B-47 Questions

[KJ_Lesnick]

I know the B-52D for example had a redesign of the bomb-shackles without any external volume change to the bomb-bay as part of the "big belly" mods which allowed a greater amount of bombs to be carried.

I do know the B-47E had a heavier bomb-load, but from what I remember it's maximum internal load was smaller (14,000 pounds vs 16,000 on the B-47A), and the 25,000 pound figure was based on hauling two heavy bombs around: I'm curious if the B-47A's bay could have physically carried more than 16,000 pounds if the bomb-shackles were re-configured and/or annular fins were used instead of box-fins (it's a physics question)?

[rickshaw]

Have you asked the B-47 Association, Kendra/Robyn?

[sandiego89]

I know the B-52D for example had a redesign of the bomb-shackles without any external volume change to the bomb-bay as part of the "big belly" mods which allowed a greater amount of bombs to be carried.

I do know the B-47E had a heavier bomb-load, but from what I remember it's maximum internal load was smaller (14,000 pounds vs 16,000 on the B-47A), and the 25,000 pound figure was based on hauling two heavy bombs around: I'm curious if the B-47A's bay could have physically carried more than 16,000 pounds if the bomb-shackles were re-configured and/or annular fins were used instead of box-fins (it's a physics question)?

I offer for discussion it is important to remember there are differences between normal and maximum bomb loads.  As with every aircraft there is a tradeoff in payload.  Fuel vs. bombs in this case.  The B-47 had weight, thrust and fuel (range) issues for its entire career.  

Some sources suggest that the "normal" bomb load, and indeed the design specification was for 10,000lbs of bombs for the "A".  16,000lbs was the "maximum", or even 22,000 lbs for special nuclear missions.  These overload weights would normally be at the expense of fuel, or by throwing out the rule book for wartime emergency.  The organization that rickshaw encouraged has some great info on their website:  http://b-47.com      click on B-47 versions.  This lists the normal A load as 10,000 lbs.

So it seems that an A could indeed carry more than the normal 10,000 or the "maximum" 16,000lb load.

I would worry about the lack of thrust with a heavy A, and brakes were a real concern early on.  Later versions had signicantly higher thrust engines, and more JATO (really RATO) hard points, better brakes, better braking chute, strengthened landing gear, etc.  

It does seem the bomb bay got shorter with later versions (the nukes got smaller) allowing for more fuel.  I have no idea on the physical size of the bomb shackles/fins angle.        

[KJ_Lesnick]

rickshaw

Have you asked the B-47 Association

It did mention the B-47B had an 18,000 pound payload, but it had a smaller bay so I'm unsure of what the A's bay could haul.


Sandiego89

I thought the 22,000 pounder was an earthquake bomb?

[Iranian F-14A]

The B-47 wasn't designed for anything other then carrying a single nuke. In that way, it wasn't too different from the B-58, except that the B-58 at it's maximum could carry 5x nukes (1x in the pod and 4x B43s attached to the belly). This is the biggest reason that these types didn't see much in the way of upgrades and were retired once better platforms came online.

[jcf]

The B-47 was configurable with a long or short bomb-bay/doors and could also be configured via kits
to carry a range of conventional bombs.

Al Lloyd's Boeing B-47 Stratojet covers the subject.

[KJ_Lesnick]

The B-47 was configurable with a long or short bomb-bay/doors and could also be configured via kits to carry a range of conventional bombs.

What was the advantage of each?

[rickshaw]

The B-47 was configurable with a long or short bomb-bay/doors and could also be configured via kits to carry a range of conventional bombs.

What was the advantage of each?

Kendra/Robyn are you deliberately trying to get people angry with you again?   

[KJ_Lesnick]

rickshaw

Kendra/Robyn are you deliberately trying to get people angry with you again?   

No, it was a simple question: Instinctively, I'd assume the bigger bomb-bay would be better on common-sense -- bigger means I could carry a larger volume inside of it and thus more bombs.  Things aren't always intuitive.

Seriously, you people should really calm down.

[KJ_Lesnick]

I was also thinking of a couple other B-47 WHIF-mod ideas and they revolve around the following

1. Airbrakes

• Early jet-engines had a slow spool up rate: The J47's took about 20 seconds to go from idle to full power
  
• While the actual plane used a small drag-chute to require the throttle position to be positioned about halfway up (allowing about 8 seconds to go to full power); I assume it only had one chute
  
• A physical brake or thrust reverser would have been more practical as it could be used repetitively
  

.
This brings up the following options

• Spoilers: Add drag, reduce lift; provided an excessive sink rate can be countered without an alpha that doesn't stall the plane (note most airliners don't put the boards up until after touchdown), whack the tail on the ground, or require excessive speed you're good.  There were proposals of fitting B-47's with spoilerons to counter aileron-reversal so a redesign could be made to allow them to work as both (Boeing used it on airliners years later).  The drawback is obviously if you cannot meet those conditions (or if spoilerons could not operate symmetrically and asymmetrically with the technology of the era)...
  
• Brakes above and below the wings: At higher speeds, they can work like split brakes or spoilers; at low-speed: Split brakes; disadvantage is at high flap settings, they may be damned near useless (that was a problem with the F-4 which used a similar brake) provided they don't interfere with the airflow over the flap (well, they are upstream of it...)
  
• Decelerons: Effectively the ailerons split to produce a speed-brake: It produces drag with no change in sink-rate except through change in speed; disadvantage is that it reduces roll-control available unless the decelerons could open in a symmetric or asymmetric fashion (which varies lift for rolling), while the B-47 had a flaperon (outboard flap) to increase roll-rate at low-speeds, the problem is the plane's roll-rate was poor at low-speeds and this became necessary to provide decent roll-control.  Furthermore, decelerons may have been patented by Northrop which would require them to pay royalties to adopt a feature required by the Air Force.
  
• Brakes the wings: A split-brake (F-86 style) could be put under the wing on either side of the fuselage: It would add drag alright.  Don't know how it would affect airflow over the flaps and how effective it'd be flaps down
  
• Redesign the tail with a V-shaped tailcone: Would alter the shape of the afterbody and be very effective; disadvantage: would potentially affect the aft turret.  While the B-47 was said to have a decent degree of maneuverability, it also was said to fly on the coffin corner at some altitudes and may have depended on the gun (It's my opinion that one should design for enough agility and speed that you don't need the gun at all a'la the Mosquito; admittedly even the Avro Vulcan with all it's agility, still possessed a tail-gun, even though it was able to out turn fighters: Go figure)
  

.
2. Different Wing

• The B-47's wing was kind of small: At some altitudes it possessed a sufficient agility to turn decently where most US fighters turned terribly; the Russian MiG-15 however could fly higher than even the B-47 and could probably turn better up there as well
  
• The B-52's wing had a lower aspect-ratio but possibly a higher taper-ratio, and a lower wing-loading (B-47A: 109.9 lbs/ft² vs B-52A: 105 lbs/ft²; B-47B: 140 lbs/ft² vs B-52C: 112.5 lbs/ft²; B-47E: 163.17 lbs/ft² vs B-52H: 122 lbs/ft²) which seemed to allow a maximum higher altitude
  

.
This presents the following ideas and limitations

• Limitations: The B-47's basic shape was premised around a bomb-bay in the middle, gears on the front and back, and a high incidence wing to allow takeoffs.
  
• Swap out the baseline wing with a B-52-esque design; then maintain the same wingspan but use the B-52's taper-ratio and aspect-ratio: The B-52 had better high altitude performance.  The only major disadvantage I can see is that the B-52 had a lower maximum indicated airspeed than the B-47 (irrelevant at high altitude, but does play a role when flying down in the weeds for NOE flights), the B-47 might have had a better L/D ratio at higher mach though I'm uncertain about this
  

[sandiego89]

:

No, it was a simple question: Instinctively, I'd assume the bigger bomb-bay would be better on common-sense -- bigger means I could carry a larger volume inside of it and thus more bombs.  Things aren't always intuitive.

Bigger bomb bay is not always better. The majority of fuel in the B-47 was carried in the fuselage. The larger the bomb bay, the less space for fuel.  The B-47 was always critical on range, so they wanted to carry as much fuel as possible, especially before air to air refueling came into widespread use. It was a constant balance between fuel and bombs.  In most realistic sceanrios I would think the B-47 would run out of usefull load before they ran out of cubic space in the bomb bay.  

Yes bigger can somtimes give you more flexibility, but remember the larger internal cubic space you have, the larger and heavier your struture becomes. More weight, then you need bigger engines, thrn you need more fuel, then you need an even bigger structure to carry the fuel....it becomes an insidious spiral.  

[jcf]

At the risk of repeating myself, Boeing B-47 Sttratojet by Al Lloyd has the info yer seeking.
... and yes Kendra, inter-library loan is available in most US metro areas.

http://firstsearch.oclc.org/WebZ/FSFETCH?fetchtype=fullrecord:sessionid=fsapp1-38189-i9oy45wx-q1rx5j:entitypagenum=5:0:recno=9:resultset=3:format=FI:next=html/record.html:bad=error/badfetch.html:entitytoprecno=9:entitycurrecno=9:numrecs=1

http://firstsearch.oclc.org/WebZ/FSFETCH?fetchtype=holdings:entityholdingsortpage=normal:holdinglimittype=default:next=html/holdings.html:bad=error/badfetch.html:format=FH:numrecs=1:resultset=3:recno=9:entitylibrarycount=30:sessionid=fsapp1-38189-i9oy45wx-q1rx5j:entitypagenum=6:0

Here's a copy at the Carnegie Library in Pittsburgh which can be requested via ILLIAD:
http://catalog.einetwork.net/search/o55644582

[sandiego89]

I was also thinking of a couple other B-47 WHIF-mod ideas and they revolve around the following

1. Airbrakes

• Early jet-engines had a slow spool up rate: The J47's took about 20 seconds to go from idle to full power
  
• While the actual plane used a small drag-chute to require the throttle position to be positioned about halfway up (allowing about 8 seconds to go to full power); I assume it only had one chute
  
• A physical brake or thrust reverser would have been more practical as it could be used repetitively
  

.
This brings up the following options

• Spoilers: Add drag, reduce lift; provided an excessive sink rate can be countered without an alpha that doesn't stall the plane (note most airliners don't put the boards up until after touchdown), whack the tail on the ground, or require excessive speed you're good.  There were proposals of fitting B-47's with spoilerons to counter aileron-reversal so a redesign could be made to allow them to work as both (Boeing used it on airliners years later).  The drawback is obviously if you cannot meet those conditions (or if spoilerons could not operate symmetrically and asymmetrically with the technology of the era)...
  
• Brakes above and below the wings: At higher speeds, they can work like split brakes or spoilers; at low-speed: Split brakes; disadvantage is at high flap settings, they may be damned near useless (that was a problem with the F-4 which used a similar brake) provided they don't interfere with the airflow over the flap (well, they are upstream of it...)
  
• Decelerons: Effectively the ailerons split to produce a speed-brake: It produces drag with no change in sink-rate except through change in speed; disadvantage is that it reduces roll-control available unless the decelerons could open in a symmetric or asymmetric fashion (which varies lift for rolling), while the B-47 had a flaperon (outboard flap) to increase roll-rate at low-speeds, the problem is the plane's roll-rate was poor at low-speeds and this became necessary to provide decent roll-control.  Furthermore, decelerons may have been patented by Northrop which would require them to pay royalties to adopt a feature required by the Air Force.
  
• Brakes the wings: A split-brake (F-86 style) could be put under the wing on either side of the fuselage: It would add drag alright.  Don't know how it would affect airflow over the flaps and how effective it'd be flaps down
  
• Redesign the tail with a V-shaped tailcone: Would alter the shape of the afterbody and be very effective; disadvantage: would potentially affect the aft turret.  While the B-47 was said to have a decent degree of maneuverability, it also was said to fly on the coffin corner at some altitudes and may have depended on the gun (It's my opinion that one should design for enough agility and speed that you don't need the gun at all a'la the Mosquito; admittedly even the Avro Vulcan with all it's agility, still possessed a tail-gun, even though it was able to out turn fighters: Go figure)
  

.
2. Different Wing

• The B-47's wing was kind of small: At some altitudes it possessed a sufficient agility to turn decently where most US fighters turned terribly; the Russian MiG-15 however could fly higher than even the B-47 and could probably turn better up there as well
  
• The B-52's wing had a lower aspect-ratio but possibly a higher taper-ratio, and a lower wing-loading (B-47A: 109.9 lbs/ft² vs B-52A: 105 lbs/ft²; B-47B: 140 lbs/ft² vs B-52C: 112.5 lbs/ft²; B-47E: 163.17 lbs/ft² vs B-52H: 122 lbs/ft²) which seemed to allow a maximum higher altitude
  

.
This presents the following ideas and limitations

• Limitations: The B-47's basic shape was premised around a bomb-bay in the middle, gears on the front and back, and a high incidence wing to allow takeoffs.
  
• Swap out the baseline wing with a B-52-esque design; then maintain the same wingspan but use the B-52's taper-ratio and aspect-ratio: The B-52 had better high altitude performance.  The only major disadvantage I can see is that the B-52 had a lower maximum indicated airspeed than the B-47 (irrelevant at high altitude, but does play a role when flying down in the weeds for NOE flights), the B-47 might have had a better L/D ratio at higher mach though I'm uncertain about this
  

You have some errors above.  You are trying very hard to come up with solutions over the drag chute.  All require some redesign and add weight and complexity.  Thrust reversers can bring other problems like improper stowing, inadvertant or assymetrical deployment, added complexity, weight and were really not in use when the 47 was being drawn up. The approach chute was perhaps inellegant, but was cheap, light and did the trick  You only need it once per flight (granted it limits touch and go training). There were two chutes:  an approach and a landing chute.  Don't pull the wrong handle!

You stated the wing was "small" and there was not an excess of lift, so adding spoilers on the wing would make things even worse.

The coffin corner seems exagerated.  Read the links others provided.  Some good stuff on there.

Suggest you do a bit more research on the MiG 15 intercepts of the B-47.  The 47 could do quite well in terms of altitude and speed.  At high atltiudes the B47 was MORE manuverable than a MiG 15.  The MiG might fall out of the sky when even trying a gentle turn to interecpt a 47. The 47 also compares favorably in speed at altiude. Do not confuse max altitude of the 15 and infer it could actually manuever well up there.  The MiG 17 was more of a threat.

A Vulcan with a tail gun?  

You are asking for a B-52 like wing and systems in the 47.  Well that is pretty much what happened with the 52 pretty much being an evolution of the 47 concept. If you consider the design and first flight dates of the 47 you can not help but be impressed. Yes the 52 was more refined but owes much to the 47.  

[KJ_Lesnick]

joncarrfarrelly

The first two links did not work, the third did but simply displayed a table of contents.  I'm going to check the attic: The book cover looks familiar and I'll see if it's in one of the many crates I have up there.


sandiego89

You have some errors above.  You are trying very hard to come up with solutions over the drag chute.  All require some redesign and add weight and complexity.

True enough.  Admittedly the B-47A went from weighing 157,000 pounds to 185,000-200,000 so I didn't think it was a major issue.

So, how would things work if it was part of the design from the outset?  Think about it, fighters were often fitted with brakes early on which had to do with the following problems: They were low-drag and slippery, particularly at low-speed; spool-up rates sucked.

Thrust reversers can bring other problems like improper stowing, inadvertant or assymetrical deployment, added complexity, weight and were really not in use when the 47 was being drawn up.

So, that's out of the question.

The approach chute was perhaps inellegant, but was cheap, light and did the trick  You only need it once per flight (granted it limits touch and go training).

That's the problem... if you miss an approach (and this does happen in bad weather)

There were two chutes:  an approach and a landing chute.  Don't pull the wrong handle!

Tell me about it...

You stated the wing was "small" and there was not an excess of lift, so adding spoilers on the wing would make things even worse.

The coffin corner seems exagerated.

Sorry, I remember reading that somewhere: Was this more of a problem at heavy weights than at 50% load?

Suggest you do a bit more research on the MiG 15 intercepts of the B-47.

If I recall five were engaged, and three were shot down...

The 47 could do quite well in terms of altitude and speed.

I know it was capable of high-speed (Mach 0.86 sounds right), I'm unsure what the highest it ever flew was, but if I recall it was in the 50,000 foot range.

At high atltiudes the B47 was MORE manuverable than a MiG 15.

I did not know that...

A Vulcan with a tail gun?

Don't know where I got that from...

You are asking for a B-52 like wing and systems in the 47.

Well, mostly the wing because of the possibility it worked better at altitude...