B-29 Modifications

[manta22]

Jaunita;

Paul Tibbits went into great detail about the differences in his B29s but that phone call was almost 50 years ago so I don't remember much. I should have recorded that phone call.

 

[SaparotRob]

So the B-29 evolves from the pinnacle of the "armed bomber will get through" theory to the Mosquito style "fly high, fly fast" plan.
Kind of settles that pre war debate.

 

[SaparotRob]

Yes, I know that the bulk of B-29 missions in WW2 were at relatively low altitude. I think the Korean conflict had it up high.

 

[chipieal]

I heard about "Silverplate" but never knew what exactly was involved. Can anyone briefly describe?
Gary

Silver plate was the password that General Groves was given in developing the Atomic Bomb. Anything he needed he just used Silver plate. I am assuming that since the B - 29 was the delivery vehicle, it made sense that Silver plate may have been used in this context

 

[GrauGeist]

Yes, I know that the bulk of B-29 missions in WW2 were at relatively low altitude. I think the Korean conflict had it up high.

It was intended to conduct higher altitude bombing missions but the Jet Stream over Japan made that impossible, so lower altitude missions were conducted instead.
The bombing missions conducted at higher altitudes in Korea were along the lines of the B-29's original design.

 

[SaparotRob]

Wasn't the slipstream one of the reasons why daylight bombing wasn't so effective in Europe?

 

[GrauGeist]

Wasn't the slipstream one of the reasons why daylight bombing wasn't so effective in Europe?

No, the prevailing high altitude currents over Europe changed seasonally and were not as critical as the Jet Stream over Japan.

The high altitude bombing accuracy over Europe is an entirely different matter and has been discussed in great length in several threads in the forums here.

 

[soaringtractor]

There were operational mods done to late production B-29 that were more role related too.

There were mods done to the cowlings to allow more airflow, the cause of the engine fires, and to the supercharger/turbochargers on the engines !!! the silverplate planes were built with the mods to carry the atomic bombs !!! Some B29s had most of the defensive guns removed especially for the low level fire bombingd, more bombs carried and less jap fighters around and more P51's to defend !!!

 

[soaringtractor]

Wasn't the slipstream one of the reasons why daylight bombing wasn't so effective in Europe?

Did you mean Jet stream ??? The winds at altitude that raised hell with accuracy of bombing ???? The winds at various altitudes blow in different directions making any bombing run sketchy !!!! The bomb sight made no difference in accuracy, only IF there was NO wind at all and that is rare !!!! Why low level bombing was employed !!!

 

[soaringtractor]

No, the prevailing high altitude currents over Europe changed seasonally and were not as critical as the Jet Stream over Japan.

The high altitude bombing accuracy over Europe is an entirely different matter and has been discussed in great length in several threads in the forums here.

The winds at altitude still played hell with bombing accuracy in Europe !!

 

[BobB]

There were many mods made during WWII. People who worked for Bell-Atlanta told me that an airplane would come off the production line in Marietta and immediately be flown to Wichita for mod work at the same time that airplanes were being flown into Marietta from other plants for mod work that was only done at Marietta. It all sounds crazy but it worked.

 

[SaparotRob]

Did you mean Jet stream ??? The winds at altitude that raised hell with accuracy of bombing ???? The winds at various altitudes blow in different directions making any bombing run sketchy !!!! The bomb sight made no difference in accuracy, only IF there was NO wind at all and that is rare !!!! Why low level bombing was employed !!!

Yup, meant jet stream. That's what happens when I stay up past my bedtime.

 

[FLYBOYJ]

There were mods done to the cowlings to allow more airflow, the cause of the engine fires, and to the supercharger/turbochargers on the engines !!! the silverplate planes were built with the mods to carry the atomic bombs !!! Some B29s had most of the defensive guns removed especially for the low level fire bombingd, more bombs carried and less jap fighters around and more P51's to defend !!!

All mentioed earlier in this thread including Silverplate

 

[GrauGeist]

The winds at altitude still played hell with bombing accuracy in Europe !!

Not like over the home islands of Japan where the Jet Stream typically exists at 30 to 39 thousand feet ASL and travels westerly at 110mph.

And the B-29s involved in the fire-bombing missions had all MGs removed but the tail-gun position in order to reduce fuel consumption and increase speed. They were not escorted as the missions were flown from either China or later from the Marianas and the Japanese did not have an effective night-fighter at the time.

 

[Zipper730]

Some of the B-29's had most of their guns removed for the nighttime fire raids.

From what I recall, the turrets remained, but the guns and ammo were removed with the exception of the tail-gun. If not all the time, sometimes the crews were retained to operate as lookouts.

For these raids, I'm curious if they removed the gun-computer, or kept that. From what I remember, 300 B-29's were built without the gun-computer installed.

"Silverplate" was the delivery program for the Atom bombs destined for Japan. . . . The size and weight of the bombs (there were four - one was tested state-side and two if the three remaining were deployed on Japan) dictated airframe modifications as well as additional instrumentation installed on all the bombers in the B-29 composite group.

What instrumentation was installed?

It was intended to conduct higher altitude bombing missions but the Jet Stream over Japan made that impossible, so lower altitude missions were conducted instead.

I thought the fact that the amount of energy to climb to high altitude made it more practical to cruise lower. From what I remember, the raids carried out over Tokyo were done at something like 5000-10000' or less. What typical altitudes were seen during daytime raids after March, 1945?

The B-29B was a lighter version, with improved performance. 311 were built.

So, those are the versions without the gun-computer?

Six B-29s were fitted with R-3350-CA-2 fuel injection engines and the revised "Andy Gump" nacelles that were intended for late production B-29As in a program to service test these new engine installations.

I guess the implementation of the new nacelles was due to the end of the war?

The single bomb bay was only on the initial test Silverplate B-29 - all of the operational ones had the standard bomb bay configuration.

Do you have any pictures of that one?

There were mods done to the cowlings to allow more airflow, the cause of the engine fires, and to the supercharger/turbochargers on the engines

I assume they loosened the cowling up? As for the turbochargers, provided I didn't misunderstand, what modifications were made there?

 

[GrauGeist]

What instrumentation was installed?

All the B-29s in the 509th composite group were able to deliver the A-bomb or monitor the drop. When Enola Gay made her run, she was accompanied by other B-29s who were acting as monitors.
When Bock's Car made their drop, Enola Gay was one of the monitors.
The instruments included weather gathering, radiation monitoring, additional radio equipment and so on.
Also, each Silverplate B-29 had an additional crew station up in the cockpit for monitoring the bomb while in the bomb bay as well as monitoring the release and detonation, called the "weaponeer station".

I thought the fact that the amount of energy to climb to high altitude made it more practical to cruise lower. From what I remember, the raids carried out over Tokyo were done at something like 5000-10000' or less. What typical altitudes were seen during daytime raids after March, 1945?

The effort to get to altitude is rewarded by more efficient cruise at those higher altitudes.
The later daytime raids were at varying altitudes (well below 30,000 feet) but the fire-bombing raids were made at roughly 5,000 feet.

 

[MIflyer]

When I was at Tinker AFB in the 70's I talked to some people there who had actually worked on the 509th BG aircraft.

It seems that it was normal procedure for B-29's coming off the production line at Wichita to go straight to Tinker Field for modifications and other tasks. One common task was to remove the fuel flow meters from the aircraft and calibrate them. But in the case of the aircraft going to the 509 BG they insisted that the fuel flow meters be calibrated while in the aircraft. This was much more difficult to accomplish but gave better accuracy.

The book "Friendly Monster" describes the work a B-29 crew had to do to get their aircraft all tuned up and everything calibrated to make it fly properly. A B-29 straight out of the factory needed a lot of work and the crew had to fly it many hours to figure out what the airplane liked and what adjustments were required.

I read of one B-29 that had the after fuselage made by a different company than the forward fuselage. I think the two companies involved were Bell and Martin. They found the aft fuselage was a slightly larger diameter than the forward fuselage and the aft section had to be crimped down to fit the forward part. And for some reason that B-29 was the fastest one in the squadron.

 

[Zipper730]

All the B-29s in the 509th composite group were able to deliver the A-bomb or monitor the drop. When Enola Gay made her run, she was accompanied by other B-29s who were acting as monitors.
When Bock's Car made their drop, Enola Gay was one of the monitors.
The instruments included weather gathering, radiation monitoring, additional radio equipment and so on.
Also, each Silverplate B-29 had an additional crew station up in the cockpit for monitoring the bomb while in the bomb bay as well as monitoring the release and detonation, called the "weaponeer station".

Fascinating

The effort to get to altitude is rewarded by more efficient cruise at those higher altitudes.

Theoretically: In practice, it appears to be affected by rate of climb and available range. If I recall correctly, the B-29 would break even by flying at 35000' if it could only fly 5500 miles (something that might have been beyond the capability of the plane with any payload). Though some sources list climb-rate figures that compare with the B-17, I'm not sure if that covered the fact that climb-speed was more limited due to engine cooling over other aircraft, and I'm not sure what weight it applied at.

The later daytime raids were at varying altitudes (well below 30,000 feet) but the fire-bombing raids were made at roughly 5,000 feet.

Did they fly 5000' from Tinian to Tokyo and back? Or did they cruise higher?

I remember hearing after the raids on Tokyo, they sometimes flew day raids at altitude, but lower than earlier flights, and I'm not sure what altitudes were typically employed.

 

[MIflyer]

The B-29's used for monitoring the atomic attacks dropped instrumented packages that transmitted data back. Just after the Hiroshima mission a group of students found one of the instrumentation packages and opened it. Inside they found a letter addressed to Japan's top physicist, explaining that the US had developed the atomic bomb. They read the letter and burst into tears, knowing that the war was lost.

When he heard of the attack the leader of the A6M design team, Jiro Horikoshi, called that same physicist and asked him what he thought it could be. The Phd replied, "We will have to find out more but it sounds like an atomic bomb." Horikoshi was thunderstruck. Before WWII he and other top experts gathered to discuss what possible weapons the USA could come up with. The atomic bomb was brought up but they concluded that was at least 100 years away. Imagine finding out suddenly that your adversary was 100 years more advanced than you had thought.

 

[Zipper730]

This is one source where I heard differences in speed: 360 knots @ 30000' which calculates to 414 mph. That said, there could be errors here, as the ability to carry 3400 nm with 20000 pounds of bombs seems to be erroneous unless they made some amazing changes to the plane.