Boeing B-52E Stratofortress

The next production version of the Stratofortress was the B-52E (Model 464-259). The B-52E was externally identical to the B-52D which preceded it. The differences were entirely internal, and most of them were related to the need to adapt the Stratofortress to the low-level bombing role. This type of mission required a more sophisticated suite of bombing and navigation avionics, and led to the development of the AN/ASQ-38 system which was fitted to the B-52E and to subsequent Stratofortress versions. In the B-52E, some internal equipment was relocated and a slight redesign of the navigator-bombardier station increased crew comfort.

With the B-52E, the second-source production line at Wichita began to assume the leading role in Stratofortress manufacture, producing 58 aircraft, while the Seattle facility produced 42.

The B-52E procurement was covered in four separate contracts, funded in fiscal years 1956 and 1957:

1. AF33(600)-31155 signed on August 10, 1955, covered 14 Wichita-built B-52Es. Serials were 56-0699/0712.
   
   
2. AF33(600)-31267 signed on October 26, 1955 was originally a B-52D contract, but 26 Seattle-built B-52Es were also included. These serials were 56-0631/0656.
   
   
3. AF33(600)-32863 signed on July 2, 1956 covered 16 Seattle-built B-52Es. Serials were 57-0014/0029.
   
   
4. The final contract which included B-52Es was AF33(600)-32864, signed on July 2, 1956. It included 44 Wichita-built B-52Es, serialed 57-0095/0138.

The first B-52E (a Seattle-built machine) flew for the first time on October 3, 1957. Wichita's first B-52E took off on its maiden flight on October 17, 1957. 100 B-52Es were accepted by the USAF between October 1957 and June 1958. The first B-52Es entered service with SAC in December of 1957, with inital deployment being to the 6th BW based at Walker AFB.

The AN/ASQ-38 bombing and navigation system introduced on the B-52E was devised by the Military Products Division of IBM. It was a hard- wired analog integrated system consisting of four parts:

• MD-1 automatic astrocompass
  
• AN/AJA-1 or AN/AJN-8 true heading computer system
  
• AN/APN-89A Doppler radar
  
• AN/ASB-9A or AN/ASB-16 bombing navigation system

It was designed for a high degree of automatic operation. The Doppler radar fed ground speed and drift information into the AN/ASB-16. Latitude/longitude information was supplied to the true heading computer and to the astrocompass.

The new ASQ-38 bombing/navigation system was at first not as accurate as had been anticipated and was difficult for ground crews to maintain. Extensive engineering changes were needed to improve its low-level terrain avoidance capability. In the late 1950s, a program known as Jolly Well was launched to bring the ASQ-38 system of the B-52E, F, G, and H models up to standards, and was not completed until 1964 after it had involved no less than 480 aircraft.

The second B-52E (56-0632) was assigned from the start to major test programs. It was used for prototyping landing gears, engines, and other major subsystems. The test aircraft later underwent permanent modifications in order to carry out specialized development projects and was redesignated NB-52E. The aircraft was intended to study electronic flutter and buffeting suppression systems, because several B-52s had been lost due to structural failures caused by aerodynamic stresses while flying at low level. Small swept winglets were attached alongside the nose, and a long probe extended from the nose. The wings was fitted with twice the number of control surfaces, and the traditional mechanical and hydraulic linkages that moved the control surfaces were replaced by electronic systems. To support its research mission, the interior of the NB-52E was loaded with measuring instrumentation. The NB-52E later participated in the Load Alleviation and Mode Stabilization (LAMS) project. Wind gusts were detected and measured by a battery of sensors, which activated the control surfaces accordingly to cut down on the amount of fatigue damage to the structure of the aircraft. In mid-1973, the NB-52E flew ten knots faster than the speed at which flutter normally would have disintegrated the aircraft.

There was one external difference between the E and D models. E models had a window on the left side of the bombardier/navigation station, whereas the D models had no window there.

57-0119 used the JB-52E designation. This aircraft was assigned to General Electric and was used as a flying testbed for the XTF39 turbofan for the C-5A program. The 40,000 lb.s.t turbofan replaced the starboard inner pair of J57 turbojets, and had as much thrust af four J57 turbojets. B-52E 56-636 was similarly modified to test the JT9D turbofan engine for the Boeing 747 program. Various design studies were carried out to investigate the feasiblity of reengining the B-52 airframe for large turbofan engines, but none of these designs were ever proceeded with.

Specification of Boeing B-52E Stratofortress

Engines: Eight Pratt & Whitney J57-P-29WA or -19W turbojets, each rated at 10,500 lb.s.t dry and 12,100 lb.s.t. Performance: Maximum speed 630 mph at 19,800 feet, 570 mph at 45,050 feet. Cruising speed 523 mph. Stalling speed 169 mph. Initial climb rate 5125 feet per minute. Service ceiling at combat weight 46,200 feet. Combat radius 3500 miles with 10,000 pound bombload. Ferry range 7875 miles. Takeoff ground run 8000 feet. Takeoff over 50-foot obstacle in 10,300 feet. Dimensions: Length 156 feet 6.9 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 174,782 pounds empty, 292,460 pounds combat, 450,000 pounds maximum takeoff. Armament: Four 0.50-inch M3 machine guns with 600 rpg in tail turret. Maximum offensive payload 43,000 pounds.

Serials of B-52E:

56-0631/0649		Boeing B-52E-85-BO Stratofortress
				c/n 17314/17332
56-0650/0656		Boeing B-52E-90-BO Stratofortress
				c/n 17333/17339
56-0699/0712		Boeing B-52E-45-BW Stratofortress
				c/n 464070/464083
57-0014/0022		Boeing B-52E-90-BO Stratofortress
				c/n 17408/17416
57-0023/0029		Boeing B-52E-95-BO Stratofortress
				c/n 17417/17423
57-0095/0109		Boeing B-52E-50-BW Stratofortress
				c/n 464084/464098
57-0110/0130		Boeing B-52E-55-BW Stratofortress
				c/n 464099/464119
57-0131/0138		Boeing B-52E-60-BW Stratofortress
				c/n 464120/464127

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. Boeing Aircraft Since 1916, Peter M. Bowers, Naval Institute Press, 1989.
   
   
4. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
   
   
5. Boeing B-52--A Documentary History, Walter Boyne, Smithsonian Institution Press, 1981.
   
   
6. Boeing's Cold War Warrior--B-52 Stratofortress, Robert F. Dorr and Lindsay Peacock, Osprey Aerospace, 1995.
   
   
7. USAF Museum website, http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2637
   
   
8. E-mail from Kevin Thompson on external difference between D and E models.