The B-47E Stratojet was the major production version of the B-47 and it was the only version that was mass-produced by all three members of the production pool, Lockheed, Douglas and Boeing. The B-47E was basically the standardized production version of the Stratojet and incorporated many innovations that had been suggested by experience with the earlier B-47s, A through D. In contrast to the B-36 program, which was on the verge of cancellation several times, there was never any significant effort to cancel the B-47 program. It employed six General Electric J47 engines, which offered a thrust of 7200 pounds with water injection. These engines had already been refitted to several B-47Bs. The 18-unit internal JATO system was retained on early models, but was soon replaced by a jettisonable rack that contained 33 1000 lbs thrust units that could be dropped following takeoff. The B-47E was fitted with an approach chute to increase drag and a brake chute to decrease the landing roll. An anti-skid braking device was also fitted. A clamshell cockpit canopy was introduced, hinged on the right side. The defensive armament was two 20-mm cannon in the tail. The A-5 fire control system could automatically detect and track pursuing aircraft and aim and fire the 20-mm cannon and was operated by the co-pilot. The undersurfaces and lower portion of the fuselage of most B-47Es were painted a glossy white to reflect the heat radiation from nuclear blasts The B-47E incorporated as standard equipment an in-flight refueling receptacle for flying-boom midair refueling on the starboard side of the nose. The use of in-flight refueling capability enabled the total fuel capacity to be reduced to 14,610 gallons, including two 1700-gallon drop tanks carried underneath the wings between the engine nacelles. The crew was provided with ejector seats as standard equipment, with the pilot and copilot ejecting upward over the tail and the bombardier/navigator ejecting downward through a hatch in the lower nose. The B-47E rapidly became the dominant component of the USAF strategic deterrent during the mid- and late-1950s and in December 1956, SAC had 27 combat-ready B-47 wings, with 1204 combat-ready B-47 crews and 1306 B-47 aircraft assigned. Spurred by the Suez crisis of 1956, SAC demonstrated its ability to launch a large striking force on short notice when in December more than 1000 B-47s flew nonstop, simulated combat missions, averaging 8000 miles each over the American continent and Arctic regions. Early in 1955, the Strategic Air Command requested the B-47 be adapted for low-level bombing, with the aircraft delivering its bomb via the toss-bomb technique. In a toss-bombing attack, the plane enters the run at low altitude, pulls up sharply into a half loop with a half roll on top and releases the bomb at a predetermined point in the climb. The bomb continues upward in a high arc, falling on the target at a considerable distance from its release point. In the meantime, the maneuver allows the airplane to reverse its direction and gives it more time to speed away to a safe distance from the blast. This technique was adopted because it was thought that high-speed B-47s flying at low level would be less vulnerable to enemy countermeasures. The existence of low-level capable B-47s would mean that a potential enemy would now be faced with threats from both high- and low-level attacks. Low-level bombing involved special crew training. A training program known as Hairclipper was started in December of 1955. However, adverse weather, excessive maintenance requirements, serious deficiencies in LABS systems and several accidents caused Hairclipper to be officially discontinued in March of 1958. However, the end of Hairclipper did not signify the end of low-level flying. A program known as Pop Up, a related training program that took advantage of recent advances in weapons developments, fared better. In the Pop Up maneuver, the aircraft came in at low level, pulled up to high altitude, released its weapon and then dove steeply to escape being spotted by enemy radars. By the end of 1959 the training program had finally been completed. On January 25, 1957, a B-47 flew from March AFB, California to Hanscom Field, Massachusetts in 3 hours, 47 minutes, at an average speed of 710 mph (assisted by strong tailwinds). In November of 1959, a B-47 assigned to the Wright Air Development Center stayed in the air for 3 days 8 hours 36 minutes, covering 39,000 miles. This broke previous time-and-distance records. A total of 691 B-47Es were built by Boeing-Wichita, Douglas-Tulsa built 264 and Lockheed-Marietta built 386. The final B-47E (53-6244) was delivered on February 18, 1957. The beginning of the phaseout of the B-47E coincided with the delivery of those final aircraft. In March of 1961, President John F. Kennedy directed that the phaseout of the B-47 be accelerated. However this was delayed in July by the onset of the Berlin crisis of 1961-62. SAC's last two B-47s went to storage on February 11, 1966. |
