Fire Bombing of Tokyo
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The Offset Aiming Point (AP) that allowed certain pathfinder B-29s equipped with APQ-23 radar equipment to put in the distance and azimuth from a radar visible point and a target point into the radar computer. This was the great-granddaddy of RNAV that allows VORs and airways to be electronically offset to provide better traffic separation between aircraft. MPI means mean point of impact. (Average distance from intended impact point.)
During WWII the MPI of radar bombardment was three miles. The MPI of all the bombs dropped in WWII was close to five miles. Today the MPI is ten-feet or less.
intervalometer was a bomb release device that spaced the release of the bombs so
as to increase the spread of the fire.
Look at #4 No ammunition will be carried. This was a very very carefully considered order by Le May Who evaluated the benefit/risk factors and proceeded according to plan. The night fighting capability of the Japanese was minimal. The altitudes selected were above the smaller caliber antiaircraft weapons and below the most effective ranges of the higher powered weapons. Once overseas the 20mm cannon used as a tail gun was immediately removed since it was not worth its weight.
The weight savings increased the effective bomb load and fuel safety margins. Flying and bombing at lower altitudes greatly improved the circular error factors (MPI) often involved in previous drops from the 20/30 thousands of feet.
Not flying in formation reduced flight stress, fuel consumption and the homing beacon aircraft would improve ease of navigation. Le May decided the reduction in risks and improvement in bomb load and accuracy were worth it. The crews were unhappy with the risks but essentially obeyed and flew as ordered. There were exceptions.
A little known aspect it the B-29 bombing procedure was the turns required prior to the straight line used to the target and the turn after "bombs away". The usual speed during the bombing procedure was 210 miles per hour. If the standard rate turns were used at both ends of the procedure it means that the needle of the turn and bank indicator would be under the 'dog house' giving a three degrees per second turn.
The actual process of plotting this turn at the intersection of two straight lines would require determining the radius of the turn based on aircraft speed. It didn't take navigators long to discover a short-cut. All you had to do was to draw the straight lines of each side of the turn and place a Lincoln-head penny in the corner so as the arc of the penny's circumference would provide a smooth transition from entry to departure of the turn.
You can do this yourself just by drawing two intersecting lines and put a penny where it gives a smooth arc between the two lines. The arc entry is the beginning of the required turn and the arc exit is resumption of level flight. Good enough for government work.
This particular mission was the beginning of a large series of missions devoted to the use of incendiary bombs. It soon became apparent that some bombs were more effective than others. In the next five months of the war critical shortages in preferred bombs resulted in the use of less effective bombs and less effective results.
At the same time of the fire bombing emphasis by most of the B-29s there were two significant programs in progress that are seldom mentioned. There were B-29s who dropped mines that had different kinds of activation. Some mines would count ships before exploding. Some would become active only after a period of time. This mining was also a part of other types of aircraft both army and navy. By the end of the war japan had only four aircraft carriers while the U.S. Navy had close to a hundred.
Another B-29 group was equipped with the APN-7 'Eagle. This a a precision bombing radar that specialized in bombing refineries and oil distribution facilities. Japan never developed the synthetic oil production as had Germany. Many naval missions by the Japanese carried only enough fuel for a one-way trip.
The bomb selection began with use of bombs that would serve as markers or aiming points for planes following. The very best crews served as 'pathfinders' and their bombs often had colored explosives. Each aircraft bombed individually with as much precision as possible to ignite the areas at the edges of existing fire.
The direction of the attack is based on forecast winds, geography of the area as divided by terrain and bodies of water.
Since Iwo Jima was still Japanese with three airfields at this time, the area had to be avoided as much as practical. P-51 fighters were coming more available with capability to interdict Japanese aircraft on Iwo as well as on the home islands of Japan. The 1400 mile flight from the Marianas to Japan and return required that fuel calculations for adequate reserves be as conservative as possible. The more fuel carried caused a reduction in bomb load.
The loss of a certain percentage of aircraft was a given for every mission. The plan was to keep the loss ratio at a level to permit a sustainable campaign. I have figured my bomb groups losses in known combat and anti-aircraft losses at five-percent. Greatest area of loss was called 'operational' This is a mix of weather, mechanical failure, pilot error and unknown took about thirty percent of the aircraft over a three year period. The loss of an aircraft was not necessarily a total loss of the eleven man crew. Nearly 70 percent of the 129 aircraft assigned to my 468th Bomb group survived the war.
In the beginning of its combat life the B-29 had several teething problems. The B-29 was the most complex aircraft of its time. It had more wiring, pressurization, electronics, weapon and engine problems than any previous aircraft. It had gun turrets that were remotely aimed and controlled by different gunners as targets presented themselves.
The wiring problems usually had to do with the plug connections into electrical boxes. Vibration, corrosion and moisture were always sources of difficulty. A common maintenance solution for plug problems was to kick the problem box. The higher altitudes of B-29 operation caused arcing of connections and failure of radio tubes.
Pressurization areas existed in the front and back of the bomb bays as well as for the tail gunner. A 20-inch crawl tube existed over the top of the bomb bay to allow some movement between areas. A 6x9 tube went to the tail gunner. Pressurization greatly added to the en route comfort of the crews. Loss of pressure due to a plexi-glass window blowing out was an always present hazard.
B-29s had more electronics that any previous aircraft. The fire control system for the machine guns was armor plated. It allowed the gunners to move their sights and thereby move the turret and guns. You set the sight primarily by knowing the wing span of the aircraft you were shooting at. All factors involved beyond that was done by computer. A very primitive computer by today's standard.
The engines of the B-29 were designed ahead of their time and pilots and engineers had to play catch up. Cooling flaps were large. Pilots had to learn that wide open engine flaps were not as efficient as partially open flaps flown at higher speeds. I believe the B-29 had the first engine with hollow sodium filled exhaust valves to improve cooling.
For the better part of a year the average B-29 in India was lucky to get 50 hours on an engine before needing a change. Taking off from India and climbing most of the 600 miles to China was very hard on the engines. By the end of the war the average was approaching 800 hours.
About one aircraft per squadron would carry Radar Counter Measures equipment and an officer specialist who would search and detect frequencies that could be jammed electronically or by dropping aluminum foil strips called chaff or window depending on length. These strips tended to produce multiple targets to confuse Japanese radar controlled antiaircraft guns.
Prior to the capture of Iwo Jima numerous surface ships, submarines and Dumbo aircraft stationed along the arrival and departure routes in case an damaged aircraft had to ditch into the ocean. Dumbo aircraft could carry and drop a rescue boat or raft. The taking of Iwo saved over 25,000 Air Force lives. One of my 468th Bomb Group B-29s was the first to make an emergency landing on Iwo.
The end of this page presents a summary of the mission. Prior to the capture of the Marianas of Guam, Saipan and Tinian B-29s were attacking Japan on an average of every three weeks via China. By April the 20th Air Force was able to attack with over 300 B-29s out of the Marianas. Three months later there were over 500 and by 1946 the available bombers would have numbered 2000.
As the end of the war the B-29s were destroying an average of over 70-percent of a large Japanese city daily.
At various times near the end of the war we were running out of the type of bombs we found most effective. At the end of the war we had used all the atomic bombs (two) available in the Pacific.
At the end of the war all specialists at the 58th Bomb Wing Training Center on Tinian posed for this picture. Over half of them were operators of the eight Link Trainers in the Quonset out of sight to the left. At the very far right is just a small corner of the shed roof covering the Diesel powered electric system to run the eight Links, Lights, twelve LORANs and three Supersonic trainers. I have yet to meet any of these men post war.
photo is taken inside a large hangar type building where a
large three dimensional relief map of the Nagasaki region of Japan is represented. I have been unable to relate it to the chart. This was done somewhere in Kansas. There were overhead cranes that could make practice simulated visual bombing missions over such pictorials.
This is the Eddie Allen in the ramp area of its base near Calcutta, India. The tents in the background are British with a double layered canvas roof. Much cooler than the single layer U.S. tents which also leaked in rain if touched from the inside.. The plane was named after Boeing's chief test pilot who died while trying to determine the reasons for so many engine fires on B-29s. He was testing the third production B-29 and crashed in an industrial area of Seattle. Note that there are only three bombs under the window and four camels for hump flights..
nose wheel is covered to protect the rubber from sun damage. The fact that
there were only two machine guns in the front top turret shows the plane to be
an older model. The seven camels are for round trips from India to China. The six bombs are for bombing missions. I would guess that the pictures
are close to two months apart.
War in the China, Burma, India (CBI) was not very efficient. Before a bombing raid could be launched from China against Japan three round trips over the 'Hump' had to be flown to get the required bomb and fuel supplies for the raid. Far more planes and crew were lost on the support flights than in combat.