B-36 - Why a Pusher??

[swampyankee]

The YB-49 was a YB-35 modified to install j35 engines so there were no YB-49s with R-4369 engines. The YB-47, basically a contemporary to the YB-49, also had J-35 engines and the B-47 later received the J-47, so, I think the J-47 was not ready for the YB-49 and I suspect there was no eagerness to upgrade the YB-49.

There is no doubt that the aircraft with the most potential for handling the future mission of enemy penetration was the B-49 due to its inherent stealthiness. The B-36 was obsolete when it became operational, only one year before the MiG-15 entered service and we know what it did to the B-29 force in Korea.

Performance comparisons using corrected NACA data (as stated in "Goodby Beautiful Wing" by Terrence O'Neill).

B-35 - B36
Empty wt. lbs 89,000 - 133,800
Wt. Cruise 135,000 - 212,000
Wt. Gross 180, 000* - 287,000 * weight reduced from max due to AF refusal to test landing gear
wt. max T/O 207,000 - 311,000
Miles-to-target 5,100 -3,600
Speed Combat (mph) 405 - 331
Design Ceiling ft. 49,000 - 40,000

Note: these B-35 numbers are using NACA corrections to previous flight test estimates using N9M reduced scale test aircraft. B-35 had the potential of performing the same mission as the B-36 at 60% of the weight.

Note also: That the B-49 radar cross section could have easily been improved significantly by moving the engine inlets to top of wing ala B-2. No need to make sophisticated ducts because there would be no airborn radar platforms above it probably well into the '50s, if not later. The B-49 could be practically invisible from the front to Russian radars.

These still don't solve the various handling problems, which were (largely) due to the inherent low pitch and yaw damping of flying wings. Indeed, the yaw damping problems were likely worse on the B-49, as the pusher propellers were stabilizing as they were behind the aircraft c/g.

 

[Koopernic]

The B-36 was born during the Blitz, when the U.S. (and many others) feared Britain would not be able to hold out.

The original range minimum proposed was a combat radius shy of 5,800 miles, so the USAAF request in spring of '41 called for a max. range of 12,000 miles but after consideration of what was possible to build in a short amount of time, revised the max. range to 10,000 miles.

Even the B-19 (the result of a USAAC request for an extra long range bomber) which was nearing it's first flight, had a max. range of 5,700 miles with a bombload, roughly half of what was needed to reach Berlin and return home.

While the timing might be correct and this may have provided extra motivation I'm a very sceptical about that is the whole story about it being a response to Britain's feared military collapse. Why was the USAAF funding the Boeing XB-15 (funded in 1934, first flight 1937), Douglass XB-19 and Boeing Y1B-20 (upgraded derivative of YB-15) as well as engines such as the Allison V-3420 to power them some 6 years before?

Wikipedia gives the combat range (ie radius of action) of the B-15 as 3400 miles. That's 5500km. That's already enough to reach Berlin and back from the Labrador/Newfoundland area.

So there is something else going on here. This is a policy going back to 1934 when the XB15 was funded and really 1933 when all the organising would have gone on. The B-36 starts back in 1933/34 with the B15. It's not just Monroe doctrine.

One of the reasons I'm curious about this is that someone has altered the B-36 entry in Wikipedia to stridently point out that the B-36 originated AFTER the Me 264 bomber. Seems to me someone is pushing a narrative but they have no comprehensive knowledge of US policy in that era.

 

[GrauGeist]

The request for the ultra long range bomber is post XLRB requirements (the B-19 being the result) and was dated early spring of 1941.
The B-10/12 was from a different era, the B-15 and B-18 were from a different era and so to, was the B-19.

Most militaries saw the need for a long range bomber, the Me264 was one such type, but it was developed from an older design which originated in the 30's.
Some people have gine so far as to say the Me264 was a "copy" of the B-29...whuch is really reaching - the only thing they might have in common, is their "greenhouse" nose.

 

[Zipper730]

Agreed. In addition to is lessor range the B-49 needed pitch and yaw dampers

I didn't know the B-49 was more unstable than the B-35. If figured the addition of the tail-fins would have restored the directional stability lost by removing the propellers, extension shafts, and filleting between shaft and wing/fuselage.

The B-49 did have handling problems which, pre-digital flight control, pre-smart bomb were intractable. It also, like most flying wings, had surprisingly large runway requirements.

From what I recall, the problem with bombing accuracy were not intractable as the design met the specifications (albeit barely).

The YB-49 was a YB-35 modified to install j35 engines so there were no YB-49s with R-4369 engines.

When I wrote it, I kind of just forgot to include a section I should have about the engines being removed and J35's put in their place. Regardless, I corrected that.

The YB-47, basically a contemporary to the YB-49, also had J-35 engines and the B-47 later received the J-47, so, I think the J-47 was not ready for the YB-49 and I suspect there was no eagerness to upgrade the YB-49.

Okay, so it wasn't about a size issue?

There is no doubt that the aircraft with the most potential for handling the future mission of enemy penetration was the B-49 due to its inherent stealthiness.

Correct, plus it also would have been harder to catch because it could fly higher (as long as the engines could keep working), and it's turning performance was said to eclipse damned near anything up that high.

That said, I'm not sure what the USSR's doctrine on standing patrols were, as they had so many aircraft available compared to us, and the YB-49 would have either been natural metal finish or white for the nuclear delivery role: Either would have provided characteristics that would have made it visible.

1. NMF: Generally has some useful traits as it reflects the sky's colors, but it's also shiny so glint can sometimes be produced at ranges beyond where the plane itself can be visually seen. In Vietnam there was at least 1 MiG that was detected this way in the middle of an aerial melee.
2. White: Self explanatory, white reflects all visual wavelengths, and it's large span would be easy to spot from below.

There's also the contrails. While I don't know exactly what atmospheric conditions produce them, they can be seen quite a distance beyond where you can see a plane, and depending on the rules of engagement, the pilot would merely have to aim a the front of the contrail.

The B-36 was obsolete when it became operational, only one year before the MiG-15 entered service and we know what it did to the B-29 force in Korea.

It would have been harder than the B-29 to shoot down because it flew higher, but yeah, it would have gotten shot apart left and right.

 

[Koopernic]

I didn't know the B-49 was more unstable than the B-35. If figured the addition of the tail-fins would have restored the directional stability lost by removing the propellers, extension shafts, and filleting between shaft and wing/fuselage.

From what I recall, the problem with bombing accuracy were not intractable as the design met the specifications (albeit barely).

The effect of airflow (suction) on the B-35 tended to stop span wise flow and stabilise the aircraft. Then there was the gyroscopic effect of those 8 huge contra rotating propellers.

Note however jets (even P80 and Meteor) almost universally had a high speed snaking problem (yaw problem) and the solution was a yaw damper it seems to have just been worse on a flying wing with pitch issues to boot. The snaking problem is worse in a swept wing aircraft and tailess aircraft are usually swept wing unless using an auto stable air foil.

The German Ho 229 jet added a bat like tail that had an upward reflex thereby turning the centre section into a auto stable air foil lifting body that didn't need a tail (Flying plank aircraft exist using these aerofoils) Even that didn't solve the problem and had dynamic stability problems and the solution was to tell the pilot to apply airbrakes to stabilise the aircraft when firing guns.

The solution to this was probably just yaw and pitch dampers. In the second world war the German Henschel Hs 129 ground attack aircraft had a yaw instability problem caused by the inertia of the very heavy armour. The solution was a yaw damper that utilised a rate gyro. If the gyro sensed a yaw rate above a certain level an electrical contact was made that progressively drove rudder trim in the opposite direction till the yaw stopped. There was probably a feed forward sensor in the rudder peddles so that genuine yaw commands weren't countered. The German that developed this was employed at Farnborough and the RAE used this research to develop a yaw damper for the Meteor F.4. They were very useful in jets who had the same concentration of mass around the middle rather than the forward of the aircraft and so had dynamic stability issues.

US engineering and autopilot manufacturers would have had no problem with all of this but apparently it took a few seconds for the autopilot to stabilise the B-49. The reality is that all the swept wing jets needed dampers for at least yaw, the YB-49 just needed it more.

 

[yosimitesam]

One of the reasons the Soviets didn't replicate the Tsar Bomba was because it was too risky for the bomber. I don't know how powerful was the Mk17, but it is, surprisingly, possible for a bomb to be too powerful. The Soviets decided that line was crossed with their Tsar Bomba. I think the USAF (perhaps surprisingly) figured it out before building one.

Most larger TN weapons (>.5MT) probably used parachutes (remember the film on the Tsar bomb?) to delay the fall and allow enough "haul ass" time to survive the shock wave. Still, I wouldn't chance it. I saw a TV documentary (whose title I cannot remember) back in the 1990's where a bomb physicist stated, more or less, that once you get to around 50MT or so, the law of diminishing returns kicks in big. Due to the finite depth of the atomosphere the explosive force starts to go upward more and more and results in a lot of the energy being used to just 'blow a temporary hole' in the atmosphere and venting upward toward space, like a shallow torpedo hit on ship, but much larger. Don't know if this is true but it sounded reasonable, at the time. Anyone see that documentary, besides me?

 

[GrauGeist]

Anyone see that documentary, besides me?

It sounds very familiar - I believe it may have been a Nova episode on PBS.

 

[yosimitesam]

While the timing might be correct and this may have provided extra motivation I'm a very sceptical about that is the whole story about it being a response to Britain's feared military collapse. Why was the USAAF funding the Boeing XB-15 (funded in 1934, first flight 1937), Douglass XB-19 and Boeing Y1B-20 (upgraded derivative of YB-15) as well as engines such as the Allison V-3420 to power them some 6 years before?

Wikipedia gives the combat range (ie radius of action) of the B-15 as 3400 miles. That's 5500km. That's already enough to reach Berlin and back from the Labrador/Newfoundland area.

So there is something else going on here. This is a policy going back to 1934 when the XB15 was funded and really 1933 when all the organising would have gone on. The B-36 starts back in 1933/34 with the B15. It's not just Monroe doctrine.

One of the reasons I'm curious about this is that someone has altered the B-36 entry in Wikipedia to stridently point out that the B-36 originated AFTER the Me 264 bomber. Seems to me someone is pushing a narrative but they have no comprehensive knowledge of US policy in that era.

There is one aircraft that was built (only 1 prototype) during that period solely because it appeared the German Uboats might make troup crossing by ship to England too dangerous and even making cargo crossings problematic: The H-4 Hercules, a.k.a 'The Spruce Goose'. This was started in 1942 when things were looking long-term bleak in the Atlantic. So there was fear that even if Britain didn't fall, the Germans would stiill 'cut them off' from the Western Hemisphere and their Dominions.

'Depend upon it, sir, when a man knows he is to be hanged in a fortnight, it concentrates his mind wonderfully.' -- Samuel Johnson

 

[Thumpalumpacus]

In tech school at Chanute AFB, I had a picnic with a galpal on nice Saturday afternoon. Ms A was in the meteorology school on base. We sat under the wing of the static-display B-36 they had there and enjoyed a great lunch.

The wings on that goddamned thing were huge, and I write this as someone who later served on a B-52 base. The only things bigger were the hallways in Grissom Hall, which we waxed twice in my eleven weeks on station.