If you are interested in the history of this aircraft type, but to have yet to read very much on them, there are some interesting reads you can find with a simple search that describe the many, MANY difficulties the Wright R-3350 Duplex Cyclone engine encountered, quite a few of them resulting in the deaths of aircrew.
By 1943 the ultimate development of the new bomber program, the Boeing B-29 Superfortress, was flying. The engines remained temperamental, and showed an alarming tendency for the rear cylinders to overheat, partially due to minimal clearance between the cylinder baffles and the cowl. A number of changes were introduced into the Superfortress' production line in order to provide more cooling at low speeds, with the aircraft rushed into operational use in the Pacific in 1944. This proved unwise, as the early B-29 tactics of maximum weights, when combined with the high temperatures of the tropical airfields where B-29s were based, produced overheating problems that were not completely solved, and the engines having an additional tendency to swallow their own valves. Because of a high magnesium content in the potentially combustible crankcase alloy, the resulting engine fires — sometimes burning with as high a core temperature approaching 5,600 °F (3,100 °C)[1] from the Duplex Cyclone's magnesium engine crankcase alloys — were often so intense the main spar could burn through in seconds, resulting in catastrophic wing failure.[2]
The following is from the
Wikipedia B-29 article;
The most common cause of maintenance headaches and catastrophic failures were the engines.[20] Although the Wright R-3350 Duplex-Cyclone radial engines later became a trustworthy workhorse in large piston-engined aircraft, early models were beset with dangerous reliability problems. This problem was not fully cured until the aircraft was fitted with the more powerful Pratt & Whitney R-4360 "Wasp Major" in the B-29D/B-50 program, which arrived too late for World War II. Interim measures included cuffs placed on propeller blades to divert a greater flow of cooling air into the intakes which had baffles installed to direct a stream of air onto the exhaust valves. Oil flow to the valves was also increased, asbestos baffles installed around rubber push rod fittings to prevent oil loss, thorough pre-flight inspections made to detect unseated valves, and frequent replacement of the uppermost five cylinders (every 25 hours of engine time) and the entire engines (every 75 hours).[N 1][20][23]
Pilots, including the present day pilots of the Commemorative Air Force’s Fifi, the last remaining flying B-29, describe flight after takeoff as being an urgent struggle for airspeed (generally, flight after takeoff should consist of striving for altitude). Radial engines need airflow to keep them cool, and failure to get up to speed as soon as possible could result in an engine failure and risk of fire. One useful technique was to check the magnetos while already on takeoff roll rather than during a conventional static engine-runup before takeoff.[23]
I think it is fair to say that with the exception of jet fighter development at the time, the B-29 was the most sophisticated aircraft being produced in it's day, and I find it frankly amazing that they produced as many as they did (3970 aircraft) in such a short amount of time (3 years - '43 to '46).
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