Icons of Aviation History: The B-47 Stratojet

The B-47 Stratojet was America’s first all-jet bomber, but it was plagued with issues.

B-47 bomber on exhibit at the Pima Air and Space Museum

As soon as it was determined that a jet aircraft engine would be feasible, around 1943, the US began designs for jet-powered bombers. But the effort really ramped up at the end of the war. As the Cold War began, the new US Air Force had to depend on the B-29 and B-50 bombers, which were not capable of delivering nuclear weapons to much of the Soviet Union. The Strategic Air Command pinned its hopes on the newest jet engines.

After World War II, the US and USSR both made frantic efforts to snatch up as much German technology and know-how as they could. One of the areas of interest was Nazi jet-engine technology, and the United States managed to score much of this material. In particular, they obtained reams of data concerning German wind-tunnel tests on swept-wing designs which indicated that a swept wing was much more aerodynamically efficient than a straight wing.

Even as the B-36 was being deployed as its frontline nuclear bomber, the US already had a new jet-powered bomber in the works, known as the XB-47. With the new data from Germany, this design was radically altered: the wings would now be swept back at an angle of 35 degrees.

The Nazis had also deployed their Arado jet-engined reconnaissance/bomber towards the end of the war, which was originally powered by two Jumo jet engines mounted underneath the wings, just as the Me-262 fighter had been. But just as the war was ending the Germans had experimented with doubling the number of engines on the Arado to four, configured in two pairs—each pair contained by a single pod that hung under a wing.

The Nazis had not built many four-engined bombers during the war, but the US had—and now they realized that the “pod” design was a good way to have engines out on the wings where they were readily accessible. The XB-47 was originally designed to have its jet engines mounted in line at the wing roots, three on each side. But the information from Germany once again altered the design significantly: now it was planned to have the engines out on the wings, two each in a pod on the inner wing and a single engine in another outboard pod.

The crew would consist of just three—a pilot, co-pilot, and bombardier—and the cockpit would be the first heavy bomber to make use of the modern solid-state electronics that had been developed during the war. There were no gunners, as the twin 20mm cannons in the tail were operated remotely from the cockpit. It was assumed that the bomber would be fast enough to avoid enemy fighters. The cockpit was fitted with an odd mix of ejection seats for the crew: the pilot and co-pilot ejected upwards through the popped canopy, while the bombardier ejected downwards through the floor.

When the prototypes began flying in 1947, however, there were  problems. The original design utilized the General Electric J-35 engine: by the time the plane was being produced the more powerful J-47 engine had become available. Even with its six jet engines, however, the XB-47 required such a long distance to take off that it was almost immediately modified by adding RATO (Rocket-Assisted Take-Off) pods, essentially small rockets under the wingtips that would help accelerate it down the runway. Conversely, it took such a long distance to stop at landing that it was fitted with a parachute in the tail to help slow it down. While cruising at high altitude, the plane’s performance envelope was only 8 mph wide—just 4 mph too slow and it would stall, just 4 mph too fast and vibrations would shake the wings apart.

The XB-47, however, had what, to American war planners, were two crippling flaws: it did not have the range to reach the Soviet Union from American bases without aerial refueling (which was then still in its infancy), and it could not carry the largest of the American thermonuclear bombs.

But it was all that was available, so SAC had to make do. Initial deployment of the B-47A “Stratojet” began in December 1950, and from 1951 these were replaced by the newer B-47-B models as they became available. Some of these were also fitted with cameras as reconnaissance planes.  The most widely-produced  model was the B-47E introduced in 1953, which was fitted with electronic countermeasures and was capable of carrying two hydrogen bombs over a range of 5,000 miles.

Although the B-47 was a technological breakthrough for its time, and virtually every large aircraft produced since then carries some of the Stratojet’s DNA, the Air Force never really liked it and only used it until the B-52 became available to replace it. The last B-47s were withdrawn from service by 1965.

In all, about 2,000 B-47s of various models were built. Today, fewer than 25 remain. The Museum of the Mighty 8th Air Force, near Savannah GA, has a B-47B model on display, while the Barksdale Global Power Museum, the Museum of Nuclear Science in Albuquerque, and the Pima Air and Space Museum have B-47E models. The US Air Force Museum in Dayton OH has an RB-47H reconnaissance version on exhibit.

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