Allison T56 ou 501-D13

Rolls-Royce is preparing to test an upgraded version of its venerable T56 turboprop to boost performance of the Lockheed Martin C-130, as well as cut fuel consumption by up to 12%.

Launched in response to U.S. government calls for reduced dependence on foreign oil, the upgrade is aimed at the C-130H’s T56-15 Series 3, and is also expected to result in improved availability and reliability. “It will save the U.S. Air Force around $80 million per year in fuel costs,” says Dennis Jarvi, president of Rolls-Royce Defense North America.

The first modified T56, dubbed the 3.5 engine enhancement program, will start tests at Rolls’s Indianapolis site in September.

“We are in discussions with the Air Force and Air National Guard to define flight-test parameters and requirements for testing,” says Jarvi, who adds that the “current plan is to perform flight tests in the first half of 2011 at Edwards AFB, Calif.”

The Air Force has loaned Rolls four T56 Series 3 engines for modification and testing. Flight trials and in-service modifications must be performed on a shipset basis, according to the company. “This is due to concerns about potential asymmetric-thrust issues as well as the risk that Series 3 and 3.5 configuration engines installed on the aircraft in combination might cause confusion in the cockpit as a result of turbine inlet temperature and fuel-flow gauge reading mismatch,” it says.

The improvement package updates the compressor inlet housing with the better flow of the Series 4 T56-427A version developed for the Northrop Grumman E-2D Advanced Hawkeye, as well as compressor-wheel knife seals derived from the same variant. The upgrade also includes remanufactured compressor blades, single-crystal first-stage high-pressure turbine blades, and aerodynamically redesigned blades and vanes throughout the low-pressure turbine.

The turbine upgrade is designed to increase component life by around 30%, and “is derived from proven technologies used on existing powerplants, including the [Rolls-Royce] AE engine,” says Jarvi. The large leap in fuel-burn improvement is expected because, as Jarvi concedes, the original Allison-developed T56 is “relatively old technology.”

Due to the requirement to install so many changes to the compressor, Rolls is planning for the 3.5 upgrade to be performed during depot-level maintenance rather than during intermediate servicing. The kits, which will also be available for international C-130 users beginning in September 2011, are expected to increase the range of the C-130H with a 20,000-lb. payload to more than 3,180 naut. mi., from 2,845 naut. mi., compared with a standard Series 3-powered aircraft under identical conditions.

The market potential is estimated to be around 2,000 engines for the C-130, though overall numbers could grow if a potential adaptation of the kit is developed for the T56-14 version that powers the P-3 maritime patrol aircraft.

The modification to the inlet module would be “notionally about six months after the T56-15s [C-130 variant] are made available, or in March 2012,” Jarvi says. Although the Boeing P-8A is in development as the long-term replacement for the P-3C, Rolls officials say the market remains viable for both potential U.S. Navy upgrades as well as international programs. The company reports 7,500 T56 engines are now in service around the world, powering about 1,325 C-130s, 415 P-3s, 37 C-2s and 108 E-2Cs.

In May, Rolls delivered the first production T56-427A for the E-2D program, which is targeted to be a 75-strong fleet, requiring 150 engines plus spares.

he U.S. Air Force has funded flight tests of upgraded Rolls-Royce T56s on a Lockheed Martin C-130H aimed at increasing reliability and service life as well as cutting fuel consumption by around 8%.

The T56-15 Series 3.5 ‘enhancement’ kit is expected to undergo tests at Edwards AFB, California, around mid-2012. Originally launched in response to U.S. government calls for reduced dependence on foreign oil, the upgrade is expected to contribute to the Air Force’s target of reducing aviation fuel usage by 10% by 2015. Rolls unveiled first details of the effort in 2009 and, at the time, hoped to see flight tests begin in early 2011. However funding issues prevented the start of testing until this year.

The upgrade includes remanufactured compressor blades, single-crystal first-stage high-pressure turbine blades, and aerodynamically redesigned blades and vanes throughout the low-pressure turbine. The turbine upgrade is designed to increase component life by around 30%, and according to an Air Force analysis report, could contribute to overall long term savings of $3.5 billion over the lifetime of the fleet.

The upgrade, which can be accomplished as part of a standard overhaul, does not require any aircraft or engine control system modifications and could be installed on up to 220 C-130Hs. The kit is also expected to be made available for international C-130 users at a later stage and could potentially be adapted for the T56-14 version that powers the P-3 maritime patrol aircraft.

Rolls says the kit will enable the C-130H to continue in operation until 2040 while improving reliability and ‘hot and high’ performance. The upgrade is expected to increase the range of the C-130H with a 20,000-lb. payload to more than 3,180 naut. mi., from 2,845 naut. mi., compared with a standard Series 3-powered aircraft under identical conditions.

Rolls-Royce, the global power systems company, and the United States Air Force have
completed flight testing for the latest enhancement for the T56 engine,
and preliminary results have exceeded expectations for reduced fuel
consumption and reliability improvements.

The Rolls-Royce T56 engine powers all legacy C-130 aircraft, with the
Series 3.5 program the latest improvement aimed at enhancing
performance. Recent flight tests with an installed Series 3.5 engine
demonstrated a 9.7% reduction in fuel consumption and more than 22%
increase in reliability, achieved through a significant reduction in
operating temperatures.

Tom Hartmann, Rolls-Royce, Senior Vice President – Defence, says, “The
flight test data from the USAF demonstrates even better results than
were expected.”

“The USAF flight test team has confirmed that by inserting new
technology we can bring dramatic improvements in fuel consumption and
engine reliability to C-130 operators,” Hartmann says.

The C-130H test aircraft completed its flights in October at Edwards Air
Force Base, CA. A final report on the test data is expected later in
the year, with Accelerated Mission Testing under way at Rolls-Royce
facilities in Indianapolis, IN. Certification of the Series 3.5 by the
FAA and qualification by the USAF are expected in 2013.

The Series 3.5 engine enhancement uses proven technologies from other
Rolls-Royce commercial and military engines, including new materials for
blades and vanes, and advanced aerodynamic designs for turbine
airfoils. The Series 3.5 will also improve performance in ‘hot and high’
conditions, and dramatically reduce emissions.

The Series 3.5 engine enhancement will enable the USAF to continue to
operate its C-130H fleet until 2040, and a USAF analysis estimated its
long-term savings from the program could exceed $2 billion.

The engine improvements can be accomplished as part of a conventional
engine overhaul, and do not require any aircraft or engine control
system modifications. Each C-130 aircraft has four Rolls-Royce T56
engines, with approximately 220 USAF C-130H models eligible for
updating.