The Martin/General Dynamics RB-57F Canberra is a specialized strategic reconnaissance aircraft developed in the 1960s for the United States Air Force by General Dynamics from the Martin B-57 Canberra tactical bomber, which, in turn, 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 the 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.
, 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 an enlarged 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 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 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 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.
Testing and production
The first test flight of the RB-57F prototype was conducted on 23 June 1963 at Edwards Air Force Base, California. The prototype showed the aircraft reaching in 18 minutes with a steady rate of climb of 2,725 f/min (831 m/min). Its RB-57D chase plane was unable to match it in maneuverability. The wing design created tremendous lift even at idle speeds; the aircraft was airborne after a takeoff roll of only at sea level. Because of this it also proved difficult to land, and if an engine failed during takeoff, TF33 main engine thrust was limited to 70% power to maintain directional control. Despite some shortcomings the design had shown exceptional performance and Big Safari authorized the First Chip production program in August 1963 for the fabrication of 19 more RB-57Fs from existing B-57 airframes.Grimes 2014, p. 81.Halpenny 2005, p. 80.
After its flight test program, the two RB-57F prototypes were sent to Rhein-Main AB, West Germany in late 1963 for operational testing and evaluation (OT&E) with the 7407th Support Squadron, where they proved their effectiveness in flights along the German border at over , taking long-range photographs over the border into East Germany. They also flew reconnaissance missions over the Baltic Sea. They returned to the United States in February 1964 and were assigned to the 58th Weather Reconnaissance Squadron at Kirtland Air Force Base, New Mexico. High altitude flights required the wearing of David Clark Company A/P22S-2 and later A/P22S-4 full pressure suits,The A/P22S-2 was developed in 1960 for the North American X-15 program and required five minutes to don properly (compared to 30 for its MC-2 predecessor). It was a three-piece ensemble consisting of helmet, coveralls and removable gloves. The A/P22S-4 was an upgrade placed into service in 1967 to supplement the A/P22S-2 and provided even greater mobility in the cockpit. Each came in eight standard sizes. In 1975 the A/P22S-6, providing 12 sizes, a heated visor and a feeding/drinking capability, replaced both earlier models. NASA pilots now wear it or the A/P22S-6A with a urine collection device. and crew pre-flight preparations were similar to those used by U-2 and SR-71 crews.Fuller 1990, p. 361.The main preparation requirements were no ingestion of medications for eight hours prior to flight, a high protein/low residue meal (typically steak and eggs), a thorough flight physical, and air-conditioned transportation to the aircraft.
The initial run of 12 aircraft for the First Chip program were converted from the 1952/1953 serial blocks of B-57B aircraft still on active duty, including the two sent to Pakistan as "Pee Wee 1" and "Pee Wee 2". They were delivered one a month through 1964; the last (First Chip 12 and formerly "Pee Wee 2") was retained as a test bed in Fort Worth. The next four conversions were to RB-57Ds that were taken out of storage under a follow-up program called Second Slice, delivered between April 1965 and February 1966. The final three were converted from RB-57A aircraft and delivered in March 1967. The converted RB-57As differed from earlier First Chip conversions by the addition of a Mk III Impact Probe in the bomb bay. In March 1968 the 63-13286 prototype was also upgraded to the First Chip standard and the two phases renamed in accordance with newly established Big Safari nomenclature that required two-word code names beginning with "Rivet." The First Chip aircraft were renamed Rivet Chip and the Second Slice as Rivet Slice.Grimes 2014, pp. 81–82.
The production aircraft were further modified with new TF33-P-11A engines that delivered even greater thrust than those of the prototypes. Foil systems developed in 1962 for the WC-130B to collect particulate debris from nuclear tests were installed in the bomb bay and the fuselage beside the cockpit. The wings had four hard points on which to mount the J60 engines and air particulate sampling pods, a gaseous sampling system was housed in the fuselage, and a KA-56 downward-looking panoramic camera mounted in the nose. Two aircraft were additionally modified to carry the Bulova 707-1000 long range camera, which had a 240-inch (6096mm) focal length that resulted in its reference designation of Big Item. These high-altitude side-looking cameras, secured by a roll-stabilized mount, could take oblique shots at 5 to 15 degrees below the horizon up to range from the aircraft and provide 30-inch (76 cm) high resolution images. The electronics were also updated on the standard F model. The nose of the aircraft was lengthened to house sophisticated navigational equipment along with sensitive detection equipment for gathering SIGINT/ELINT intelligence. The cockpit was provided with a modified Lear MC-1 autopilot.Mikesh 1995 The average cost of each RB-57F conversion approximated $1.5 million.Approximately $11,000,000 per conversion in 2015 dollars using 1966 as a baseline. (U.S. Inflation Calculator)
Operational history
Weather reconnaissance The official mission of the RB-57F was weather reconnaissance, and all RB-57Fs were assigned to meteorological units of the 9th Weather Reconnaissance Wing, Air Weather Service, Military Air Transport Service (MATS), headquartered at McClellan Air Force Base, California: 55th Weather Reconnaissance Squadron, McClellan AFB, California 56th Weather Reconnaissance Squadron, Yokota AB, Japan 57th Weather Reconnaissance Squadron, Avalon Airport, Avalon, Victoria, Australia 58th Weather Reconnaissance Squadron, Kirtland AFB, New Mexico.
Air Weather Service RB-57Fs duties involved high-altitude atmospheric sampling and radiation detection work in support of nuclear test monitoring, mostly on behalf of the Atomic Energy Commission, including collection of airborne debris in a program of ongoing monitoring of nuclear tests. Most of this activity was centered on nuclear tests carried out in People's Republic of China, but monitoring air in the aftermath of U.S. underground nuclear tests was also conducted. One RB-57F is known to have been used for research into airborne laser equipment by the Air Force Logistics Command research laboratory at Kirtland AFB. In 1968, the Air Weather Service's RB-57Fs were redesignated WB-57F.Jackson 1989.
Strategic reconnaissance
MATS (and its successor organization Military Airlift Command) was frequently used by the USAF for clandestine, special operations missions prior to the establishment of Air Force Special Operations Command in the 1980s. The RB-57F, with its extreme high-altitude ceiling was frequently used as a strategic reconnaissance platform. The four Rivet Slice aircraft (converted from RB-57D airframes) were equipped with covertly mounted cameras and assigned specifically to reconnaissance work in 1965, Rivet Slice 2 and 3 with the 6091st Reconnaissance Squadron at Yokota AB and Rivet Slice 1 and 4 with the 7407th Support Squadron at Rhein-Main AB.Grimes 2014, p. 85.