The biggest bomber ever flown by the US Air Force, the Convair B-36 can either be considered to have been a huge waste of money or the most effective deterrent in modern warfare. One thing it was not was subtle. With six huge engines pushing it along1, it could drop its massive load of nuclear weapons at targets oceans away. However, in its operational life, it never saw combat, justifying its name as the Peacemaker.
In 1941, the United States of America was looking nervously at the map. It was only a matter of time before it had to enter the war against fascism in Europe; however, its only remaining ally, Britain, looked like it could fall to Germany, leaving the US Army Air Corps without a base.
The Air Corps felt the need for a bomber that could attack German targets from bases within the continental US. The design brief was for a bomber with a 450mph top speed, able to cruise at 275mph, have a ceiling of 45,000 feet, have a range of 12,000 miles at 25,000 feet and carry a 10,000lb bomb load to a target 5,000 miles away and return. It should have a maximum bomb load of 72,000lb2, and should be able to take off from a 5,000-foot runway.
Given that the standard US heavy bomber at the time, the B-17 Flying Fortress, could only carry 8,000lb of bombs, and that the heaviest bombs dropped during the war were 22,000lb3, it was obvious that whatever the outcome of the design brief, it would be far in advance of anything at the time.
Boeing and Consolidated Aircraft companies were asked for designs, and Northrop Aircraft was asked to expand its flying wing proposal.
On 19 August, 1941, a conference of high-ranking United States Army Air Force (USAAF) officers decided to lower the requirements for the plane, in order to speed up the project. Range was reduced to 10,000 miles, cruising speed was set at somewhere between 240 and 300mph, and the service ceiling was lowered to 40,000 feet.
On 3 October, 1941, the Material Division of the USAAF reviewed data from Boeing, Consolidated and Douglas, and decided that the designs submitted by Consolidated showed the most promise. Chief of the USAAF, Major General Henry H Arnold, gave the project a green light on 16 October, and a month later a contract for two XB-36 experimental aircraft was issued.
The plan was that the two XB-36s would be built in San Diego, California, and be delivered by May 1944. The design called for the plane to be pushed by six 28-cylinder engines. Not only had no plane on this scale exclusively used pusher engines, but the engines themselves only existed on paper. The plan was to connect two 14-cylinder Pratt & Whitney R-1830 Twin Wasp engines together, and to connect them to propellers 19 feet in diameter.
These engines were mounted in a seven and-a-half-feet-thick sweptback wing that had a span of 230 feet and a huge area of 4772 square feet. Inside the wing were passageways so the engines could be accessed for maintenance, and six fuel tanks allowing 21,116 US gallons of fuel to be stored. The wings were to be mounted high on the fuselage.
The long, round fuselage had relatively clean lines and was affectionately called 'The Big Stick.'
The fuselage itself had four separate bomb bays, with a capacity of 42,000lb. Inside, only the front cabin, the rear gunners sighting stations and the tube linking the two were pressurised. The tube, which measured only 25 inches in diameter, ran for 80 feet alongside the bomb bays, and crew used a wheeled trolley to slide back and forth.
The original plan called for 15 crew to be on board:
- Flight Engineer
- Two Radiomen
- Three Forward Gunners
- Five Rear Gunners
The plane was to be heavily armed, with four retractable turrets and a radar-directed tail gun all remotely controlled from sighting stations distributed across the plane. The armament consisted of five 37mm cannons and ten 0.50-inch machine guns.
The mock-up was inspected in July 1942, and the inspecting committee felt that the plane had too many guns and too many crew for it to make the 10,000 mile range requirement. They recommended drastic cuts; however, some members of the committee along with the USAAF thought that the changes would leave the bomber tactically useless. With the USAAF threatening to pull the plug, a compromise was met.
Because Consolidated were busy churning out B-24 Liberators for the war effort, the B-36 project was moved to a government-leased plant in Fort Worth, Texas in August 1942, delaying the project by several months as staff, machines, drawings and the mock-up were moved.
March 1943 saw Consolidated Aircraft Corporation merged with Vultee Aircraft Inc., becoming Consolidated Vultee Aircraft Corporation. This was often known by its shortened form, Convair.
That spring, it looked like China, the USAAF's main launch pad for B-29 raids on Japan, was going to fall to Japanese forces. The long-range B-36 looked like it would be the only way the US had of attacking Japan if it could not secure bases nearby. Around the same time, the president of Convair was complaining that sub-contractors were difficult to obtain for a small run of planes, and that having a large scale order would make the project run at much greater speed. On 19 June a production run of 100 examples was ordered, with the first production model arriving in August 1945.
By mid-1944, the Marianas campaign in the Pacific was coming to an end, and preparations were being made to deploy B-29s to bases within range of Japan. The Air Force considered the super-long-range B-36 a lower priority and diverted Convair's main effort onto the B-32 project. After Germany's surrender, the USAAF drastically cut back its orders for planes, but losses in reclaiming the Pacific Islands and the need for a bomber that could carry the new atomic weapons without the need for forward bases led to the B-36 remaining on order.
On 8 September, 1945, the first XB-36 emerged from Fort Worth. Sitting on main wheels that were 110 inches in diameter, the plane had to be restricted to only three runways in the United States with concrete thick enough to support it. The maiden flight took place on 8 August, 19464 and lasted 37 minutes. Beryl A Erickson and GS 'Gus' Green piloted what was then the heaviest and largest landplane ever to fly.
The test flight highlighted a number of problems such as the flap system, engine cooling and propeller vibrations caused by airflow over the wings. The speed and range were well below requirements and, worryingly, the XB-36 had not carried the full armament or equipment of the production models. The future of the project was in the balance, but the decision that the B-36 should not be judged on the XB-36 led to the project being saved again.
YB-36 was the designation of the second production prototype. It featured a new cockpit design and easily outperformed the XB-36.
Convair B-36A Peacemaker
General George S Kenny, the commander of Strategic Air Command (SAC), suggested limiting the run of the B-36 to just a few aircraft, citing the Boeing B-50 as a better aircraft. Other heads of the air staff disagreed, saying that until the B-52 arrived, the B-36 was the only long-range bomber available. The newly-created US Air Force (USAF) set up a board in August 1947 to determine what the best weapons were to use for the Air Force's long-term plan. Some board members thought that the B-36 was obsolete in the face of jet bombers; however, the USAF strategy was heavily based on long-range strategic bombing, and the B-36 was the only plane that fitted the bill. It was to remain in service until replaced by the B-52.
Another 21 B-36As were made; initially none of these featured any armament either. The first was delivered on 26 June, 1948. These were mainly used to train crew. During test flights, these bombers managed a number of 33-hour flights while carrying bombs.
In early 1950, these planes were fitted with uprated engines, turbo jets and cameras and were designated as reconnaissance planes, redesignated RB-36Es.
The B-36C was an attempt to improve performance by using Pratt & Whitney R-4360-51 variable discharge turbine (VDT, or turbocompound) engines, rated at 4300hp each. However, the design of the engine meant that they had to be in tractor rather than pusher configuration. This would have meant changing the design of the whole airframe. This and the engine's performance drop-off at altitude led to the B-36C being abandoned.
Convair B-36B Peacemaker
The B-36B was the first full scale production version, using R-4360-41 Wasp Major engines that had an extra 500hp each over the engines used in the B-36A. It had better performance, a bigger bomb load, better equipment and could operate from shorter runways than the B-36A.
The B-36B was also armed from the start. Its 16 20mm cannons gave it the most formidable armament of any warplane. The guns were mounted on platforms that retracted into the fuselage when not in use.
The endurance and bomb capacity of the B-36B was demonstrated by some of its test flights:
On 5 December, 1948, a 4275-mile, 14-hour mission at 40,000 feet with an average cruise speed of 303mph.
An 8000-mile plus, 35 and-a-half-hour simulated bombing run, with 10,000lb bombload from Carswell AFB to Hawaii on 7-8 December, 1948.
A pair of 42,000lb bombs were lifted on 29 January, 1949 from Muroc AFB; one was dropped at 35,000 feet, the other at 40,000 feet.
A 9600-mile flight, 5000 miles of which carrying 10,000lb of bombs, in 43 hours 37 minutes in March 1949.
However, problems with the armaments and other complex systems, combined with parts shortages, meant that some B-36Bs were cannibalised to keep others flying. Full operational status was not achieved until 1952.
64 of the 73 B-36Bs built were redesignated B-36Ds when they got turbo jet engines added to them.
Convair B-36D Peacemaker
In order to address critics' concerns that the B-36 was too slow and needed too long a runway, Convair added two pairs of General Electric turbo jets to the plane for short bursts of speed over targets and at takeoff. These engines were mounted in pods at the wing tips. These B-36s, designated B-36D had a top speed of 435mph over target, and reduced the takeoff runway needed by 2,000 feet.
Sixty-four of the B-36B aircraft were converted to B-36Ds, and another 26 were built from scratch.
The B-36D could carry 86,000lb of bombs, a record not equalled until the modified 'Big Belly' B-52Ds in service during the Vietnamese war.
The first B-36s to fly outside of US territory were six B-36Ds that flew to RAF Lakenheath in the UK in January 1951. In the late summer of 1953, the 92nd Heavy Bombardment Wing made a mass flight to the Far East, mainly to prove that the US was still willing to maintain operations after the end of hostilities in Korea. The 92nd were the first wing to be fully deployed overseas, departing for 90 days in Guam in October 1953.
Despite its massive size, the B-36D could fly on just three piston engines during a cruise, with the others shut down.
Some B-36Ds were stripped of armaments and crew comfort, with crew reduced by two. These Featherweight5 B-36Ds could reach altitudes about 50,000 feet.
Twenty-four photo-reconnaissance versions of the B-36D were made, the RB-36D. These had 14 cameras, 80 flash bombs, ECM6 equipment and an extra fuel tank taking up the bomb bays. The crew was increased to 22, including a photo technician who could develop the camera films in the plane's dark room. The extra fuel gave it a 50-hour endurance.
The B-36F was similar to the B-36D; however, it had uprated piston engines and improved radar and countermeasures. The first B-36F flew in November 1950, and the last of the 34 was delivered early in 1953.
Some of the B-36Fs were converted to RB-36Fs. One of these was used as a test bed for project Tom Tom, where two RF-84F Thunderflash jet reconnaissance fighters were attached to the end of the wings of the B-36 as a way of increasing their range. The same project was tried with the smaller B-29; however, vortexes generated at the wingtips of the B-29 caused the fighters to roll violently and all three planes crashed. The B-36 version of the project almost ended with tragedy as an RF-84F was torn from the wing of its mother ship. The project was abandoned soon after.
Another abandoned project was the GRB-36 FICON7, where a fighter was grabbed by a cradle mounted on the B-36. This was vaguely successful, but the arrival of the long-range U-2 reconnaissance craft meant that there was little need to increase the range of the existing RF-84Fs.
Eighty-three B-36Hs were built as the main production version of the B-36. This version had a new and improved gun radar but otherwise was similar to the B-36F. It first flew in December 1952. Seventy-three long-range reconnaissance RB-36Hs were also built, giving a production run of 156.
One B-36H was converted to a tanker, in the hope that it could refuel at altitudes that the B-29 based tankers couldn't reach. The tanker craft could be converted back to a standard bomber in 12 hours. No other B-36Hs were converted since it was more economical to use tankers based on the B-29, B-50 and KC-97.
Three B-36Hs were modified to test the Bell GAM-63 Rascal8 rocket-powered nuclear missile. These were designated DB-36H, and the rocket was carried recessed under the fuselage. It was decided in 1955 that the B-47 would carry the missile, and the plan to convert another 11 B-36Hs was abandoned.
The B-36 with serial number 51-5712 became the test bed for the WS-125A nuclear-powered bomber project. Air was to enter a compressor, be heated by a nuclear reactor and get exhausted from a jet nozzle. The test plane carried a 1000kw, 35,000lb reactor that didn't actually power the plane. The crew were housed in a special rubber and lead compartment, with a four-ton lead shield in the middle of the plane. Only the pilots could see through the leaded glass windshield that was 12 inches thick. The craft was redesignated XB-36H9 and first flew in September 1955. It flew over sparsely-populated areas and was followed by a plane load of Marines in case it crashed. The last of its 47 flights was made in March 1957.
By June 1956, only four years after the B-36 became fully operational, the 42nd Bomb wing, equipped with B-36Hs, began converting to the Boeing B-52 Stratofortress.
The 33 B-36Js were the last production run of the B-36. They featured additional fuel tanks. The final 14 were all Featherweights. The B-36J first flew in 1953, with the final one arriving in 1954.
By 1950 the call had already gone out for a replacement heavy bomber. Convair responded with the B-36G, soon renamed YB-60, all-jet bomber. It was based on the B-36; however, it had a much more swept wing, longer fuselage and was taller. It shared much of its design and parts with the B-36, so it was relatively cheap compared to its competitor, the Boeing B-52. However, the B-52 was a much superior design and got the nod. Convair, out of desperation, even tried to get the military to let them build their remaining allocation of B-36s as B-60s free of additional charge, but the Air Force rejected the idea.
The End of the Line
By the mid-1950s, the Boeing B-52 was replacing the B-36 as SAC's main bomber. From February 1956, B-36s were being flown to Davis Monthan AFB in Arizona where they were scrapped. Defence cutbacks, leading to a slowdown in B-52 procurement and some updating work by Convair, meant that the operational life was extended by a few years. The last B-36J - serial number 52-2827 - was flow to Amon Carter Field in February 1959 where it was left on permanent display.
In total 383 B-36s were accepted by the Air Force. Of these, 11 aircraft were lost in accidents. They arrived in service too late for the Korean War and were out of service by Vietnam. They saw no action in their lifetime, so were these giant planes a waste of money, or did the threat that these planes carried act as a deterrent to the USSR?