Convair B-36A "Peacemaker"

thethrill8284257 · May 3, 2024, 11:28pm

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Convair

B-36A “Peacemaker”

USAF

Background

Spoiler

I know that some of you on here like reading the background to aircraft, I’m making quite the long one, and I’ll be sectioning it.

Contract

The impetus for the creation of a long-range bomber was driven by the impressive military achievements of Nazi Germany during the early stages of World War II. Despite the delay in the planned invasion of the British Isles, the security of the United Kingdom appeared uncertain in the autumn of 1940. If Britain were to fall, the United States would be left without European allies and lacking military bases beyond the Western Hemisphere. Consequently, the Air Corps recognized the necessity for a long-range bomber capable of launching attacks against any adversary from the American continent. The escalating triumphs of the German offensive against Russia in June 1941 further intensified America’s apprehension.

On April 11th, 1941, the Air Corps initiated a design competition for an intercontinental bomber that would possess exceptional speed, operate at high altitudes, carry a substantial bombload, and have an unprecedented range. The Consolidated Aircraft Corporation and the Boeing Aircraft Company were both invited on April 11th to conduct preliminary design studies. On May 27th, the Northrop Aircraft, Incorporated was contacted and requested to perform additional design studies for a “flying wing” bomber, capable of covering a range of 8,000 miles at an altitude of 25,000 feet, while carrying 1 ton of bombs. Shortly thereafter, the Douglas Aircraft Company joined the competition for long-range bombers. However, the Glenn L. Martin Company, solicited much later, declined the invitation due to a shortage of engineering personnel.

The initial specifications outlined in the Air Corps’ request for proposals in April 1941 included a bomber that could reach a top speed of 450 mph at 25,000 feet, maintain a cruising speed of 275 mph, operate at a service ceiling of 45,000 feet, and have an overall range of 12,000 miles at 25,000 feet. These characteristics were revised during a conference on August 19th, which was attended by Robert A. Lovett, Assistant Secretary of War for Air, Maj. Gen. George H. Brett, Chief of the Air Corps, and other high-ranking officers of the Air Staff. The primary objective of the conference was to expedite the bomber project, leading the participants to scale down their requirements. However, even with the revision, the new specifications remained demanding, calling for a minimum overall range of 10,000 miles and an effective combat radius of 4,000 miles with a 10,000 pound bombload. This combat radius was approximately four times that of the Boeing B-17, which was the newest and most advanced bomber in the AAF’s fleet at the time. Additionally, the conference attendees specified that the future intercontinental bomber should have a cruising speed ranging from 240 to 300 miles per hour and a service ceiling of 40,000 feet, which was 5,000 feet lower than the original request.

Contract Work, Review, and Issues

The initial agreement (W535 ac-22352) dated November 15, 1941, complied with the terms set by Consolidated. On November 22, just 7 days after the contract was approved, Wright Field Engineering Division determined that the 6-engine design should be chosen instead of the 4-engine design. This decision did not pose any issues as it was one of the options provided by Consolidated. To prevent confusion with the Northrop “flying wing” called the B-35, on December 10, the Model35 was renamed as Model 36. At that time, there were no indications of the challenges that would arise in the near future.

Following over 6 months of meticulous refinement of the selected design, with a focus on weight control, drag reduction, and ironing out developmental issues, the B-36 mock-up underwent inspection. The scrutiny sparked controversy that almost led to the cancellation of the experimental program. The Mockup Committee proposed cutting down firepower and crew to meet the 10,000-mile range requirement for the B-36. However, some members argued that such alterations would render the aircraft strategically ineffective and redundant, especially considering the existence of the “flying laboratory” XB-19 by the Experimental Engineering Division. If these modifications were deemed necessary, it was suggested that the AAF should halt the project and redirect resources towards more fruitful bomber programs. Eventually, the Mockup Committee reached a consensus to eliminate “less essential” equipment from the aircraft, resulting in reduced weight and a temporary reprieve for the future of the B-36.

One month after inspecting the B-36 mockup, Consolidated proposed relocating the XB-36 project from San Diego, California to its newly leased government plant in Fort Worth, Texas. Despite completing the move in September 1942, just under 30 days after receiving approval from the AAF, the development process experienced a setback of several months. Numerous unresolved issues remained, but Consolidated requested that the AAF award a contract for a production quantity of the new aircraft. The contractor argued that by initiating preliminary work on production B-36s without waiting for the completion of the experimental planes, the development cycle could be shortened by 2 years. Unfortunately, Consolidated’s request was poorly timed. Due to military setbacks in 1942, particularly in the Pacific, and the fact that the B-36 could not become operational in the near future even under ideal circumstances, the AAF could not allocate scarce resources for its production.

In the summer of 1942, Consolidated made another request that yielded somewhat better results. The AAF agreed to the development of a cargo version of the XB-36, on the condition that one of the two experimental bombers be produced at least three months prior to the cargo plane, referred to as the XC-99. Consolidated intended for the XC-99 to serve as a testbed for the engines, landing gear, and flight characteristics of the upcoming XB-36s. The contractor also believed that the XC-99 could be ready to fly much earlier than either of the two XB-36s since it would not include armament and other military equipment. The AAF accepted these conditions, and a contract worth $4.6 million was approved by the end of the year.

As engineers continued to grapple with challenges related to weight increases and other developmental issues, the significance of the B-36 was unexpectedly heightened due to war problems. Military setbacks that had previously hindered the program in 1942 escalated in the spring of 1943, particularly as China faced the threat of collapse. The B-17 and B-24 lacked the necessary range to cover the vast distances of the Pacific, while the Boeing B-29, still in its early production phase, encountered more difficulties than anticipated. The development of the Convair B-32, initially seen as a backup to the B-29, did not progress as smoothly as expected. Given the higher priority placed on the B-29, the B-32 appeared less promising. Despite potential production delays, neither aircraft could reach Japan until victories were secured to establish bases in the Mariana Islands. Accelerating the development of the B-36 emerged as a potential solution, perhaps the only one, for launching attacks on Japan and boosting Chinese morale. Consequently, on June 19th, General Arnold authorized the procurement of 100 B-36s. However, the order was subject to reduction or cancellation in case of excessive production challenges. Convair officially signed the AAF letter of intent for 100 B-36s on July 23, 1943.

Despite its prestigious status, the B-36 program made minimal progress. The crucial wind tunnel tests for the new design were delayed until the spring of 1944 due to higher priority projects and the unavailability of alternative testing facilities. In addition to the usual engineering challenges, Convair was deeply concerned about the increasing weight of the Pratt & Whitney X-Wasp engine chosen for the experimental B-36. Convair believed that relying on a single engine design for the XB-36 was a mistake. However, the exploration of the Lycoming BX liquid-cooled engine, known for its lower fuel consumption, had been discontinued because it would require significant resources that were not available. The AAF also insisted that developing a new engine would only hinder the efficient progress of the B-36 design. Consequently, the B-36 was pushed to a secondary position, with the Convair B-32 taking precedence.

On July 23rd, 1943, the letter of intent was followed by the Letter Contract W33-038 ac-7 on August 23rd, 1943. After a year, a definitive contract was established. This contract amounted to $160 million, which included a fixed fee of $6 million and covered the expenses for all spare parts and engineering data. The contract remained in effect for the production of 100 B-36s, but it no longer held any priority rating. Despite this change, the delivery schedules remained unchanged. The first B-36 was scheduled for delivery in August 1945, whileWar contracts were carefully reviewed for potential cancellation or significant reduction as victory seemed imminent. On May 25th, 1945, aircraft production was actually decreased by 30 percent, resulting in a reduction of 17,000 planes over an 18-month period. However, the B-36 contract remained untouched during this evaluation. The necessity of a long-range bomber was unquestionable, considering the high cost in terms of lives and resources that had been paid to secure advanced bases in the Pacific. Additionally, with the atomic bomb potentially losing its status as an exclusive American weapon, the need for swift U.S. retaliation became even more crucial. Conquering distant bases would not be feasible within the limited time frame, making a long-range bomber the most practical war deterrent for the foreseeable future. From an economic perspective, the B-36 also proved advantageous. It outperformed both the B-29 and the B-35 “flying wing” in terms of long-range missions and was significantly more cost-effective, with operating expenses half that of the B-29 in terms of cost per ton per mile. Consequently, on August 6th, 1945, General Arnold approved the Air Staff’s recommendation to maintain the B-36 production contract without any changes. the final one was expected in October 1946.

War contracts were carefully reviewed for potential cancellation or significant reduction as victory seemed imminent. On May 25th, 1945, aircraft production was actually decreased by 30 percent, resulting in a reduction of 17,000 planes over an 18-month period. However, the B-36 contract remained untouched during this evaluation. The necessity of a long-range bomber was unquestionable, considering the high cost in terms of lives and resources that had been paid to secure advanced bases in the Pacific. Additionally, with the atomic bomb potentially losing its status as an exclusive American weapon, the need for swift U.S. retaliation became even more crucial. Conquering distant bases would not be feasible within the limited time frame, making a long-range bomber the most practical war deterrent for the foreseeable future. From an economic perspective, the B-36 also proved advantageous. It outperformed both the B-29 and the B-35 “flying wing” in terms of long-range missions and was significantly more cost-effective, with operating expenses half that of the B-29 in terms of cost per ton per mile. Consequently, on August 6th, 1945, General Arnold approved the Air Staff’s recommendation to maintain the B-36 production contract without any changes.

During the course of the B-36 program, the fate of the project fluctuated due to changing wartime priorities. Unfortunately, the development of the aircraft progressed at a painfully slow pace. By 1945, Convair was still concerned about the weight of the R-4360-25 engine. The addition of nose guns necessitated significant rearrangement of the forward crew compartment. A mockup of the new nose section had received approval in late 1944 and would serve as a prototype for the second XB-36. However, the inclusion of radio and radar equipment in the new nose would increase the overall weight by at least 3,500 pounds. This weight could potentially be even higher if the AN/APQ-7 radar antenna could not be installed in the leading edge of the wing. Additionally, the installation of 6 new engines would result in a substantial increase of 2,304 pounds, posing a serious problem. Selecting suitable wheels for the aircraft’s landing gear was also a challenging task. The decision to have dual main wheels was based on the idea of simplified maintenance without requiring special tools. However, the single-wheel type had its own advantages. These debates came to an end in mid-1945 when Maj. Gen. Edward M. Powers, Assistant Chief of Air Staff for Materiel, Maintenance, and Distribution, recommended the development of a new landing gear system. This new system aimed to distribute the weight of the aircraft more evenly, thereby reducing the need for specially constructed runways.

In the meantime, the experimental B-36 encountered issues with faulty workmanship and the use of substandard materials. AAF inspectors also observed the unfortunate loss of qualified workers at the project’s inception, as well as the failure of the airfoil contour of the aircraft wing to meet specifications. It is important to note that substituting materials was a commonly accepted practice for urgently awaited experimental planes, and Convair should not bear the sole responsibility for other discrepancies. However, the contractor did promise to promptly rectify these issues. Despite some progress being made, labor strikes at the Fort Worth plant in October 1945 and February 1946, which were a normal part of postwar adjustment, caused significant delays in the program. On the 25th of March, General Powers expressed concerns that the forthcoming XB-36’s structural limitations might render it useless, except as a test vehicle for the initial flight.

First Flight, Reviews, Concerns, Improvements, and Beyond

Despite all efforts, the XB-36, an all-metal, semimonocoque aircraft, did not take flight until nearly six years after the development contract was signed. The initial flight on August 8th, 1946, lasting 37 minutes, was considered a success. However, the wing flap actuating system and overall performance of the aircraft fell short of the original expectations. In addition to its known structural limitations, the XB-36 featured an outdated single-wheel landing gear, carried only essential components, and lacked the nose armament intended for the second XB-36. Nevertheless, this marked the beginning of its journey. Following a period of grounding in late 1946 for modifications, the XB-36 underwent 160 hours of test flights by pilots from the Air Materiel Command (AMC). Subsequently, the aircraft was sent back to the contractor for further testing, including a successful test flight where it dropped 72,000 pounds of bombs on June 30th. In mid-1948, the United States Air Force (USAF) retrieved the XB-36. As General Powers had predicted, the experimental B-36 had limited operational value and was primarily utilized by the Strategic Air Command (SAC) for training purposes.

On December 12, 1946, General Kenney, who had achieved the rank of 4-star general in March 1945 and had been leading SAC since April 1946, proposed reducing the procurement contract for 100 B-36s to a few service-test aircraft. After reviewing the available performance estimates for the B-36, the SAC Commander believed that it was inferior to the upcoming B-50, a Boeing development based on the renowned B-29. The B-50 and the B-36 were the only two piston-powered bombers produced during the postwar era of jet bombers. General Kenney pointed out several shortcomings of the B-36, including a limited useful range of only 6,500 miles, inadequate speed, and insufficient protection for the bomber’s fuel supply. However, both the Air Staff and Lt. Gen. Nathan E Twining, the Commanding General of the Air Materiel Command, disagreed with General Kenney. General Twining argued that the XB-36, which had just entered testing, could not be used as a basis for judging the B-36. He emphasized that all new aircraft faced developmental challenges, as demonstrated by the B-17 and other successful planes. Furthermore, he anticipated numerous improvements in the near future, and the B-36 was the only aircraft far enough in its development to serve as an interim long-range atomic carrier until the arrival of the B-52. Gen. Carl Spaatz, the new Commander of the AAF, fully supported General Twining’s viewpoint. Consequently, the B-36 contract was retained in its entirety.

Despite facing numerous challenges, the B-36 program persevered as engineers continued to make progress. By mid-1947, Convair was confident that the first production model B-36A would be equipped with the 4-wheel landing gear. While this model and 21 others would still use the R-4360-25 engine from the XB-36, the conversion of this engine had been approved in December 1946. The new R-4360-41 engine, with water-injection and 3,500 horsepower, would enable subsequent B-36B productions to take off in a shorter runway distance. It would also provide slightly improved performance at high and cruising speeds. However, further enhancements were still needed. Therefore, Convair was developing an even more powerful version of the R-4360 engine, which would include a variable discharge turbine (VDT). Convair claimed that the VDT engine, also proposed for the B-50, would give the B-36 a top speed of 410 miles per hour, a service ceiling of 45,000 feet, and a range of 10,000 miles with a 10,000 pound bombload. To cover the cost of adapting the VDT engine to the B-36, Convair suggested funding the airframe modification for one prototype B-36 with the VDT engine by reducing the current procurement contract by three B-36s. This proposal was approved by the Commanding General, AAF, in July 1947. Although Convair hoped that additional VDT-equipped B-36s (B-36Cs) would be ordered if the prototype proved successful, a decision on this matter was postponed.

The establishment of an independent Air Force naturally resulted in increased authority and greater responsibility when it came to selecting fundamental weapon systems. In light of this, General Vandenberg, the Deputy Chief of Air Staff, promptly established the USAF Aircraft and Weapons Board. This platform allowed senior officers to recommend the most suitable weapons to support the Air Force’s long-term plans for development and gradual expansion. The board convened for the first time on 19 August, and due to the emergence of atomic weaponry, strategic bombing and the methods to carry out such missions took precedence. The B-36 emerged as the sole bomber capable of launching an immediate atomic counterattack without the need for overseas bases. Despite its vulnerability to enemy fighters due to its relatively low speed, the B-36 offered a significant advantage: its extensive range increased the likelihood of the crew successfully completing their mission. However, it was anticipated that future supplies of atomic bombs would be limited, necessitating plans that also accounted for the potential use of conventional bombs. The board members held differing opinions on how to address these intricate challenges. Some regarded the B-36 as outdated and advocated for the purchase of fast jet bombers, despite the obvious risk of insufficient range and the lengthy wait for their availability. Others proposed enhancing the B-36’s speed with the new VDT engine and utilizing it as a versatile bomber. Alternatively, some favored the B-50, which boasted greater speed than the B-36 and could achieve even greater range and velocity with the addition of VDT engines. Following extensive deliberation, a consensus was reached to retain the B-36 as a specialized bomber. This particular B-36 would eventually be replaced by the B-52, provided that the latter proved satisfactory and no superior means of delivering the atomic bomb emerged. Given the specialized nature of the endorsed B-36, there were multiple reasons for not incorporating the VDT engine into a prototype B-36. There would be no need for additional B-36 procurement. Furthermore, despite the enticing promised enhancements, retrofitting the VDT engines would result in a delay in completing the 100 B-36s that were already ordered and would escalate costs. General Spaatz promptly approved the recommendations of the board, and the B-36 prototype equipped with VDT was subsequently canceled on the 22nd of August, 1947.

The issue of weapon selection raised numerous unresolved problems. One solution was to limit the procurement of B-36 aircraft, while another challenge was to find a purpose for the soon-to-be idle government-owned Fort Worth plant. The Air Force couldn’t afford to ignore the fact that Convair’s disheartened B-36 workforce might secure more stable employment before the completion of the B-36 program. Additionally, there were complications regarding the allocated funds for the 100 B-36s during the war. If any amount remained unspent by June 1948, it would require reappropriation by a potentially different-minded Congress. One proposed solution was to increase production speed. However, due to shortages of government-furnished equipment, accelerating production proved to be impossible. This turned out to be fortunate as it would have hastened the end of the Fort Worth activities. Instead, the endorsed monthly production rate of 4 B-36s posed another challenge by delaying the delivery of the last B-36 until November 1949. This extended the production time by 10 months, leaving Convair uncertain about the availability of funds to complete the program. Recognizing the contractor’s predicament, the Air Force assured them that a request for reappropriation of B36 funds would be made when Congress reconvened in early 1948.

When it became evident that obtaining a faster B-36, known as the B-36C, equipped with VDT engines was not feasible, the Air Force contemplated canceling the entire B-36 program once again. However, several factors needed to be taken into account. Twenty-two of the initial B-36s, which were relatively slow, were already nearing completion, and a significant amount of money had already been invested in the controversial program. Consequently, the Air Force decided to postpone any decisions. It directed the Air Materiel Command to forgo modifying several shop-completed B-36s that were awaiting adjustments and expedite their delivery. This would enable Convair to accelerate the aircraft’s flight test program, as consistently recommended by the Air Force. Additionally, new benchmarks were established to compare the performance of the basic B-36 with that of other bombers under similar conditions. These benchmarks assessed the four most crucial and interconnected characteristics of any given bomber: speed, range, altitude, and load capacity.

Although the test results were not extraordinary, they favored the basic B-36. They demonstrated that the slower B-36 outperformed the B-50 in terms of cruising speed over long distances, had a higher altitude, larger load capacity, and a significantly greater combat radius compared to the B-50 or the B-54, a B-50 variant that was being considered but ultimately canceled in 1949. It now appeared that the B-36 had the potential to be a much more impressive aircraft than initially anticipated. Consequently, hastily reducing the contract could jeopardize the program just as it was on the verge of success. The commencement of the Russian blockade of West Berlin on June 18, 1948, spared the Air Force from further indecision. On the 25th, Air Force Secretary W. Stuart Symington and other top USAF officials, deeply concerned by the aggressive actions of the Soviets, unanimously agreed to continue with the B-36 program.

The Air Force officially accepted the B-36A in May 1948, and it was subsequently delivered to the Air Force Proving Ground Command 44 on June 18th for extensive testing. This particular aircraft was a fully functional production model, unlike the first B-36A (designated as the YB-36A), which had limited components, no engines, and only underwent static testing.

On June 26th, 1948, the 7th Bomb Wing of the Strategic Air Command (SAC) at Carswell AFB in Texas received the first batch of 5 B-36As. These initial deliveries, as well as subsequent ones, were not armed and primarily used for training and crew conversion purposes. It was only after being converted to the reconnaissance configuration that they joined the operational forces.

One B-26A was delivered in May, Five in June (mentioned above), Five in July, Four in August, and Five in September of the year 1948. The 22nd and 23rd B-36A’s were accepted into service in February, 1949.

Most if not all B-36A Models were later converted to either RB-36E or B-36B and following Models.

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