# B-36 - Why a Pusher??



## Piper106 (Apr 28, 2012)

Does anyone have any data or links to technical papers on why the B-36 was built with pusher engines?? 

I assume that the Convair engineers (and the Northrup engineers working on the B-35) calculated that the drag reduction by not having the propeller airflow over the wing more than made-up for the losses resulting from the propeller having to work in the wake from the wing, but was the difference significant?? 

I notice that some other 'clean sheet of paper' very long range aircraft (Me 264, and the Nakajima G10N) were conventional tractor designs, so I assume the difference in efficiency between tractor and pusher was pretty close, but that is just a guess. 

Comments??

Piper106

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## iron man (Apr 28, 2012)

Piper106 said:


> Does anyone have any data or links to technical papers on why the B-36 was built with pusher engines??
> 
> I assume that the Convair engineers (and the Northrup engineers working on the B-35) calculated that the drag reduction by not having the propeller airflow over the wing more than made-up for the losses resulting from the propeller having to work in the wake from the wing, but was the difference significant??
> 
> ...



First off...The "Peacemaker" (while impressive, within it's own context) was a massive waste of money.
The entire program was funded on an "we're already too far into this to walk away" basis.
Aerodynamicallly? Pushers had their merits.
Realistically? The _power plants themselves _were a major PITA for those who had to deal with them...this is well documented.
Forwards or backwards, the_ engine_was a nightmare to deal with.

A "Bridge to Far", IMO.
'
Not that the B-47 was that much of a improvement either

Interesting times indeed.

There are tons of "B-36" resources on the net...do a little reading. You might find specifics that relate to the question you're asking. I've read boatloads of material on the B-36, yet I've never seen this particular issue addressed.

Perhaps look for NACA reports, with regards to this line of inquiry? 

Love the "Magnesium Overcast"...what a STATEMENT. 

It now seems silly how we were "duck and covering", when the USSR were actually _so far behind the curve_, as to make the whole thing kind of laughable (in hindsight) ...


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## FLYBOYJ (Apr 29, 2012)

iron man said:


> First off...The "Peacemaker" (while impressive, within it's own context) was a massive waste of money.
> The entire program was funded on an "we're already too far into this to walk away" basis.
> Aerodynamicallly? Pushers had their merits.
> Realistically? The _power plants themselves _were a major PITA for those who had to deal with them...this is well documented.
> ...



Agree to a point but disagree about the B-47 - entered service in 51', phased out as a bomber till 65 and finally retired in 77, it flew like a fighter and for a while scared the crap out of the Ruskies. It was a good plane and served well Compared to the B-36 was a maintenance godsend

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## Siegfried (Apr 29, 2012)

A B36 must have had 28 x 2 x 6 = 168 spark plugs. Essentially ubmaintainable. It's no surprise that commercial operators avoided this engine.


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## tyrodtom (Apr 29, 2012)

Siegfried, that's a fail on arithmetic. 28x2x6=336.
The Wasp Major R-4360 used in the B-36 was used by plenty of other aircraft so it was maintainable. The B-50, C-97, C-119, C-124, and about 20 other well known aircraft used the same engine, but not as a pusher.

The B-36 was the only aircraft in the American arsenal that could carry the early largest H-bombs until the B-52 came along.

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## woljags (Apr 29, 2012)

i always understood that the B47 was for a while faster than the Russian fighters of the time it entered service or is that incorrect


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## JoeB (Apr 29, 2012)

Piper106 said:


> Does anyone have any data or links to technical papers on why the B-36 was built with pusher engines??
> 
> I assume that the Convair engineers (and the Northrup engineers working on the B-35) calculated that the drag reduction by not having the propeller airflow over the wing more than made-up for the losses resulting from the propeller having to work in the wake from the wing, but was the difference significant??


I haven't ever seen quantitative papers or books about this design decision, but qualitatively speaking it's more or less as you said. The B-36 specification heavily emphasized long range and thus cruise performance. As a rule a pusher configuration will be more efficient in cruise, subject to considerations like rotation on take off, which might force the pusher prop to be smaller diameter to clear the ground on rotation. However in B-36 case they found that pusher was definitely more efficient in cruise. Some early concepts leading to the B-36, and some wind tunnel models even, had push-pull nacelles or conventional tractor nacelles. but the designers believed pusher would win, and at least at the state of the art in wind tunnel testing at the time the tests proved them right.

The disadvantage of pusher is not so much that wing downwash will actually make it less efficient net, but the vibration considerations of uneven flow, not only wing downwash in cruise, but also the engine exhaust stream flowing through the prop. These were issues with the B-36 which had flight restrictions related to prop vibration. Also, besides the cruise configuration, the wing interaction issues become more serious with flaps down. Note in photo's of B-36's even fully extended flaps are continued right in front of the props. And also in low speed flight, the tractor prop helps generate lift which the pusher doens't to the same degree. And then there's more potential for FOD from stuff thrown into the props by the main gear; again see B-36 photo's: the main gear legs are within the radius of the inboard props.

Re: B-47, can't see how it could be compared to the B-36 in practically any way. The whole concept of its use was different, relying on friendly bases close to the USSR (many B-47's were homebased in CONUS, but practically speaking would need staging bases in Allied countries, even with aerial refueling). And it was an example of much more advanced state of art. The planes shared the J47 engine, but those were just an add on to the B-36, rather than the engine techology around which the B-47 was designed. And the B-47 was close enough in speed to enough of the Soviet interceptor force to make large scale B-47 nuclear raids essentially unstoppable (and there were lots of B-47's), even if groups of subsonic MiG's could intercept a single B-47 as they proved in certain RB-47 intrusions into Soviet territory or nearby. Although, even the B-36's capabilities were adequate to make the US nuclear deterrent credible v the USSR into the late 1950's. It's one thing to shoot down a bomber or cause a few % losses per sortie and make a conventional bombing campaign too costly. It's quite another to shoot down enough planes to make a nuclear attack's results tolerable: that was extremely difficult to do, requiring almost perfection for the defense and giving every advantage to the offense.

Joe

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## GregP (Apr 29, 2012)

The B-47 was a great plane. I have friends who flew them and they heap praise upon it as fast, easy to fly, able to hit the target, and just a plain old kick to be assicoated with. As a first-generation jet bomber design after WWII, it was among the best of the lot. If Boeing hadn't developed the B-52, who knows? We might still be flying it.

There are a lot of people out there who are not familiar enough with the B-52 to even begin to understand why we are still flying it. suffice to say that if you vew it from above, all that wing area is not there for nothing. It can hit you from a LONG way up in the air, with iron bombs, smart bombs, cruise missiles, antiradtion missiles, and even sir-to-air missiles. It may be old, but it still has a great set of teeth!

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## Siegfried (Apr 30, 2012)

tyrodtom said:


> Siegfried, that's a fail on arithmetic. 28x2x6=336.



*Yes but I can pose the correct question, even with 1/2 bottle of Cabernet.*



tyrodtom said:


> The Wasp Major R-4360 used in the B-36 was used by plenty of other aircraft so it was maintainable. The B-50, C-97, C-119, C-124, and about 20 other well known aircraft used the same engine, but not as a pusher.
> 
> The B-36 was the only aircraft in the American arsenal that could carry the early largest H-bombs until the B-52 came along.


*
Yes, but no civilian customers.*


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## Jenisch (Apr 30, 2012)

Siegfried said:


> Yes, but no civilian customers.


 
It was used in the Boeing 377 and it's Mini Guppy and Pregnant Guppy variants, and in the SNCASE Armagnac.


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## tyrodtom (Apr 30, 2012)

Siegfried said:


> *Yes but I can pose the correct question, even with 1/2 bottle of Cabernet.*
> 
> 
> *
> Yes, but no civilian customers.*



LOL, Since when do we judge the success of a military engine or aircraft by how successful it was on the civilian market?


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## Jenisch (Apr 30, 2012)

I don't know if we can say the B-36 was a "failure". The plane was developed to attack Germany from the US and Canada if Britain fell. It would be avaliable earlier if needed. It also could attack any target inside the Soviet Union in case Stalin turned out against the West (this for justify it's development during WWII). So, I think it gave flexibility to the USAAF/USAF.

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## tyrodtom (Apr 30, 2012)

The B-36 program got put on the back burner pretty early in it's developement program, by mid 1944 everybody, probably even Hitler, knew Germany was on the downhill road to defeat.


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## Siegfried (Apr 30, 2012)

Jenisch said:


> It was used in the Boeing 377 and it's Mini Guppy and Pregnant Guppy variants, and in the SNCASE Armagnac.



56 + 9. I wouldn't call that commercially successfull in any way.


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## Jenisch (Apr 30, 2012)

Siegfried said:


> 56 + 9. I wouldn't call that commercially successfull in any way.



Indeed. The 377 had to make scales because oil would be running low, not fuel. The turboprop put those nice but complex and expensive to maintein radials in the grave.


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## Siegfried (Apr 30, 2012)

tyrodtom said:


> LOL, Since when do we judge the success of a military engine or aircraft by how successful it was on the civilian market?



It would have been a maintenance and resource hog and that also suggests a militarily inefficient aircraft. By the time it could have been ready it would have been rendered ineffective by SAM missiles, ( an easy target for wasserfall )should it have been needed it was also well within interception capability of any 1945 or 1946 Luftwaffe. A more creatively designed jet aircraft could have exceeded its range by 1949 anyway by which time the b36 was barely ready anyway. It should have been caned and the US Navy had its super carriers funded. They'd still be around.


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## Jenisch (Apr 30, 2012)

_Lycoming XR-7755 was the largest piston-driven aircraft engine ever produced; with 36 cylinders totaling about 7,750 in³ (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts). It was originally intended to be used in the "European bomber" that eventually emerged as the Convair B-36. Only two examples were built before the project was terminated in 1946.

The resulting design used 9 banks of 4 cylinders arranged around a central crankshaft to form a four-row radial engine. Unlike most multi-row radials, which "spiral" the cylinders to allow cooling air to reach them, the R-7755 was water-cooled and so each of the cylinder heads in a cylinder bank were in-line within a cooling jacket. Contrast this with the Junkers Jumo 222, which looked similar from the outside but ran on a V-style cycle instead of a radial. The XR-7755 was 10 ft (3 m) long, 5 ft (1.5 m) in diameter, and weighed 6,050 lb (2,740 kg). At full power it was to produce 5,000 hp (3,700 kW) at 2,600 rpm, maintaining that with a turbocharger to a critical altitude that was apparently never published.

Each cylinder bank had a single overhead cam powering the poppet valves. The camshaft included two sets of cams, one for full takeoff power, and another for economical cruise. The pilot could select between the two settings, which would shift the camshaft along its axis to bring the other set of cams over the valve stems. Interestingly, the design mounted some of the accessories on the "front side" of the camshafts, namely two magnetos and four distributors. The seventh camshaft was not used in this fashion, its location on the front of the engine was used to feed oil to the propeller reduction gearing.

The original XR-7755-1 design drove a single propeller, but even on the largest aircraft the propeller needed to absorb the power would have been ridiculously large. This led to a minor redesign that produced the XR-7755-3, using a new propeller gearing system driving a set of coaxial shafts to power a set of contra-rotating propellers. The propeller reduction gearing also had two speed settings to allow for a greater range of operating power than adjustable props alone could deliver. Another minor modification resulted in the XR-7755-5, the only change being the replacement of carburetors with a new fuel injection system._

Lycoming XR-7755 - Pictures Photos on FlightGlobal Airspace

Now imagine this monster people.

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## tyrodtom (Apr 30, 2012)

Siegfried said:


> It would have been a maintenance and resource hog and that also suggests a militarily inefficient aircraft. By the time it could have been ready it would have been rendered ineffective by SAM missiles, ( an easy target for wasserfall )should it have been needed it was also well within interception capability of any 1945 or 1946 Luftwaffe. A more creatively designed jet aircraft could have exceeded its range by 1949 anyway by which time the b36 was barely ready anyway. It should have been caned and the US Navy had its super carriers funded. They'd still be around.



Of course, as usual, you're presenting something that never made it beyound the prototype stage of developement, with your usual magic enhancement of it's capabilities, to someting that got built and actually put on operations, but in the B-36's case after WW2. Because it wasn't needed to defeat Germany as it WAS.


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## drgondog (Apr 30, 2012)

To the B-36 detractors - It was the ONLY weapon the US had through the early 50's which could carry the big boomers (internally) and destroy anything, anywhere on this earth. The late 40's brought out the MiG 15 which was the only Soviet fighter capable of getting an altitude advantage and it was a point interceptor which would have to be reasonably close to the course track to intercept the late model 36's.

Waste of money? How does one determine that, had the 36 not been around in strength in 1948-1950? The Russians did NOT pile on in Korea for a reason.

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## Jenisch (Apr 30, 2012)

BTW, how the USAAF would obtain weather information to attack Germany from the US like the B-36 was planned? I can think of submarines and ships providing today's SHIP reporting for the Atlantic, but don't know more details about the meteorology in those days.


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## fastmongrel (Apr 30, 2012)

tyrodtom said:


> LOL, Since when do we judge the success of a military engine or aircraft by how successful it was on the civilian market?



Exactly how many military engines went on to major civilian success. If that was the criteria for success then every German engine, every Japanese engine and the vast majority of Allied engines were failures.


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## michaelmaltby (Apr 30, 2012)

At the outset of the Cold War before the rules had settled down to MAD, the B-36 was a symbol that the USA could keep A bombs in the air all the time, anywhere in the world. The B-36 was never a great favorite of mine but it sure made an impression at the Toronto air show and brought credibility to the Strategic Air Command operations and philosophy.

It was 10 years before the Soviets had the Tupolev Bear to project their air power over distances, and the Peace Maker was much more capable than the Bear, IMO.

Why did it employ pusher engines -- speed and streamlining, same reason the Bear had swept wings 

MM


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## Jenisch (Apr 30, 2012)

_View: https://www.youtube.com/watch?v=ruE8yhkHke8_

To put the B-36 in one word: nice!


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## wuzak (Apr 30, 2012)

michaelmaltby said:


> It was 10 years before the Soviets had the Tupolev Bear to project their air power over distances, and the Peace Maker was much more capable than the Bear, IMO.



In what way?





michaelmaltby said:


> Why did it employ pusher engines -- speed and streamlining, same reason the Bear had swept wings



I don't think the B-36, without the auxiliary jets, cold ever have been described as fast. The Bear was 150mph faster. At least.

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## JoeB (Apr 30, 2012)

drgondog said:


> To the B-36 detractors - It was the ONLY weapon the US had through the early 50's which could carry the big boomers (internally) and destroy anything, anywhere on this earth. The late 40's brought out the MiG 15 which was the only Soviet fighter capable of getting an altitude advantage and it was a point interceptor which would have to be reasonably close to the course track to intercept the late model 36's.
> 
> Waste of money? How does one determine that, had the 36 not been around in strength in 1948-1950? The Russians did NOT pile on in Korea for a reason.


I believe the B-36 was an effective deterrent, but I would shift the timeline to the right. When in March 1951 the FEAF floated the idea of conventional B-36 missions from CONUS over North Korea with dual purpose of helping that effort and providing realistic training, SAC replied that only around 30 were fully mission capable. The B-36's real combat capability in numbers only dated from late 51-early 52 and by same token real B-47 capability post dated the Korean War, though it didn't have the degree of teething problems as the B-36. Also, the SAC of formidable repuation for relentless training and readiness was a work in progress in pre KW period. But on the defense, it was really more like ca. 1957 when the Soviet air defense system seriously compromised the crediblity of the B-36 year round*, especially after B-36's were stripped down for higher altitude operation from around '54 (in part to counter improved Soviet capabilities and in part because the retractable gun turret system was never fully debugged). The B-36 was an effective nuclear strike a/c from around '52-'57, give or take a year on either end, not long by today's standards but long enough to be important in those times.

In the very early Cold War the number of US nukes and credible delivery systems was pretty limited, though the number of bombs was skyrocketing by early Korean War, and training and readiness of B-29 and B-50 units had reached a level where they posed a significant nuclear threat to at least parts of the USSR. By same token, the US acted circumspectly about Soviet capabilities once they detonated their nuclear test device in 1949, but in reality the operational versions failed their initial test, and the Soviets had no real deliverable nuclear weapons until around '52, and a very limited capability v CONUS for some years after that. But both sides tended to assume a worst case, so in morale terms you might be right that the B-36 was important even before 1950, but it lacked much actual operational capability until later on.

*since operations v the USSR would often cross high latitudes, 'day and night' tended to mean 'summer and winter'. The Soviets lacked enough high performance radar equipped interceptors to credibly counter B-36's in non-VFR conditions until around '57. The arrangement using radar directed searchlights and non-AI radar MiG-15's to bring down a few B-29's at night over Korea, in 100's of tries, defending only a small area, was not a credible counter to a general nuclear attack on the USSR.

Joe

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## michaelmaltby (Apr 30, 2012)

"... In what way?"

Bigger bomb load. Longer range. Higher operational ceiling.

By the time the Bear came along, the B-52 was there, once again with .... Bigger bomb load. Longer range. Higher operational ceiling. AND FASTER.

"... I don't think the B-36, without the auxiliary jets, cold ever have been described as fast.."

No one claims it was - but it was almost 100 mph than the B-29 - and that is the gold standard for advanced bombers. (And without which the Soviets would never have mastered the tricks of building pressurized strategic bombers)

MM


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## Siegfried (Apr 30, 2012)

tyrodtom said:


> Of course, as usual, you're presenting something that never made it beyound the prototype stage of developement, with your usual magic enhancement of it's capabilities, to someting that got built and actually put on operations, but in the B-36's case after WW2. Because it wasn't needed to defeat Germany as it WAS.



Wasserfall had flown nearly 50 test launches by wars end under rather difficult conditions. The B-36's first flight was in August 1946 so we can say that the EMW Wasserfall SAM was running at least 1.33 years ahead of the B-36. In fact I'd put it well ahead of that since the first lauches were in 1944 not at wars end 1945.(April 1945). Both progrms were somewhat delayed by shifting priorities.


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## tyrodtom (Apr 30, 2012)

Like I already said the B-36 wasn't needed, Britain was still in the war, so they didn't need the ability to bomb Germany from the USA.
They didn't even need to shift the B-29's to Europe to take out Germany, they knew they could do it with what they had.
As for the Wasserfall, CSWBD.


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## wuzak (Apr 30, 2012)

michaelmaltby said:


> "... In what way?"
> 
> Bigger bomb load.



Yes, the B-36 had a bigger bomb load than the Tu-95 Bear.

The B-36 was as heavy empty as the Tu-95 was loaded.





michaelmaltby said:


> Longer range.



Incorrect. The Tu-95 had a longer operational range. The B-36 could beat the Tu-95's range when run in ferry condition.





michaelmaltby said:


> Higher operational ceiling.



Doesn't appear to be true.





michaelmaltby said:


> By the time the Bear came along, the B-52 was there, once again with .... Bigger bomb load. Longer range. Higher operational ceiling. AND FASTER.



The B-52 looks to have a smaller bomb load than the B-36, still greater than the Tu-95. The B-52 has a shorter range than the Tu-95. The B-52 did have a higher ceiling and was faster than the Tu-95 - but not by as much as you may think!





michaelmaltby said:


> "... I don't think the B-36, without the auxiliary jets, cold ever have been described as fast.."
> 
> No one claims it was - but it was almost 100 mph than the B-29 - and that is the gold standard for advanced bombers. (And without which the Soviets would never have mastered the tricks of building pressurized strategic bombers)


 
The B-29 was capable of 357mph. The B-36 with 4 jets and 6 props was capable of 418mph.

The B-50 with 4 R-4360s was capable of similar.

The Tu-95 could do 575mph.

I also think you do the Soviet engineers a disservice. While they may have used the B-29 as a basis for their pressurised long range bombers but I am sure they could have managed to develop such an aircraft by themselves if needed.

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## michaelmaltby (May 1, 2012)

"... I also think you do the Soviet engineers a disservice. While they may have used the B-29 as a basis for their pressurised long range bombers but I am sure they could have managed to develop such an aircraft by themselves if needed."

Oh - no doubt. They managed to build a Shuttle, wuzzak.


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## davparlr (May 2, 2012)

wuzak said:


> I also think you do the Soviet engineers a disservice. While they may have used the B-29 as a basis for their pressurised long range bombers but I am sure they could have managed to develop such an aircraft by themselves if needed.


You are most likely correct. The Soviets had some great designers. However, development would have taken much longer. I believe that the Soviets themselves would say that the B-29s they got during the war was a watershed to their aircraft industry.

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## tyrodtom (May 2, 2012)

I'm sure the Soviet designers never wanted to copy the B-29 to make the TU-4. But when Stalin tells you to copy it, you copy it, and keep your opinions to yourself.

How they carriered out that order almost sounds like a comedy, it may just be a myth, but Tupolev had to work up his courage to ask Stalin in he wanted the national markings copied too.

The fuselage of the TU-95 is just a evolution of the TU-4, which is a copy of the B-29.


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## davparlr (May 3, 2012)

I am also sure they were very happy to get their hands on it.


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## muscogeemike (May 6, 2012)

My ex-father in law was a USAF mechanic and worked on the B-36 in the ‘50’s. His main problem with the plane was that there was no hanger capable of holding it - meaning that all maintenance had to be done outdoors. Imagine changing all those sparkplugs outdoors on the Artic circle!


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## michaelmaltby (May 7, 2012)

The sheer size of the B-36 airframe made it a natural for "nuclear" power -- seriously. It was studied and reflected in the pop culture of the times - Terry and the Pirates - IIRC  - featured a nuclear-powered US bomber for a number of weekly "strips" .

Had a Camp Councillor who was ex-USAF B-36 aircrew (Tech of some trade) and spoke of railroading between compartments - on his back. True .....?

MM


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## Piper106 (May 7, 2012)

"Had a Camp Councillor who was ex-USAF B-36 aircrew (Tech of some trade) and spoke of railroading between compartments - on his back. True .....?"

Yes. As in the B-29 the forward pressurized compartment was connected to the rear pressurized crew compartment via a small diameter tube over the bomb bays.
For personnel to move front compartment to rear compartment they laid down on a cart and pulled themself thru the tube. 

Piper106

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## Matt308 (May 7, 2012)

muscogeemike said:


> My ex-father in law was a USAF mechanic and worked on the B-36 in the ‘50’s. His main problem with the plane was that there was no hanger capable of holding it - meaning that all maintenance had to be done outdoors. Imagine changing all those sparkplugs outdoors on the Artic circle!



On an Alaskan 30ft scaffolding, with 40+mph winds, using thick gloves to manipulate small parts to go into impossibly small fittings.

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## PWR4360-59B (Sep 29, 2012)

Jenisch said:


> Indeed. The 377 had to make scales because oil would be running low, not fuel. The turboprop put those nice but complex and expensive to maintein radials in the grave.



Had resurect this thread. Radials were not and are not even close to the expense of turbines, especially in those days. The turbines way more than make up for some maintenance on the recips, through their fuel consumption as number 1, and their overhaul cost as number 2. 
The major costs of turbines at overhaul time is the very expensive exotic materials the parts are made of and the difficulty to make them. I know of some engine parts of years past now like 12 or more years ago that you could stick in your pocket (jet engine part) that cost $20,000. I suppose the same of equivalent parts
are much more nowadays. I think the engine required 8 of those parts. So lets again compair turbines to recips. What an R-4360 at cruise what 150 gallons per hour? Some jets are in the gallons per second range. Wasn't it Eddy Rickenbacker that wanted nothing to do with turbines?


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## evangilder (Sep 29, 2012)

I agree on the parts cost factors and fuel consumption. I would think the 4360, with four rows of cylinders, would be a bit of a feat to maintain and/or rebuild. I'm not an expert on aircraft engines, but what about the weight of the engines? Is the 4360 heavier than a comparable jet engine? What about power to weight ratios? Just some things to consider.


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## wuzak (Sep 29, 2012)

Pratt Whitney T34 - 2590lb, 5500hp + 1250lbf
Pratt Whitney R4360 - 3900lb, 3800hp


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## wuzak (Sep 29, 2012)

An earlier turboprop, the experimental XT-31
1980lb, 2300hp.


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## ccheese (Sep 29, 2012)

I just saw this thread, and had to go all the way through it. I am probably the only person on the forum who has actually flown in the B-36. I was stationed at Wheelus AFB, in Tripoli, Libya 1954-1955. I made two flights on the B-36 as an observer (non-crew). Both times we went from Wheelus to somewhere over Europe, then turned around and came back by a different route. I thought it was an enjoyable plane to fly in. On the down side, on both flights we had to shut down the #3 engine. First time for overheating and the second time for a pitch control failure of some kind. The plane flew just as well without it !

As for the pros and cons of the plane, as in the discussion of the thread, I honestly don't know that much about the technical aspects of the plane.

Charles


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## chipieal (Jul 7, 2013)

Hello,
For years - I have pondered the reason for pusher type aircraft? Especially in the B36 configuration. Any thoughts?


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## Matt308 (Jul 7, 2013)

Reduction in drag hiding those 6 radials in the wing.


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## OldSkeptic (Jul 9, 2013)

chipieal said:


> Hello,
> For years - I have pondered the reason for pusher type aircraft? Especially in the B36 configuration. Any thoughts?



Stupidity, idiocy, insanity???? There are no gains here at all. Harder to make, harder to service, poorer lift on takeoff, poorer climb, worse stall, cooling issues (especially on an air cooled engine) and so on.

As for the cruising drag issue of a twin tractor it is just down to careful engine nacelle/wing design (near the engine of course), do that then it becomes a non issue.

Bit like the Do-335, a tribute to monomania about a single issue and showed a complete lack of creativity.

Not even sure this even a solution for more economical high speed cruising at high altitudes, as you will need a bigger wing for the lift (=more drag) and/or a higher angle of attack (=more drag).

Write this off as a dud..... Brewster Buffalo or Defiant stuff. Sort of like the ideas we all get after a few too many drinks and get all excited about ... then write off in the cold light of the day (after the hangover had gone).


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## cimmex (Jul 9, 2013)

OldSkeptic said:


> Stupidity, idiocy, insanity???? There are no gains here at all. Harder to make, harder to service, poorer lift on takeoff, poorer climb, worse stall, cooling issues (especially on an air cooled engine) and so on.
> 
> As for the cruising drag issue of a twin tractor it is just down to careful engine nacelle/wing design (near the engine of course), do that then it becomes a non issue.
> 
> ...


what is your statement based on? The B-36 program had cost a lot of money and I think the men who made the decision knew what they are doing. The best aircraft engineers of that time were working on the pusher design and it is kind of strange when 70 years later someone criticize this without any proof.
cimmex


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## tyrodtom (Jul 9, 2013)

A wing without the propeller in front to mess up the airflow is going to be more efficient.
But a propeller in the rear, in the turbulent air coming off the rear of the wing, isn't going to be at it's best possible efficiency.

On the B-36 the designers evidently thought that they'd gain more on the first, than they'd lose on the second.
Were they right ?

Also the propeller being in the wing's slipstream was the reason for the B-36's throbbing drone, I've read.


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## swampyankee (Jul 9, 2013)

The B-35 had a different problem. It's difficult to get enough yaw stability and pitch and yaw damping with a flying wing, and the pusher propellers, well behind the center of gravity added both.


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## OldSkeptic (Jul 10, 2013)

cimmex said:


> what is your statement based on? The B-36 program had cost a lot of money and I think the men who made the decision knew what they are doing. The best aircraft engineers of that time were working on the pusher design and it is kind of strange when 70 years later someone criticize this without any proof.
> cimmex



Sadly, being a big project and costing a lot of money, with lots of people working on it is no guarantee that it is not a completely dumb project.
The world is awash (and history replete) with really dumb 'big projects'.

Note that the military does not have a monopoloy on this by any means (though in recent times you might struggle to find a non 'really dumb military project that costs a lot of money and is completely useless'.

Take for example here in Australia. In the State I live in we built the world's biggest desalination plant at the cost of 10s of billions of dollars, that almost certainly will never be used and even it ever is the water it produces will probably be undrinkable anyway. Huge amounts of 'smart' people 'who knew that they were doing' worked on that one.

I could list some of the 'really dumb' military projects in recent decades .... but I don't think a 100,000 word post would be appreciated.

By modern standards I suppose the whole B-36 saga is a drop in the ocean, after all in the end it sort of worked (ish), which is more than you can say for many things.

But never forget my 1st law of life: never underestimate human stupidity.


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## GregP (Jul 10, 2013)

My first two laws are:

1) Never piss into the wind.
2) Never stand next to anyone pissing into the wind.

All else follows these two.

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## Matt308 (Jul 11, 2013)

There is an "intolerable people" thread in the miscellaneous section. I would highly suggest that you curmudgeons check it out. You will fit right in with the rest of us.


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## OldSkeptic (Jul 12, 2013)

cimmex said:


> what is your statement based on? The B-36 program had cost a lot of money and I think the men who made the decision knew what they are doing. The best aircraft engineers of that time were working on the pusher design and it is kind of strange when 70 years later someone criticize this without any proof.
> cimmex



Being more serious, this reminds me of the Do-335. To solve a single problem (similar sort of logic to the B-36) of drag caused by a normal tractor, wing mounted twin engine setup, they went to incredible time and effort to create a whole new set of problem for themselves.

In the end they came up with something that was not any faster (the whole purpose of the design) than a Dh Hornet, with far poorer overall performance such as agility, climb, etc plus additional maintenance issues and their own problems with overheating (even though they used liquid cooled engines).

DH took the sensible way of dealing with this issue, design the engine/nacelle/wing interface properly to minimise drag (did the same with the Mosquito) and maintain all the advantages of the twin tractor design (plus be a lot easier to make, debug and maintain). 

Dornier took the dumb way and produced a pig that in the end never worked, DH took the smart way and produced a superb aircraft, that was successful in service (and if the jet age hadn't come in then would have had a very long career).

Following this logic the designers of the B-36 should have followed the same process, especially when they were using air cooled engines and it was a given from the start that overheating would be an issue.
Some of those late model US air cooled engines were very marginal in cooling anyway, plus they were designed for an airflow coming in from the font.

The advantages would have been immense, for a start they could have got away with a far smaller wing.
But they didn't and in trying to solve that one issue they created a whole new set of problems for them. Much better to focus on that one issue and minimise all the other problems.


One of the ways (to take a single example) of minimising drag from the tractor design was to make sure the propeller was well away from the leading edge of the wing, reducing turbulance. An example is the British Halifax which long had problems with its Merlin version because the props were too close, causing turbulence and vibration problems, as opposed to the Lancaster which maintained a good distance and never suffered those issues.

The engine nacelle design was critical to maintaining good airflow with minimal drag, this is very important on both the upper and lower parts of the wing. Look at the pictures I have posted on the Mosquito and see the carefully designed engine pod/nacelle. The end result of that (and other careful attention overall) was that a clean light Mossie (eg the early PR ones) was faster with the same power/wetted area ratio than a Spitfire.

So if I was designing a B-36 I'd be looking at all that first, especially the frontal drag caused by using an air cooled engine and good non turbulent air over the top and bottom of the wings. Do all that and you could easily get the same low drag, high altitude performance, but with easier construction, easier maintenance and, almost certainly, a smaller wing.


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## Shortround6 (Jul 12, 2013)

Wing size may have had very little to do with engine placement as the engines were not actually _IN_ the wing but in the nacelles at the rear of the wing. 







There are no extension shafts. Propellers are mounted on a "normal" propshaft/gearbox and the engines are pretty much in line with the flaps. Engine power section (cylinders) is much smaller than the whole nacelle, The turbos, intercoolers and ducting taking up quite a bit of space. 

See: http://www.angelfire.com/dc/jinxx1/B36/B36J522217_10.jpg


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## drgondog (Jul 12, 2013)

A couple of simple facts:
1.) until the B-52 it was the Only bomber the US had which could strike Moscow with a Thermonuclear weapon in 1950, multiple nuclear weapons in 1947.
2.) When powered properly it was fast and could go a long way at high altitude.
3.) No nuclear wars occurred on its watch.

The wing was pretty low drag/high CL through all cruise speed angles of attack - good L/D despite fat wing

The pusher does provide less drag over the forward 25% of the airfoil than conventionally mounted engine/prop/nacelle combinations mounted on leading edge.

The B-35 and B-49 also demonstrated excellent L/D


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## Timppa (Jul 13, 2013)

drgondog said:


> until the B-52 it was the Only bomber the US had which could strike Moscow with a Thermonuclear weapon in 1950, multiple nuclear weapons in 1947.



The first thermonuclear explosion was the "Ivy Mike" shot in 1952. On February 28, 1954, the U.S. detonated its first deliverable thermonuclear weapon (which used isotopes of lithium as its fusion fuel), known as the "Shrimp" device of the Castle Bravo test.

The Mark 17/24 were the first mass-produced hydrogen bombs deployed by the US, yielding 25 megatons, produced between October 1954 and November 1955.

The world's first air-dropped fusion bomb test was RDS-37, 22nd November 1955 at Semipalatinsk Test Site, Kazakhstan, yield 1.6 Megatons 
It was the Soviet Union's first test of a two-stage radiation implosion (aka Sakharov's "Third Idea", and Teller-Ulam) design.
The bomb's yield was reduced from its design yield for the test by about half by replacing part of the Li-6 D fusion fuel with "a passive material" (probably ordinary lithium hydride). The yield was within 10% of the predicted value.


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## drgondog (Jul 13, 2013)

You are correct Timppa - relying on my memory at the age of 5-7 and the cover of Life magazine is not reliable. Having said this, the B-52 fleet was not ready in 1954.


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## swampyankee (Jul 13, 2013)

I wish people would echoing the "radials have tons of drag" meme. It is false. Properly designed radial engine installations have no more drag than properly designed liquid-cooled engine installations. 

One way is to look at this logically: a 1,000 shp piston engine has to get rid of so much waste heat (probably three or four times its shaft power). Some goes out through the exhaust, some through oil coolers, and some has to be rejected to the air, either directly, through cylinder fins, or indirectly, through radiator fins. Proper cooling design is highly non-trivial for piston-engined aircraft, and it may be a bit easier with radiators, but, reading the literature will show that cooling drag correlates well with power (not a surprise), but there is no distinct advantage to conventional liquid cooled engines vs air-cooled ones. Some unconventional systems, like the surface radiators used on the Schneider Trophy aircraft are much different, although even those will have cooling drag (heating a surface will tend to destabilize a laminar boundary layer, thereby increasing skin friction).


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## Shortround6 (Jul 13, 2013)

That is the theory, practice took a while to catch up with theory although by the time the B-36 took to the air practice and theory were pretty much in agreement. This was NOT so in late 30s and only so in early 40s in rare situations. ( FW 190 being a leader)


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## Timppa (Jul 14, 2013)

> In June 1948, Convair delivered the first operational B-36A to SAC's 7th Bomb Group at Carswell Air Force Base, across the runway from its Fort Worth plant. Big as the B-29 Superfort was, it could nearly fit beneath one wing of a B-36. Despite the difference in size, the two airplanes had similar vertical tails, and they had slim fuselages, like cigarettes, round in cross-section, with two pressurized crew cabins separated by two bomb bays and connected by a tunnel.
> 
> But the wings were different. The Superfort's were thin, straight, and glider-like, while the B-36's wings were more than seven feet thick at the root, enough for a crewman to crawl in and reach the engines or the landing gear in flight. The wings were tapered, with the leading edges swept back, and the effect of that, combined with the wings' location so far back on the fuselage, made the airplane appear out of balance. Strangest of all, the B-36's six Pratt Whitney Wasp Major engines were faired into the trailing edges, with the propellers located aft in the pusher configuration. Although it was supposed to reduce the propeller swirl's turbulence over the wing, the pusher design was rarely used on U.S. aircraft. Apparently it worked, though, because the B-36 had very low drag. The main drawback was that air for cooling the engines was ducted from intakes in the leading edge of the wing, and there was never enough of it, especially at high altitude.
> 
> ...



The whole article:
B-36: Bomber at the Crossroads | History of Flight | Air Space Magazine


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## GregP (Jul 14, 2013)

Shortround, when I crawled all over the B-36 that used to be at Chanute AFB in Champaign-Urbana, Illinois, the engines were in the wing. The nacelles didn't extend far enough aft of the trailing edge to do anything but prevent the props from cutting into the wing.

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## OldSkeptic (Jul 14, 2013)

Shortround6 said:


> Wing size may have had very little to do with engine placement as the engines were not actually _IN_ the wing but in the nacelles at the rear of the wing.



Don't forget you get a loss of lift compared to a tractor. The fast air flowing over the wing from the propellers causes lift shortening takeoff and aids altitude performance.

Therefore just to take off you are going to need a bigger wing anyway for the same weight, wing area, power, etc.

Then you get into complex calculations, the larger wing has more drag (especially one as thick as that) raising the question of whether or not you are any better off than a well designed tractor setup.


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## cimmex (Jul 14, 2013)

is there a big difference if the airflow is sucked or blown? I don’t think so.
cimmex


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## Elmas (Jul 14, 2013)

Once a Very Top Brass of the Bluesuiters was asked about wich, among all the aircrafts under his command, had been the best.
_“B-36, no doubt”_, was the reply.
_“But General, B-36 never dropped a single bomb in anger...”_
_“Exactly.”_

(From the Internet)


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## OldSkeptic (Jul 14, 2013)

cimmex said:


> is there a big difference if the airflow is sucked or blown? I don’t think so.
> cimmex



If that was meant for me, I have clarified the post just in case of confusion. 

Note that there are no 'sucking' forces, only 'pushing' ones when dealing with gases.

Though, possibly by accident, you may have raised an interesting issue about propeller efficiency in a pusher arrangement. 
I'm thinking of turbulent air coming off the wing and hitting the propeller reducing its efficiency (and possibly creating vibration issues?).

Anyone else got any ideas on that?


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## Aozora (Jul 14, 2013)

B-36 engine design features (from Graham White R-4630ratt Whitney's Major Miracle):

Intake ducting:







"Airplug" and engine diffuser duct:










Oil Supply and cooling:






Airflow and turbochargers:














NACA reports on designing the XB-36 engine installations:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050019376_2005009862.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050019239_2005009918.pdf

Whichever way you look at it the B-36's engine installation, while a considerable engineering feat once perfected, was complex and naturally required thick, structurally massive and heavy wings. One wonders how the aircraft would have performed with tractor engines in aerodynamically efficient nacelles mounted on a thinner wing? eg; Republic XR-12:


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## Aozora (Jul 14, 2013)

OldSkeptic said:


> If that was meant for me, I have clarified the post just in case of confusion.
> 
> Note that there are no 'sucking' forces, only 'pushing' ones when dealing with gases.
> 
> ...



White believes that the position of the propellers above the centre of the wing trailing edges on the Northrop XB-35 resulted in airflow separating off the wings and creating asymmetric turbulence against the propellers, which exacerbated vibrations inherent in the long prop shafts required by the engines. In addition the sweep back of the wings meant that each side of the propeller disk received different degrees of turbulence from the airflow (White, pages 364-365):






The B-36's wings had straight trailing edges and the centres of the propellers were directly in line with the trailing edge airflow which reduced turbulence, although it wouldn't eliminate the problem entirely. In fact the early fabric covered magnesium flaps had to be replaced by heavier duralumin covered flaps because the turbulent airflow ripped off the fabric covering (White, page 429).


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## 11bwmech (Jul 10, 2014)

One small correction. When going aft, you had to hold yourself back. The aircraft was normally nose up to some degree. The pulling happened when going forward.

Ralph


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## GregP (Jul 10, 2014)

Anyone who thinks there is no suction froma 19 foot propeller should try standing in front of one at full power ... and hope like hell you are tied back with a safety belt.

I'm pretty sure there was some extra airspeed going over the wings that would not have been there without the huge prop sucking in air ... though admittedly not near so much as the prop wash from a conventionallly mounted engine of the same power.

If you're still not convinced of the power of suction, stay away from the intakes of running larger jet engines or you'll find out different is a very bad way.


_View: https://www.youtube.com/watch?v=5FsrNEeqd6Q_


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## FLYBOYJ (Jul 10, 2014)

11bwmech said:


> One small correction. When going aft, you had to hold yourself back. *The aircraft was normally nose up to some degree.* The pulling happened when going forward.
> 
> Ralph



And how about trim?


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## rinkol (Jul 10, 2014)

I recall that the B-36 had a laminar flow wing and that the pusher engine configuration was chosen in an effort to avoid disturbing the air flow over the forward portion of the wing as far as possible. This configuration also enabled the engines to be buried within the wings, an idea that was in vogue in the late 1930s and 1940s. The buried engine concept was a major consideration in the design of the Hyper engines, particularly the O-1230 and Tornado, but presented airframe designers with difficult design problems including structural and maintainability issues and finding space for the storage of fuel and the undercarriage.


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## GregP (Jul 10, 2014)

A 200 pound man moving from the tail to a position in the nose would move some 150 feet. I bet that's enough delta moment to cause a significant trim change.


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## FLYBOYJ (Jul 10, 2014)

GregP said:


> A 200 pound man moving from the tail to a position in the nose would move some 150 feet. I bet that's enough delta moment to cause a significant trim change.



Of course, and that's why we have that big wheel to the right of the pilot's knee..


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## Koopernic (Jul 11, 2014)

FLYBOYJ said:


> Of course, and that's why we have that big wheel to the right of the pilot's knee..



Amazing to think a single human could control such a large 180 ton aircraft using non powered flight controls (though with spring servo tabs). A similar sized aircraft of the era, the Bristol Brabazon went all hydraulic.


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## OldSkeptic (Jul 13, 2014)

GregP said:


> Anyone who thinks there is no suction froma 19 foot propeller should try standing in front of one at full power ... and hope like hell you are tied back with a safety belt.
> 
> I'm pretty sure there was some extra airspeed going over the wings that would not have been there without the huge prop sucking in air ... though admittedly not near so much as the prop wash from a conventionallly mounted engine of the same power.
> 
> ...




Still a pushing force. Feels like being sucked into the prop/intake but you are actually being pushed by all the other air trying to fill the low pressure area right in front of the props/intake.
Nature abhors a vacuum and all that.


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## GregP (Jul 13, 2014)

That's one way to look at it. But they have argued for YEARS about whether Mr. Bernouli was right or downforce causes lift, and they're still at it.

The rerason for the air moving in is low pressure caused by the suction of the prop, so it can be looked at a suction, too.

If you go study the SR-71 you'll find that 70% of the thrust at Mach 3 is caused by suction at the inlets, not air pushing into the inlets. At least Kelly Johnson thought os. I'd be inclined to agree with him.


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## Shortround6 (Jul 13, 2014)

What is going on in front of inlets/props at zero speed of the aircraft and what is going on at flying speeds may not be the same thing. And even flying speeds change what is going on or there wouldn't be much need for variable pitch propellers.


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## swampyankee (Jul 13, 2014)

Koopernic said:


> Amazing to think a single human could control such a large 180 ton aircraft using non powered flight controls (though with spring servo tabs). A similar sized aircraft of the era, the Bristol Brabazon went all hydraulic.



Boeing used servo-tabs on the flight controls for the B-17, the 707, and most versions of the B-52. I am mystified by that last, as I think the earlier B-47 used hydraulics.


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## Koopernic (Jul 13, 2014)

swampyankee said:


> Boeing used servo-tabs on the flight controls for the B-17, the 707, and most versions of the B-52. I am mystified by that last, as I think the earlier B-47 used hydraulics.



I think I can help there, the B-52 used small 'feeler' ailerons with servo tabs on the outboard section of the wing. Hydraulic boosted controls on main aileron and spoiler mirrored it. It's written in a book by Abzug on the history of flight control and stability. I think they may have changed the arrangement for the H.

The fear was something called PCO or Pilot Coupled Oscillation caused by flutter or shock-waves knocking the pilots control column around. The pilot would try and correct but because of the complexity of the phenomena only amplify the phenomena. What was wanted was 100% power controls that were 'irreversible'. The hydraulic system used in P-38J boosted ailerons only assisted the pilot rather than doing all of the work. This meant forces could get back to the pilot. F-86 controls latter went from boosted to irreversible.

What could go wrong is shown by what happened with the DeHaviland DH108 Swallow in which Geoffrey DeHaviland Jnr died. The aircraft initially had a blunt nose taken over from the vampire. Near the speed of sound it 'shock stalled' and smashed the pilot up against the canopy while also forcing the vibration from all this shaking about from pilots hands back into the controls, which worsened it. Eric Brown thinks DeHaviland, who was tall, broke his neck while he being shorter managed to survive.

Naturally this meant a loss of feel, so artificial feel was created to tension the controls on the basis of dynamic pressure (speed squared x pressure) from say the pitot tube. Stick shakers were added to vibrate controls on the basis of angle of attack instruments.

At some point Boeing learned how to make manual controls that were relatively free from these phenomena and so we saw a return to manual controls if only as a backup or on some of the flight surfaces. One could fly a 727 or 707 using pure manual controls via the servo tabs if there was a hydraulic failure however in the case of the B-747 one relied on the windmilling effect of the 4 engines to provide enough pressure. Many aircraft have a RAT ram air turbine, including the latter F-86.

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## swampyankee (Jul 13, 2014)

Koopernic said:


> I think I can help there, the B-52 used small 'feeler' ailerons with servo tabs on the outboard section of the wing. Hydraulic boosted controls on main aileron and spoiler mirrored it. It's written in a book by Abzug on the history of flight control and stability. I think they may have changed the arrangement for the H.
> 
> The fear was something called PCO or Pilot Coupled Oscillation caused by flutter or shock-waves knocking the pilots control column around. The pilot would try and correct but because of the complexity of the phenomena only amplify the phenomena. What was wanted was 100% power controls that were 'irreversible'. The hydraulic system used in P-38J boosted ailerons only assisted the pilot rather than doing all of the work. This meant forces could get back to the pilot. F-86 controls latter went from boosted to irreversible.
> 
> ...



Thanks. Somewhere in the deep, dark past I saw some articles about flying these aircraft, and I remember it said the 707 and B-52 did not use hydraulic flight controls. Nice to get the right information..


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## FLYBOYJ (Jul 13, 2014)

Koopernic said:


> Many aircraft have a RAT ram air turbine, including the latter F-86.


I believe the F4J Fury had a RAT, I'm not sure that latter model F-86s did.


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## GregP (Jul 14, 2014)

The F-86 E, F, and H and Canadair Sabre Mk 6 don't have an RAT.


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## Koopernic (Jul 17, 2014)

GregP said:


> The F-86 E, F, and H and Canadair Sabre Mk 6 don't have an RAT.



I must have mistaken the F-100 super sabre's systems with that of the F-86 Sabre. The F-100 had a RAT inside the intake duct. The pilots manual for the F-86E says that there are two independent hydraulic systems; should both supplies fail then an electric pump with 8 minutes of battery power will provide hydraulic pressure for the flight control surfaces. If that fails as well the pilot can pull and handle to connect up fully manual controls that are suitable for flighty up to 200 mph, a nice feature seemingly abandoned in recent aircraft.

The F-86E added an all flying tail and fully irreversible hydraulic controls.


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## Donivanp (Jul 17, 2014)

Applications[edit]
Aero Spacelines Mini Guppy
Aero Spacelines Pregnant Guppy
Boeing 377 Stratocruiser
Boeing B-50 Superfortress
Boeing C-97 Stratofreighter
Boeing KC-97 Stratotanker
Boeing XF8B
Boeing XB-44 Superfortress
Convair B-36
Convair XC-99
Curtiss XBTC
Douglas C-74 Globemaster
Douglas C-124 Globemaster II
Douglas TB2D Skypirate
Fairchild C-119 Flying Boxcar
Fairchild C-120 Packplane
Goodyear F2G Corsair
Hughes H-4 Hercules ("Spruce Goose")
Hughes XF-11
Lockheed R6V Constitution
Martin AM Mauler
Martin JRM Mars
Martin P4M Mercator
Northrop YB-35
Republic XP-72
Republic XF-12 Rainbow
SNCASE SE-2010 Armagnac
Vultee XA-41


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## FLYBOYJ (Jul 17, 2014)

Koopernic said:


> I must have mistaken the F-100 super sabre's systems with that of the F-86 Sabre. The F-100 had a RAT inside the intake duct. The pilots manual for the F-86E says that there are two independent hydraulic systems; should both supplies fail then an electric pump with 8 minutes of battery power will provide hydraulic pressure for the flight control surfaces. If that fails as well the pilot can pull and handle to connect up fully manual controls that are suitable for flighty up to 200 mph, a nice feature seemingly abandoned in recent aircraft.
> 
> The F-86E added an all flying tail and fully irreversible hydraulic controls.



The rudder was still controlled with cables.

IIRC the hydraulic back up pump worked for 8 minutes providing you lost electric power but I could be wrong, It's been a few years since I've been around an F-86. We actually had Canadair Mk 5 and 6s


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## l'Omnivore Sobriquet (Jul 17, 2014)

The tractor front-engine, blowing onto the wing, adds some drag.
The pusher at the back, doesn't.


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## Shortround6 (Jul 17, 2014)

This is true, however the pusher prop doesn't _always_ have the same efficiency as as tractor prop. Sometimes is does and sometimes, depending on fuselage/wing/nacelle/prop extension shaft housing you don't.


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## hajafri (Nov 27, 2015)

can you explain? are flaps used in this a/c? if yes which type and how? are LE slats also used? asif


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## mexchiwa (Dec 5, 2015)

There was a tractor B-36 proposal - the YB-36C. Forget the reason, additional thrust from exhaust?


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## Piper106 (Dec 5, 2015)

Yes, the B-36C was to be powered by the R-4360 VDT (Variable Discharge Turbo) that had significant exhaust thrust.


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## 11bwmech (Jun 7, 2018)

I am not an aeronautical engineer, but I suspect the airflow across the wing was pretty smooth and not turbulent at all. Big difference in pressure above and below, though. That's probably why they had to use three bladed props, to keep from having two blades crossing the plane of the trailing edge in opposite directions at the same time. Made for a very big prop, 19 ft. in diameter. 

I also suspect that were it not for the B-36, we might all be speaking Russian.

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## Zipper730 (Jun 7, 2018)

iron man said:


> First off...The "Peacemaker" (while impressive, within it's own context) was a massive waste of money.


Why?


> Realistically? The _power plants themselves _were a major PITA for those who had to deal with them...this is well documented.


The R-4360 had lots of issues with maintenance and cooling...


> It now seems silly how we were "duck and covering", when the USSR were actually _so far behind the curve_, as to make the whole thing kind of laughable (in hindsight) ...


I guess the idea was to make it easier to justify dropping the nukes?



FLYBOYJ said:


> Agree to a point but disagree about the B-47 - entered service in 51', phased out as a bomber till 65 and finally retired in 77


I didn't know it served until 1977...


> it flew like a fighter


It had a normal g-load of either 2.0-3.0g depending on variant when fully loaded, 3.0-3.6g at combat weight, and ultimate loads ranging from 3.0-4.8g based on this. At high altitude, it could outrun early fighters (F-80, F-84 probably), and turned better than them up high (40,000+).

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## fubar57 (Jun 7, 2018)

You're asking someone (iron man) who hasn't been here for over two years questions


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## fubar57 (Jun 7, 2018)

11bwmech said:


> I also suspect that were it not for the B-36, we might all be speaking Russian.



... и что с этим не так, товарищ?

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## GrauGeist (Jun 8, 2018)

fubar57 said:


> ... и что с этим не так, товарищ?



много неща, много неща.
това е какво!

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## Zipper730 (Jun 8, 2018)

fubar57 said:


> ... и что с этим не так, товарищ?


С чего начать Fubar?


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## pinehilljoe (Jun 9, 2018)

fubar57 said:


> ... и что с этим не так, товарищ?


m
If not speaking Russian, a lot of men may have died on the ground. The B-36 gave a method to deliver the bomb that until AIM, SAM or second generation jet fighters were developed couldnt be shot down. Wings and Airpower did an article on the 36 interviewing pilots, they would practice with F-84 and 86s trying to intercept them, and the fighters couldn't reach the altitude the 36 was flying at. They would watch them trying to zoom up and just couldnt reach the 36. For a few years it gave the US a great deterrent. One could always argue too many were built, and the program cost could have been lowered. 

The other part of the thread on the 47, I've read the 47 had wing fatigue issues, and some were lost in flight from wing failure, when doctrine change to low altitude flying with a pop up to release bombs. The USAF was not sorry to retire the 47

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## Zipper730 (Jun 9, 2018)

pinehilljoe said:


> If not speaking Russian


Basically, Fubar 57 wrote something to the effect of "What's wrong with that Comrade?" to which I replied "How to start, Fubar?" This was not necessarily a perfect translation (Google), but it was a flippant remark to a (presumably) flippant question.


> The B-36 gave a method to deliver the bomb that until AIM, SAM or second generation jet fighters were developed. Wings and Airpower did an article on the 36 interviewing pilots, they would practice with F-84 and 86s trying to intercept them, and the fighters couldn't reach the altitude the 36 was flying at. They would watch them trying to zoom up and just couldnt reach the 36.


The problem with attempting to intercept the B-36 was basically

How far out it could be detected
How long it took for aircraft to accelerate to speed and climb to altitude
The turning radius of the B-36 at altitude
The turning radius of fighters at altitude
While the fighters could muster a much higher g-load and could essentially wipe their asses with the B-36 at lower altitudes, once you get up to higher altitudes the F-84 and F-86 found themselves basically in a condition where they were barely flying. The B-36 had a massive wing area, a high aspect-ratio, and thick wings which meant it could keep lifting when the F-84 and F-86 could not. One has to also consider that during intercepts, the fighters might still be at a high fuel load and the B-36 would be around 63-64%


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## swampyankee (Jun 9, 2018)

When I was in college, a friend said a friend of his father's flew F-86D's for Air Defense Command; the pilot reported that an F-86D got one pass as a B-36 at altitude: the fighter didn't have the performance to re-intercept if the first pass failed.

Leaving aside Soviet intentions, I seriously doubt the B-36 kept the Soviets from invading the US or even Western Europe. I think the Soviets _really_ thought they'd win by ideology. Here, they were defeated by liberalism.

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## Zipper730 (Jun 9, 2018)

swampyankee said:


> When I was in college, a friend said a friend of his father's flew F-86D's for Air Defense Command; the pilot reported that an F-86D got one pass as a B-36 at altitude: the fighter didn't have the performance to re-intercept if the first pass failed.


That seems to add up: The F-86D couldn't turn fast enough at altitude to reposition itself...


> Leaving aside Soviet intentions, I seriously doubt the B-36 kept the Soviets from invading the US or even Western Europe.


The Russians believed it would be possible to fight even in the aftermath of a nuclear explosion. Remember, you have to remember how much of a disregard for human life your enemy has.

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## swampyankee (Jun 9, 2018)

Zipper730 said:


> T
> The Russians believed it would be possible to fight even in the aftermath of a nuclear explosion. Remember, you have to remember how much of a disregard for human life your enemy has.


Alas, so did -- and possibly, do -- many US planners. The Soviets, if what I've read is correct, were of the belief that there was not some qualitative difference between tactical nuclear weapons and conventional weapons. This, I find more than slightly frightening, and Putin isn't making me any less nervous.

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## Zipper730 (Jun 10, 2018)

swampyankee said:


> Alas, so did -- and possibly, do -- many US planners.


That's probably true enough: General Power more or less saying that if there are two Americans and one Russian left, that we won...


> The Soviets, if what I've read is correct, were of the belief that there was not some qualitative difference between tactical nuclear weapons and conventional weapons. This, I find more than slightly frightening


Yeah, and there's of course a qualitative difference: Nuclear bombs are way more destructive per bomb, and mass, and they leave a nice radioactive bonus that regular bombs do not.


> Putin isn't making me any less nervous.


Yeah, the sad thing is he's not pulling all the strings even in Russia (high finance)

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## Dimlee (Jun 14, 2018)

Regarding the Soviet (not Russian, of course, - that ended in 1920-1922) doctrine... 
Ultimate political goal remained unchanged until mid-1980s and that was creation of world wide "socialist camp" and moving towards "Communist society". But military strategic planning was not static. In my opinion, since the end of WWII USSR's military doctrine was revised 5 or 6 times.

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## XBe02Drvr (Jun 14, 2018)

Zipper730 said:


> Y





pinehilljoe said:


> The other part of the thread on the 47, I've read the 47 had wing fatigue issues, and some were lost in flight from wing failure, when doctrine change to low altitude flying with a pop up to release bombs. The USAF was not sorry to retire the 47


What would you expect? The B-47 was the first really large swept wing multi-engine jet to go into service in large numbers and accumulate a fleet operating history. There was no fatigue history to guide designers in building a long life swept wing of that flexibility, aspect ratio, and size with engines mounted outboard on pylons. All the calculations and projections in the world can't compensate for a lack of hard data to base them on. Boeing was "exploring the dark side of the moon", and I think they achieved a miracle equivalent to solving the S-duct issue with the 727.
Now they weren't perfect; I've seen a number of pieces of wing structure wreckage from an early model B-52 crash site, and they were full of cracks with patches on top of patches. And that was early days, when they were still high altitude bombers.
Cheers,
Wes

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## XBe02Drvr (Jun 14, 2018)

Zipper730 said:


> That seems to add up: The F-86D couldn't turn fast enough at altitude to reposition itself...


Never mind turning, the Dog Sabre couldn't breathe adequately at altitude with that radome schnozzola obstructing half its intake, and the engine couldn't reach its theoretical thrust output for lack of intake volume. The higher you flew, the worse it got, affecting speed, climb, and energy in a turn.
Cheers,
Wes

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## Barrett (Jun 14, 2018)

I grew up on the ranch in NE Oregon, beneath the low-level route from Fairchild AFB (Spokane) and Mountain Home. My most vivid childhood memory is that huge behemoth motoring overhead. The sound was impressive but so was the FEEL. You could sense that massive thrashing of the atmosphere before the 36 hove into view. Man o man. The first 52 I saw was a disappointment!

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## XBe02Drvr (Jun 14, 2018)

Barrett said:


> I grew up on the ranch in NE Oregon, beneath the low-level route from Fairchild AFB (Spokane) and Mountain Home. My most vivid childhood memory is that huge behemoth motoring overhead. The sound was impressive but so was the FEEL. You could sense that massive thrashing of the atmosphere before the 36 hove into view. Man o man. The first 52 I saw was a disappointment!


The practice area at my home airport was under an "Oil Burner" low level navigation route, and I would be frequently out with a student at 3500 - 4500 ft when a BUFF or a KC would come over at 6000 - 7000 ft. Sometimes even we would see a "conjugating pair", an awesome sight from just underneath, and audible over the sputter of our O-200.
Cheers,
Wes

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## ktank (Jun 15, 2018)

pinehilljoe said:


> The other part of the thread on the 47, I've read the 47 had wing fatigue issues, and some were lost in flight from wing failure, when doctrine change to low altitude flying with a pop up to release bombs. The USAF was not sorry to retire the 47



Interesting that the same thing happened to the Vickers Valiant when it was moved to low altitude roles (and it caused the premature retirement of the type).


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## XBe02Drvr (Jun 15, 2018)

ktank said:


> Interesting that the same thing happened to the Vickers Valiant when it was moved to low altitude roles (and it caused the premature retirement of the type).


Fatigue happens. You just gotta count on it and roll the dice. Whatever you design it NOT to do, you can count on somebody going out and doing it.
Cheers,
Wes

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## Zipper730 (Jun 15, 2018)

XBe02Drvr said:


> Never mind turning, the Dog Sabre couldn't breathe adequately at altitude with that radome schnozzola obstructing half its intake, and the engine couldn't reach its theoretical thrust output for lack of intake volume. The higher you flew, the worse it got, affecting speed, climb, and energy in a turn.


I didn't know that...

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## XBe02Drvr (Jun 16, 2018)

Zipper730 said:


> I didn't know that...


There was a really good article on the Dog Sabre in "Wings" or "Airpower", or maybe it was "Flight International" back in the day (70s?) that described the teething problems it had. It, like all the interceptors of its generation, was pushing the frontiers of several different technologies at once.
Cheers,
Wes

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## Vahe Demirjian (Jan 22, 2020)

Convair had a design for a flying boat based on the Model 37 airliner version of the B-36 bomber with Wasp Majors arranged in tractor configuration and high-mounted wing. 

Reference:

Johnson, E.R. (2009). _American flying boats and amphibious aircraft : an illustrated history_. Jefferson, N.C.: McFarland & Co.


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## BiffF15 (Jan 24, 2020)

Vahe Demirjian said:


> Convair had a design for a flying boat based on the Model 37 airliner version of the B-36 bomber with Wasp Majors arranged in tractor configuration and high-mounted wing.
> 
> Reference:
> 
> Johnson, E.R. (2009). _American flying boats and amphibious aircraft : an illustrated history_. Jefferson, N.C.: McFarland & Co.



Vahe,

PLEASE STOP!

V/R,
Biff


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## swampyankee (Jan 25, 2020)

Piper106 said:


> Does anyone have any data or links to technical papers on why the B-36 was built with pusher engines??
> 
> I assume that the Convair engineers (and the Northrup engineers working on the B-35) calculated that the drag reduction by not having the propeller airflow over the wing more than made-up for the losses resulting from the propeller having to work in the wake from the wing, but was the difference significant??
> 
> ...




The B-35 for the same reason as the N9M: getting enough yaw stability on a flying wing is difficult; engines behind the center of gravity are stabilizing, unlike engines in front, which are destabilizing. 

This doesn’t answer the question about why the B-36 was a pusher, but there were a few contemporary US bomber projects with wing-mounted pusher props, but none got built except the B-36. I suspect there were some wind tunnel model tests that showed an advantage.


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## Joe Broady (Jan 26, 2020)

In "Convair B-36" (Meyers K. Jacobsen, 1997) is a photo of a wind tunnel model with six tractor engines. The caption says, "Had it not been for wind-tunnel tests, the B-36 might have looked like this model with tractor nacelles, Davis wing, and a twin tail — a sort of oversized but streamlined B-24 Liberator. Installation of pusher-type powerplants was almost a foregone conclusion, for designers knew that pushers would decrease nacelle and wing drag, with corresponding increase in range using same fuel and weight. However, and to make tests complete in all respects, this tractor-type model was given a workout in the M.I.T. wind tunnel. The wooden 1/26th scale model had a nine foot wingspan. November 1941."

The photo is a plan view of the model, which appears to have the same leading edge sweepback as the production B-36 but an unswept trailing edge. Another illustration is a drawing (no date) with the propellers changed to pusher but the same straight trailing edge. The production B-36 trailing edge had a 3 degree sweepback, and the propellers were parallel to it and thus not exactly aligned to the direction of flight.

An interesting B-36 characteristic is the approach to power-on stall. The flight handbook says, "you will notice an unusually high deck angle during the approach. Propeller induced airflow, as shown in figure 6-1, maintains smooth air flow over the center section of the wing well beyond the angle at which a stall would normally occur. This extreme nose-high attitude combined with very low airspeed is another stall warning."

One advantage of the pusher design with the engines at the trailing edge is that engine fires — and they did occur on the B-36, especially in the early years — blow away from the wing, not into it.

You do pay a penalty in the form of extra stress as the props rotate through the wing wake. The flight handbook has graphs of the forbidden ranges of airspeed and rpm. These are different for the two blade manufacturers, Curtiss and A.O. Smith! Years ago I read in a book ("Men of the Contrail Country"?) the tale of a B-36 whose flight engineer made a blunder which damaged the oil seals on all six engines. The plane barely got on the ground before the oil supplies gave out. Possibly this was a case of operating for a prolonged time in the red zone.

In some circumstances it forced a departure from optimum power settings. "Deviations from the basic power schedule are caused by propeller vibration restrictions and turbosupercharger limitations." (AN 01-5EUG-1, "Flight Handbook USAF Series B-36H Aircraft," 1953)

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## Koopernic (Jan 27, 2020)

In terms of the B36's minor sweep back I will offer a educated guess. I was watching a documentary on the National Geographic Chanel Regarding DC3 development. Charles Lindbergh was called in as a consultant to ensure TWA didn't get bad aircraft. As a result Douglass did a lot of wing tunnel testing and found that its pitching characteristics and stability od their DC3 were not good. A slight sweep was added, this ensured that as the angle of attack increased the wing tips generated a forward pitch. The sweep was not so much so as to cause span wise flow handling issues and tip stall issue. I suspect this effect was utilised on the B36 as well. There may have been Centre of Gravity and structural issues it helped as well.

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## Peter Gunn (Jan 27, 2020)

Hey, if the B-36 was good enough for Jimmy Stewart and Harry Morgan, it's good enough for me.

Ditto the B-47.

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## 11bwmech (Jan 15, 2021)

Probably WX info could be obtained with the recon version, the RB-36. Don't know the numbers, but the AF had about as many of these as the bomber version. The B-36 was aptly named "Peacenaker" (not an official designation), as it never dropped a bomb in anger, but held the Russians at bay during the early to mid 1950s. Yes, it was a maintenance nightmare, but it could fly for a day or two without refueling, and the loss of an engine or two was not usually a big problem. I remember one made it back to base with all four inboard engines out, plus one jet. And to add to the drag, they windmilled at least one (not sure if one or two; memory is a little hazy after all this time) inboard engine for electrical power, as only engines 2 through 5 had alternators. Only problem they had was they almost ran off the end of the runway because they still had more power than they thought they did.

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## SaparotRob (Jan 15, 2021)

I’m glad this thread was resurrected. Lots of cool info.


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## Zipper730 (Jan 15, 2021)

XBe02Drvr said:


> There was a really good article on the Dog Sabre in "Wings" or "Airpower", or maybe it was "Flight International" back in the day (70s?) that described the teething problems it had. It, like all the interceptors of its generation, was pushing the frontiers of several different technologies at once.


The statement "teething problems" seems to make me wonder if they were able to rework the intake...

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## 11bwmech (Jan 16, 2021)

JoeB said:


> I believe the B-36 was an effective deterrent, but I would shift the timeline to the right. When in March 1951 the FEAF floated the idea of conventional B-36 missions from CONUS over North Korea with dual purpose of helping that effort and providing realistic training, SAC replied that only around 30 were fully mission capable. The B-36's real combat capability in numbers only dated from late 51-early 52 and by same token real B-47 capability post dated the Korean War, though it didn't have the degree of teething problems as the B-36. Also, the SAC of formidable repuation for relentless training and readiness was a work in progress in pre KW period. But on the defense, it was really more like ca. 1957 when the Soviet air defense system seriously compromised the crediblity of the B-36 year round*, especially after B-36's were stripped down for higher altitude operation from around '54 (in part to counter improved Soviet capabilities and in part because the retractable gun turret system was never fully debugged). The B-36 was an effective nuclear strike a/c from around '52-'57, give or take a year on either end, not long by today's standards but long enough to be important in those times.
> 
> In the very early Cold War the number of US nukes and credible delivery systems was pretty limited, though the number of bombs was skyrocketing by early Korean War, and training and readiness of B-29 and B-50 units had reached a level where they posed a significant nuclear threat to at least parts of the USSR. By same token, the US acted circumspectly about Soviet capabilities once they detonated their nuclear test device in 1949, but in reality the operational versions failed their initial test, and the Soviets had no real deliverable nuclear weapons until around '52, and a very limited capability v CONUS for some years after that. But both sides tended to assume a worst case, so in morale terms you might be right that the B-36 was important even before 1950, but it lacked much actual operational capability until later on.
> 
> ...





JoeB said:


> I believe the B-36 was an effective deterrent, but I would shift the timeline to the right. When in March 1951 the FEAF floated the idea of conventional B-36 missions from CONUS over North Korea with dual purpose of helping that effort and providing realistic training, SAC replied that only around 30 were fully mission capable.





Shortround6 said:


> Wing size may have had very little to do with engine placement as the engines were not actually _IN_ the wing but in the nacelles at the rear of the wing.
> 
> View attachment 237926
> 
> ...


Oh, the


Shortround6 said:


> Wing size may have had very little to do with engine placement as the engines were not actually _IN_ the wing but in the nacelles at the rear of the wing.
> 
> View attachment 237926
> 
> ...





Shortround6 said:


> Wing size may have had very little to do with engine placement as the engines were not actually _IN_ the wing but in the nacelles at the rear of the wing.
> 
> View attachment 237926
> 
> ...


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## Koopernic (Jan 16, 2021)

ktank said:


> Interesting that the same thing happened to the Vickers Valiant when it was moved to low altitude roles (and it caused the premature retirement of the type).



In the case of the B-47 the Boeing designers combined the new swept wing technology that George Schairer had found in Germany with thin laminar wings. The thin wings were completely unnecessary and not used in the subsequent B-52 yet they complicated the design, created aeroelasticity problems and structural issues. The Valiant suffered a somewhat short design and development so that it would be ready quickly to carry Britain's nuclear weapons and probably suffered a few minor shortcomings from this. When fatigue did become a problem the Victor and Vulcan were ready.


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## XBe02Drvr (Jan 16, 2021)

Koopernic said:


> In the case of the B-47 the Boeing designers combined the new swept wing technology that George Schairer had found in Germany with thin laminar wings. The thin wings were completely unnecessary and not used in the subsequent B-52 yet they complicated the design, created aeroelasticity problems and structural issues.


And taught Boeing more about large swept wing design with pylon mounted engines than anyone else in the world knew, or would know, for years to come.


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## XBe02Drvr (Jan 16, 2021)

Zipper730 said:


> The statement "teething problems" seems to make me wonder if they were able to rework the intake...


AFAIK they never completely fixed the problem throughout the life of the plane. The Dog Sabre lived up to its name from beginning to end. One of my mech school instructors, a retired career fighter pilot and Sabre veteran of MiG alley, (2 tours) spent over half his career in various versions of the Sabre (including a USN/USMC exchange tour in Furies) and hated his two years in the "Dawg" as the low point in his career. Even worse than his tour in C124 Globemasters or his tour as an interceptor squadron liaison officer at SAGE. "I was always an "eyes out" fighter pilot. Never had any use for that scope dope stuff. Even that sorry excuse for a fighter plane, the F94, hauling a clueless sergeant RO around in the back seat, was better than the Dawg! At least it had a 'burner and an engine that would stay lit. Never had much use for overweight swept wing gliders and windmilling airborne relights"

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## SaparotRob (Jan 16, 2021)

As long as I’m not the one jacking this thread, I read a long time ago that the “best” version of the F-86 was a Canadair variant. Just wondering.


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## SaparotRob (Jan 16, 2021)

The F-86 is one of the few jets that caught my fancy.

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## fastmongrel (Jan 16, 2021)

SaparotRob said:


> As long as I’m not the one jacking this thread, I read a long time ago that the “best” version of the F-86 was a Canadair variant. Just wondering.



That's always been my understanding. The Mk6 version with the Orenda 14 engine of 7,500 lb thrust.

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## Koopernic (Jan 16, 2021)

fastmongrel said:


> That's always been my understanding. The Mk6 version with the Orenda 14 engine of 7,500 lb thrust.


There was an Australian version with an Avon, CAC-27 Avon Sabre with twin 30mm Aden guns and almost twice the thrust. 60% of the fuselage was altered to fit the shorter wider Avon.

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## fastmongrel (Jan 16, 2021)

Koopernic said:


> There was an Australian version with an Avon, CAC-27 Avon Sabre with twin 30mm Aden guns and almost twice the thrust. 60% of the fuselage was altered to fit the shorter wider Avon.



Not twice the thrust of an Orenda 14. Practically the same but definitely not twice


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## SaparotRob (Jan 16, 2021)

Koopernic said:


> There was an Australian version with an Avon, CAC-27 Avon Sabre with twin 30mm Aden guns and almost twice the thrust. 60% of the fuselage was altered to fit the shorter wider Avon.


Just looked up the CAC-27. Cool airplane.


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## XBe02Drvr (Jan 16, 2021)

Koopernic said:


> 60% of the fuselage was altered to fit the shorter wider Avon.


We had an Avon at mech school. Hard to imagine a Sabre wrapped around that fireplug.


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## Koopernic (Jan 16, 2021)

XBe02Drvr said:


> And taught Boeing more about large swept wing design with pylon mounted engines than anyone else in the world knew, or would know, for years to come.



The pylons on the B-47 were dimensioned such that they damped rather than helped excite the resonant aeroelastic flutter frequency of the wings. That idea itself came from the forward swept wings of the Junkers Ju 287. Because of the aeroelastic problems of the forward swept wings Junkers designers used a twin spar design with strong skins to ensure high torsional rigidity. This required the engines to be suspended in pods so that the skin was not interrupted. The pods pendulous frequency was dimensioned to avoid anticipated flutter.

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## Joe Broady (Jan 19, 2021)

Joe Broady said:


> You do pay a penalty in the form of extra stress as the props rotate through the wing wake. The flight handbook has graphs of the forbidden ranges of airspeed and rpm. (AN 01-5EUG-1, "Flight Handbook USAF Series B-36H Aircraft," 1953)



I may have given the impression that prohibited speed and rpm combinations were something unique to pushers. Not at all. "The possibility that flight and ground operation might take place at engine and aircraft conditions where flexural propeller vibration stress levels exceed allowable limits has resulted in operating restrictions." (1C-124A -1, C-124 flight manual). For instance, 1250 - 1850 rpm was prohibited on the ground except to quickly pass through that range. In flight there were additional restrictions that depended on weight and speed.

The B-36 flight handbook says, "These limitations are primarily based on propeller vibration limits but the vibrations may be of such nature that they can also weaken the propeller shaft. The vibratory forces are caused by power impulses imposed as each cylinder fires; by the aerodynamic disturbances created as a blade or blades pass through a region of turbulent air behind the wing or adjacent to the fuselage; and by other causes such as misfiring cylinders, malfunctioning vibration dampeners, and extended flaps."

Both the B-36 and C-124 used Curtiss 3-blade propellers.

Earlier I mentioned the B-36 propellers were parallel to the wing trailing edge, which was swept back 3 degrees.. This was a factor when you feathered a propeller. "On this airplane the engine nacelles are not parallel with the fuselage center line in the horizontal plane. The nacelles are 'toed in' at the propeller end, resulting in the propellers on one wing having a slightly different relative wind than those on the other wing. This condition may lead to propellers on engines No. 1, 2, and 3 windmilling in a direction opposite to normal operation when they are feathered."

That slow reverse windmilling will eventually damage an engine due to inadequate lubrication., so the engineer (coached by a gunner in the rear compartment) would jiggle the manual pitch switch to stop the rotation.

Finally, a bit of B-36 trivia. It's well known the plane entered service as a 6-engine bomber, and the jet pods were added later. What is not well known is that the pods were removable! "Occasionally, it may be desirable to operate the airplane without the pods installed to obtain maximum range (with a sacrifice in possible top speed)." Pod removal reduced the B-36H operating weight (crew + crew equipment + ammo + unusable fuel + other fluids fully serviced) from 181.800 to 167.600 lb, or a 14,200 lb loss. Max weights were 357,000 and 330,000 respectively. I have never seen a photo of a de-podded B-36. It must have happened rarely, if at all.

Those max weights are from the flight handbook charts, but the same charts show the B-36H can fly with an massive overload if you accept the risk. With one jet pod (or any two piston engines) inoperative, the weight necessary to bring service ceiling down to sea level is more than 550,000 lb.

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## nuuumannn (Jan 19, 2021)

XBe02Drvr said:


> AFAIK they never completely fixed the problem throughout the life of the plane. The Dog Sabre lived up to its name from beginning to end. One of my mech school instructors, a retired career fighter pilot and Sabre veteran of MiG alley, (2 tours) spent over half his career in various versions of the Sabre (including a USN/USMC exchange tour in Furies) and hated his two years in the "Dawg" as the low point in his career.



Great info. Funny thing was, give a dog a different designation, tweak the internals a bit and sell it to your allies, with one of them putting it into production to boot, as NATO common equipment and voila! the F-86K becomes a standard NATO all-weather fighter!

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## XBe02Drvr (Jan 19, 2021)

nuuumannn said:


> Great info. Funny thing was, give a dog a different designation, tweak the internals a bit and sell it to your allies, with one of them putting it into production to boot, as NATO common equipment and voila! the F-86K becomes a standard NATO all-weather fighter!


With a redesigned intake duct, an engine with a little more oomph and a little more tolerance of Intake turbulence, it might have been a world beater. Oh yes, and a lighter weight more compact electronics package would have helped, too.

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## special ed (Jan 20, 2021)

The B-36 Featherweight program, classified for many years, did not use the J-47 pods as I remember. Now I will have to look it up.


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## GrauGeist (Jan 20, 2021)

XBe02Drvr said:


> With a redesigned intake duct, an engine with a little more oomph and a little more tolerance of Intake turbulence, it might have been a world beater. Oh yes, and a lighter weight more compact electronics package would have helped, too.


Maybe get rid of the front armor and fool with the CoG a little bit and...oh, wait...

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## XBe02Drvr (Jan 20, 2021)

GrauGeist said:


> Maybe get rid of the front armor and fool with the CoG a little bit and...oh, wait...


Alright, enough already! We "Groundhog Warriors" are embarrassed enough as it is. You don't have to rub it in!
I wannabe a "Warthog Warrior" when I grow up...

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## special ed (Jan 20, 2021)

In 1960 USAFA cadets were at Wright Pat and viewing the outdoor aircraft. One climbed up to look in the B-36 waist blister and seeing the rows of bunks for crew relief exclaimed " It's a flying whorehouse."

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## Zipper730 (Jan 20, 2021)

XBe02Drvr said:


> With a redesigned intake duct, an engine with a little more oomph and a little more tolerance of Intake turbulence, it might have been a world beater. Oh yes, and a lighter weight more compact electronics package would have helped, too.


I doubt the electronics would have been negotiable, but what kind of changes could have been made to the intake duct?



special ed said:


> The B-36 Featherweight program, classified for many years, did not use the J-47 pods as I remember.


I've heard of the Featherweight modifications, but I don't know any details of them. If it's declassified, please post what you find.


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## special ed (Jan 20, 2021)

Internet shows feather weight kept J-47 pods, but years ago Wings or Airpower had a very good article and pictures. I seem to remember there was also featherweight III. The max altitude was in excess of 50,000 feet. A brief bit of trivia: The local hobby shop had a part time helper in the 1980s who was ex-Airforce. Once he and another customer were discussing their respective USAF careers and I heard the clerk say he had been in the featherweight B-36 program. At the time, it meant nothing, but when the magazine Article came out I mentioned it to him and he looked shocked as if I just exposed top secret info.

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## XBe02Drvr (Jan 20, 2021)

Zipper730 said:


> I doubt the electronics would have been negotiable, but what kind of changes could have been made to the intake duct?


Actually, even back in electron tube days, the second generation of a system was often lighter and more compact than the original, as long as designers could resist the urge to cram in new features.
I'm no expert on intake ducting, but my understanding is that the Dog Sabre's intake was not the straight shot down the throat of the compressor that the "open mouth" Sabres had, due to the bend around the radome. Early jet engines tended to be a little fussy about smooth airflow into the face of the compressor, and would sometimes compressor stall or flame out just from the wakes of bullets or cannon shells leaving the nose guns. The early axial flow versions were especially susceptible to this. Sometimes a sudden yaw or the wake turbulence from another aircraft would cause a flameout. My instructor said he got a lot of practice at windmilling relights in the dog.

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## Zipper730 (Jan 20, 2021)

XBe02Drvr said:


> Actually, even back in electron tube days, the second generation of a system was often lighter and more compact than the original, as long as designers could resist the urge to cram in new features.


If I recall the F-86's radar had some new features built into it to reduce workload.


> I'm no expert on intake ducting, but my understanding is that the Dog Sabre's intake was not the straight shot down the throat of the compressor that the "open mouth" Sabres had, due to the bend around the radome.


It was an S-duct.


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## XBe02Drvr (Jan 20, 2021)

Zipper730 said:


> It was an S-duct


For a jet that's going to be expected to maneuver at near-sonic speeds and has an engine fussy about intake flow, that's got to be a problem. The fine points of airflow turbulence and compressibility in ductwork were still being worked out on sliderules in those days, and before the advent of variable stators, the range of airflow conditions compressor blades could handle without stalling was relatively narrow.


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## SaparotRob (Jan 20, 2021)

I love aviation gobbledygook!


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## Joe Broady (Jan 21, 2021)

Joe Broady said:


> With one jet pod (or any two piston engines) inoperative, the weight necessary to bring service ceiling down to sea level is more than 550,000 lb.



That's a purely theoretical figure, well beyond any possible weight. If fuel tanks and bomb bays are loaded to capacity (184,000 + 84,000 lb) the B-36H weighs 449,000 lb. Max allowable weight by the book is 357,000 lb, which gives a load factor of 2.0, "the minimum generally considered acceptable." Nevertheless it does say, "gross weight limitation is 455,000 pounds for 8,000 foot ground run. (Rate of climb with normal rated power 675 FPM.)"

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## 11bwmech (Jan 21, 2021)

ccheese said:


> I just saw this thread, and had to go all the way through it. I am probably the only person on the forum who has actually flown in the B-36. I was stationed at Wheelus AFB, in Tripoli, Libya 1954-1955. I made two flights on the B-36 as an observer (non-crew). Both times we went from Wheelus to somewhere over Europe, then turned around and came back by a different route. I thought it was an enjoyable plane to fly in. On the down side, on both flights we had to shut down the #3 engine. First time for overheating and the second time for a pitch control failure of some kind. The plane flew just as well without it !
> 
> As for the pros and cons of the plane, as in the discussion of the thread, I honestly don't know that much about the technical aspects of the plane.
> 
> Charles


You aren't the only one. I was a B-36 prop mechanic and flew in it a lot. The props had their own oil supply which had to be serviced after every flight. So when they had an RON, a prop man had to go along.

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## 11bwmech (Jan 21, 2021)

FLYBOYJ said:


> And how about trim?


That's what I was talking about. The aircraft was usually trimmed with a positive angle. I'm not an engineer, but when I was flying in a B-36, that's the way it was.


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## rinkol (Jan 21, 2021)

JoeB said:


> I haven't ever seen quantitative papers or books about this design decision, but qualitatively speaking it's more or less as you said. The B-36 specification heavily emphasized long range and thus cruise performance. As a rule a pusher configuration will be more efficient in cruise, subject to considerations like rotation on take off, which might force the pusher prop to be smaller diameter to clear the ground on rotation. However in B-36 case they found that pusher was definitely more efficient in cruise. Some early concepts leading to the B-36, and some wind tunnel models even, had push-pull nacelles or conventional tractor nacelles. but the designers believed pusher would win, and at least at the state of the art in wind tunnel testing at the time the tests proved them right.
> 
> The disadvantage of pusher is not so much that wing downwash will actually make it less efficient net, but the vibration considerations of uneven flow, not only wing downwash in cruise, but also the engine exhaust stream flowing through the prop. These were issues with the B-36 which had flight restrictions related to prop vibration. Also, besides the cruise configuration, the wing interaction issues become more serious with flaps down. Note in photo's of B-36's even fully extended flaps are continued right in front of the props. And also in low speed flight, the tractor prop helps generate lift which the pusher doens't to the same degree. And then there's more potential for FOD from stuff thrown into the props by the main gear; again see B-36 photo's: the main gear legs are within the radius of the inboard props.
> 
> ...



In the case of the B36, the pusher arrangement lent itself to burying the engines in the wings. In the 1940s, this was seen as a good way to reduce drag - special engines, such as the Wright Tornado, were built to facilitate such schemes. There was also the idea of trying to preserve laminar air flow over the wing. though I am not sure to what extent this was achieved.

The pusher installation had the problem of requiring drive shafts at the cost of extra mechanical complexity and weight. The B-35 was supposed to use a pusher engine configuration with contra-rotating propellers, but this failed to mature.


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## 11bwmech (Jan 21, 2021)

special ed said:


> The B-36 Featherweight program, classified for many years, did not use the J-47 pods as I remember. Now I will have to look it up.


Featherweights used jets. They got rid of gun turrets, insulation and "crew comfort" items. I'm not sure what else.


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## Builder 2010 (Jan 21, 2021)

I had to page through the entire thread to make sure that no one posted this. It's the thing that the B-36 was designed to haul. It's the Mark 17 Thermonuclear weapon that weighs 45,000 lbs. They built the Peacemaker around it, just like they built the A-10 around the 30mm cannon. The B-36's bomb bay is like a banquet hall. It is vast. They duplicated it in the B-52.

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## XBe02Drvr (Jan 21, 2021)

Builder 2010 said:


> It's the Mark 17 Thermonuclear weapon that weighs 45,000 lbs.


"Holy fireball, Batman, that's max gross for a Fokker F27!"


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## Simon Thomas (Jan 21, 2021)

With a bomb that powerful, does the plane that dropped it have any chance of surviving the kaboom?


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## swampyankee (Jan 21, 2021)

I'm barely old enough to have seen B-36s in flight. When I was a mere lad, barely higher than a grasshopper's knees, I would see (or hear) them on the last leg of their flight from wherever the hell they were based to the Arctic and back, although I wanted to fly B-47's.


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## GrauGeist (Jan 21, 2021)

Builder 2010 said:


> I had to page through the entire thread to make sure that no one posted this. It's the thing that the B-36 was designed to haul. It's the Mark 17 Thermonuclear weapon that weighs 45,000 lbs. They built the Peacemaker around it, just like they built the A-10 around the 30mm cannon. The B-36's bomb bay is like a banquet hall. It is vast. They duplicated it in the B-52.
> 
> View attachment 609717


With all due respect, the B-36's design and specs dated to '41 with it's original completion date by '45 (it was delayed and finally first flew in '46).
The Mark 17 was developed in the early 50's - ten years after the B-36 was being prototyped.

There was a postwar modification called the "Grand Slam Installation", initiated in 1950, to allow for larger nuclear weapons.

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## swampyankee (Jan 21, 2021)

Simon Thomas said:


> With a bomb that powerful, does the plane that dropped it have any chance of surviving the kaboom?



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.

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## nuuumannn (Jan 21, 2021)

XBe02Drvr said:


> Early jet engines tended to be a little fussy about smooth airflow into the face of the compressor, and would sometimes compressor stall or flame out just from the wakes of bullets or cannon shells leaving the nose guns. The early axial flow versions were especially susceptible to this.



I'm looking at YOU, first gen RR Avon in the Hunter!

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## GreenKnight121 (Jan 22, 2021)

swampyankee said:


> 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.


Mk 17 yield was 15 megatonnes. 

Tsar Bomba had a yield of 50 Mt (210 PJ). It was to be the basis of a larger bomb, but used inert material in what was to be the 3rd stage of the larger bomb.
In theory, the bomb would have had a yield in excess of 100 Mt (420 PJ) if it had included a uranium-238 fusion tamper but, because only one bomb was built to completion, that capability has never been demonstrated.
The test of a complete, three-stage, 100 Mt bomb was rejected due to the extremely high level of radioactive contamination that would be caused by the fission reaction of large quantities of third stage uranium.

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## chipieal (Jan 22, 2021)

One of the historical mysteries surrounding the 36, why the B-60 was never produced. It would seem in the cost conscious atmosphere of post WWII, a proven airplane which had swept back wings and all jet engines would be far more desirable than a clean sheet bomber that essentially did the same thing. The few sources I have found, talked about "inferior performance" to the 52. Could it be that Boeing had better lobbyists than Convair? I think in this configuration, the true advantage of The 36 air frame would finally be utilized. I hate to what if, but the 36 was and is my favorite bomber ever since the first time a viewed Strategic Air Command. (at 8 years old)


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## special ed (Jan 22, 2021)

For anyone genuinely interested why the B-35 & B-49 bombers were cancelled, there still exists on you tube a half hour video I first saw on TV about 30 years ago. It is a story of greed, politics and power. Spend the time to watch: Flying Wings-John K. Northrop's final interview-1979 
Afterwards one might check Symington's interference with the NFL (Wikipedia).


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## XBe02Drvr (Jan 22, 2021)

chipieal said:


> One of the historical mysteries surrounding the 36, why the B-60 was never produced.





chipieal said:


> the 36 was and is my favorite bomber ever since the first time a viewed Strategic Air Command. (at 8 years old)



To anybody who wasn't already a B36 true believer, the answer should be pretty obvious.
Large scale multi engine swept wing technology was a whole new arena with no body of experience to rely on, and Boeing was acquiring that experience with the B47 before the B36 was even in service. By the time Convair had any spare brain cells available to look beyond the B36 and all of its other projects, the B52 was already well underway and on track to be a more advanced and capable aircraft.

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## rinkol (Jan 22, 2021)

swampyankee said:


> 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.


From what I understand, increasing the power of large hydrogen bombs had long reached the point of diminishing returns. Basically, you were just blasting a larger hunk of atmosphere into space.


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## XBe02Drvr (Jan 22, 2021)

rinkol said:


> From what I understand, increasing the power of large hydrogen bombs had long reached the point of diminishing returns. Basically, you were just blasting a larger hunk of atmosphere into space.


I think the goal was to come up with a weapon that with a properly placed air burst could ignite a huge area all at once, creating the mother of all firestorms, which would then move downwind, devastating and depopulating entire regions. Scorched earth without the effort of invading and occupying. Then along came the concept of nuclear winter and the folly of supermegatonnage began to sink in.
As a teenager, I read all kinds of articles about these ideas.


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## Zipper730 (Jan 22, 2021)

Builder 2010 said:


> I had to page through the entire thread to make sure that no one posted this. It's the thing that the B-36 was designed to haul. It's the Mark 17 Thermonuclear weapon that weighs 45,000 lbs. They built the Peacemaker around it, just like they built the A-10 around the 30mm cannon.


While Grau Geist had largely addressed this, the design of the B-36 wasn't to carry a huge nuclear warhead: It was to be able to fly from the Continental United States, bomb Germany, and return.

The requirements initially called for a range of 12000 miles while carrying 4000 lb. of bombs, at an altitude of 40000' at 275 mph true airspeed, a maximum speed of 450 mph, while carrying adequate defensive armament. Far as I know, these stipulations also called for the ability to carry heavier loads over shorter distances as well.

It wasn't long before the requirements called for a range reduction of 10000 miles while hauling 10000 lb. of bombs, with the same cruise and maximum speeds, and altitude requirements. I don't think there was any change in defensive armament requirements at the time. This might have been out of a desire to hit Japan from the United States, as well as heap more bombs on either.

Around 1944, there appeared to be a requirement for the aircraft to carry it's own escort fighter onboard, given that escort fighters were seen as virtually essential to daytime bombing (something that was generally the USAAF's preference), and the range of the B-35 or B-36 would make a traditional escort fighter all but impossible. The requirements initially called for either a plane that was partially submerged inside the plane, then one that was carried completely inside the bomb-bay (I don't know if there were proposals for piston or jet powered aircraft, but ultimately a jet-powered design would be built called the XF-85).

Somewhere between 1944 to 1945, there was a change in altitude requirements from 40000' to 50000' and a range increase from 10000 statute to 10000 nautical miles as well. I don't know if there were any changes to the defensive armament at the time, but I do remember seeing some proposals that included 37mm cannon in the turrets, though it'd later change to 20mm cannon.

Because the aircraft was large and required large components to be built to standard, and not everybody realized this: It resulted in lots of components being built below or outside the specified standard; because this required time to undo and rebuilt, as well as the fact that the economy quickly slowed from wartime to some semblance of peacetime: The aircraft wouldn't fly until August of 1946, around a year late; with the intended supercharger either cancelled, or not available in time: The aircraft was limited to around 10000'-15000' instead of the intended goal for a considerable period of time; while an appropriately suitable turbocharger was installed: The altitude ended up below the specified amount, as well as the top-speed (though the cruise speed might have been a little higher), though changes were made to trim off weight (some proposals might have involved the removal of at least some of the turrets), I'm not sure if the aircraft ever achieved the intended altitude over target, particularly when loaded, and it's range came up a bit below the 10000 nm figure.

Like most aircraft it had some basic problems that had to be overcome, such as the landing-gear design, which produced excessive footprint pressure, that meant only 3 airfields could operate the plane, but it was also the first USAF bomber that could be adapted to accommodate nuclear weapons with no major issue. That said, the four bomb-bays the aircraft had were eventually modified into two positively enormous weapons bays, and the normal maximum payload was 72000 pounds, with an overload capacity, often listed as 86000 lb, possibly as much as 87200 lb., while carrying 2 x Cloudmakers (they were basically earthquake bombs inspired by the Tallboy and Grandslam) which weighed around 43,600 pounds apiece. This also made it a natural fit for the first aerially deliverable hydrogen-bombs.

While I could be wrong about this, the first H-bombs actually carried liquid deuterium and tritium instead of the later lithium deuteride: This resulted in some degree of boil-off, and the need for dewar-flasks to replenish the stuff in flight. I think these were called "Emergency Capability" bombs (as in "It's an emergency -- we gotta bomb the Soviet Union into the stone-age!)


> The B-36's bomb bay is like a banquet hall. It is vast. They duplicated it in the B-52.


Though I don't know the dimensions of the B-52's bomb-bay, it didn't seem anywhere NEAR as large as the B-36. That said, it wouldn't be the first time I was wrong.



Simon Thomas said:


> With a bomb that powerful, does the plane that dropped it have any chance of surviving the kaboom?


If I recall, it was either doubtful that the airplane would escape the blast at best, and most likely, they'd be hoist by their own petard: Interestingly, the high power of hydrogen-bombs lead to a proposal of a modified B-47 designed to fly as a drone. Ultimately, a less extreme solution revolved around a ribbon chute that would deploy in the fall, to extend the escape time.



GreenKnight121 said:


> Tsar Bomba had a yield of 50 Mt (210 PJ). It was to be the basis of a larger bomb, but used inert material in what was to be the 3rd stage of the larger bomb.


It used a lead-tamper for the third stage. The yield likely would have been around 100 MT, and with modifications, they had anticipated up to 150 MT.


> The test of a complete, three-stage, 100 Mt bomb was rejected due to the extremely high level of radioactive contamination that would be caused by the fission reaction of large quantities of third stage uranium.


From what I recall, the reason had to do with the fact that the Tu-95 that carried it would probably get incinerated or vaporized by the bomb it dropped.

Interestingly there was a proposal to use the basic design of the weapon as an ICBM warhead: The UR-500 (later Proton Rocket) was to haul it to a city near us. Fortunately it was not used in that role, and instead proved a very effective means of launch stuff into space.



special ed said:


> For anyone genuinely interested why the B-35 & B-49 bombers were cancelled, there still exists on you tube a half hour video I first saw on TV about 30 years ago. It is a story of greed, politics and power.


Was there any corruption with the B-35 prior to 1944? I remember most of the corruption that occurred was after 1946 or so.

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## special ed (Jan 23, 2021)

The corruption occurred late 1940s as Symington appears to have invested in Convair. Since Bill Northrop resisted the merger, Northrop did not get aircraft contracts until the 1959 privately funded N-156 became the F-5A for Military Assistance to smaller countries. Eventually, it was seen that a trainer version would be beneficial hence the T-38.


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## GrauGeist (Jan 23, 2021)

special ed said:


> Northrop did not get aircraft contracts until the 1959 privately funded N-156 became the F-5A



Northrop's F-89 (N-24) was purchased by the Air Force in the late 40's.

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## emu27 (Jan 23, 2021)

Met reports were available, the British and Canadians ran regular passenger/mail services on non stop flights between Prestwick and Dorval during the war with C-87 and Lancastrian aircraft.


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## ThomasP (Jan 23, 2021)

My understanding is that the 10,000 mile range with the 10,000 lb payload specification for the B-36 was the minimum needed to allow hitting any target of realistic potential (ie Europe, USSR, China, etc) from bases in the US and continue on to a safe recovery point on or over friendly/neutral territory. This would allow recovery in the UK or North Africa if the target was in Europe/western USSR - Saudi Arabia or Turkey if the target was in central USSR - Japan, Korea, Australia, if the target was in eastern USSR or China. For the most part, the longer range missions were planned to be one way. As far as I know the range requirement was found to be unrealistic (a max effective range of about 7,500 miles was achieved) and plans were to launch from closer to the target (the missile installations in the USSR) with recovery as before, or in many cases a true one-way mission.

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## special ed (Jan 23, 2021)

GrauGeist is correct. Forgot all about them. I think those contracts were well under way and they were hoped to stop the Tu-4s should they come over the pole. I remember being told by a "B-89" driver that a tail chase of a Tu-4 was impossible and if he missed the intercept, he may as well go home and refuel.


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## Joe Broady (Jan 24, 2021)

rinkol said:


> In the case of the B36, the pusher arrangement lent itself to burying the engines in the wings.



But B-36 engines were not buried in the wings, though the myth has been around for decades. "The big R-4360s were buried in the thickest part of the wing and drove the pusher propellers through long rearward extension shafts." (Herschel Smith, "Aircraft Piston Engines," 1981)

In reality, the B-36 had its Wasp Majors almost as close to the propellers as a conventional tractor installation. There was just a short extension case for a little more separation. (That from a manual for engine students at Sheppard AFB, which is on the web, I can't remember where.) This is clear if you look at any photo (sorry, haven't got a link at hand) of B-36 maintenance with nacelle access panels removed. The engines are just ahead of the props.


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## ThomasP (Jan 24, 2021)



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## swampyankee (Jan 24, 2021)

chipieal said:


> One of the historical mysteries surrounding the 36, why the B-60 was never produced.



Because, from all published data, its performance was much worse than the B-52.

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## rinkol (Jan 24, 2021)

Joe Broady said:


> But B-36 engines were not buried in the wings, though the myth has been around for decades. "The big R-4360s were buried in the thickest part of the wing and drove the pusher propellers through long rearward extension shafts." (Herschel Smith, "Aircraft Piston Engines," 1981)
> 
> In reality, the B-36 had its Wasp Majors almost as close to the propellers as a conventional tractor installation. There was just a short extension case for a little more separation. (That from a manual for engine students at Sheppard AFB, which is on the web, I can't remember where.) This is clear if you look at any photo (sorry, haven't got a link at hand) of B-36 maintenance with nacelle access panels removed. The engines are just ahead of the props.


From a frontal view, it is apparent that the engines make only a small contribution to the frontal area of the plane. They are not completely buried, but the B-36 comes closer to a buried engine installation than nearly all other contemporary multi-engine bombers. As always, there is a host of engineering trade-offs to consider.


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## wuzak (Jan 24, 2021)

ThomasP said:


> My understanding is that the 10,000 mile range with the 10,000 lb payload specification for the B-36 was the minimum needed to allow hitting any target of realistic potential (ie Europe, USSR, China, etc) from bases in the US and continue on to a safe recovery point on or over friendly/neutral territory. This would allow recovery in the UK or North Africa if the target was in Europe/western USSR - Saudi Arabia or Turkey if the target was in central USSR - Japan, Korea, Australia, if the target was in eastern USSR or China. For the most part, the longer range missions were planned to be one way. As far as I know the range requirement was found to be unrealistic (a max effective range of about 7,500 miles was achieved) and plans were to launch from closer to the target (the missile installations in the USSR) with recovery as before, or in many cases a true one-way mission.



I believe the long range required was the fear that the UK would fall. If that were the case and the US was at war, then bombing missions would need to be flown from the Continental United States to bomb targets in Europe.


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## ThomasP (Jan 24, 2021)

Hey wuzak,

I may be wrong, but I thought the original range specification for the B-36 was 12,000 miles with X payload, and that it was decreased to 10,000 miles with 10,000 lb (ie a Mk III A-bomb) after(?) the war.


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## GrauGeist (Jan 25, 2021)

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.

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## Zipper730 (Jan 25, 2021)

special ed said:


> The corruption occurred late 1940s as Symington appears to have invested in Convair.


That seems to fit with what I understand: The B-35 was initially favored by the bomber-generals, possibly because it was more aerodynamic, longer-ranged, was actually lighter, had better defensive armament coverage, and may have been able to fly faster, and higher.

It appears to have fallen out of favor around 1944, and while I don't know the reasons, if directional control and stability was realized to be a problem, it seems to explain matters pretty well. The B-36 was slated to fly at that point.

Whether there was any intent to fly the XB-35 as a proof of concept in 1944 anyway is unclear, but post-war, there did seem to be some interest, but it's around this time (far as I remember), that things went sideways: There were basically three problems that plagued the B-35 with two being technical, and one being corruption.

The technical issues comprised...

Stability issues
The aircraft seemed to have serious issues with directional stability, showing a profound tendency to fish-tail, and wallow all over the place: This would have affected bombing accuracy, something that was actually a problem on the B-24, though to a much lesser extent. It would also have resulted in a longer bomb run than say the B-29, and B-36.
The aircraft appeared to be a bit twitchy on pitch: This seems to be a problem with flying wing-designs and some tailless aircraft (depending on the length of the mean aerodynamic chord), which might be related to the fact that, in order to have workable pitch control: You need to have sufficient spacing from the control surfaces to the bulk of the aircraft's mass, so the bulk of the mass ends up bunched in the middle (and given the choice between a little too much or a little too little controllability, most designers would opt for a little too much). I've been told this also affects dynamic stability as well, setting up oscillations (I'm not sure if the B-35 had issues with this on pitch). Interestingly, at high AoA, the pitch was fairly stable, possibly owing to the use of slots on the wings.

Mission priority changes: In the post-war period, there was a change from delivery of bombs and incendiaries, to the delivery of nuclear bombs.
As with the B-36, it was designed to carry 10,000 pounds of bombs a distance of 10,000 nautical miles normally, with the ability to carry larger loads over shorter distances, which it was completely capable of. It could also carry 51,000 pounds of bombs maximum, but the biggest bombs it was capable of carrying were 4000 pounds.
The only 4000 pound bomb that I know of in the US inventory was the AN-M56 which was 117.25" in length, with a body diameter of 34.25" to 36", and a total diameter of 47.625".

Early nuclear bombs were quite large owing to poor fission efficiency early on, which resulted in them being larger than many of the bombs used in WWII in one dimension or another (often diameter).
Mk-1 (Little Boy): The weapon weighed between 8900-9700 pounds (depending on source) as released, and was 28" in diameter by 128" in length. While it was fairly slim by the standards of nuclear weapons: Only 5 were built, of which one was expended on August 6th of 1945.
Mk-3 (Fat Man): The weapon weighed 10300 pounds and, while the same length, it was 60" in diameter, and 120 of them were built, making it a considerably more popular design that such a plane would be expected to carry.
Mk-4: It was the first assembly-line nuclear weapon to be produced, 550 were built, and, while it was about the same size as the Mk-3, it was about 500-600 pounds heavier.
The Mk-1 and Mk-3, if not all, required the bombardier to climb into the bomb-bay to assemble the weapon.


...where as corruption appeared to have started up with Floyd Odlum, connecting down to Symington, and into some of the USAAF's ranks. While it appeared physically possible to, in one way or another, graft a bomb-bay into the design, or enlarge the bay to accommodate a weapon, and the eventual development of the Mk-5 which was slightly smaller than the AN-M56 in diameter (though a 1-3" longer than the Mk-3 & Mk-4), but the USAF wouldn't let them modify the airplane to carry nuclear weapons (and this was after they told them they wouldn't accept the plane if it couldn't deliver a nuclear bomb -- think about that -- they structured a no-win into the procurement process).

There was also a lot of disinformation spread that the aircraft should not even be spin-tested because it would be too dangerous to do so, but it was nonsense: Tests were performed to this effect. While I wouldn't be surprised if it was difficult to recover from a spin, at the same time, it was physically possible.


> Since Bill Northrop resisted the merger


Wait, they wanted Northrop to merge with Convair? I thought they wanted a plant that was then currently used by Convair to manufacture the planes, which Northrop felt was unfair to his employees. If I recall, some of Northrop's underwriters also managed to ensure that he didn't get to make any decisions, or they had to pass through somebody else.

It's interesting to note that most of the problems with the aircraft were essentially fixable. Otis (yep, the old elevator designer) had developed an early stability augmentation device (which originated on elevators, which is why they slow down as they near the top rather than just go *BANG*) which corrected for the yawing issues. While I'm not sure if this was ever applied on the YB-35, it was on the YB-49.

The YB-49, as I understand it, had the 4 x R-4360's and the propellers that went with them removed, with 8 x J35's (supposedly they couldn't accommodate the J47's but I can't figure out why, unless it was weight related, as their dimensions were basically identical) placed in their spot, with fins grafted on where the propeller shafts were located to add stability back that was taken away. With roughly the same stability, the system was said to meet the specifications for bombing accuracy (admittedly, the description seemed to indicate it barely met the requirements).


> Northrop did not get aircraft contracts until the 1959 privately funded N-156 became the F-5A for Military Assistance to smaller countries. Eventually, it was seen that a trainer version would be beneficial hence the T-38.


Well, GrauGeist already pointed out that the F-89 ended up being developed for the USAF.


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## special ed (Jan 25, 2021)

See post #159 and look up the you tube interview.

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## Koopernic (Jan 26, 2021)

swampyankee said:


> Because, from all published data, its performance was much worse than the B-52.



Agreed. In addition to is lessor range the B-49 needed pitch and yaw dampers, they took a while to work and it couldn't carry certain nuclear bombs. No one is going to go back to the special physics guys and tell them to miniaturise their bomb some more because although the B-36, B47 and B52 could carry their bomb they're not a nifty as a flying wing.

The flying wing technology should have been perused more. The corruption allegations are likely true, they usually are but the aircraft couldn't do the job as well.

The B-49 needed flight control 'augmentation' something that I believe came to maturity with the SR-71/YB12A. Maybe some other aircraft.


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## swampyankee (Jan 26, 2021)

I was referring to the B-60, not the B-49. 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.

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## davparlr (Jan 26, 2021)

Zipper730 said:


> The YB-49, as I understand it, had the 4 x R-4360's and the propellers that went with them with 8 x J35's (supposedly they couldn't accommodate the J47's but I can't figure out why, unless it was weight related, as their dimensions were basically identical), with fins grafted on where the propeller shafts were located to add stability back that was taken away.


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.


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## swampyankee (Jan 26, 2021)

davparlr said:


> 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.
> 
> ...



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.

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## Koopernic (Jan 26, 2021)

GrauGeist said:


> 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.


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## GrauGeist (Jan 26, 2021)

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.


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## Zipper730 (Jan 26, 2021)

Koopernic said:


> 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.



swampyankee said:


> 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).



davparlr said:


> 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.

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.
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.


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## Koopernic (Jan 27, 2021)

Zipper730 said:


> 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.


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## yosimitesam (Jan 28, 2021)

swampyankee said:


> 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?

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## GrauGeist (Jan 28, 2021)

yosimitesam said:


> Anyone see that documentary, besides me?


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


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## yosimitesam (Jan 30, 2021)

Koopernic said:


> 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.
> 
> ...



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

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## Thumpalumpacus (Apr 11, 2021)

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.

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