Designed during WW II with first flight in August, 1946, the Convair B-36J Peacemaker became operational in June, 1948. Six Pratt & Whitney R-4360 and four General Electric J47s powered the B-36 to 435 mph. The B-36 carried nuclear or conventional bombs totaling 86,000 lbs up to 10,000 miles. The wingspan reaches 230 feet compared to a 747's 196 feet. The original main gear consisted of two tires 9 feet 2 inches tall, 3 feet wide, and weighing 1,320 pounds. These tires restricted the B-36 to three airfields due to the weight they concentrated on the runway. The single wheel and tire was quickly replaced by a four wheel bogey.