60 was 175'2" long, and the sweptback tail was 60'S" high.  Eight Pratt & Whitney XJ-57-P-3 turbo-jets, 8,700 lb. thrust each, were paired in four pods.  While bomb capacity remained the same as the B-36F, the three forward turrets were omitted from the start, and the four retractable rear turrets were later deleted, leaving only the twin 2Omm tail guns controlled by ANIAPG-32 radar. Crew requirements were then limited to five men, all in the forward pressurized compartment. A retractable tail wheel was added to balance load changes.  Weight was calculated at 153,016 lb. empty, and 410,000 lb. at takeoff.   At a combat weight of 260,250 lb. performance included a top speed of 508 mph at 39,250, a 44,650 ft. combat ceiling, a combat radius of 2,920 miles with 10,000 lb. bomb load, and a ferry range of 6,192 miles with a 38,500 gallon fuel load.  In spite of an impressive improvement over the performance of the B-36, the YB-60 was inferior in most respects to the Boeing B-52.

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This top view of the YB-60 clearly shows the sweep of the wings and the design of the horizontal and vertical stabilizers.  The tail design was a contract requirement and was nearly identical to the B-52.

The YB-60

About 40 hours were logged by the YB-60-1 before it was finally officially delivered on June 25, 1954.  Full tactical equipment, including guns, K-3A system and ECM were supposed to have been installed on the second YB-60, but the Air Force never did supply engines, and the aircraft was delivered without flight tests July 8, 1954.  Both were scrapped shortly afterwards.  A proposal to have B-60 replace the B-36 on Fort Worth production lines was never seriously considered in view of the B-52's superior performance.

A swept-wing configuration for the B-36 was proposed in 1950, initially with propeller-turbines then with eight 8,7001b St XJ57-P-3 turbojets paired in under wing pods, as on the B-52.  This version was designated B-36G, but by the time two prototypes were ordered on 15 March, 1951, from the B-36F production line, the designation had been revised to YB-60.  The 35 degrees swept-back wing reduced the wing span by 24ft., but the wider centre chord increased the wing area to 5,239sq. ft.   All except the twin 20mm tail guns were removed and a pointed nose cap ended in an instrument probe.  The tail shape was streamlined and heightened by 2ft.  Bomb capacity remained unchanged and the five crew members were housed in a pressurized compartment similar to that of the B-36F.

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During final assembly of the YB-60,  large weights were mounted to the nose gear.  Without all of its equipment installed, and with the fuel tanks empty, the aircraft was tail heavy.

 

 

 

Nose gear detail

With 72 per cent parts commonality with the B-36, the first YB-60 (49-2676) was completed in eight months, and with Beryl A. Erikson as pilot, made its first flight at Fort Worth on 18 April, 1952, three days after the YB-52.  Flight tests at Edwards AFB revealed that the YB-60 was over 100 mph slower than the B-52 and thus plans for the B-60 to replace the B-36 on the line at Fort Worth were shelved.

Only about 40 hours were flown by the first YB-60 and the USAF never delivered engines for the second (49-2684).  Although officially handed over to the USAF in mid 1954, both were already cocooned and they were scrapped soon afterwards.   A commercial transport version was not proceeded with.

Eight Pratt & Whitney 8,700 lb. static thrust J57-P-3 turbojets.
Span 206 ft. 0 in.;  length 171 ft. 0 in.; height 50 ft. 0 in.;  wing area 5,239 sq. ft.
Weight empty 153,016 1b.;  gross weight (estimated) 300,000 lb.
Maximum speed 508 mph at 39,250 ft. Ceiling 44,650 ft.;  combat radius 2,920
miles with 10,000 1b. load;  ferry range 6,192 miles (38,500 US gal. fuel capacity).

 

 

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