B-1B weapons bay fuel tank

[LanceB]

In building the Academy 1/144 B-1B, I started wondering something about the fuel tank installation in the weapons bay.

 

Academy has you fit the tank into the forward bay, then bombs in the center and aft bays.

 

But, I have seen pics (somewhere, can't find them now, darn it...) of the tank in the aft bay leaving the bays forward of the gear for weapons.  I seem to recall the 1/48 Revell kit also had this setup if built according to the instructions.  And, while this could be my mind playing tricks on me, I also seem to remember reading somewhere that "tank in the aft bay" was the "normal" fit, as the pilots could burn off that fuel first which lightened the tail and kept trim problems down when then doing a high-speed, wings-swept approach to target, as the CG moves aft on variable-sweep aircraft when the wings are swept and lightening the back end early helped counter that.

 

Which makes sense to me, and the Academy tank (and bombs) can be swapped between the bays with no extra work, so can anyone tell me if I am remembering things right and that it would indeed be "more protypical" for the three bays to be bombs, bombs, tank from fore to aft rather than tank, bombs, bombs as Academy's instructions say?

 

TIA

Edited October 23, 2019 by LanceB

[Specter1075]

Check out the B-1B Builder's Support Group on Facebook. They have former operators and crew guys that can get into the very fine details of the B-1B. The question of the forward fuel tank came up, and if I remember correctly, the tank went in the front bay because dropping ordinance from the front bay created higher chances of FOD damage to the engines.

[ElectroSoldier]

I remember years ago when they were still painted in teh strategic scheme while on display the tank was fitted in the arf bay. I remember it 100% but the kit always confused me as it says to fit it forward

[Finn]

Check the bottom of this Page to see a tank in the forward bay:

 

https://www.daytonipms.org/b-1b-lancer

 

Jari

[LanceB]

 

Check out the B-1B Builder's Support Group on Facebook. They have former operators and crew guys that can get into the very fine details of the B-1B. The question of the forward fuel tank came up, and if I remember correctly, the tank went in the front bay because dropping ordinance from the front bay created higher chances of FOD damage to the engines.

 

Ah, I could see that.... probably the safety wire that held the spinners on the fuses in place until they were dropped....

 

Yeah, you wouldn't want to suck that up.

 

Thanks!

Edited October 23, 2019 by LanceB

[Finn]

But bombs could still be carried in the fwd bay:

 

 

Jari

[LanceB]

 

But bombs could still be carried in the fwd bay:

 

Jari

Yes, but one thing I learned working on aircraft is there are things that can be done, and things that are done, normally.

 

An AV-8B can carry three Mk.82 on the inboard pylons - but we would never load that except for static display at an event as there were fears of the inboard bomb hitting the plane when the bomb was dropped off the TER.  Likewise, rockets could be loaded on the inboard pylons - but we never would, because of concerns of the exhaust gasses being sucked into the engine.

[Winnie]

Also issues with center of gravity i'm sure... 

[habu2]

 

Also issues with center of gravity i'm sure... 

 

This.  Locations determined by mission profile and loadout.  Have to consider the aft CG during all phases of the  mission, pre & post weapon delivery, and fuel consumption throughout the flight.

[habu2]

Found this Rockwell graphic in William Holder's B-1 book (2nd ed) 

 

ISBN page says the book is from 1988.

 

It doesn't show a single tank for any combo so this may not reflect USAF loading.

 

[Alternative 4]

Do I read that diagram correctly in that the B-1 can carry external fuel?

[Camus272]

 

It doesn't show a single tank for any combo so this may not reflect USAF loading.

 

 

 

 

I'm not sure about a fully armed operational load, but I have seen just one tank in the aft bay, with the forward empty.

[CHris_B-1B]

2400 hours in the airplane and always flew with the tank in the forward bay if one was required at all.

[LanceB]

 

2400 hours in the airplane and always flew with the tank in the forward bay if one was required at all.

Thanks for your insight, I think that settles things authoritatively.

 

If you can answer this question, Chris: the kit includes parts for two bays' worth of GBU-31 and two bays' worth of GBU-38.  In your experience, was it "common" to carry all of one or all of the other, or as CAS seems to be the most common usage of the Bone in recent conflicts, was one bay of each generally loaded to offer flexibility "on-scene" depending on what the ground pounders required?

[habu2]

 

2400 hours in the airplane and always flew with the tank in the forward bay if one was required at all.

 

Do you know the tank sequencing?  Do you feed off the bay tank first or last?  Or is it all auto-scheduled by the flight computer to control CG?

 

Not exactly a modeling question but I'm just curious about such things.....

[CHris_B-1B]

 

 

Do you know the tank sequencing?  Do you feed off the bay tank first or last?  Or is it all auto-scheduled by the flight computer to control CG?

 

Not exactly a modeling question but I'm just curious about such things.....

The Fuel Center of Gravity Management System (FCGMS) controlled the fuel sequencing automatically to maintain CG - helpful when you're moving the wings around a lot.  I don't remember how the sequencing was scheduled.  We may have burned the tank fuel early.  You could also move fuel around manually as well.

[CHris_B-1B]

 

Thanks for your insight, I think that settles things authoritatively.

 

If you can answer this question, Chris: the kit includes parts for two bays' worth of GBU-31 and two bays' worth of GBU-38.  In your experience, was it "common" to carry all of one or all of the other, or as CAS seems to be the most common usage of the Bone in recent conflicts, was one bay of each generally loaded to offer flexibility "on-scene" depending on what the ground pounders required?

It really depends on the mission and the weapon release restrictions in place.  If there are collateral damage concerns, then you may have 500 pound GBU-38s loaded versus 2,000 pound GBU-31s.  We tried not to put GBU-38s in the aft bay as those on the upper aft stations had a tendency to pitch down dramatically when they come out of the bay.  I think the standard loads varied a lot over the years.  A tank or GBU-38s in the forward bay, GBU-31s  or GBU-38s in the mid bay, and GBU-31s in the aft bay is viable.

The advantage of the B-1 was payload at range over a long period of time.  I always told people that it was a flying Coke machine.  You want a Diet Coke, you got it.  Orange Fanta, you betcha.  Sprite, no problem.  You could put a B-1 with 24 GBU-31s with Joint Programmable Fuzes (allowed you to change fuze settings in flight) over the center of Afghanistan and due to being able to sweep the wings and haul fool, you could be anywhere in the country in 15-20 minutes.  Then you have the gas to stay there and keep puking weapons out.  The Sniper pod really revolutionized the B-1 as well.  It allowed the airplane to become an surveillance asset and it also enabled CAS to be much easier as you now had an optical sensor to positively identify targets.  It also allowed GBU-56 Laser JDAM moving target capability.

[Specter1075]

Hey Chris!

Thanks for the insights! I really like the coke machine analogy! How varied could the load-outs get? I know the B-1B is capable of deploying CBU-105's, but wondered if it ever had cause to. Would you see a load-out with one bay of CBUs and a bay of GBU-38 or -31s? I guess put another way, would munitions be of a completely mixed use, or would they be mixed only from the standpoint of weight class?

[LanceB]

Hi Chris,

 

Great information, thanks for taking the time to write it out!