Military


Boeing 707

The Boeing 707 transport was the first of the long-range and, for its day, high-passenger-capacity aircraft that marked the real beginning of the revolutionary jet age in air transportation. Even today, many people consider the terms 707 and jet transport to be synonymous. The prototype of this remarkable aircraft first flew in July 1954, and an early production version first entered airline service in the fall of 1958. Over 900 Boeing 707 commercial transports have been built, but by 1980 the 707 was no longer in production as a commercial transport.

Although many people have described the KC-135 as a military version of the Boeing 707 airliner they are actually two totally different aircraft although they are both developments of the Boeing model 367-80. When compared with the 707 the KC-135 is a shorter, narrower, smaller aircraft. A tanker version of the aircraft, the KC-135, was built in large numbers for the USAF; and the Airborne Warning and Control System aircraft (AWACS).

Boeing 707 History

The prototype of the 707 was known in the Boeing Company as the model 367-80, and within the company it has always been referred to as the Dash-Eighty. The Boeing 367-80, the prototype for both the 707 and the military KC-135 Stratotanker, first flew on 15 July 1954. The aircraft served as a test vehicle for the exploration and development of new ideas for many years. Finally retired in 1972, it was presented to the Smithsonian Institution.

The Boeing 367-80 was the first turbojet transport to fly in the United States and that occurred on July 15, 1954. The heritage of the Dash 80, which was the first prototype 707, had been the Boeing success with larger bombers which emerged from the XB-15 (XC-105) long-range experimental bomber XBLR-I of the late 1930's, the Model 255 which became the B-17 (1934), the B-29 (1944), and the B-50 (1947). These were all four-engine propeller-driven airplanes. The knowledge gleaned from Germany led Boeing to the design of the swept-wing six-jet B-47 which first flew in December 1947, and the swept-wing eight-jet B-52 which first flew in April 1952.

The Dash 80 outgrowth was privately financed by Boeing with a view toward commercial passenger use and military tanker use, both of which were achieved. The first of a long and historic series of the 707 family began service with PAA in October 1958. Military derivations of the 707 type airframe are the E-3 sentry (AWACS), E-6, the EC-18 Advanced Range Instrumentation Aircraft (ARIA), the C-137 (Air Force One), and the KC-135 Strato tanker.

On 13 October 1955 the aviation industry learned that Pan American World Airways had placed the first order for jet airliners to be produced in the United States, ordering both the Boeing 707 and Douglas DC-8. CAA certificated the aircraft, a four-engine, long-range plane with a maximum capacity of 189 passengers on Sep 23, 1958.

On 04 October 1958 British Overseas Airways Corporation inaugurated the first transatlantic jet passenger service, using de Havilland Comet 4 aircraft flying between New York and London. On the 26th of the same month, Pan American World Airways began the first U.S. scheduled jet service with Boeing 707 flights between New York and Paris. On Dec 10, 1958, National Airlines used leased 707s to begin the first U.S. domestic scheduled jet airline service, flying between New York and Miami.

On 25 January 1959 transcontinental jet airliner service began as American Airlines inaugurated Boeing 707 flights between New York and Los Angeles. The new service also made American the first U.S. airline to begin domestic scheduled jet flights using its own aircraft. High-altitude radar advisory service was also established, using FAA-military radar teams based at 17 military installations across the United States.

By any measure, the 707 series of aircraft must be ranked as one of the most successful transports ever produced. On 30 August 1991, Boeing announced an end to production of the 707. The company built 857 of the 707s, selling the last as a radar surveillance plane earlier in 1991.

Boeing 707 Design

The wing of the Boeing 707 is mounted in the low position at the bottom of the fuselage; this wing location has been preferred on transports designed for passenger use since the Boeing 247 and Douglas of the early 1930's. The wing has an aspect ratio of 7.1 and employs a 35 sweepback angle. This wing geometry provides a combination of good cruising efficiency at high subsonic speeds, low structural weight, and large internal volume for fuel. The main landing gear consists of two struts to which are mounted four-wheel bogies. The landing gear is attached to the wing and is retracted inboard into the thickened juncture of the wing and fuselage. The nearly straight trailing edge of the wing near the fuselage is dictated by the required storage space for the landing gear in the retracted position. The two-wheel nose gear retracts forward into the fuselage.

The four engines are mounted similarly to the manner pioneered by the B-47 bomber. Each engine is contained in a single nacelle that is attached to the bottom of the wing by a sweptforward pylon. Consideration was given to mounting two engines in each of two nacelles; such an arrangement was employed in mounting the four inboard engines of the B-47. This engine configuration was abandoned on the transport because of the possibility that disintegration of one engine might cause failure of an adjacent engine. This possibility was apparently not acceptable on a passenger-carrying transport. Early versions of the 707 were powered with turbojet engines. Several different engines were used, but most of these early aircraft employed the Pratt & Whitney JT3C engine, which is basically a civil version of the military J-57 turbo jet used by such aircraft as the Boeing B-52 bomber and the North American F-100 fighter. Most 707 aircraft manufactured since the early 1960's, however, have been powered with a turbofan version of this engine. The Pratt & Whitney JT3D turbofan engine utilizes the same basic gas generator as the J-57 but has a front-mounted two-stage fan with a pressure ratio of about 1.8. The bypass ratio is 1.43, and the sea-level static thrust is about 19 000 pounds. The fan discharges through a short duct that appears somewhat similar to a NACA cowling of the type employed on many radial-type piston engines. Thrust reversers are employed to assist in stopping the aircraft on its landing rollout. Reverse thrust may also be used to increase the rate of descent.

The lateral control system of the aircraft consists of a combination of spoilers and ailerons that are mixed in their use according to the speed regime in which the aircraft is flying. The spoilers are also used for reducing the stopping distance of the aircraft on landing and for rapid descents in flight. Descent rates of as high as 15 000 feet per minute can be achieved by deployment of the spoilers and the use of reverse engine thrust.

The elevators and ailerons are aerodynamically balanced and are manually operated by aerodynamic servotabs. In this type of control system, the pilot's primary flight controls deflect tabs on the main control surfaces. The hinge moment of the control surface is altered by deflection of the tab, and, consequently, the floating angle of the surface is altered. This change in angle of the main surface provides the necessary control moments for the aircraft. The spoilers and rudder on the 707 aircraft are operated hydraulically. Small changes in longitudinal trim are made with the use of trim tabs on the elevators. Changes in trim, such as those caused by flap deflection, are balanced, by adjusting the angle of the horizontal stabilizer. Movement of this surface is power actuated.




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