La corsa ai nuovi motori ..... si parte !
GE, Rolls, Pratt Vie For B-52 Engine Upgrade .....
James Drew - Aerospace Daily & Defense Report (AW&ST) - Mar. 13, 2017
Engine manufacturers are lining up to upgrade or replace the Boeing B-52H’s outdated and inefficient Pratt & Whitney TF33 low-bypass turbofan engines to keep the mighty Cold War bomber flying beyond 2050.
U.S. Air Force Vice Chief of Staff Gen. Stephen Wilson told Congress on March 8 that the service must explore options for replacing the TF33, which powered the first H-model B-52 flight on March 6, 1961, almost six decades ago.
GE Aviation, Pratt & Whitney and Rolls-Royce tell Aviation Week they are actively engaged with the Air Force about the re-emerging requirement, offering ready-made commercial derivative engines or, in Pratt’s case, a TF33 upgrade package.
Their proposals come after the Air Force and Boeing proposed swapping the TF33 for eight modern, 17,000-19,000-lb.-thrust-class regional/business jet engines instead of earlier four-engine alternatives, which were deemed too risky because of the necessary structural modifications and airflow changes around the bomber’s nuclear-armed weapons.
The service once proposed a quartet of CF6 high-bypass turbofans, which are derived from the Lockheed C-5 Galaxy’s TF39.
It also considered the 757-class PW2040 and RB211 series.
But recent analysis points to an eight-engine solution to limit airframe modification.
That would require at least 608 powerplants for today’s operational feet of 76 B-52Hs, plus several sets of spares.
The Air Force has not commissioned or conducted any wind tunnel or flight tests of candidate engines in the past several years.
But market research suggests there are enough engine options on the commercial market to warrant a competition.
A request for information issued in 2014 sought alternative solutions that achieve 10-25% better fuel consumption and 15-25 years of use between schedule depot overhauls.
On Feb. 3, the government issued another RFI, this time seeking TF33 replacements, specifying “regional/business-size jet engines.”
“Acquisition strategies are in the process of being formed for both the purchase of the engine and the integration on the aircraft,” a service spokesman said on March 13.
“If the Air Force decides to fund a re-engine program in the future, it will assess all procurement options to create the best value for the government.”
GE Aviation CF34-10
GE Aviation is a longtime propulsion system supplier for the Air Force’s bomber force, including the four-engine Boeing B-1B (F101-102) and Northrop Grumman B-2A (F118-100).
The company says it supports the Air Force’s B-52 re-engining plan and would offer the 18,000-lb.-thrust-class CF34-10, developed from the TF34/CF34 family.
The smaller 9,000-lb.-thrust TF34-100 powers the service’s Fairchild Republic A-10 “Warthog” attack aircraft.
The latest commercial CF34-10 series powers the Brazilian Embraer 190, 195 and Lineage 1000 and Chinese Comac ARJ21 regional jets.
“While no GE engines have been demonstrated on the B-52, the CF34-10 is an economical eight-engine replacement,” says Karl Sheldon, GE vice president and general manager of large military turbofan engines.
“We are excited to compete for the opportunity to fly the CF34 on this strategic asset.”
Pratt & Whitney Engine Enhancement Package
Nobody has more experience with the 56-year-old TF33 than the original designer and manufacturer, P&W.
The company says it could offer a new commercial engine, but believes an upgrade makes the most sense.
“Commercial engines offer advantages of higher fuel savings, extended mission range, reduced aerial refueling and minimized overhaul maintenance,” a company spokesman says.
“However, all commercial engines in this class require increased ability to support the B-52H electric and hydraulic load requirements, and would also require extensive airframe integration and flight testing.”
The firm’s engine enhancement package would address the TF33’s performance, durability, reliability, fuel consumption and time between scheduled overhauls as much as possible without needing to buy new.
“The TF33 currently meets all B-52H power and performance specifications and would not require any changes to the aircraft structure,” the company says.
P&W is pitching this as the “affordable option.”
Digitally-controlled commercial propulsors would also need to be militarized and hardened against electromechanical pulses resulting from nuclear explosions as well as cyberattacks.
Headquartered in Indianapolis, British engine maker RR’s U.S. division has already had “several conversations” with the Air Force about a B-52 propulsion upgrade.
The company would offer something from its BR700 series, which already powers the Air Force’s Gulfstream V/C-37A personnel transport fleet and the Bombardier E-11A Battlefield Airborne Communications Node - based on the Global Express.
The alternatives in the B-52’s thrust class are the BR715 and BR725 series, but the company has not decided which to offer.
“A decision has not been reached yet, as we await the specific requirements,” says Thomas Hartmann, RR’s senior vice president for U.S. customer business.
“We are confident we can meet the technical and availability requirements.”