This article is published in Aviation Week MRO, part of Aviation Week Intelligence Network (AWIN), and is complimentary through May 02, 2024. For information on becoming an AWIN Member to access more content like this, click here.
CHICAGO—CFM International has begun delivering Leap-1A new-production engines with its new reverse bleed system (RBS) designed to prevent a fuel nozzle problem linked to carbon deposits and expects to have retrofits available by mid-year.
The problem, known as coking, occurs when core engine hardware releases heat, or soaks back, after shutdown. The RBS is designed to eliminate the issue as well as related maintenance inspections and nozzle swaps in place now to mitigate risk.
CFM earned certification for the Leap-1A RBS from the FAA and European Union Aviation Safety Agency (EASA) in 2023. The first new-delivery engines with RBSs are expected to enter service around mid-year, on Airbus A320neo-family variants, CFM announced at Aviation Week’s MRO Americas April 9.
CFM is working on an RBS for the Leap-1B, which powers the entire Boeing 737 MAX fleet. Both will be available as retrofits as well, with the Leap-1A becoming available by mid-summer.
Installation can be done on-wing “in as few as 10 hours,” CFM said. RBS installation training for airlines and MRO shops is available at the GE Customer Technical Education Center in Springdale, Ohio; Safran Aircraft Engines Customer Training Center in Montereau, France; Aero Engine Maintenance Training Center in Guanghan, China; and CFM Aircraft Engine Support South Asia in Hyderabad, India.
Coking occurs when residual heat soaks back and heats fuel nozzles’ certain thresholds. If the nozzles get hot enough, unburned fuel around the nozzles is hardened into solid carbon, which affects fuel flow and causes uneven internal combustor temperatures. This leads to reduced on-wing life and in the most extreme cases, in-service issues.
The RBS’s main elements are a valve and a blower. After engine shutdown, the valve activates and the blower directs air, in reverse, through the engine bleed duct system into the flow path. This keeps fuel nozzles cool enough to prevent coking.
CFM identified the issue several years ago and issued service bulletins with recommended engine inspection and nozzle replacement procedures. Regulators mandated some of them.
“This RBS is part of a broader plan to improve engine durability, that will see additional upgrades introduced throughout the year,” CFM President Gaël Méheust said.
CFM, a 50-50 GE Aerospace/Safran joint venture, also is introducing redesigned turbine blades to improve durability. New Leap-1A blades are expected to enter service in 2024, while -1B blade testing is just getting started.
Related Content
