PARIS—Boeing has issued a request for information (RFI) to engine makers for advanced ducted propulsion systems in the 30,000 lb.-thrust sector suitable for powering a future single aisle replacement for the 737.
Boeing says the RFI is part of ongoing moves to assess the latest state-of-the-art engine concepts and confirms its continued preference for ducted propulsion systems over open rotor or open fan engines for its next-generation studies.
The RFI, which is believed to be the fourth such request to industry of its type, comes as Boeing continues low-profile future product development studies of a 737 replacement for the 2030s and beyond. Although Boeing has backed away from any potential new product launch in the near-to-mid-term while it returns to financial health and production stability, assessments continue of technology capable of delivering efficiency improvements of at least 20% or more over the current 737 MAX family.
The emergence of the RFI is in line with statements by Boeing President and CEO Kelly Ortberg who recently told Aviation Week, “in terms of what’s next, I view it as different work streams: One: ‘When is the market ready?’ Two: ‘When is the technology ready?’ And three: ‘When are we ready and can financially handle that?’”
“We’re not ready on any of those work streams today, but we need to be when the market is ready for a new aircraft,” Ortberg said.
Respondents are expected to include Rolls-Royce and Pratt & Whitney, both of which are also proposing geared, ducted turbofans to Airbus for its next-generation single aisle (NGSA). General Electric-Safran joint venture CFM is also expected to supply details of a ducted engine based on technology now being developed under its Revolutionary Innovation for Sustainable Engine (RISE) program. Although the main thrust of RISE is the development of an unducted open fan, tests of which will be conducted with Airbus, elements of the initiative such as the high-pressure core would be applicable to a ducted version.
Safran has previously indicated a ducted-fan RISE version would be more affordable but would offer lower performance. Speaking in November 2024 on the sidelines of an engine event in Belgium, Eric Dalbies, Safran’s CTO and EVP of strategy said, “while RISE targets a 20% fuel burn reduction, the ducted-fan variant’s benefit would stand at between 10% and 12%.”
The ducted RISE version, believed to be called the Advance, is thought to be configured with an 85-in. diameter fan. Although CFM declines to comment on the ducted design, program sources say the engine could also be flight tested for possible use on the Airbus NGSA using the same A380 testbed designated for evaluations of the open fan. Proposals for modifying the testbed for tests of ducted engines have been made under the most recent call for projects being considered by the European Clean Aviation research program.
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