General Aviation News reader Jack Handy recently sent in a batch of U.S. Air Force photos that were gathered by Wilber Clouser, an Air Force Systems Command technical editor of handbooks after World War II.
One interesting subset of these photos shows aircraft from several manufacturers that were efforts to meet the needs of the oncoming jet age. Some designs shunned jets, using more economical piston engines as stopgap powerplants until jet developments rendered those aircraft obsolete in the early 1950s.
The problems facing the Air Force, and designers, revolved around jet engine developments and the need for range and speed unheard of during the recently concluded World War II.
In an era when cutting and bending aluminum was the mainstay of airframe builders, it was relatively easy for contractors to build a few prototypes. Designs proliferated in the last half of the 1940s, but not all bore the fruit of long-term production.
Martin Aircraft had a distinguished career building piston-engine bombers for the Air Force and seaplanes for the Navy, but its forays into jets in the 1940s were abbreviated.
This Martin XB-48 jet bomber first flew in June 1947. Powered by six J-35 turbojets, the B-48’s performance was penalized by its straight wing design. The B-48’s range and speed were inferior to the performance of the sweptwing Boeing B-47 that flew in December of that year, and the Martin design never matured beyond the two prototypes.
The XB-48 was the first of the postwar jet bombers to employ so-called bicycle landing gear, with two sets of tandem mainwheels, located ahead of and behind the bomb bay, retracting into the fuselage. To keep the XB-48’s wingtips from tipping to the pavement, the underslung engine nacelles each housed a spindly outrigger landing gear for balance. This gear arrangement was necessitated by the thin and high-mounted wing of these bombers.
Early jet fighters lacked the intercontinental range needed to escort bombers in the late 1940s, so the Strategic Air Command bought some unusual F-82E Twin Mustangs as escort fighters. With two cockpits, pilots could take turns on long-range missions.
This F-82E shows evidence of four underwing pylons capable of carrying large drop tanks, giving the F-82E a range greater than 2,500 miles.
But the Twin Mustang’s role as a long-range escort fighter was short lived, and later models of the F-82 saw combat in Korea as radar-equipped night fighters before jets owned the skies for good.
Another contender in the jet bomber contest of 1947, the Convair XB-46 flew in April 1947. It used a more traditional landing gear arrangement, and had a towering vertical tail reminiscent of Convair’s earlier PB4Y-2 Privateer, a shape also conjured on that company’s later Tradewind flying boat for the Navy. The landing gear used only two mainwheels, something that contributed to limiting its gross weight to less than that of the B-47.
The XB-46’s four J-35 jet engines could only bring it up to a top speed of 491 miles per hour at sea level — far less than the Boeing XB-47’s top speed of 578. However, the XB-46 did edge out the XB-47 on range by about 200 miles, with the Convair design claiming 2,870 miles with an 8,000-pound bomb load compared with the XB-47’s 2,650-mile range while carrying 10,000 pounds of bombs.
Only one XB-46 was built, at Convair’s San Diego plant. But if Convair lost this bomber race to the Boeing B-47, Convair still had a lot of work with the giant B-36 and, in the 1950s, a string of delta wing high speed jet fighters and the B-58 bomber.
The last aircraft design to bear the name of Curtiss was the glossy black XF-87 (originally XP-87) Blackhawk, intended to meet an Air Force requirement for a fast all-weather radar-equipped jet fighter. Flown briefly in 1948, the Blackhawk was large, spanning 60′ with a fuselage length of 62′.
The prototype’s four J-34 jet engines were to be replaced by a pair of more powerful J-47 engines, but Air Force interest in the XF-87 quickly waned. The funds for an all-weather fighter would go instead to the smaller Northrop F-89 Scorpion and the Lockheed F-94 Starfire, both of which outperformed the big Curtiss.
Lockheed produced a pleasingly streamlined jet fighter in the XF-90 of 1949. A pair of J-34 jet engines powered the XF-90.
The airframe was robustly built and its weight, coupled with the J-34 jets, gave the first XF-90 poor performance. Jet Assisted Takeoff (JATO) bottles were frequently needed to get it airborne for testing.
The second XF-90 had J-34s with afterburners, but performance was still lacking and the project was abandoned in favor of more promising jet fighters. The competing McDonnell XF-88 later gave rise to the successful McDonnell F-101 Voodoo.
One XF-90 was used for static destruction tests by the National Advisory Committee for Aeronautics (NACA) at Cleveland, Ohio, and the other served as a test airframe in the Nevada desert, where atmospheric nuclear tests damaged it for later study on blast effects.
This sole surviving XF-90 is now part of the collection of the National Museum of the U.S. Air Force at Dayton, Ohio.
This civilian Northrop prototype known as the N-23 Pioneer carries a photo number consistent with Air Force photo indexing procedures, plus a penciled notation on the back about the C-125.
It’s a curiosity — a short-field trimotor transport developed by Northrop for a perceived bushplane market that was dominated by cheap surplus transports that lacked the Pioneer’s performance.
First flown in December 1946, the N-23 Pioneer did not enter production. But the Air Force’s evident interest in the N-23 manifested itself in a larger version with wing dihedral and other changes.
The outgrowth was the Northrop model N-32 called the Raider and adopted in limited numbers by the Air Force as the C-125. Only 23 C-125 Raiders were built for the Air Force. The civil N-23 Pioneer came to grief in a crash that killed pilot L.A. Perrett in 1948.
The original Pioneer had a wingspan of 85′; the C-125 spanned 86.5′. The Pioneer could take off in less than 400′. With JATO, the bigger C-125 could take off in less than 500′.
Both Northrop trimotors could be fitted with dual mainwheels to spread their weight better on soft unimproved landing strips.
This one’s almost a B-52. But the wings are closer to the cockpit and the shape of the tail looks almost cartoonish. That’s because this is an artist’s conception of the Boeing Model 464-63 from October 1949, two years before the first actual XB-52 emerged from Boeing’s Seattle plant.
The Model 464-67, just a few design iterations later, was the prototype XB-52 and YB-52. The Boeing Model 464 underwent an arduous evolution from a straight-wing turboprop concept to the ultimate eight-engine jet bomber that was built.
Issues of range and fuel economy plagued bomber designs, but the Boeing team was able to promise the XB-52 with a range of more than 5,000 miles. Aerial refueling became a key component of B-52 mission rationale.