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Thread: B-36 - Why a Pusher??

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    B-36 - Why a Pusher??

    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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    Quote Originally Posted by Piper106 View Post
    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
    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 enginewas 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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    IP/Mech THE GREAT GAZOO FLYBOYJ's Avatar
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    Quote Originally Posted by iron man View Post
    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 enginewas 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) ...
    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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    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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    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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    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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    Quote Originally Posted by Piper106 View Post
    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
    Last edited by JoeB; 04-29-2012 at 02:25 PM.

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    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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    Quote Originally Posted by tyrodtom View Post
    Siegfried, that's a fail on arithmetic. 28x2x6=336.
    Yes but I can pose the correct question, even with 1/2 bottle of Cabernet.

    Quote Originally Posted by tyrodtom View Post

    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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    Quote Originally Posted by Siegfried View Post
    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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    Quote Originally Posted by Siegfried View Post
    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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    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.
    Last edited by Jenisch; 04-30-2012 at 11:13 AM.

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    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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    Quote Originally Posted by Jenisch View Post
    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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    Quote Originally Posted by Siegfried View Post
    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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