CFM Leap 1A Reverse Bleed System Retrofits Set To Begin

Operators of CFM Leap 1A engines will soon have access to reverse bleed system (RBS) retrofit kits, the engine manufacturer announced, hitting its planned deadline of having the durability-improvement kits available around mid-year.

A service bulletin detailing the retrofit process is set for release in the coming days, CFM confirmed during the recent Farnborough Airshow. Kits have been pre-positioned to help keep up with expected demand for the solution to a nagging problem.

CFM developed the RBS to prevent coking, or temperature-induced evaporation of unburned fuel around nozzles that inject fuel into the combustor. The condition results from residual heat in the engine core hardware “soaking back” after shutdown.

If the fuel nozzle temperature exceeds the coke formation threshold, solid carbon forms. Eventually, the deposits can affect fuel flow and cause uneven internal combustor temperatures, which leads to reduced on-wing life and in the most extreme cases, in-service issues such as in-flight shutdowns.

The coking has led to high rates of fuel-nozzle replacements. Some operators have been replacing up to 10 fuel nozzles during performance restorations, GE Aerospace says. The company’s goal is to cut this to one. The Leap 1A has 19 fuel nozzles, while the Leap 1B has 18.

New Leap 1As began shipping with line-fit RBSs earlier in 2024. At the time, CFM said a retrofit kit would be available by “mid-summer.”

Operator feedback on the line-fit RBSs has been positive, CFM president and CEO Gaël Méheust says, adding, “We’re seeing good results from more than 100 RBS-equipped engines already in service with 24 customers.”

CFM said some of its CFM-branded service agreement (CBSA) and other licensed third-party shops are expected to offer the retrofits. CFM’s overhaul network comprises five CBSA facilities and 11 other approved shops alongside 19 OEM-owned repair stations.

A similar system is being developed for the Leap 1B and is slated to be available in 2025. Early testing on the GE9X, which powers the Boeing 777-9, revealed signs of coking conditions, so GE added an RBS to its newest widebody turbofan. GE and Safran are 50/50 partners in CFM.