97 et al
Here, entirely unedited, are pages from 131 to 136 of a document that I recalled covering B-29 operations during the transition from high altitude precision bombing to low altitude area incendiary saturation and back to medium-low precision bombing. Some of my statements and conclusions appear to be endorsed by quotes from LeMay, but of course he may be wrong.
<<180 Degrees Out: The Change in U.S. Strategic Bombing Applications, 1935-1955
By C2008
John M. Curatola B.A. University of Nebraska, 1987
M.A. George Mason University, 2001
M.M.A.S. U.S. Army Command and General Staff College, 2002
Submitted to the Department of History and the Faculty of the Graduate School of the University of Kansas
In partial fulfillment of the requirements for the degree of Doctor in Philosophy
Date defended: October 21, 2008
The number of problems that the B-29 experienced took years to correct and the Air Force was still modifying the plane when withdrawn from service in the late 1950s.126 As for the R-3350 itself, it eventually became a reliable design and was eventually utilized on the Douglas AD-1 Skyraider attack aircraft and Lockheed Constellation airliner.127 The first operational B-29 raid occurred against the Makasan Rail yard in Bangkok, Thailand in June 1944.128 Despite the promise of the design, this raid yielded disappointing results. Out of the one hundred B-29s launched for the mission, only seventy-six returned to their home station having dropped their bombs.129 Eighteen had to turn back due to mechanical failures and six others had to ditch or land at alternate airfields.130 During the first XXI Bomber Command mission against Japan on November 24, 1944, twenty-six out of the one hundred and eleven aircraft launched were forced to turn back or abort enroute due to mechanical difficulties.131 Natural phenomenon accounted for many aborts as the temperature differential between the tropical conditions on the ground coupled with the freezing temperatures at altitude caused considerable problems for both the airframe and aircrew.132 During these early operations the number of B-29s bombing the primary targets declined as crews either bombed secondary targets or salvoed their bombs harmlessly.133 Most of the aircraft losses during the first B-29 missions were due to mechanical failures as the long climb to thirty thousand feet stressed the R-3350 engine.134 After studying B-29 performance, LeMay decided that he needed to bring 132 the bombing formations down to lower altitudes where the engines and other equipment would not be under such constant strain.135 By lowering B-29 cruising and bombing altitudes, the stress on engines was significantly reduced. This reduction in stress on the engine lowered operating temperatures of the cylinders that increased aircraft operational availability. The long strenuous climb to high bombing altitudes and the fuel weight associated the climb was reduced when B-29 aircrew lowered their operating altitudes from thirty thousand to ten thousand feet. Through his observation of operational missions LeMay concluded that: With the overheating engines, it began to seem that this high altitude stuff was strictly for the birds. The airplanes had been breaking down. There are something like 55,000 different parts in a B-29; and frequently it seemed that maybe 50,000 of them were all going wrong at once. I felt that the majority of our losses were due more to our own mechanical problems than they were to the Japanese defensive system. [The] Main thing to do, it seemed, was to get them [the B-29s] down in altitude. Then we’d get a lot more hours service out of each engine.136 After making mission profile changes, LeMay found that 91 percent of all B-29s bombed their primary targets instead of the abysmal 36 percent from previous missions.137 Because of the reduction in altitude, maintenance “down time” dropped and more bombers became available to conduct bombing raids. Since the engines avoided the stress of climbing to thirty thousand feet, the number of mechanical failures dropped and aircraft availability rose. During the March raids, aircraft availability climbed appreciably from 59 to 83 percent.138 Additionally, the decision to lower bombing altitudes also went hand-in-glove with the desire to avoid bombing through the difficult Japanese weather while also evading the excessive winds of the 133 jet stream. As well, this drop in operating altitudes was to yield a third and more deadly benefit for LeMay and the 20th Air Force. In addition to the heat, fire, and valve problems, the R-3350 also did not produce the power necessary to fly the new bomber and its advertised payloads. Since aircraft performance is dependent upon density altitude (the amount of air molecules in a given body of air), the hot weather combined with the weight of the B- 29 had severe consequences for B-29 aircrew. During CBI operations in October 1944, LeMay wrote to Arnold, and stated: To a large extent our bomb load is limited by gross take-off load. This is in turn influenced by operating technique, runways, high free air temperature and power available. The take-off is a very serious problem with the B-29, and is the high point of any flight. All crews, in discussing a mission, invariably talk about their take-off and not about flak, fighters or other enemy opposition. Even partial power loss from one engine almost invariably results in a crash from which there are very few survivors.139 Later in the letter LeMay further stated: The B-29 airplane is capable of considerable higher performance than the R- 3350 engine now installed will permit, as the maximum gross weight is limited by power available for take-off and climb. Until more power is available, we cannot fully capitalize on the capabilities of the airplane.140 By lowering bombing altitudes, LeMay allowed for increased bomber payloads. Because LeMay was anxious to increase aircraft sortie rates and try to work around the uncooperative Japanese weather, the lowering of cruise and bombing altitudes allowed the B-29 to carry a larger bomb load. According to LeMay: One of the main advantages in going down to less than 10,000 feet over the target was the increased bomb load. We could increase the bomb load of each plane from about two and one-half tons to 10 tons. This was possible because each individual attack required no assembly into formation over the base at the start of the mission, and because aircraft would go directly from base to 134 target and return, saving tremendous amounts of gasoline. Better weather would be encountered at lower altitudes and the heavy gas-consuming winds of high altitudes would be avoided. The weight of extra crew members, armament, and ammunition would go into bombs.141 The amount of fuel a B-29 used to climb to bombing altitude, given a specified weight, could use as much as twelve hundred gallons (weighing seven thousand two hundred pounds) when climbing at a gross weight of one hundred and thirty thousand pounds. In order to compensate for this fuel weight, power settings had to be increased for the long climb to altitude, creating an additional strain on an engine.142 When bombing by prescribed USAAF methods, the weight of bombs carried in the B- 29 had to be reduced from ten to three tons because of the fuel needed to climb to and fly at higher altitudes.143 An average B-29 used seven thousand gallons of gasoline on a mission. The pragmatic LeMay surmised that using over twenty-one tons of fuel to drop three tons of bombs did not make sense.144 He determined that by lowering altitudes, and negating the requirement to carry the fuel used for climbing to high altitude, bomb loads increased significantly.145 The B-29’s poor high altitude performance necessitated the lowering of bombing altitudes and this is turn facilitated higher aircraft reliability figures while simultaneously allowing larger payloads. In this regard mass became an important aspect of the American bombing effort. Increased number of B-29s equated to more destructive and deadly raids. American industry built bombers and fighters at a rate with which the Axis powers could not cope. This massive air armada overwhelmed axis air defenses. Toward the end of the war in both the Pacific theater as well in European, mass itself became an important aspect of the strategic campaign. As more 135 planes and aircrew became available, more bombs were dropped. This same application of mass became ever more important in American strategic methodologies in the nuclear atomic age. The technical problems of the R-3350 engine and the B-29 mandated that mission profiles be adjusted to utilize lower altitudes. This change in profiles in turn facilitated the hauling of larger and more destructive bomb loads of M69 incendiaries. By summer 1945 much of the Japanese homeland became a vast wasteland. Certainly, one of the primary reasons for this was the substantial rise in the number of B-29s over the islands and the greatly increased bomb tonnage dropped on each mission. With lower altitudes, LeMay was able to raise the 2.6-ton load of each aircraft to 7.4 and keep more aircraft in the air.146 The ability to carry more bomb tonnage meant greater destructiveness. Despite the fact that the B-29 was designed for high altitude precision bombing, the state of the 20th Air Force and the imperfect design of the airframe required a modification to bombing operations. The USSBS noted that: The preceding 9 months had seen the B-29 committed in general to the doctrine of very high altitude precision bombing. Designed specifically for this type of operation, it was logical and mandatory that the doctrine be thoroughly tried before it was modified. Many factors militated against the achievement of this objective, among the foremost of which were insurmountable weather obstacles, strain imposed on equipment by high altitude operation, insufficient force, low sortie rate, and low bomb loads.147 The Survey further noted: By lowering the bombing altitude, the effectiveness of each B-29 was increased tremendously. Bomb loads more than doubled; using radar bombing methods the weather ceased to be a serious factor; the number of aircraft dropping on the primary target soared from 58 to 92 per cent . . . decreasing bombing altitude meant less operating strain which added up to more sorties per air craft.”>>
Sorry for the lengthy excerpt, but it was presented without editing. The numbers, of course, reference footnotes. Anticipating some quibbling, the term "insurmountable weather obstacles" refers to cloud cover and fog as well as winds. When I have more time, I'll paste the web address so you all can read all 200+ pages including footnotes and more of LeMay's observations about where the "bugs" resided in the '29.
Dynasoar