ch12-6

Quest for Performance: The Evolution of Modern Aircraft


Part II: THE JET AGE


Chapter 12: Jet Bomber and Attack Aircraft


An Air Force Night Intruder



[390] Korean war experience revealed an urgent USAF need for a high-performance jet-powered night-intruder aircraft capable of precise nighttime and bad-weather weapons delivery on moving targets located hundreds of miles from home base. The need was considered so pressing that the time usually required for development of a new aircraft was deemed unacceptable. Hence, an existing "off the shelf " aircraft was sought to fill the mission requirements. From a number of candidate vehicles, including the previously discussed North American B-45 Tornado, the English Electric Canberra bomber was selected to fill the USAF night-intruder role. Contracts for its license production in the United States were given to the Martin Company.

The Canberra was originally developed in response to a British requirement issued in 1945 for a high-altitude bomber. First flight of the aircraft took place in May 1949. The first Martin-produced Canberra, known as the B-57 in USAF nomenclature, made its initial flight in July [391] 1953; before production of the Martin-built B-57 ended, 403 examples of the type had been produced. In England, total production of the Canberra was 984 units. By the summer of 1980, about three decades after the first flight of the Canberra, the type was still in the active inventory of 12 countries. The aircraft is no longer in active service with combat units of either the USAF or the RAF although a few are still used by the United States Air National Guard. A number of B-57 aircraft also fill a variety of utility roles with different United States Government agencies. An interesting account of the various versions of the B-57 is contained in reference 135.

A Martin B-57A is shown in figure 12.2 1, and data for a B-57B are contained in table VI. As with so many of the early jet aircraft, configuration of the B-57 was similar in concept to contemporary twin-engine propeller-driven aircraft but with jet engines replacing the reciprocating units. The unswept wing had a relatively low aspect ratio of 4.27 and airfoil thickness ratios that varied from 12 percent at the root to 9 percent at the tip. With so low an aspect ratio, the maximum lift-drag ratio might be expected to be very low. On the contrary, the large....




Figure 12.21 - Martin B-57A night intruder. [mfr via Martin Copp]

[392]...surface area of the wing relative to that of the fuselage and other elements of the aircraft gave a low zero-lift drag coefficient of 0.0 119 and a maximum lift-drag ratio of 15.0. Power was provided by two nonafterburning Wright J65-W-5 turbojet engines of 7200 pounds thrust each. These Wright engines were an American-built version of the British Rolls-Royce Avon. The location of the engine nacelles is clearly shown in figure 12.21. Conventional rudders, ailerons, and elevators were used for control of the aircraft. Simple high-lift flaps were located in the wing trailing edge between the engine nacelles and the sides of the fuselage.

The two-man crew of the B-57 consisted of a pilot and navigator-bombardier-radar operator who were seated in a tandem arrangement. As compared with the B-57A shown in figure 12.21, later versions of the aircraft had an extended canopy to enhance visibility for both crew members. Pressurization, air-conditioning, and ejection seats were provided for the crew. Various types of weapons such as bombs and rockets could be carried externally as well as in an internal bomb bay located in the fuselage. A Martin innovation, not included on the British Canberra, was the unique rotary bomb door described in the section on the P6M flying boat. In the closed position, bombs were attached to the inner side of the door, and bomb release took place after the door was rotated through 180°. Armament consisted of eight .50-caliber machine guns.

The B-57 is usually considered to be a light bomber; however, this classification must be related to the time frame under discussion. With a gross weight of 53 721 pounds, the B-57B was only 2000 pounds lighter than the Boeing B-17G, one of the standard heavy bombers of World War II. Mission radius of the B-57B was 948 miles with a payload of 5240 pounds, and ferry range was 2722 miles. Maximum speed was 598 miles per hour (Mach 0.79) at 2500 feet and cruising speed was 476 miles per hour. Comparison of the data given in table VI for the B-57B and the B-45C shows that the performance characteristics of the two aircraft have many similarities. Being about twice as heavy as the B-57B, the B-45C carried nearly twice the payload for approximately the same mission distance.

The Canberra class of aircraft has seen action in many wars, including service with the USAF in Vietnam. More recently, it was used by the Argentine Air Force in the undeclared war with Britain in the Falkland Islands. Although the B-57 was originally procured by the USAF as a night intruder, it has been successfully used in many other roles, including photoreconnaissance and strategic bombing. No [393] distinctive design innovations were incorporated in the purely subsonic B-57; however, its pertinent design parameters were chosen in such a way that the aircraft was readily adaptable to a variety of roles calling for diverse characteristics.

Although not a technically exciting aircraft, the B-57 has certainly proved its worth in many years of effective operation. Because of its wide range of capabilities and docile handling characteristics, the B-57 has sometimes been likened to a Goony Bird with jet engines. ("Goony Bird" is the nickname for the USAF version of the famous Douglas DC-3.) Could a more complimentary epithet be found for any aircraft!