On Monday Rolls-Royce announced that it had “run the world’s most powerful aerospace gearbox for the first time, marking a significant step in the development of its new UltraFan™ engine design.” At the company facility in Dahlewitz, Germany, a series of tests will see the gearbox reach up to 100,000 horsepower.
First revealed in 2012, this new engine should have an 15:1 BPR and a 70:1 pressure ratio and deliver 25% lower fuel burn than the Trent 700. Even as one must be impressed by these numbers, the secret sauce has to be the new gearbox, shown below. The engine will also consist of a new engine core architecture and carbon/titanium fan blades and a composite casing to reduce weight.
The engine will be available for both widebody and single aisle aircraft. While Rolls has not offered any guidance as to its use or target airframe, we can say a few things. It will be focused on widebody aircraft. Rolls has not provided any thrust guidance. But they say the concept is scalable. Although the gearbox will be tested to 100,000HP, it will be able to be scaled to handle thrust from about 25,000lb to over 100,000lb.
Even if Rolls does not offer any details at this stage we might consider, as rough guidance, what we know of the Pratt & Whitney GTF. The GTF has a gear that handles about 30,000 horsepower. Pratt also describes their engine as scalable. It already provides propulsion to the small MRJ and all the way up to the A321LR – from about 16,000 pounds to 35,000 pounds. There is no direct relationship between engine thrust and gear horsepower capabilities.
But we can be certain that what the GTF has meant to Pratt & Whitney, the UltraFan could be to Rolls-Royce. We now have two of the major engine OEMs focused on gears. One wonders when the other OEM will also move in this direction?
It will be interesting to see how GE and Snecma respond to this, together or separately. The only alternative that I know of is the three-spool technology, but Rolls-Royce has abandoned it.