Are they not going from a turbojet to a higher bypass ratio turbo fan?

That would require new nacelles as the by-pass duct geometry is quite different.

New pylons should also be in the works.

Wonder if they would include thrust reversers?

bt

bikerthai wrote:

Wonder if they would include thrust reversers?

bt

After 2500 hours or so in the Buff, I can certainly guarantee you it won't happen. It's too much additional weight, too complex and most important of all, too much problems with directional control with asymmetrical reverse on a contaminated runway. A drag chute and anti-skid work just fine.
If you look at the KC-135R mod, they didn't add reverse on that mod. Will never happen.

Not to be pedantic, but the KC-135 received thrust reversers when they were reengined from A to E.

The B-52 is, of course, a far different beast. TRs just aren’t worth the hassle to put on now.

Thrust reversers were offered with the KC-135R reengine program, the CFM-56 (F-108) engines were equipped with the mountings. SAC maintenance did not want them, fearing it would add to maintenance hours per tanker. So they were designed out of the modification. The modification did include new landing gear and 5 rotor brakes.
SAC KC-135 aircrews actually wanted TRs on thier airplanes, the extra weight was not a problem, and it would have opened KC-135R/T operations to many more airports than KC-135R/Ts without TRs.
The ANG was a little stuck with TRs for the KC-135E, but they wanted them anyway. The JT-3D (TF-33) engines were from donor B-707s that included the engine struts and horizontal stabilizers, throttle quadrant, engine instruments, and all associated mounting brackets and equipment. Everything came as a complete package. The "E" model included rebuilt landing gear and 5 rotor brakes.
Most KC-135 ANG pilots were also commercial airline pilots and a lot of the maintenance crews were also commercial airline maintenance people, TRs were less of a 'problem' for the maintenance people.
The "E" modification also found its way into some other air command's C-135 airplanes as well as a few SAC KC-135s based at OFF.

One of the engines considered for the B-52 reengining program is the GE CF-34-10E, with 20,360 lbs. of thrust (a modest increase over the current TF-33-P-3/-103, which has 17,000 lbs. of thrust), but has a dry weight nearly 1,000 lbs. lighter than the older engine (TF-33-P-3/-103 = 4,650 lbs. vs. CF-34-10E = 3,700 lbs.).

LyleLanley wrote:

Not to be pedantic, but the KC-135 received thrust reversers when they were reengined from A to E.

The B-52 is, of course, a far different beast. TRs just aren’t worth the hassle to put on now.

Nothing wrong with being pedantic, but go back and read my thread. I specifically talked about the R model.

kc135topboom wrote:

Thrust reversers were offered with the KC-135R reengine program, the CFM-56 (F-108) engines were equipped with the mountings.

And at the end of the day, they weren' equipped with them.

Thrust reversers on eight engines will add a lot of weight and maintenance and will not happen.
But I repeat it one more time :
Adding new engine pairs with different weights and/or different external aerodynamical pylon/engine shapes will require wing modifications due the changes in load distribution over the relative thin flexible wing.

IMHO the USAF has two options :

- Low risk option : adding of new aerodynamical identical engine cowlings /pylons for the new engines, with approx the same weight at each pylon. This configuration will not require a wing modification, but only the lower TSFC of the engines will be the gain + reduced maintenance costs.

- All new (high risk) option : adding optimal (different) shaped engine cowlings / pylons for the new engines and use the lower engine weights for increased payload. This modification will require extensive wing modifications and could introduce a lot of unknown issues (wing flutter). Also the certified external weapon loads will have to be re-certified. The extra gain will be : a little more fuel saving and/or increased payload.

bikerthai wrote:

Are they not going from a turbojet to a higher bypass ratio turbo fan?

No, That already happened when they got the TF-33.

mmo wrote:

LyleLanley wrote:

Not to be pedantic, but the KC-135 received thrust reversers when they were reengined from A to E...

Nothing wrong with being pedantic, but go back and read my thread. I specifically talked about the R model.

I know. But when you bring forth examples of reengined aircraft and specifically reference the AF's refusal to add TRs I thought it was proper to mention when the AF did add TRs. Especially if its the same aircraft you mention - the KC-135.

There was a video online where sales guys from the 3 different manufacturers gave some spiel about each of their offering. If it was solely based on those guys, RR would win it (the P&W just kept saying it was a great time to upgrade lol). Offering a fairly technical talk through.
RR had a model with a couple of their engines in a B52 style pod, it was essentially a lot shorter than the current pods, not sure if that was just for the show or whether that’s the pod design the propose (the imagine behind them also shows a similar pod, looks more like the pod for the jp57!


https://www.defensenews.com/video/2019/ ... 4-options/


Sent from my iPhone using Tapatalk

It makes sense that RR, Pratt and GE would change the nacelle cowling design. 3 of the 4 engines have mixed exhaust and the even unmixed CF34 has a much larger bypass ratio than the TF33, so whichever the choice, it really should be aerodynamically optimized.

The efficiency of the engines also depends o the duct shape which is dependent on the by pass ratio. When was the last time, if ever, the nacelles were re designed? New nacelles with new materials woul help reduce the overall weight as well.

And could reduce the noise foot print, if they should chose to put money and weight back in.

bt

It got new nacelles with the current engines.

The Rolls mock nacelles in that video with the exhaust mixers almost look like the old J57 turbojet B-52s

Interesting to see what kind of IR signature the engine choice will produce. One of the nice things about flying low-level in a Buff is it was almost impossible to get a lock on at low-level. The IR signature was masked by the wings. So unless a fighter wanted to get below us, he couldn't get any lock on. Flying Red Flag and Cope Thunder and Cope North was always a fun time. The Red pilots could not understand how we could get so low and why they couldn't get a lock on.

mmo wrote:

Interesting to see what kind of IR signature the engine choice will produce. One of the nice things about flying low-level in a Buff is it was almost impossible to get a lock on at low-level. The IR signature was masked by the wings. So unless a fighter wanted to get below us, he couldn't get any lock on. Flying Red Flag and Cope Thunder and Cope North was always a fun time. The Red pilots could not understand how we could get so low and why they couldn't get a lock on.

I actually LOL’d at this, thx. I don’t care what the red flag etc. exercises did, or “Flight of the old dog” (Dale Brown) discussed/theorized, it’s not even remotely likely any B-52 will ever enter hostile air space contested at any level again. It’s a stand off platform for the next 40 years.

The B-52 radar sig is larger than the A380. It’s impossible to hide at any level.

Thought it was worth adding the following podcast from Aviation Week to the discussion.

Podcast: Why Bombers Are Back

https://aviationweek.com/defense-space/ ... s-are-back

One of the interesting things mentioned with the B-52 re-engine discussion is the amount of contract credit awarded for meeting and exceeding performance metrics. For the fuel burn they will award up to US$379 million off the contract charge (making the submission $379 million cheaper compared to other submissions) for an engine which meets their objective fuel burn. Additionally they will award approximately US$125 million for an engine that can meet the unscheduled engine removals metric, 0.26.

Would anyone want to take a guess at evaluating the fuel efficiency of the respective submissions noting that in the end it will come down to overall bid price that factors in a whole lot of different metrics?

texl1649 wrote:

I actually LOL’d at this, thx. I don’t care what the red flag etc. exercises did, or “Flight of the old dog” (Dale Brown) discussed/theorized, it’s not even remotely likely any B-52 will ever enter hostile air space contested at any level again. It’s a stand off platform for the next 40 years.

The B-52 radar sig is larger than the A380. It’s impossible to hide at any level.

You are correct to a point. There is a good possibility low-level could return in cases where there is little air threat. However, there could be a threat no matter what precautions are taken. There are some scenarios such as the mining of a harbor or access to a harbor where the use of a Buff would be prudent. The only other option is a P-8 which has little in counter ECM. I never said anything about a radar signature but I can assure you from first-hand experience if you have no emissions you can get pretty close to a Russian carrier without being detected. Most of the SIOP low-level strike packages were based on avoiding SAM sites and using the terrain to mask the radar return.

Seems that RR got going with this project back in 2017, hence they are quite advance in their product offering having already submitted a lot of detail. They are currently stating a 34% improvement in fuel burn.
They stated back in 2017 the existing engine would cost an additional $10b over the lifetime in terms of fuel and overhauls


https://www.flightglobal.com/rolls-royc ... 89.article

I’m not an engineer, is this normal to build a mock up in dealing with the upgrades?


https://oklahoman.com/article/5666431/n ... on-project

Buckeyetech wrote:

I’m not an engineer, is this normal to build a mock up in dealing with the upgrades?


https://oklahoman.com/article/5666431/n ... on-project

Boeing is being awarded the work to upgrade a number of the componentsand wing structures and will likely be the location where whichever OEM wins the engine deal with conduct their integration. Hence yes it is very normal to plan this out and complete the building work required before the engine selection is made. I expect Boeing isn't paying for this themselves, it would be part of the risk reduction for the program and whole or part funded by the USAF.

Buckeyetech wrote:

I’m not an engineer, is this normal to build a mock up in dealing with the upgrades?


https://oklahoman.com/article/5666431/n ... on-project

The answer is not typically for a digital airplane. But the '52 are not digital.

So lets take the wing for example. If they were to build up a new wing, they could take the time to make a digital version of the wing to aid in manufacturing. Once modeled in the computer, they can then easily route the systems knowing that the newly built wing will have good enough tolerance that things will fit together when they do the mod.

For something really old with no existing digital model, they have to build a mock-up to help the Engineer plan out the system routing before they get their hands on the real thing. The problem is because of variations from plane to plane, the mock up can only account for so much. You have to build in manufacturing excess to adjust the system on-the-fly as you modify each air frame.

Given enough lead time, like what Boeing had with the AWACS upgrade, they would spend the money to take the old roll drawings, digitize them, and generate a digital mock-up for the mod. You would spend lots of time and money up front to do this, but you would benefit at the tail end with improved routing of system.

Of course you are talking about a frame that is even older than a 707, so trying to digitize a 52 may be just too much and would not buy you much if the tollerance variation is significant.

bt

mmo wrote:

You are correct to a point. There is a good possibility low-level could return in cases where there is little air threat.

Sure but why? The whole point of low level is to evade high-intensity threats. If only low intensity threats exist the altitude profile will be whatever is best conductive to fuel burn and the airframe itself, which is definitely not low level for any airframe. If low level cannot survive in a high intensity threat environment then it is simply obsolete.

It is interesting they are bringing in a representative sample, of the fuselage and wings, for analysis/preparation. Presumably, this won't be from the current active fleet. It was only through some herculean efforts that a mothballed example was brought back last year from the boneyard.

The 60,770 square-foot building will hold a wing and fuselage from a retired U.S. Air Force B-52 bomber, so engineers can work hands-on with the airframe as they design new radar and engine components.

Could a similar effort be involved in this project if only for purposes of getting the re-engining program underway/properly set up?

https://www.military.com/daily-news/201 ... rvice.html

It's been 30 years but there was a room in Sunnyvale that had exact mockups of all of the submarine launched missiles: Polaris A1, A2, and A3, Posidon C3, Trident I C4, and the Trident II D5 was in testing at the time. Even with digital design these days real mock ups are valuable - for example the new GE T901 engine recently had its full mockup completed and in testing to see if it actually fits in an Apache or Blackhawk and can be maintained.

It is quite hard in digital design to see the actual spaces needed to maintain something it tight spaces. For example, there might not be enough hand room to turn the wrench a sufficient angle.

BT noted that pre-digital there were more variations between articles than today, quite true, but as the current B-52H represented the last 102 made of 742 over 3 years, with the G being in production for 3 years also & 193 of those made it should have settled down to being quite alike. For replacing wing skins on an old plane, it would be vital to be able to remove the part, digitally map the geometry, make a first article, fit it in, adjust, then make a batch of the parts.

BT's note of tolerance variation is quite true, I would guess that the drawings were not fully updated, the actual production plane used as a mockup would be much closer to the active duty planes than the drawings. Lots was adjusted in the shop to get things to actually fit. Probably only a few % difference, but enough to cause heartache getting things to fit without buckets of shims.

A Tulsa based company, Nordam, won in January a B-52 cowling contract. Interesting they are doing composite vs the original metal.

https://www.tulsaworld.com/archive/nord ... ef69e.html

SuperiorPilotMe wrote:

mmo wrote:

You are correct to a point. There is a good possibility low-level could return in cases where there is little air threat.

Sure but why? The whole point of low level is to evade high-intensity threats. If only low intensity threats exist the altitude profile will be whatever is best conductive to fuel burn and the airframe itself, which is definitely not low level for any airframe. If low level cannot survive in a high intensity threat environment then it is simply obsolete.

Did you read my comments? I specifically stated "little air threat". That would mean a low threat environment. I can think of several reasons. The ingress/egress area is low threat but there is a possibility of an a2a threat. It is almost impossible to get an IR lock-on on a Buff low level. Mining is also done low level. There are still requirements for low-level sorties so there must be some situations where it is complicated.

Your comments about fuel burn and airframe are really meaningless as the major mission was that mode for over 30 years, so either everyone was wrong and didn't have a clue or your comments are incorrect.

Really? Because you seem to be the one quite mistaken.

First of all the threats from likely OPFOR nations are in turn likely to be S2A as that type of defense is more in practice with the affordability and doctrine of those nations, except for the PRC which is still going to possess a significant S2A threat anyway. Not to mention even rudimentary, basic interceptors are going to have look-down shoot-down radars anyway. That is the whole reason why low level became obsolete anyway. That is the whole reason why the Soviet Union pursued this capability. If airborne threats are that much of a concern of course you’ll throw up a CAP.

And while I’ll admit mining may not exactly be a rare mission I’d regard it as outside the typical offensive mission profile anyway.

As for your final comment, airframe fatigue for the Buff was a major issue back then too.

JayinKitsap wrote:

I would guess that the drawings were not fully updated

True story. There are 767 parts that we still use on other new built aircraft today. One day a few years back the parts started to come in out of tolerance.

They found that the photo contact master of the part has aged to the point that mylar prints are no longer reliable. They had to back engineer the part and reloft it in a digitized format.

Now imagine what kind of drawings they have to work with for the 52. Heck I don't know if they have anything left that is usable other than the airplanes themselves.

bt

bikerthai wrote:

JayinKitsap wrote:

I would guess that the drawings were not fully updated

True story. There are 767 parts that we still use on other new built aircraft today. One day a few years back the parts started to come in out of tolerance.

They found that the photo contact master of the part has aged to the point that mylar prints are no longer reliable. They had to back engineer the part and reloft it in a digitized format.

Now imagine what kind of drawings they have to work with for the 52. Heck I don't know if they have anything left that is usable other than the airplanes themselves.

bt

Not sure about aviation but for both Marine and Buildings in the 50's the original drawings were ink on vellum, a fine linen cloth that was plasticized. It was more durable but as it was less translucent it was slower to make blueprints from. In the late 1990's blueprinting pretty much went away as the ammonia was hazmat and really expensive to throw away. In the 60's ink on Mylar was the way to go as it gave sharper blueprints at higher speed. As you noted, the Mylar both shrinks and cracks.

When they were building the B-52's they would have never expected it to be flying 60+ years, after all the B-17 went to the boneyard at about age 15, the B-29 about the same and 23 Bombers got listed since that were mostly stillborn. Suddenly, the BUFF is going for possibly 100 years of service, unheard of then, still amazing now.

SuperiorPilotMe wrote:

Really? Because you seem to be the one quite mistaken.

First of all the threats from likely OPFOR nations are in turn likely to be S2A as that type of defense is more in practice with the affordability and doctrine of those nations, except for the PRC which is still going to possess a significant S2A threat anyway. Not to mention even rudimentary, basic interceptors are going to have look-down shoot-down radars anyway. That is the whole reason why low level became obsolete anyway. That is the whole reason why the Soviet Union pursued this capability. If airborne threats are that much of a concern of course you’ll throw up a CAP.

And while I’ll admit mining may not exactly be a rare mission I’d regard it as outside the typical offensive mission profile anyway.

As for your final comment, airframe fatigue for the Buff was a major issue back then too.

I am not going to lower myself to respond to your remarks and will deal with only the FACTS.

First of all, your justifications are all wrong. Look down shoot-down is a very difficult task when you try it on a Buff. Having flown several Red-Flags I can tell you from personal experience it is extremely difficult. If flown correctly, the Buff, even with its large return is very difficult to lock on at low level, with an IR shot, it is, again, very difficult due to the location if the underwing engines. A fighter is going to have to get lower or at the same level as the Buff and given the task saturation in the fighter it's not going to happen.

An SA-2 is not going to pose a major threat at low-level however a MANPADS will. That is why the tactics were changed. You seem to forget on a SIOP sortie the Buff will arrive about 8 hours after the first warhead goes off. There isn't going to be much in terms of SAM threats. Most of the targets will be fairly soft targets or DA assessment for ICBM sites.

Finally, I did check with some people who are still flying the aircraft and low-level is still a training event that is required for MR status and it is still taught during a visit to the schoolhouse. You might not think mining is a big mission, the Navy does and the Buff is a major player in their delivery. MOMAG still uses the Buff as a major delivery vehicle and has no plans to change that.

As far as fatigue goes, you are somewhat correct again. But, you don't realize the H was changed when they were built to handle the low-level mission. By the time the H models rolled off the production line, the low-level tactics had been in place for a few years and the fatigue issue on the earlier models was well known. The D and G were beefed up during depot visits to handle the stress.

Guys, superiorpilotme is basically a troll account. Back to the topic; how are they getting that retired airframe to OKC? Which frame will it be? I am very curious how/when this will work out.

texl1649 wrote:

Guys, superiorpilotme is basically a troll account. Back to the topic; how are they getting that retired airframe to OKC? Which frame will it be? I am very curious how/when this will work out.

Are some of the retired planes still flyable, just for a single flight? After all they flew there, but that was 10-15 years ago for one of the latest models. Still would take a maintenance crew months to get it ready. Certainly need to hang 'green' engines all around and a lot of stolen parts from others in the desert.

If it still has engines on it, would replacing say 4 be enough along with 4 remaining. It would have to assume that it could be flying with just 4 engines not 8.

JayinKitsap wrote:

texl1649 wrote:

Back to the topic; how are they getting that retired airframe to OKC? Which frame will it be? I am very curious how/when this will work out.

Are some of the retired planes still flyable, just for a single flight? After all they flew there, but that was 10-15 years ago for one of the latest models. Still would take a maintenance crew months to get it ready. Certainly need to hang 'green' engines all around and a lot of stolen parts from others in the desert.

If it still has engines on it, would replacing say 4 be enough along with 4 remaining. It would have to assume that it could be flying with just 4 engines not 8.

It has been done before, https://www.airforcetimes.com/news/your ... -boneyard/

Didn't they truck a B-1 up to Seattle for testing? They can probably do the same.

It would be cheaper.

bt

IIRC, there is or should be an H model floating around that had a LOX issue which caused damage to the airframe. There was a second H rescued from DM, Wise Guy, which is currently at Tinker having depot maintenance completed. I would assume the H model which had the malfunction was still at BAD.

I think the re-engine plan included all the active fleet and those stored in DM.

mmo wrote:

I am not going to lower myself to respond to your remarks and will deal with only the FACTS.

Ok then.

First of all, your justifications are all wrong. Look down shoot-down is a very difficult task when you try it on a Buff. Having flown several Red-Flags I can tell you from personal experience it is extremely difficult. If flown correctly, the Buff, even with its large return is very difficult to lock on at low level, with an IR shot, it is, again, very difficult due to the location if the underwing engines. A fighter is going to have to get lower or at the same level as the Buff and given the task saturation in the fighter it's not going to happen.

Who said anything about an IR shot? Look-down shoot-down is a somewhat rudimentary capability today. I mentioned that in my post, except I guess that's one of my "remarks" that you don't want to "lower" yourself down to answering.

An SA-2 is not going to pose a major threat at low-level however a MANPADS will. That is why the tactics were changed.

Ok. That seems to be an argument for going higher in altitude, away from MANPADS engagement range.

You seem to forget on a SIOP sortie the Buff will arrive about 8 hours after the first warhead goes off. There isn't going to be much in terms of SAM threats.

So why go low level at all? The only reason to go low-level is to evade threats; why, if no threats exist anymore?

Most of the targets will be fairly soft targets or DA assessment for ICBM sites.

I'm sorry, Buffs will be dropping free-fall nukes as part of a nuclear second strike? I thought it was pretty clear we were NOT talking about a nuclear peer state scenario, in which case rational people would figure Buffs would be launching cruise missiles well outside of engagement range anyway.

Finally, I did check with some people who are still flying the aircraft and low-level is still a training event that is required for MR status and it is still taught during a visit to the schoolhouse. You might not think mining is a big mission, the Navy does and the Buff is a major player in their delivery. MOMAG still uses the Buff as a major delivery vehicle and has no plans to change that.

All of that is exceedingly different from flying low-level as a routine mission profile.

As far as fatigue goes, you are somewhat correct again. But, you don't realize the H was changed when they were built to handle the low-level mission. By the time the H models rolled off the production line, the low-level tactics had been in place for a few years and the fatigue issue on the earlier models was well known. The D and G were beefed up during depot visits to handle the stress.

You're correct, I didn't realize the H model was changed. I didn't realize it was changed to a degree where fatigue cracks would be made physically impossible over 60-70 years of sustained flight.

You said you were going to engage in FACTS with us taking your word on your "years of Red Flag exercises" and "friends" but your post is rife with bad-faith misinterpretations and vagueries. Several OPFOR air defense weapons have proliferated that pose a legitimate challenge to a Buff regardless of altitude profile - Tor, Buk, double-digit MANPADS systems, radar upgrades and even standard radars to Flanker, Fulcrum and even older legacy fighters, potential newer adversaries like the JF-17 and even 4.5 or 5 generation jets. If there are threats that exist that require low-level penetration, then these are threats that require F-35s and soon B-21s. You don't address any of this.

I'm not saying it's not worth putting in the training syllabus, but why put extra stress on the airframe for low-level missions if there's no point beyond mining?

So, how many hours do you have? How many in the Buff? What other military/defense experience do you have? AMF!!!

You two are like ships passing in the night. You both have valid points but seems to be arguing to different points.

The reason to re-engine is clear to me as a non-pilot. It's a matter of having enough frames in the air to complete the mission on a multi-front war. Sure it's not ideal to have such an old frame flying. But what choice do we have? There are not enough B-1 & B-2 out there to do the job and the B-3 have yet to fly with who knows what cost escalation in the years ahead.

And don't start talking about large UAV. We are not there yet with sufficient quantity.

They will be using the 52 as a bomb truck with other roles in a pinch. They need reliable engines that burn less fuel and not damage the ear drums of the locals.

Sure it's not ideal. Neither is buying a bunch of Eagles because you can't train enough pilots to fly 35s even if you gave enough 35s to go around.

bt

Loren Thompson has a hired gun article, typical of him. This time it is to nudge P&W to be selected. Back to all the big risk talk of not having too big of engines, how to keep the balance, the nacelle size, FADEC or not, and on. Not a lot learned other that the program seem to be moving forward.

https://www.forbes.com/sites/lorenthomp ... 6ac9509219

JayinKitsap wrote:

Loren Thompson has a hired gun article, typical of him. This time it is to nudge P&W to be selected. Back to all the big risk talk of not having too big of engines, how to keep the balance, the nacelle size, FADEC or not, and on. Not a lot learned other that the program seem to be moving forward.

https://www.forbes.com/sites/lorenthomp ... 6ac9509219

I don’t see where he is pushing the P&W option over GE or RR?

Overall I thought a reasonable review and a couple of things that we haven’t really discussed in the thread.

Ozair wrote:

Overall I thought a reasonable review and a couple of things that we haven’t really discussed in the thread.

Sure, if one is taking in by the quantity of his argument vs quality.

Worried that the new engine will produce too much thrust that it will impact the wing structure? You can always have the thrust, but cap it with a regulator.

Worried about the supply chain of any new engine? It should be a consideration when selecting the new engine but anything would be better the the supply change of the current engine.

Nacelle re-design impacting the air flow over the wing? A legitimate argument if the new engine is larger than the current ones. Here, I will trust the Engineers to do their due diligence with the CFD.

Cyber security? Lets just say if they haven't figured it out with the P-8A or the Navy drone, then we are in more trouble than we know.

There will be opportunity for cost escalation. Most of which will be around the capability of the wings and whether they can stand the mod. If the prevailing thought is that those wings are stout as heck, then the risk should be acceptable.

Any graphics out there comparing the size of the new vs the old engines? Will they need modify the new fan to match the aero profile of the old engine? This would give us insight into the risk.

bt

One item that would concern me is the vibration profile of new engines. Sonic and vibration mode can be analysed, but the analysis is black magic to me. Never really got the grasp of structure dynamics in school.

bt

So any news on the re-engine program? I assume that we're still in the pre-bid stage?

washingtonflyer wrote:

So any news on the re-engine program? I assume that we're still in the pre-bid stage?

The award is expected in June or July. I do think bid submissions...are in already. GE bid two engines, Pratt and RR 1 of course, each.

RR could really use the win on this one, although its probably more likely it will be Pratt or the GE passport. Hopefully not the CF-34, but if The KC-46 and its nearly 40 year old PW4000's is any indication, it probably will be the CF-34.

I still favor the RR bid. Made in Indiana, already in inventory for USAF, same nacelles, perfect fit, imho. But I picked wrong on both the engine and Northrop on the ATF competition as well...

I picked wrong on the ATF as well. I've since gotten used to the fact that the USAF almost always chooses technology readiness level over more advanced technology.

One thing that doesn't make sense about the RR bid is that the same nacelle can be used. The BR-715 doesn't have a bypass cowl like the TF-33 and instead has an exhaust mixer like the Passport and PW800. The J-57 nacelles would work, but not the TF-33 nacelles (at least not without modification), I think that would be insanely draggy.

Has anyone seen a comparison table published with the specs of the various proposals and the TF33 ?

I haven't seen a nice chart, zeke. Closest I've seen;



This is a decent article from a couple years ago.

https://aerospaceamerica.aiaa.org/featu ... -a-legend/

The official usaf flow chart for 'best value indicators' is here;

https://fas.org/sgp/crs/weapons/IN11413.pdf

texl1649 wrote:

I haven't seen a nice chart, zeke. Closest I've seen;



This is a decent article from a couple years ago.

https://aerospaceamerica.aiaa.org/featu ... -a-legend/

The official usaf flow chart for 'best value indicators' is here;

https://fas.org/sgp/crs/weapons/IN11413.pdf

In the older B-52 thread viewtopic.php?f=10&t=1395589&start=50&hilit=%26amp%3Bquot%3BB+52%26amp%3Bquot%3B+CF+34


A link to another article on this
https://fighterjetsworld.com/air/re-eng ... ber/20478/

I posted the following in a reply to you regarding the engine dimensions and weights. The picture you showed was one of the sources for my info, the balance came from web sources. Page 2 for some reason there are not post numbers.

JayinKitsap wrote:

texl1649 wrote:

I don't want to make this a tanker derail but it doesn't make sense to re-engine the KC-135's (again). The airframes/wings are about shot, and while it will be difficult to replace them all in the 2030's now it is a real need. They are just too old to soldier on into the 2040's, and can't be easily modified to enable that (realistically the KC-10's could but again that's another long tanker war topic; my prediction is the KC-10 fleet will be taken back up from AMARG in around 12 years).

Somewhere I missed the second engine replacement program for the KC-135 that retrofitted 354 aircraft with new CFM International CFM56 (military designation: F108) from the TF33. No engine replacements beyond that, but agreed that this goes to the tanker discussions.

So on the BUFF the existing TF33-P-3 has 17,000 lbf (75.62 kN) thrust, weight of 4,605 lb, 53"D x 142" long.

The replacements proposed are:

GE Passport: 18,900 lbf thrust, weight of 3,950 lb, 52"D x 103" long.
GE CF-34-10: 20,360 lbf thrust, weight of 3,760 lb, 53"D x 88.7" long.
RR F130 (BR725) 16,900 lbf thrust, weight of 3,605 lb 50"D x 130" long.
PW 800: 18,000 lbf thrust, weight of 3,190 lb 50"D x 130" long.

So all are lighter than the current engine, the lightest saves 5,400 lb per aircraft. Do any of these engines have a real advantage over the competition?

All 4 appear reasonable, the PW800 and BR725 look like the best to fit inside of the existing nacelles but it is likely the CG of the engine as mounted being as close to the TF33's so as to not change the wing torque from the engine.

Anyone know if the F130 already has the hardened controls, that could be a very big deal.