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bikerthai
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 8:32 pm

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
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 9:05 pm

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.
If we weren't all crazy we'd all go insane!
 
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LyleLanley
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 9:18 pm

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.
"I've sold monorails to Brockway, Ogdenville, and North Haverbrook, and, by gum, it put them on the map!"
 
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kc135topboom
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 11:31 pm

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.
 
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kc135topboom
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 23, 2020 12:53 am

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.).
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 23, 2020 5:59 am

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.
If we weren't all crazy we'd all go insane!
 
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747classic
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 23, 2020 6:50 am

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.
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
rlwynn
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 23, 2020 7:02 am

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.
I can drive faster than you
 
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LyleLanley
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 23, 2020 10:08 pm

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.
"I've sold monorails to Brockway, Ogdenville, and North Haverbrook, and, by gum, it put them on the map!"
 
giblets
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New advertisement: B-52 re-engine back in the mix?

Sun May 24, 2020 8:16 am

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/


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744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Mon May 25, 2020 6:37 pm

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.
 
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bikerthai
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 26, 2020 1:18 pm

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
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
rlwynn
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 26, 2020 2:44 pm

It got new nacelles with the current engines.
I can drive faster than you
 
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afterburner33
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 26, 2020 7:17 pm

The Rolls mock nacelles in that video with the exhaust mixers almost look like the old J57 turbojet B-52s
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 26, 2020 7:41 pm

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.
If we weren't all crazy we'd all go insane!
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 26, 2020 11:22 pm

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.
 
Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Wed May 27, 2020 1:05 am

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?
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Wed May 27, 2020 9:31 am

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.
If we weren't all crazy we'd all go insane!
 
giblets
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Re: New advertisement: B-52 re-engine back in the mix?

Wed May 27, 2020 10:22 am

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
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