The B-29 resulted from Boeing proposals to create a follow-on to the B-17 which would meet Army demands for a long-range weapons carrier. The B-29 was a radical departure; the biggest change was not in size, although the B-29 was almost twice as heavy and had almost twice the horsepower. The primary difference was in improved and more precise manufacturing. It had a flush-riveted, super-strong shell with pressurized crew compartments. The wing was an extremely thin, long surface with a very high wing loading (_ 80 psf). Its area was 1,738 ft2 compared to the B-17's 1,420 ft2. Max gross weight was 41,000 lb; top speed was 358 mph at 25,000 ft; and range was 4,100 mi. The test program was agonizing--engine failures and fires were a daily occurrence. Eddie Allen, Boeing's chief test pilot, and crew, crashed and burned in Feb 43 near the Seattle waterfront in XB-29 number 2. Nevertheless, test efforts progressed in 1943. The principal danger remained the new R-3350 engine which had an excellent power-to-weight ratio but presented cooling and carburetion problems that were not completely solved until after war's end. Initial deployment was on 5 Jun 44 against Bangkok, Thailand. The second raid on 15 Jun with 68 aircraft was against a steel plant at Yawata, Japan. On 6 Aug 45, "Enola Gay" departed Tinian loaded with "Little Boy" which was dropped on Hiroshima 0815 from 31,600 ft. On 9 Aug, "Bockscar" dropped "Fat Man" on Nagasaki.