B-52 Re-engine Resurfaces As USAF Reviews Studies

[Hood]

It would have made more sense had they followed through on this a decade or so ago. Now the B-52 fleet only has potentially a decade left in service it will be harder to recoup those capital costs.
If they are looking at fitting eight engines that suggests they are looking for a straight swap to fit the existing nacelles (or modified versions of) to avoid any extra costs of aerodynamic and structural trials etc. with four big turbofans and the time that would take.

 

[TomcatViP]

The structural test will be largely irrelevant, all the plane having aged differently. It will be better to stick to what was identified during the EMD phase and swap the engines only with a close match in term of impact on the dynamic structural modes.

That what they are doing now as it seems.

 

[bobbymike]

http://www.defensenews.com/air/2017/09/14/rolls-royce-offers-br-725-engine-for-b-52-propulsion-modernization/

 

[sferrin]

http://www.defensenews.com/air/2017/09/14/rolls-royce-offers-br-725-engine-for-b-52-propulsion-modernization/

At only 16k it would be under powered.

 

[mkellytx]

The Rolls-Royce BR725 A1-12 is take-off rated at 16,900 which is close enough to the TF33's 17,000. That's close enough to be a wash in my book, a 0.6% difference is pretty small.

 

[GTX]

Speaking of re-engined B-52: CF-6 power

Source

 

[bobbymike]

The Rolls-Royce BR725 A1-12 is take-off rated at 16,900 which is close enough to the TF33's 17,000. That's close enough to be a wash in my book, a 0.6% difference is pretty small.

Do you know the fuel consumption of each? How much extra range could be achieved with this re-engining?

 

[Dragon029]

According to http://www.jet-engine.net the TF33 in the B-52H has a TSFC of 0.52lb/lbf/hr. The Rolls Royce BR710 has a TSFC of 0.39lb/lbf/hr; the BR725 is an upgraded version of that engine that according to RR has 4% better fuel efficiency (so theoretically a 0.375lb/lbf/hr TSFC): https://www.rolls-royce.com/products-and-services/civil-aerospace/business-aviation/br725.aspx
So overall it should have somewhere in the ballpark of a 25-30% longer range.

 

[bobbymike]

According to http://www.jet-engine.net the TF33 in the B-52H has a TSFC of 0.52lb/lbf/hr. The Rolls Royce BR710 has a TSFC of 0.39lb/lbf/hr; the BR725 is an upgraded version of that engine that according to RR has 4% better fuel efficiency (so theoretically a 0.375lb/lbf/hr TSFC): https://www.rolls-royce.com/products-and-services/civil-aerospace/business-aviation/br725.aspx
So overall it should have somewhere in the ballpark of a 25-30% longer range.

Thanks much appreciated

 

[mkellytx]

The Rolls-Royce BR725 A1-12 is take-off rated at 16,900 which is close enough to the TF33's 17,000. That's close enough to be a wash in my book, a 0.6% difference is pretty small.

Do you know the fuel consumption of each? How much extra range could be achieved with this re-engining?

Example problem 8 in the performance annex of the -1 gives 20,100 lb/hr for a 360,000 lb BUFF, at 37K, .765M with 12 GBU-31, which is a mid-weight aircraft. Rule of thumb we used back in my flight test days, 20K/hr clean, 25K/hr with HSAB's only and up to 35K/hr with the HSAB's loaded. Stateside the BUFF is limited to below 30kft or above 41kft since they lack RVSM, so burns will be higher than in the sandbox where you can cruise/loiter at 35kft.

So, conservatively obtaining a 25% reduced fuel burn would yield numbers of 15K/hr, 18.75K/hr, 26.25K/hr. Those kind of numbers are almost and F-16's worth of fuel per hour

The big advantage of doing this is the lower stress on the airframes, since less fuel is needed to fly the same mission. Lighter aircraft have lower stress on the airframe.

 

[GeorgeA]

Also takes pressure off the very overworked tanker fleet.

 

[Kadija_Man]

There was movement at the station, the word had got around...

USAF details scope and schedule for B-52 re-engining

 

[sferrin]

There was movement at the station, the word had got around...

USAF details scope and schedule for B-52 re-engining

"A notional schedule using the two-stage bidding process indicates the full programme will take 17 years to complete."

It took just over half that to produce over 700 aircraft AND their engines. That's what I call progress.

 

[Triton]

Stephen Trimble on Twitter:

And that’s what a B-52 looks like if you take off the TF33s and stick on (sorry about the technical term) eight modern turbofans.

Source:
https://twitter.com/FG_STrim/status/966995742597492737

 

[bobbymike]

http://aviationweek.com/defense/usaf-nuke-chief-not-expecting-easy-b-52-engine-upgrade?NL=AW-05&Issue=AW-05_20180502_AW-05_455&sfvc4enews=42&cl=article_2&utm_rid=CPEN1000000230026&utm_campaign=14703&utm_medium=email&elq2=5b1662b629be4f3081dee95458857660

As the U.S. Air Force embarks on a major re-engining of the Boeing B-52H, its leadership is under no illusions about the difficulty of the task at hand.

Delivered by Boeing in 1960 and ’61, the Stratofortress has been the service’s principal nuclear-armed strategic bomber for almost six decades. So when it comes time to crack open those old engine cowlings and run new wiring through the wings, artisans can expect to find plenty of surprises.

“Every time you renovate an old house, you didn’t realize there was going to be asbestos behind the walls,” says Lt. Gen. Jack Weinstein, the Air Force’s Deputy chief of staff for strategic deterrence and nuclear integration. “Am I going to stand here and say we’re not going to have problems with the re-engining? I’m not going to say that. But there has been an awful lot of work gone into evaluating how to re-engine it, and what’s the best way to do that.”

Over the past few years, the Air Force has engaged with engine manufacturers and potential prime contractors about the possibility of upgrading the B-52H’s eight Pratt & Whitney TF33-103s. In the past, the Air Force has considered a four-engine swap, but that approach isn’t practical.

 

[Airplane]

http://aviationweek.com/defense/usaf-nuke-chief-not-expecting-easy-b-52-engine-upgrade?NL=AW-05&Issue=AW-05_20180502_AW-05_455&sfvc4enews=42&cl=article_2&utm_rid=CPEN1000000230026&utm_campaign=14703&utm_medium=email&elq2=5b1662b629be4f3081dee95458857660

As the U.S. Air Force embarks on a major re-engining of the Boeing B-52H, its leadership is under no illusions about the difficulty of the task at hand.

Delivered by Boeing in 1960 and ’61, the Stratofortress has been the service’s principal nuclear-armed strategic bomber for almost six decades. So when it comes time to crack open those old engine cowlings and run new wiring through the wings, artisans can expect to find plenty of surprises.

“Every time you renovate an old house, you didn’t realize there was going to be asbestos behind the walls,” says Lt. Gen. Jack Weinstein, the Air Force’s Deputy chief of staff for strategic deterrence and nuclear integration. “Am I going to stand here and say we’re not going to have problems with the re-engining? I’m not going to say that. But there has been an awful lot of work gone into evaluating how to re-engine it, and what’s the best way to do that.”

Over the past few years, the Air Force has engaged with engine manufacturers and potential prime contractors about the possibility of upgrading the B-52H’s eight Pratt & Whitney TF33-103s. In the past, the Air Force has considered a four-engine swap, but that approach isn’t practical.

Its worrisome that they are still talking about this. If they don't let the buff die a dignified death, we will never procure enough of the 21s. Based on the length of time they say it will take, it sounds more like an effort to flip money to a contractor than it sounds like a much needed defense initiative.

Its a shame they denuked the bones because that's a more surivivable platform than the 52s. The 52 should have been the conventional bomber platform... Seems like everything is done ass backwards in the DoD. An upgraded bone with agm129s is what we SHOULD have. Not a re-engined buff.

 

[marauder2048]

De-nuking the B-1B paradoxically hurt its conventional capability since it can't accommodate anything larger than
JASSM internally; the impact of outsized external stores like say X-51a on range is too pronounced.

If possible, I think they should just wait and see what happens in 2021: New START could just expire.

 

[mkellytx]

Its worrisome that they are still talking about this. If they don't let the buff die a dignified death, we will never procure enough of the 21s. Based on the length of time they say it will take, it sounds more like an effort to flip money to a contractor than it sounds like a much needed defense initiative.

Or an effort to extend the life of a lower cost per flying hour, more available, nuclear certified cruise missile carrier with plenty of flying hours left on the airframe.

[quote author=Airplane]
Its a shame they denuked the bones because that's a more surivivable platform than the 52s. The 52 should have been the conventional bomber platform... Seems like everything is done ass backwards in the DoD. An upgraded bone with agm129s is what we SHOULD have. Not a re-engined buff.
[/quote]

More survivable how? Low level? Gravity bomb only (SIOP)? The BUFF does carry and use more conventional bombs than the Bone, I've personally seen one drop 3 different types of conventional bombs on one bomb run (5 x GBU-31, 2 x CBU-103, 3 x Mk82), I conducted that test flight. With 1760 in the bay 3 different types of smart bombs on the same run is possible.

AGM-129 was retired for a reason...but for the sake of argument the Bone would be external carry and a complete pig. All of the engine thrust in the world won't make up for the small wings and fuel burn will be terrible considering how low it will cruise with that kind of load. The draw on tankers would be terrible. The old girl does quite nicely with externals under the wings and can cruise at efficient altitudes.

I have first hand knowledge of both airframes and would make the exact same decision to replace B-1's with B-21's and re-engine BUFF's and give them a new strategic cruise missile. The old girl still has plenty of life left in her.

 

[mkellytx]

De-nuking the B-1B paradoxically hurt its conventional capability since it can't accommodate anything larger than
JASSM internally; the impact of outsized external stores like say X-51a on range is too pronounced.

Huh? The nuke Bone was AGM-69, B-61 and B-83 with 84 x Mk82 for the conventional mission. De-nuking the Bone brought the 10 by CEM and eventually 1760 on the rotaries and the 10 by's. The abrupt retirement of the AGM-69 left it gravity bomb only, ALCM never happened, even then it was 8 internal in the movable bulkhead bay with a short tank forward and 12-14 external. Good thing it went conventional only when it did and JDAM came along, otherwise without OEF/OIF the Bone would have retired by 2005.

X-51 was a one off experimental program. They flew it on Balls 50 b/c NASA retired Balls 8 and let Balls 25 fall into disrepair forcing us to fly it out to Shepard to end its life at the maintenance tech school as a trainer. They had to come to the 419th b/c all the NASA birds were no longer at Edwards. Any operational hypersonic weapon will fit in a B-52 or B-21 bomb bay.

[quote author=marauder2048]
If possible, I think they should just wait and see what happens in 2021: New START could just expire.
[/quote]

The biggest benefit to letting START expire would be more B-21's

 

[Airplane]

Its worrisome that they are still talking about this. If they don't let the buff die a dignified death, we will never procure enough of the 21s. Based on the length of time they say it will take, it sounds more like an effort to flip money to a contractor than it sounds like a much needed defense initiative.

Or an effort to extend the life of a lower cost per flying hour, more available, nuclear certified cruise missile carrier with plenty of flying hours left on the airframe.

[quote author=Airplane]
Its a shame they denuked the bones because that's a more surivivable platform than the 52s. The 52 should have been the conventional bomber platform... Seems like everything is done ass backwards in the DoD. An upgraded bone with agm129s is what we SHOULD have. Not a re-engined buff.

More survivable how? Low level? Gravity bomb only (SIOP)? The BUFF does carry and use more conventional bombs than the Bone, I've personally seen one drop 3 different types of conventional bombs on one bomb run (5 x GBU-31, 2 x CBU-103, 3 x Mk82), I conducted that test flight. With 1760 in the bay 3 different types of smart bombs on the same run is possible.

AGM-129 was retired for a reason...but for the sake of argument the Bone would be external carry and a complete pig. All of the engine thrust in the world won't make up for the small wings and fuel burn will be terrible considering how low it will cruise with that kind of load. The draw on tankers would be terrible. The old girl does quite nicely with externals under the wings and can cruise at efficient altitudes.

I have first hand knowledge of both airframes and would make the exact same decision to replace B-1's with B-21's and re-engine BUFF's and give them a new strategic cruise missile. The old girl still has plenty of life left in her.
[/quote]

Well, we all have experience then don't we? The 129 was designed to be carried externally and handle the aerodynamic loads. The bone has always been a bit of a compromise. It certainly never broke any altitude records. What it did do was have a superior offensive/defensive suite and very high speed at very low altitude in all atmospheric conditions with near fighter maneuverability and a smaller RCS.

If you want to have a discussion on what is better... A big slow lumbering med/high altitude aircraft which is easily tracked or a high speed low in the weeds penetrator, the. I suggest starting a new thread.

The 129s so called issues were easily fixable and if you want to talk about what's the better ALCM, I would suggest its quite obvious which we should have in service today and its not the one that was developed when Led Zeppelin was still touring.

 

[marauder2048]

More survivable how?

Pre-launch survivability mainly; the B-1 is twice as hard and can cover about 50% more distance during flyout.

Of course, that's only for bombers on alert...

The B-1 will be missed in the maritime strike role...

 

[Foo Fighter]

Would it not be wise to have the Buff retained for the missions the B-1B/B2/B21 are overkill for? The depth of ability is surely more valuable than the savings made by new engines and kit NOT being supplied and junking the airframes. Losing the Buff would appear to be very short sighted.

 

[TomcatViP]

What the bone do best will have no value tomorrow. It's then a cost- effect equation where the Buff excel (even today with her derelict engine technology).

Then add the proven external carriage of heavy load and you've got the winner.

 

[sferrin]

What the bone do best will have no value tomorrow. It's then a cost- effect equation where the Buff excel (even today with her derelict engine technology).

Then add the proven external carriage of heavy load and you've got the winner.

Well, that's one opinion. The B-52 sure as hell isn't going to carry 24 LRASM/JASSM internally (or in ANY way). It's also got a smaller bomb load than the B-1B. It's less survivable, slower, inferior sensors, etc. etc. The ONLY thing the B-52 has going for it is unrefueled range and two big hardpoints on the wings. Oh, and it's cheap. If that's all that mattered we'd still be flying F-4s. We're not.

 

[mkellytx]

Well, we all have experience then don't we? The 129 was designed to be carried externally and handle the aerodynamic loads. The bone has always been a bit of a compromise. It certainly never broke any altitude records. What it did do was have a superior offensive/defensive suite and very high speed at very low altitude in all atmospheric conditions with near fighter maneuverability and a smaller RCS.

Great then you've also conducted weapons integration tests on both air frames? "Bit of a compromise...near fighter maneuverability," the Bone struggles to make more than a 30 degree banked turn with any gas and internal bomb load above 20kft. It can pull 3.5 G with no bombs and little fuel with the wings all the way back. Other than the different radar technology do you know the differences between the two offensive suites? The defensive suite on the Bone has a great reputation and history. I won't comment on the BUFF, I used to sit next to the EWO and watch him work.

The radar blockers in the inlets will be of little use for long wave EW and OTH radars, cruise missile shooters shouldn't be getting anywhere close to an X-band radar.

[quote author=Airplane]
If you want to have a discussion on what is better... A big slow lumbering med/high altitude aircraft which is easily tracked or a high speed low in the weeds penetrator, the. I suggest starting a new thread.
[/quote]

The BUFF will do .92 M above 20kft quite nicely (been there done that) and even do a banked turn at 35kft without losing altitude, try either in a Bone with an external load. Heck, the Bone's weapon's bays are limited to .94 M, so it's not that much faster when on a bomb run.

Back on topic, there are few places that the Bone is more survivable than a BUFF that won't require a B-21. A re-engined BUFF with a new strat radar is sufficient for the stand off cruise missile role and useless dirt missions in the ME, at a lower cost per flying hour and greater availability than the Bone. Retiring the Bone first frees up more money for B-21's.

 

[marauder2048]

The X-band story is a little more nuanced since the counter-cruise missile radars
out there like Sentinel are projected to attain fairly massive increases in range;
the same is true for those radars in the maritime environment.

Hard to see how subsonic bombers can match the supersonic dash, good loiter and
plentiful payload of cheap PGMs that have been the B-1's calling card.
For the medium and low threat environment, it's just about the ideal platform.

The B-52 does have a larger aperture for its radar and other sensors
so maybe a combination of that with an air-launched, supersonic missile that can deliver loitering munitions
is close enough. Or as was pointed out an increase in the number of bombers on station.

 

[NeilChapman]

There seems to be a lot of back and forth over which is better to keep, B-52 or B-1.

It certainly doesn't make sense to maintain 4 different bombers. Too many different maintainers, too many different parts. It's a logistics nightmare. And they're already having trouble ensuring they have enough maintainers.

You're spinning up a new production line for B-21. So that one definitely stays.

The new one is basically a newer, smaller, more advanced B2. Probably going to be easier to maintain. Easier to upgrade. It's likely the AETP engine will work for B-21. More runway availability around the world. There's only 20 B-2's. Dropping the B-2 is a no brainier.

There's probably 40 or so combat coded B-1's with a MCR of ~50%

There's probably 45 or so combat coded B-52's with a MCR of ~70%

It's seems obvious that neither of the two can penetrate near-peer air defense systems. B-52, however, is relatively easy to re-engine. If you've got to keep one of them it seems to me a no brainer to drop the B-1.

The question remains why keep the B-52? Why not replace all them with B-21s? It's versatile. It can be a bomb truck. But cost is the primary reason. It's not the operational cost. It's the replacement cost. You can fly the buff until the wings fall off. You're going to replace it with a B-21 or perhaps some new unmanned bomb truck.

That being said. I'd be asking NG what it would cost to get the production rate up to 20 per year. They're going to want 200 B-21's.

 

[fightingirish]

Pratt & Whitney is likely to offer its PW815 engine for the B-52 re-engine program.

 

[sferrin]

Hmm. Went with a less powerful engine than the existing one. I wonder why. ???

 

[SpudmanWP]

Why do you think it's less? The wiki says the PW800 Family is 10-20lbs and the TF33 is 17k. The PW815GA is 16k, but the version for the B-52 has not been spec'd. Seems like an easy 1:1 swap.

 

[TomS]

Hmm. Went with a less powerful engine than the existing one. I wonder why. ???

The current PW815GA is rated around 16,000 lbf, but it wouldn't take much tweaking to increase that to 17,000 lbf if needed. Technically, I guess that would be a PW817. The PW800 family is supposed to scale to 20,000 lbf as needed, so the design work probably exists already.

 

[Airplane]

Hmm. Went with a less powerful engine than the existing one. I wonder why. ???

The current PW815GA is rated around 16,000 lbf, but it wouldn't take much tweaking to increase that to 17,000 lbf if needed. Technically, I guess that would be a PW817. The PW800 family is supposed to scale to 20,000 lbf as needed, so the design work probably exists already.

Such a waste of resources. If we begin this year, the job will be done in 2034. Save the money for more raiders. God forbid something unforeseen develop like the longeron issue on the eagles that forces the buff to be put away early. Northrop was going to build, as I recall, close to 20 spirits annually.... I am sure they still could build that many raiders annually if congress allows it. The J20 is being built to nullify the buff at long range as one of its missions. The buff is totally irrelevant unless you're bombing Iran or NOKO. I would rather have more raiders and more ICBMs than keep the buff around any longer. Everything we said was going to happen with the termination of the spirit has come to pass. Even a B-1C would have been better than the literal irrelevant production run of spirits.

 

[kcran567]

1. money grabbing scam
2. Stealth is obsolete from China, Russian technical developments and at $500B each
No B-2 Spirit (or Raider)bomber can be risked.
3. Whoever gets the re-engine contract needs work and $$$ for "favors."
4. Putting new engines on old B-52s because we need to take money away from
The Raider program for some dumb reason.
5. Something isn't going right in the Raider program.

 

[bobbymike]

http://www.airforcemag.com/Features/Pages/2018/July%202018/GE-Aviation-to-Offer-Two-Engines-in-USAFs-B-52-Re-Engining-Program.aspx?utm_source=&utm_medium=&utm_campaign=

GE Aviation plans to offer two engines in the Air Force’s B-52 re-engining program, which is finally gaining steam after decades of debate.

Speaking to reporters at the Farnborough International Air Show in England last week, company CEO David Joyce said GE is confident that both the CF34-M and the more advanced Passport engine are “good candidates” for the program.

Joyce said the Dash-M, which flies on the Embraer 190, is proven technology, with 7,000 departures every day. It’s not only “incredibly reliable,” but also the “perfect thrust size” for the B-52, he added. However, if the service prioritizes fuel efficiency, Joyce said GE can offer the Passport, which will allow for about 14,000 hours time on wing.

 

[fightingirish]

Air Force Magazine - March 2019 - Rolls-Royce Will Build F130 in Indianapolis If It Wins B-52 Re-Engining

Rolls-Royce has officially selected the F130, a variant of the commercial BR700, as its entrant in the B-52 re-engining competition, and will build the powerplant at its freshly renovated Indianapolis, Ind., facility if it wins the contract, company Vice President for Military Strategic Systems John Kusnierek told reporters during a telecon on Monday. [...]

 

[Phos]

For laughs: a single GE9X has almost half again as much (4/3) thrust as the B-52's current engines, though I've leave picturing how such a thing would be fitted up to you.

The B-1 is cool and all but there was a time and place for it and those seem gone. I figure anyone who can shoot down a B-52 can probably shoot down a B-1 nowadays.

1. money grabbing scam
2. Stealth is obsolete from China, Russian technical developments and at $500B each
No B-2 Spirit (or Raider)bomber can be risked.
3. Whoever gets the re-engine contract needs work and $$$ for "favors."
4. Putting new engines on old B-52s because we need to take money away from
The Raider program for some dumb reason.
5. Something isn't going right in the Raider program.

None of these are mutually exclusive. 2, though, I find to be unlikely as any advancement that renders stealth ineffective is only going to widen the gap in terms of how much easier a non LO aircraft is to detect. Look down radar also greatly diminished the utility of flying low as a means of radar penetration.

 

[marauder2048]

From Hyten's testimony, New START looks likely to fall apart so the outsized loads that the B-1B can't carry internally
because of the treaty-compliant bulkhead would no longer be an issue.

And then the advantages of better hardening, great loiter and supersonic dash are compelling.
I'm assuming here that B-21 does not have supersonic dash....it was a possibility for NGB but
I doubt it got out of the Gates for the LRS-B scrub.

 

[sferrin]

Not to mention external hard points.

 

[marauder2048]

Not to mention external hard points.

Good point. Did they get as far as a weapons release test on that front?

 

[_Del_]

The biggest thing working against the Bone is the fact it has been out of production for over 30 years, and there is not a giant pool of parts sitting out in the desert ready to draw from at essentially no cost and zero leadtime. It affects the already low mission availability rates, and the only fixes involve even larger scale purchases of "new" thirty year old equipment which is largely antiquated and/or fund upgrades to newer available systems.
On a BUFF if most anything breaks, they don't need to ask a contractor to scratch build a new one to spec. They just scavange a part. Faster and cheaper.

On the flipside, when it's flying, the Bone is absolutely more survivable and brings some unique abilities to the table. I love it. Wish they'd keep it, but I understand the reasons it's on the block.