Mechanical Engineering of World War II

Sometime during the summer of 1998 during a family vacation I visited the Air Force museum in Dayton, Ohio. During that trip i saw a plane sitting outside the hanger that almost immediately caught my interest and began a fascination with aircraft that has lasted a lifetime. It was giant, with six big propellers and four jets, the wings were seven feet thick and it dwarfed everything around it. The plane I saw was the B-36.

The B-36 “Peacemaker” was America's first intercontinental bomber.

It was a 10 engine piston and jet powered long range high altitude post-World War 2 bomber, designed to strike at targets in Europe and Asia from the mainland U.S. It had six radial engines and four jets and could fly over 40 hours non stop without refueling. The “peacemaker” was instrumental in early cold war strategy and nuclear deterrence.

The U.S. government was worried early in 1940 that Great Britain would fall to Nazi Germany and the U.S. would have no mainland allies to base from when they entered into World War 2. The Army Air Corps commissioned Consolidated and Boeing to produce prototypes and the B-36 was born. The Bomber was in development when the U.S. entered World War 2 after Pearl Harbor in early December 1941. At that point it was put on the back burner while Consolidated focused on B-24 production instead. (Jenkins, Dennis R)

Originally, the Air Corps asked for a plane that had a top speed of 450 mph, cruising speed of 275 mph, a service ceiling of 45,000 feet, could carry 10,000 lbs payload, and fly non-stop for 12,000 miles. Due to technology limitation of the time that proved to be impossible. The Air Corps then lowered its requirements to 4,000 mile range, with 10,000 lb payload, cruising speed of 240-300 mph, and a ceiling of 40,000 ft. (Jenkins, Dennis R)

The first plane used six Pratt and Whitney R-4360-25 Wasp Major engines in a pusher set up. The Wasps put out 3,000hp, with a top speed of 325 mph and a max takeoff weight off 310,380 lbs. The Wasp Major was the last of Pratt and Whitneys Wasp engine line and the biggest radial engine ever to be mass produced in the United States. (Jenkins, Dennis R)

The Wasp engine started its life in 1925. It was desgined and submitted to the U.S. Navy as a nine cylinder single row radial producing 410 horsepower. It was accepted by the Navy and the first planes begain using it. Ten years later the Twin Wasp was prouced, using 14 cylinders, proucding 1,000 horsepower. Not long after the 18 cylinder 2,000hp R-2800 Double Wasp was rolled out. Not satitfied the NAvy asked for more, and in 1940 Pratt and Whitney started working on the Wasp Major.

The Wasp Major was designated the R-4360. Having 28 cylinders in a sprial pattern with four rows of seven each. The sprial pattern was used to force air over each cylinder to imporve cooling and prevent the massive amounts of heat prouced to dammage the engine. The Wasp Major had a 5.75 inch bore and a 6.00 inch stroke in each cylinder. Usng 2,500 pounds of 115/145 av-gas and needing 25,000 pound of air per hour at max output. The engine weighed 3,670 pounds and had tow superchargers( one gear drivin and an exaust driven tourbosupercharger).(Jenkins, Dennis R)

Toward the end of WW2 the B-36 development was back online with the first prototype being rolled out August 8, 1946 for its maiden flight.It carried 24,121 gallons of fuel and 10,000 lbs bomb load with a radius of action of 3,880 miles. Serverl test flights were conducted starting in mid 1948. On 8-9 April 1948 a B-36-A flew its first long range flight. The flight lasted 36 hours and covered 6,922 miles dropping a 10,000 lbs of dummy 500 lb bombs on an Air Force test range in Arizona. The flight ran into some problems, when two of its six engines had to be shut down and limited the speed to 215mph. A second long-range test a month later was a success in all aspects, followed by many more over the next few months. Each test went farther, higher, and longer. Even with all the testing the A model had server maintenance issues and was short lived.(Jenkins, Dennis R)

The B model was first introduced in July of 1948 with several improvements but, like the A, it took quite some time to come into its own. The first major improvement was upgrading to the Wasp Major R-4360-41 which had 500 more horsepower, provided for shorter takeoffs and higher cruising speeds as well as top speed. A reconfigured bomb bay added 14,000 lbs of bomb carrying capacity and it was the first aircraft to be able to carry atomic weapons by design. The B was designed to carry F-85 Parasite Fighters but none were ever mounted. It was also the first truly combat capable B-36 as it had a defensive armament.The first B-36-B was delivered to the Air Force on November 25 1948. Many test flights were flown on this model as well topping the A on every aspect of flight. Most notable was on December 7th 1948 a B-36-B flew a simulated bombing mission consisting of a 36 hour round trip flight to Hawaii dropping 10,000 lbs of dummy bombs in the ocean of the coast. The flight penetrated Hawaii's airspace undetected by the defensive forces and embarrassed them greatly (considering that it was the seven year anniversary of pearl harbor). (Jenkins, Dennis R)

The B-36 next production model was the D, a B-36 C was designed but never produced. The D model added 2 General Electric J47-GE-11 turbojets in pods at the tips of each wing. The jets were modified to use the same av-gas as the piston engines in order to only have to carry one type of fuel. The aircraft made its first flight on March 26, 1949, but the GE jets were not yet available so it had Allison J35-A insead. The B-36D went through extensive testing flying over 500 hours during 73 days. Each flight was a simulated tactical mission at 40,000 feet with one lasting over 39 hours. The last test flight ended in November 1950 and the Air Force started receiving combat capable aircraft in August of that year. All preexisting B-36-A and -B’s were soon modified to the -D model soon after.(Jenkins, Dennis R)

The B-36-F was the next model ordered by the Air Force. The major difference in the plane was the change from the R-4360-41 to the R-4360-53 engine. The -53 produced 3800 hp and had direct fuel injection, allowing the aircraft to reach a new top speed of 417 mph and a ceiling of 44,000 ft. The new engines were designed and capable of being completely removed and replace within 4 hours.The -F model also included a chaff system to help confuse enemy radar. The -F was already in flight testing before the -D model was even delivered, having the first flight test in November 1950. Testing ended in July 1951 and the first combat plane was delivered in August of 1951.(Jenkins, Dennis R)

The next few B-36 models really had all the kinks worked out. The B-36-H was the major production version of the plane. After all the testing and changes the B-36 went through it led to the H model. The main notable difference from the -F is a newly designed 3 blade flat headed propeller and a slightly different internal layout. The final model was the B-36-J in which the only really big change was the addition of extra wingtip fuel tanks, and upgraded landing gear. The last -J model was delivered in August of 1954.(Jenkins, Dennis R)

There were many modification programs and other variants of the B-36, most notably the Featherweight and Rb-36. The Featherweight modification program began in January of 1954, and was designed to raise the ceiling and increase the range of the bomber. Featherweight planes had all of the defensive armaments except the tail gun removed.The crew comfort equipment and observation blisters were also removed reducing the crew size and lighting the aircraft. This allowed for a 25 to 50 percent range increase and the top speed rose to 423 mph. Eventually, the entire B-36 fleet would undergo the featherweight conversion. The RB was a reconnison variation of the aircraft, with a larger crew, 22 verses the 15 of the B-36, and no bomb payload.(Jenkins, Dennis R)

In early 1951 there was a plan to design and test a nuclear powered aircraft and the B-36 was chosen to be the test vehicle. The NB-36H was designed to house a reactor that power its jet turbines. In 1955 a B-36H was designed to house an air cooled, 1000 kilowatt reactor in its number four bomb bay. Although the engines were never tested, the reactor was mounted and, in September of 1955, several test flights were performed. Every test flight was accompanied by a C-97 carrying a platoon of Marines in case the NB-36H went down. The Marines would parachute out and secure the reactor site until a documentation and security crew could be brought on site.The NB-36-H flew 47 test flights with the reactor online in 21 of them. The nuclear engines were never developed due to fear of what would happen if the aircraft was shot down or crashed on its own in friendly territory. The project was cancelled in late 1957.(Jenkins, Dennis R)

The B-36 was a doomed plane before it ever really got started. In 1953, the Air Force decided to start phasing the plane out in anticipation of the upcoming B-52. In 1956 the plane was scheduled to start being decommissioned although defense cutbacks slowed that to 1959. Although never flown in combat and only in service for a decade, the B-36 was an integral part of the post-World War 2 Air Force. (Jenkins, Dennis R)

In 1901, Theodore Roosevelt said, “Speak softly and carry a big stick” in a

famous speech at the Minnesota State Fair. The B-36 was America's first true “Big Stick”. It gave us the ability to drop an atomic bomb anywhere in the world from the continental United States, an ability that no other country possessed at the time. The B-36 marked the United States as the first true super-power and the toughest kid on the block.

References

1. Jacobsen, M. K. (1999). Convair B-36 Peacemaker: A photo chronicle. Schiffer Pub.
2. Jenkins, D. R., & Jenkins, D. R. (2008). Magnesium overcast: The story of the Convair B-36. Specialty.
3. Post-World War II Bombers, 1945-1973. (1978). Office of Air Force History.

Did you like this example?

410

17