The B-36H had a rearranged crew compartment and additional twin tail radomes to store the components of the AN/APG-41-A radar. The AN/APG-41A was far superior to the AN/APG-32 gun laying radar employed by the preceding B-36Ds and B-36Fs.
By this point in time, modifications to the B-36 were relatively minor with each subsequent upgrade. An attempt to convert the B-36H into a tanker was undertaken, but such models never entered service.
The B-36H and B-36F prototypes were first flown at almost the same time (November 1950). Yet, B-36H deliveries did not start until December 1951, when the Air Force already had most of its 34 B-36Fs. The B-36H's marked improvement over the F accounted for the delay between production. The Air Force bought 156 B/RB 36Hs more than double the production total of any other B-36.
Once underway the production flow of B/RB-36Hs was steady, averaging 8 aircraft per month during 1952, and 6 monthly between January and September 1953.
By 1952, engineering on the B-36 was little more than correction of rather minor deficiencies showing up in service. The B-36H (like the B-36F) had 6 R 4360 53 engines, but the early troubles of these new engines were virtually under control. Other problems arose, however. During a few months in 1952, all B-36s were restricted to an altitude of 25,000 feet after an RB-36 accident at 33,000 feet was traced to a faulty bulkhead. This restriction remained in effect until all deficient bulkheads were discovered and replaced.
The B-36's original propeller blades carried flight restrictions that hampered performance. A new blade, made by a special flash welding process, could be used freely except for landing and takeoff. This blade weighed an extra 20 pounds, but its greater efficiency promised to compensate for the loss in aircraft range. A batch of 1,175 was ordered for prompt installation.
In March, defective landing gears caused a series of accidents. After 2 crashes, the Air Force grounded all B-36s except the first 152. This meant that almost all of the last half of B/RB-36F productions and some 30 B/RB-36Hs already accepted by the Air Force could not be flown. Investigations from the start had blamed the aircraft's landing gear pivot shaft. Since a heavier bar could be devised and serve until a permanent alteration could be made, the grounding orders were soon lifted.
Some B-36Hs and B-36H reconnaissance versions were reconfigured by Convair in 1954. They were returned to SAC in the same year as B/RB-36H-111s, having undergone the same stripping and overall modification as other featherweight B/RB-36s. No troubles were met with during the fulfillment of the B/RB-36H or other featherweight modification contracts. The crew of each modified aircraft was cut. For high altitude operations, B-36s carried only a crew of 13 (a decrease of 2); RB-36s, a crew of 19 (a decrease of 3).
A total of 83 B-36Hs were accepted. The Air Force accepted 32 B-36Hs in fiscal year 1952--7 in December 1951, 5 in January 1952, 3 in February, 5 in March, and 4 in each of the next 3 months. It received 43 B-3611s in FY 53-4 in July 1952, 4 in August, 7 in September, 3 in October, 4 in November, 2 in December, 4 in January 1953, and 3 during each of the next 5 months. The last 8 B-36Hs were accepted in FY 54- 3 in July 1953, 3 in August, and 2 in September.
All B-36Hs, including the last one built, had been accepted by the end of September.
In round figures, the B-36H and B-36F prices were alike. In reality, the B-36H cost an additional $11,321. Airframe costs were much lower, but the price of the engines showed a steep increase. Armament, electronics, and propeller cost also had gone up. The new costs were: airframe, $2,077,785; engines (installed), $874,526; propellers, $214,186; electronics, $80,272; ordnance, $30,241; armament, $872,436.
RB-36H: The Air Force bought 73 long range reconnaissance versions of the B-36H. Twenty-three were accepted in FY 52 (all during the first 6 months of 1952); 42 others in FY 53 (between July 1952 and June 1953). The last 8 were delivered in FY 54. The RB-36H price matched that of the B-36H and did not include the featherweight modification costs of 1954.
B-36H (Tanker):Searching for a tanker that could refuel jet aircraft at higher altitudes and higher speeds, SAC in early 1952 became interested in a readily convertible B-36 bomber tanker. The Air Force therefore asked Convair to equip one B-36 with a probe and drogue refueling system. The modification contract was approved in February 1952 and the work was completed in May. Testing, postponed to the end of the month because of the late delivery of one B-47 receiver aircraft, was satisfactory enough. Yet, no other tests took place until January 1953, after a new and vastly improved British made probe and drogue refueling system was installed. The British had developed refueling techniques to the point where they were actually in use on commercial airplanes, and the Air Staff in late 1947 had already begun to consider adapting the British technique to combat aircraft refueling. This would allow short range but relatively speedy bombers of the B-50 type to get to a distant and heavily defended target with the atomic bomb-a task allocated to the B-36, but especially hazardous due to that long range bomber's slow speed.
The converted B-36H tanker subsequently flown could refuel one or more receiver aircraft. The 9 crewmember tanker could be returned to its standard bomber configuration in some 12 hours. But the B-36's bomber commitments never really allowed SAC to exploit these features.
Conversion of SAC's heavy bomb wings to B-52 aircraft began in June 1956, with the B-36H equipped 42d Wing at Luring AFB, Maine. The 93d Bomb Wing at Castle AFB, Calif., fully equipped with B-52s in April 1956, had been a B-47 outfit prior to conversion. Nonetheless, like the final B-30s, the much improved B-36Hs were among the last to go.
A total of 83 B-36Hs were accepted, starting in 1952. Phaseout (replaced by B-52s) took place from 1956-1959.
One B-36 was modified by Convair in 1952 to carry guided air missiles (GAMS), specifically the GAM 63 Rascal, under development by the Bell Aircraft Corporation since 1946. The name Rascal derived from the guidance system used during the missile's dive on the target. This system was called a Radar Scanning Link, and the word Rascal was formed by combining the underlined letters of the 3 words.
A mockup inspection of the B-36/Rascal prototype disclosed no major obstacles, and 11 other B-365 were programmed to be modified as director aircraft (DB-36s) for the new missiles. Several factors soon dictated changes in USAF plans. The principal ones were ongoing Rascal difficulties, imposition of new technical requirements, and reorientation of the program to achieve the best aircraft/missile operational combination. Although testing with the DB-36 would go on for awhile, the Air Staff decided in mid 1955 that it definitely wanted the B-47, not the B-36, to carry the Bell rocket powered GAM 63. Time lessened the decision's importance when the Rascal program was canceled in November 1958. At a top speed of Mach 2.95, the Rascal could carry a 3,000 pound nuclear warhead 90 nautical miles. Still, it remained unreliable and was overtaken by technological progress. Most of the DB-36 modification contract was canceled. Convair completed only 3 aircraft and reimbursed $1.6 million to the Air Force.
One B-36H (Serial No. 51 5712) never reached SAC. The Air Force reserved it for special tests that it hoped would lead to the design of the world's first atomic powered plane. The future nuclear propelled B-36 (temporarily labeled the X-6) did not materialize. Even so, the modified and redesignated B-36H (NB-36H) saw extensive duty as a nuclear reactor test bed. Fortyseven test flights were made, yielding valuable data on the effects of radiation upon airframe and components. The NB-36H had undergone various modifications prior to testing. The most important one added a crew compartment to the fuselage nose section. This shielded all crew members from radioactive rays, when the nuclear reactor in the aft bomb bay operated. Composed of lead and rubber, this compartment completely surrounded the crew. Only the pilot and copilot could see out through the foot thick, leaded glass windshield. A closed circuit television system enabled the crew to see the reactor as well as other parts of the aircraft.
On 6 April 1955 a B-36 launched a guided missile with an atomic warhead from 42,000 feet. The explosion took place 6 miles above Yucca Flat, Nevada. It was the highest known altitude of any nuclear blast at the time.
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