All,
To quote one of the many reports on this subject that have floated about over recent years:
An unsolicited proposal for reengining 94 aircraft in the B-52 fleet was submitted to the Air Force by Boeing North American, Inc. in June 1996. Boeing proposed modernizing the B-52 fleet by replacing the current TF-33 engines with Allison/Rolls Royce RB-211 engines through a long-term leasing agreement, and providing fixed-cost, privatized maintenance based on the number of hours flown each year.
Boeing initially projected reengining cost savings of about $6 billion, but later revised the projected savings to $4.7 billion. An Air Force team formed to study Boeing’s proposal analyzed the lease and purchase alternatives and concluded that both options are cost prohibitive compared to maintaining the existing TF-33 engines.
The General Accounting Office estimated that Boeing’s unsolicited proposal to reengine the B-52 fleet would cost the Air Force approximately $1.3 billion rather than save approximately $4.7 billion as Boeing projected.
It is accepted that the newer engines would be far more fuel efficient than the old TF33s with the added bonuses of getting longer ranges per fillup, or having to haul less fuel overall or even giving a longer on station loiter time and reducing the amount of mid-mission tanking that would be required.
Heres another piece from a discussion thread of just over three years ago that seems to put doubt on the USAFs counter-argument that the cost savings are minimal. As with all things, theres always two sides to an argument !
By any measure, the venerable B-52 bomber is a gas hog. It burns 3,334 gallons per hour through eight jet engines that were designed in the 1950s, when the B-52 first entered service.
The B-52 remains the Air Force’s main big bomber. The Air Force has rejected proposals over the past decade to replace the plane’s eight engines with four new, efficient jets. The Air Force said spending $4 billion on new engines would save only a net $400 million and then only if the plane kept flying for another 40 years.
The Science Board study said the Air Force incorrectly calculated fuel costs. Each gallon of jet fuel was priced as if the airplanes were filled up by tanker trucks at the B-52s’ main home base. However, about 10% of the fuel is delivered by aerial tanker, which costs about 10 times more than regular fueling.
In addition, many of the planes flying with a full load, such as those in use over Afghanistan, take off from remote bases, such as Diego Garcia, an island in the Indian Ocean, where special fuel shipments are required.
The Science Board’s study of replacing the B-52 engines estimated $9 billion in savings, and that was when fuel prices were half their current level.
One benefit would be that regular missions from Diego Garcia to Afghanistan could be done without aerial refueling. Such refueling, which involves a tanker plane extending a fuel line to the B-52 flying below, is often dangerous and exhausting for pilots. It also slows the mission.
I dont claim to know the answer to this question, however, I do know that old stuff costs shedloads more to maintain, and i do find it suprising that the option hasnt been explored further by doing the mod on a couple of a/c and actually trying it!
Lets face it – we’ve all seen what a change the CFM56 has made to the -135 series, i would have thought that that lesson would have been patently obvious.
The re-engined tanker, designated the KC-135R, can offload 50 percent more fuel, is 25 percent cheaper to operate and is 96 percent quieter than the KC-135A.
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