There is an old joke that runs through the bomber fleet that when the B-1 and B-2 bombers are retired, the pilots will be flown home from the boneyard in the B-52 Stratofortress.
The U.S. Air Force’s fleet of B-52H heavy strategic bombers are on track to becoming a fleet of flying centenarians. The service wants to purchase over 600 new engines for its B-52s, ensuring that the “Big Ugly Fat Fella” can fly on to 2050 or later. This will practically ensure that some bombers, delivered in the early 1960s, will still be dropping bombs in the early 2060s.
The B-52’s versatility makes it invaluable to the modern U.S. Air Force, which is determined to keep it flying as long as possible. It can haul up to 70,000 pounds of laser-guided bombs, GPS-guided bombs, and unguided bombs, plus the JASSM air-launched cruise missile and Quickstrike series of naval mines. In the nuclear mission it carries the AGM-86B air launched cruise missile. The B-52 will outfly both the B-1B Lancer and B-2 Spirit stealth bombers, in large part because of plans to fit it with new, powerful, more fuel efficient engines.
Each B-52 is equipped with eight Pratt & Whitney TF33-PW-103 engines, the same engines the jets were delivered with in the early 1960s. The engines give the bomber an un-refueled combat range of 8,800 miles. As good as the TF-33 is, it’s more than a half-century old technology. Turbofan tech has come a long way, with more powerful, fuel efficient engines available. Much of that innovation has been driven by the commercial airline industry.
The draft Request for Proposal is the Air Force’s way of asking industry what engine options it has for B-52. Flightglobal has the list, which includes engines from Pratt & Whitney (again), Rolls-Royce, and GE. The Air Force wants the new engines to be quieter and cheaper to operate.
The Air Force’s B-52H bomber fleet is the last of 744 B-52 bomber built during the Cold War. The service operates 75 of the -H models, split between 57 jets in the Air Force and another 18 in the Air Force Reserve. The jets were delivered between May 1961 and October 1962. Originally conceived as a nuclear bomber, the B-52H’s mission set expanded over the decades to include, as the service describes, “strategic (nuclear) attack, close-air support, air interdiction, offensive counter-air and maritime operations.”
The major requirement, however, is fuel efficiency. According to FlightGlobal the Air Force doesn’t necessarily want more powerful engines: the TF-33 can produce 17,000 pounds of thrust and that’s still the thrust target. Instead, the Air Force wants “higher bypass ratio and digital engine controls,” resulting in greater fuel efficiency. The new engines will stretch the B-52’s 8,800 range by another 20 to 40 percent, resulting in a new un-refueled range of up to 12,320 miles. That’s to allow a B-52H fly to any point on Earth.
The Air Force wants 608 engines delivered over a 17 year period—enough to keep 76 bombers flying—plus spares and maintenance equipment. The bomber airframes, though six decades old, have “thousands” of hours left. All of this adds up to an airplane the Air Force thinks can fly until the 2050s—if not much longer. As long as the heavy bombers don’t suddenly become too expensive to fly, it is conceivable the same B-52H bombers could stay on active duty for 100 years.
The first production B-52A first flew on August 5, 1954, with the first in-service B-52B’s following a short time later. Despite being powered by eight Pratt & Whitney J57 engines, the bomber felt underpowered from the start. Even with water-injection added for additional thrust at take-off, the aircraft suffered from marginal performance with a full weapons load on a hot day.
In early 1956, Major General Al Boyd, Deputy Commander for Systems, Air Re-search & Development Command (ARDC), requested the feasibility of replacing the pair of J57’s with a single afterburning J75 engine on each of the outboard pylons to achieve better performance. The prototype XB-52 was made available and the aircraft made a series of flights in this configuration between November 1957 and August 1958, logging over 140 flight hours. Despite the final report stating a ‘substantial performance improvement’, the configuration was not adopted for the fleet.
When the last B-52 was delivered to the Air Force on October 26, 1962, this final H-model variant was now utilizing the Pratt & Whitney TF33 turbofan engines which gave much better performance than the original J57s.
Another attempt to find new engines came in 1969 when Boeing began a study to re-engine the B-52 fleet and again in August 1971 when the Air Force and Boeing performed a more detailed study on replacing the engines with High Bypass Ratio Turbofan engines on all B-52G & H models. Boeing studied a concept using a sin-gle turbofan on each of the four wing pylons and another that used two engines on a single inboard pylon. B-52 Single Pod EnginesDuring 1975, with the highly-contested Rockwell B-1 program in full swing, members of Congress offered a re-engined and upgraded ‘B-52I’ as a replacement. Again, it was not adopted.
The 1980’s saw Pratt & Whitney making a de-tailed study into replacing the eight TF33s with four PW2000 (F117) engines. Since it was expected that the B-52 would be replaced by the B-1 and B-2 by the mid-1990’s, this idea never gained traction. The issue was studied again in January 1996 after an incident with B-52H #60 -0054 when a double engine failure caused engines number 3 & 4 to depart the aircraft in flight. In this case, Boeing and Rolls-Royce teamed up and proposed the use of the Rolls- Royce RB211-535 similar to those used on the commercial 757 aircraft. The Air Force once again rejected the proposal.
By 2003, the cost of overhauling the old TF33 engines had tripled and another USAF/Boeing study on re-engining the fleet determined it would cost approximately $4.5 billion to complete, but would yield a cost savings of nearly $15 billion over the life of the bomber in addition to increasing the combat range by 22% and reducing greenhouse gas emissions. The engine competition between the Pratt & Whitney PW2000, Roll-Royce RB211-535 and CFM International CFM56 (F108) could be partially financed under the Energy Sav-ings Performance Act which allows the Federal Government to partner with private industry on energy conservation methods. Despite the amount of effort put into this proposal, nothing was to become the engineering effort.
Once the Air Force decided that the B-52 would be in service until at least 2040, by which time the service plans to have retired all B-1B and B-2 bombers, a new proposal in 2018 was undertaken to re-engine the 76 plane fleet to fly alongside the next-generation Northrop B-21 Raider. This latest effort is known as the Commercial Engine Replacement Program (CERP) with the idea of outfitting the legendary aircraft with commercial off-the-shelf, in-production business jet engines. The goal is 20 to 30 per-cent better fuel efficiency with a 40 percent increase in range, ease of maintenance utilizing the latest onboard diagnostic equipment and lower greenhouse gas emissions. Pratt & Whitney, Rolls-Royce and General Electric are expected to compete for the multi-year contract to purchase over 600 replacement engines with Boeing serving at the systems integrator.Rolls-Royce F130 Engine
One day a new aircraft will be designed to replace this legendary machine and this latest effort may be the best hope to keep this iconic aircraft flying for at least another quarter century proving that old soldiers never die, they simply fade away.