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The Martin/General Dynamics RB-57F Canberra is a specialized strategic reconnaissance aircraft developed for the United States Air Force by General Dynamics in the 1960s from the Martin B-57 Canberra tactical bomber, which itself was a license-built version of the English Electric Canberra. It was operationally assigned to the Air Weather Service for weather reconnaissance involving high-altitude atmospheric sampling and radiation detection in support of nuclear test monitoring, but four of the 21 modified aircraft performed solely as strategic reconnaissance platforms in Japan and Germany. Three of the modified aircraft were destroyed with loss of their crews while performing operationally. The remainder were re-designated ''WB-57F'' in 1968. Four of the survivors were subsequently used by NASA for high-altitude atmospheric research. The others were retired from 1972 to 1974 and placed in storage. As of 2015, three WB-57Fs are the only B-57 aircraft model still flying, in service with NASA. ==Design and development== The RB-57F was the result of an Air Force ''Big Safari'' requirement for a high-altitude reconnaissance platform with better performance than the existing and similar RB-57D, some of which had been grounded as a result of wing spar failures. A more urgent need to field an aircraft capable of high altitude signals intelligence arose in 1962 when a SIGINT operation conducted by United States Navy against the Soviet Union from Peshawar, Pakistan, ended abruptly because the Pakistani government evicted the Navy for committing too many violations of restricted airspace.〔Grimes 2014, p.61.〕 Two B-57Bs dubbed "Pee Wee 1" and "Pee Wee 2" were quickly modified by ''Big Safari'' with antennas and a modular telemetry receiver suite packaged in a pressurized canister and sent to Pakistan in January 1963 as an interim measure under an operation named ''Little Cloud'' to continue the mission. In the meantime ''Big Safari'' authorized the ''Pee Wee III'' project to develop the new high-altitude platform from existing B-57s. Because General Dynamics was responsible for contract maintenance on the D model, its Fort Worth Division was given the sole-source contract for the development of the ''Pee Wee III'' RB-57F prototypes.〔Grimes 2014, pp. 59-69.〕 The two aircraft chosen for initial development were Martin B-57Bs 52-1559 and 53-3864, which supplied the fuselage and horizontal stabilizers around which the rebuild was made. The prototype RB-57Fs incorporated many major changes from the RB-57D, the most obvious of which was a more enlarged and computer-designed wing to enable it to operate at extreme altitudes. The wing had a span of more than , which was longer than the RB-57D and nearly twice the length of the B-57B fuselage on which it was installed. Extensive use was made of aluminum honeycomb wing panels in the wings that bonded outer and inner aluminum skins to a honeycomb of aluminum and fiberglass. All control surfaces had tightly sealed gaps in order to reduce drag, and there were no wing flaps. In addition, the size of the empennage was redesigned so that the vertical stabilizer had nearly twice the area of that of the standard B-57B. Its height was increased to and the width increased, improving longitudinal and asymmetric control for greater stability at very high altitudes (up to .〔Grimes 2014, p. 62.〕〔(RB-57F "Canberra" ). USAF Fact Sheet, Hill Aerospace Museum, USAF Museum System. Retrieved: 11 October 2015.〕〔("USAF Serial Number Search." ) ''rcn.com.'' Retrieved: 30 October 2011.〕 Another obvious change was the replacement of the Wright J65 turbojets with Pratt & Whitney TF33-P-11 turbofan engines. The TF33s gave the aircraft more than double the thrust of the B model. The RB-57F was also fitted with two detachable Pratt & Whitney J60-P-9 turbojets mounted in pods attached to the wings outboard of the main engines. These auxiliary engines were air-started and only for use at altitude in flight. At altitudes above , the J60s generated about of thrust each and increased the maximum altitude of the RB-57F by .〔〔 To perform their Pakistani mission, the two prototypes were uniquely equipped with high-gain phased array antennas in their wingtips, an extended radome, and a canister package developed by HRB-Singer known as "System 365" installed in the bomb bay. The size of two 55-gallon drums, System 365 was a semi-automatic signal collection system that used 12 continuously scanning receivers and had a manual fixed-frequency coverage capability with pre-selected frequencies. The system automatically recorded up to six hours of collected signals on tape.〔Grimes 2014, p. 63.〕 The extensive modifications of ''Pee Wee III'' resulted in virtually a new aircraft and new serial numbers for fiscal year 1963 were assigned to the 21 modified aircraft.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Martin/General Dynamics RB-57F Canberra」の詳細全文を読む スポンサード リンク
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