BARCELONA—Installations of systems designed to prevent fuel nozzle coking on CFM International Leap 1A engines are ramping up and data from the initial retrofits shows the kits are working as intended, a senior GE Aerospace official says.
About 300 engines are flying with reverse bleed systems (RBS), including 30 that have been retrofitted since work began for the in-service fleet in August, CFM's Leap Customer Technical Director Mike Hoffmeister told Aviation Week ahead of MRO Europe here in Barcelona.
While deliveries of new engines with RBSs, which started in April, will remain relatively stable, retrofit work is rising quickly.
“We’ve shipped over 100 retrofit kits to airlines and our MRO shops since the beginning of October,” Hoffmeister said. “That’s a multiple of what it was the couple of weeks prior to [Oct. 1]. Now it only matters when those parts get installed, but it’s a really nice leading indicator that shows us evidence that we’re on track.”
The RBS was developed to counter the Leap’s tendency to develop carbon deposits when residual heat soaks back and heats fuel nozzles. Unburned fuel around the nozzles is hardened into solid carbon if certain thresholds are exceeded. This 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.
Coking affects both Leap 1As that power some Airbus A320neo-family aircraft and the Leap 1Bs found on all Boeing 737 MAXs. A Leap 1B-spec RBS is under development with a timeline running about a year after the 1A’s unit, roughly matching the gap between the two engines’ entry-into-service dates.
Hoffmeister says the Leap 1A RBS’s functionality has been validated with data from the initial installations. The in-service fleet includes some aircraft with one RBS-equipped engine and one unmodified engine that allow comparisons with identical operating environment variables.
“Exactly the same flights, exactly the same exposure,” he said. “We can look at data like the [exhaust gas temperature] probe variation, which without RBS [will] evolve, and that spread will get bigger over time as evidence of nozzle coking. What we see on the RBS-equipped engines ... it’s flat. There’s really no evolution of the indicators of coking in the engines flying with RBS.”
Hoffmeister said CFM, the 50-50 partnership of GE Aerospace and Safran, is working with airlines to time RBS upgrades with already-planned fuel nozzle swaps.
“Our goal is, every time there’s a fuel nozzle set change, let’s get RBS on the engine [and] avoid multiple heavy work scope interventions at the same part of the engine by integrating the tasks,” he said.
The retrofit plan also is benefiting from a growing set of sources that can do the work. Besides operators trained to do the installations and on-wing support programs from GE Aerospace and Safran, 26 third-party providers are licensed and trained to install RBSs.
“Many of those third parties were not CFM’s idea,” Hoffmeister said. “It was our collaboration with the airlines. They’ll say, ‘I already have [a specific company] as a maintenance provider. I would love for them to be able to do my RBS retrofits.’ When we hear that, we engage, and not in every case but in the majority of cases, convert those companies into a licensed, trained, ready-to-go third-party [provider].”
As more installations are completed, CFM, airlines and MRO providers are sharing best practices to help streamline the process.
“This is a fairly heavy work scope,” Hoffmeister said. “We’ve done a lot of training. We’ve done a lot of Lean events to refine our training and to try to get the procedure as efficient as possible.”
