Rolls-Royce is putting all its cards on a new engine to power future single-aisle aircraft and told AIN that as far as it is concerned, “the numbers do not stack up” for re-engining either the Airbus A320 or Boeing 737.

The company insists that an all-new engine for an all-new aircraft is the only solution that makes business sense, whether the engine is an advanced turbofan, as proposed by CFM International, or an open-rotor design. Rolls-Royce has already rejected Pratt & Whitney’s geared-fan engine. “It’s no better than an advanced turbofan,” said Robert Nuttal, Rolls-Royce head of strategic marketing.

Nuttal gave AIN three reasons for not pursuing any re-engining program. “First, we don’t think it offers any significant net financial benefit to the industry. Second, at the manufacturing level the program will be only half as long as a new engine program, so the returns are far less. And third,” he said, “if re-engining occurs, it delays an all-new aircraft, which will bring real benefits in terms of fuel economy and emissions.”

The costs of modifying the aircraft, the replacement engines and the loss of residual airframe value would leave Rolls-Royce “struggling to find a business case for re-engining,” he added.

Nuttal said offering all-new engines for new airframes has been company philosophy all along. “Rolls-Royce believes in relentless pursuit of advanced technology to bring new engines to market.” He cited the case of the all-new Trent 700, developed for the Airbus A330. Rolls-Royce had the lowest sales on the aircraft at entry into service, but now holds 50 percent of the orders and has won 70 percent of orders in the last three years. “We got tremendous benefits from that approach,” Nuttal said.

Rolls-Royce believes open rotors remain the only “game-changing” technology around, with the potential to deliver at least 10 percent lower fuel burn than any advanced turbofan under consideration. This puts the UK company fundamentally at odds with Pratt & Whitney, which told AIN developments of its PW1000G engine will have similar fuel economy as an open rotor.

Nuttal said the four open-rotor rig tests carried out to date by Rolls-Royce have revealed the concept will comfortably meet Stage 4 noise requirements and produce a 30-percent fuel saving over today’s engines. “We’ve cracked the physics. Now its an engineering problem,” he added.