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B-52 Re-engine Resurfaces As USAF Reviews Studies

helmutkohl

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is it possible to refit from those 8 engines to 2 large ones.

the original B-52 engines are 76 kN x 8 or 608kN of thrust
the GE GEnx (as on the 787) produce 280kn to 320kn, meaning it can produces 560 to 650kn of thrust, similar to what it had before, but with just two engines. probably far more fuel efficient.
 

TomS

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So what happened to the B-52I?
Two theories:
- the designation was already used by a Secret Project to supply a strategic bomber force to an I airforce (8 candidates starting with Iceland, ending with Italy)
- the USAF is skipping the letter so that the airplane won't be perceived as an Apple product (made in China, designed in California)
Or, MDS naming logic skips letters I and O for modifiers due to the potential for confusion with numerals 1 and 0.
You know, like the B-21/B-2i fiasco?

Or has that since been debunked as a myth?
[/QUOTE]

Never heard that one. B-2i would break so many MSDS rules I've lost track (out of order, no lower case letters, etc.). And B-21 was pretty clearly announced in print as the Bomber for the 21st Century, as dumb as that sounds. It's not like the X-35 to F-35 screwup, where you can actually hear the general getting it wrong in real-time on the broadcast.
 

TomS

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is it possible to refit from those 8 engines to 2 large ones.

the original B-52 engines are 76 kN x 8 or 608kN of thrust
the GE GEnx (as on the 787) produce 280kn to 320kn, meaning it can produces 560 to 650kn of thrust, similar to what it had before, but with just two engines. probably far more fuel efficient.
No. Some initial B-52 reengine concepts went down to four engines but the discussion in this thread covers lots of reasons why even that is a bad idea. I really really doubt a B-52 would have enough rudder authority to survive an engine out on takeoff event with only one engine per side.
 

sferrin

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is it possible to refit from those 8 engines to 2 large ones.

the original B-52 engines are 76 kN x 8 or 608kN of thrust
the GE GEnx (as on the 787) produce 280kn to 320kn, meaning it can produces 560 to 650kn of thrust, similar to what it had before, but with just two engines. probably far more fuel efficient.
Yeah, if you don't care about performance.
 

Josh_TN

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Again, asymmetrical thrust would be an issue. An engine failure would be an aircraft loss. The B-52s control surfaces weren’t designed with that configuration in mind.
 

gtg947h

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So what happened to the B-52I?
Two theories:
- the designation was already used by a Secret Project to supply a strategic bomber force to an I airforce (8 candidates starting with Iceland, ending with Italy)
- the USAF is skipping the letter so that the airplane won't be perceived as an Apple product (made in China, designed in California)
Or, MDS naming logic skips letters I and O for modifiers due to the potential for confusion with numerals 1 and 0.
You know, like the B-21/B-2i fiasco?

Or has that since been debunked as a myth?
Never heard that one. B-2i would break so many MSDS rules I've lost track (out of order, no lower case letters, etc.). And B-21 was pretty clearly announced in print as the Bomber for the 21st Century, as dumb as that sounds. It's not like the X-35 to F-35 screwup, where you can actually hear the general getting it wrong in real-time on the broadcast.
[/QUOTE]

I’m still of the mid that it was supposed to be the B-2.1...

;)
 

eagle

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That's probably it, although the rule isn't always applied (see F-15I for the Israelis). Still, I like the idea of a secret squadron of Viking iBombers (yes, I know Iceland doesn't officially have an air force - that would be part of the secret)
That's most likely it:

omitting "I" and "O" to avoid confusion with numerals "1" and "0"
from: http://www.designation-systems.net/usmilav/aircraft.html

F-15I et al. are not official USAF designations afaik...
 

aeroengineer1

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Again, asymmetrical thrust would be an issue. An engine failure would be an aircraft loss. The B-52s control surfaces weren’t designed with that configuration in mind.
This is a red herring. Sizing of the aircraft moment arms and control surfaces is in the same range or exceeds other four engined aircraft. Issues relate to fan blade out capability as stated in my previous post.
 

sferrin

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Again, asymmetrical thrust would be an issue. An engine failure would be an aircraft loss. The B-52s control surfaces weren’t designed with that configuration in mind.
This is a red herring. Sizing of the aircraft moment arms and control surfaces is in the same range or exceeds other four engined aircraft. Issues relate to fan blade out capability as stated in my previous post.
And let's not forget this:

 

_Del_

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Eh, they flew that back by using asymmetric thrust, as I remember. Would have been hard to do that without 25% of your power available on oneside. And putting it down like that is a completely different scenario than suddenly losing power on one side during takeoff anyway.
 

helmutkohl

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according to FG

The USAF wants a military derivative of a commercial engine to replace those turbines.


GE Aviation, Pratt & Whitney and Rolls-Royce have expressed interest in bidding on the programme.


GE Aviation plans to offer two bids: CF34-10s, which powers commercial aircraft like Bombardier and Embraer regional jets, and Passport turbofans, which power Bombardier’s Global 7500 business jet. Pratt & Whitney plans to offer the PW800 engine, which powers Gulfstream G500 and G600 business jets. R-R plans to offer the F130 engine, a military derivative of the company’s BR700, which powers Gulfstream business jets and other aircraft.


The USAF wants a replacement engine that has a similar size, thrust and weight compared to the legacy P&W powerplants. Each of those engines generate 17,000lb-thrust (75.7kN).


However, the service also wants a modern turbofan with a higher bypass ratio and digital engine controls. It wants that engine to have reduced fuel consumption, noise, emissions and operating costs.


The B-52H has an unrefuelled range of 7,650nm (14,200km). Depending on the engine selected, it is thought that the aircraft’s range could be increased by 20% to 40%.

--

basically a 1 to 1 update rather than 2 to 1
 

mkellytx

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Again, asymmetrical thrust would be an issue. An engine failure would be an aircraft loss. The B-52s control surfaces weren’t designed with that configuration in mind.
This is a red herring. Sizing of the aircraft moment arms and control surfaces is in the same range or exceeds other four engined aircraft. Issues relate to fan blade out capability as stated in my previous post.
It's not a red herring, it is fact. I've read the EP in the -1, the rudder lacks the authority to counteract the yawing moment at high gross weights when both engines in an outboard pod are lost. Every high gross weight takeoff I was primed and ready to pull the handles should that happen. The moment arm and tail size may be in the ballpark of 4 engine transports, the size of the rudder is not. As a percentage of cord, the rudder is tiny compared to those other aircraft you're using, it's unable to generate the needed moment.

I spent 15 years in aerospace before leaving for greener pastures, have a graduate engineering degree in the field and spent some time in the school house at Edwards studying equations of motion then practicing flight test techniques.

FWIW the H model -1 is floating around on the interwebs...

T.O. 1B-52H-1 section 3-16

TAKEOFF WITH ONE OR MORE ENGINES
INOPERATIVE
Takeoff with one or more engines inoperative is not
recommended. However, if conditions are such that
it becomes necessary to fly the aircraft to another
location, such takeoffs are possible. It will be necessary
to consider carefully the field altitude, ambient
runway temperature, available runway length,
wind velocity, and gross weight at takeoff.

A successful takeoff will be possible by use of the
normal takeoff procedure. Charts are provided in
Part 2 of T. O. 1B-52H-1-1 giving takeoff distances
required for seven-and six-engine takeoffs. When
using partial thrust procedures under these conditions,
it is necessary to check climbout performance
to assure that climbout is not critical with the failure
of an engine.

CAUTION

Because of marginal lateral directional control, it is
recommended that no takeoffs be made with two
engines inoperative on the same side.

T.O. 1B-52H-1 section 3-128 Change 1:

TWO ENGINE FAILURE
If two outboard engines located on the same side
are inoperative and a go-around is necessary, there
may be an insufficient amount of rudder available
to completely balance out the turning force encountered
at the low go-around speeds. However, by applying
appropriate lateral control as well as full
rudder, straight ahead directional control can be
maintained. See figure 3-15 for minimum speeds for
directional control. At light gross weights where
sufficient thrust is available, the directional control
problem may be relieved by reducing thrust from
the unbalancing engines. If rudder trim is used,
limitations established by Section V will be observed.
Rapid rudder manipulations will be avoided
because of the structural limits of the vertical tail
and rudder. Steady flight conditions can be established
only with the thrust deficient wing a few degrees
high.
 

riggerrob

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A couple of points about engine-out yaw control.
All the early B-52 - before G model - had vertical fins 8 feet taller. Perhaps retrofitting original-sized fins would help with engine-out control … 4-engined update.

The other point is that some multi-engine airplanes (e.g. STOL PZL Skytruck) are so over-powered that a single engine can over-power rudder(s), so the first point in the engine-out check list is to reduce power on the engine that is still running … perhaps to 75 percent (?).
 

TomcatViP

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IMOHO, it's certainly something they have been looking at. I made my mind early that adding the extra section could overstress the fatigued fuselage in torsion. But hard to tell.
 

In_A_Dream

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Poor BUFFs, it's like watching an older person getting injections and implants, stretching their skin to stay young & relevant. She sure is beautiful though.
 

Archibald

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Let's unearth the Hustler!
The incoming Reagan administration apparently had this on their "to do" list in 1981 and was disappointed when the USAF reported back that the fleet had been turned into beer cans. Whatever the merits of taking the B-58 out of service, scrapping them almost immediately after withdrawal seems an unusual decision and is usually the type of thing done amid political controversy to drive a stake through the heart of a program to prevent a resurrection. That seems like an unlikely goal for the Nixon & Ford administrations. The Carter administration's failure to destroy the B-1A prototypes and tooling made the B-1B program much more feasible.
Perhaps scrapping the fleet was required by the SALT treaty.
O RLY ??
 

Apophenia

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Let's unearth the Hustler!
The incoming Reagan administration apparently had this on their "to do" list in 1981 and was disappointed when the USAF reported back that the fleet had been turned into beer cans. Whatever the merits of taking the B-58 out of service, scrapping them almost immediately after withdrawal seems an unusual decision and is usually the type of thing done amid political controversy to drive a stake through the heart of a program to prevent a resurrection. That seems like an unlikely goal for the Nixon & Ford administrations. The Carter administration's failure to destroy the B-1A prototypes and tooling made the B-1B program much more feasible.
Perhaps scrapping the fleet was required by the SALT treaty.
O RLY ??
"As early as 1965, Secretary McNamara decided to scrap 300 B-58 bombers, which were then only 3 years old."

Military Implications of the Treaty on the Limitation of Strategic Offensive Arms and Protocol Thereto (SALT II Treaty), Hearings before the Committee on Armed Service, United States Senate, Ninety-Sixth Congress, First Session, July 23, 24, 25, 26, 1979, page 679
 

Archibald

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Except that only 116 were build :p

I know McNamara bad rep, but really, destroying 184 non-existing aircraft ?

The B-58 might have been an impressive machine, it was also a crew-killer, short ranged, and saddled with insanely expensive maintenance costs.
 

Josh_TN

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Retaining the eight engine configuration seems like the safest engineering move in any case. It's probably not how you'd design a bomber of that configuration now adays, but for the existing airframes it seems like the lowest risk upgrade. I'm just happy it looks like it finally is really going to happen this time, along with some much needed avionics upgrades.
 

helmutkohl

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another link in addition to above on the re-engining

The Air Force wants fuel efficiency savings of about 30 percent on the new powerplants versus the in-use Pratt & Whitney TF33 engines, and reliability such that the engines never have to come off the B-52 for service during the bomber’s remaining lifetime. This in turn will sharply diminish or eliminate the need to stockpile large quantities of parts, resulting in further savings. The Air Force has said that it expects fuel savings will pay for the cost of the re-engining program, which would also drive a reduction in maintainers assigned to the airplane. With the fuel efficiency, USAF is also looking for an increase in persistence or range of up to 40 percent.


The re-engining is the centerpiece of an overall B-52 technology refresh that will also include new radars, connectivity enhancements, and capability for new weapons, such as hypersonic missiles. Boeing, the original prime on the B-52, will handle integration of the new engines.


Rolls-Royce is offering its F130 engine, a variant of the commercial BR725, for the program, noting it is “already in the Air Force fleet,” company Senior Vice President Craig McVay said in a press release. The commercial version of the engine powers E-11s and C-37s.


“Should Rolls-Royce win the competition, the F130 engines for the B-52 would be digitally engineered, manufactured, assembled and tested at our facilities in Indianapolis,” he said, adding the company is “excited to move to the proposal stage” of the program.


GE is offering its CF34-10 and Passport engines, touting either as meeting USAF’s requirements. The CF34-10 has a track record for the time-on-wing USAF wants, and it has the lowest cost of ownership of any engine in the competition, the company said. The Passport offers the lowest fuel burn of any engine in its class for more payload and range, the company said.


GE also promotes itself as having done more re-enginings than any other company, noting the KC-135, C-5, and U-2 programs, adding that it provided the engines for the B-1 and B-2 bombers.
 

Foo Fighter

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Not interested in who gets the contract, I just hope they get the best engines. Aircrew will be putting their lives in this aircraft and should have the best available.
 

Josh_TN

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Any of the offerings would be an improvement. I'm glad the air force is going for time on wing as a metric rather than shear thrust. Any of those engines will provide sufficient thrust with big fuel economy and maintenance savings.
 

TomcatViP

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You are already convinced. Still, have a look at the expected time on station ;)
 

overscan (PaulMM)

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