The NTSB is urging the FAA to ensure flight crews are aware of risks posed by a CFM International Leap-1B safety device that can cause smoke in the cockpit and wants an in-progress software modification to the system fast-tracked and mandated by regulators.
In a final report and set of recommendations made June 18, the board expressed concern that Boeing 737 MAX pilots may not understand the system, called a load reduction device (LRD), or the ramifications if it activates.
The LRD activates when an engine’s fan suffers severe damage. The system separates the fan rotor from the rest of the engine, so the fan’s vibrations do not damage the surrounding structure. But the process causes oil to enter the flow path, which routes smoke and fumes into bleed ports that provide flight deck and cabin air.
Boeing and CFM are developing a software modification that is expected to be ready in the first quarter of 2026. The change will automatically close a valve in the system and minimize risk to those onboard, notably pilots already dealing with whatever engine emergency prompted the LRD activation. Prompted by two bird strikes aboard Southwest Airlines 737-8s that activated LRDs in March 2023 near Havana and December 2023 near New Orleans, Boeing in 2024 also issued updated pilot instructions and a related flight crew operations manual (FCOM) change explaining the system and specific steps pilots can take to minimize smoke risks.
“It is critical to ensure that pilots who fly airplanes equipped with CFM International Leap-1B engines are fully aware of the potential for smoke in the cockpit if the load reduction device is activated during a critical phase of flight (takeoff or landing),” the board said in its June 18 report on the December 2023 incident. “The NTSB is aware, based on conversations we have had with several pilots who fly Boeing 737 airplanes equipped with CFM Leap-1B engines, that some pilots may not be fully aware of the [New Orleans] and Havana incidents despite Boeing’s QRH [quick reference handbook] and FCOM updates. Because of this, and given the projected time frame for completion of CFM’s and Boeing’s planned modification and the time it will take to incorporate it, the NTSB concludes that it is critical to ensure that pilots who fly airplanes equipped with CFM Leap-1B engines are fully aware of the potential for smoke in the cockpit if the LRD is activated during a critical phase of flight.”
The concern prompted the board to issue an “urgent” recommendation to the FAA to ensure Boeing’s FCOM instructions are known to pilots so they “are aware of actions to take if they encounter smoke in the cockpit or cabin after load reduction device activation.”
The board also urged CFM and Boeing to “complete the development and certification process” for the software update, and recommended the FAA mandate the change be implemented on the entire 737 MAX fleet, which is powered exclusively by Leap-1Bs.
NTSB also wants the FAA, the European Union Aviation Safety Agency (EASA), and the Civil Aviation Administration of China to examine potential risks on the LRDs outfitted to Leap-1As that power some Airbus A320neos and Leap-1Cs developed for the Comac C919. EASA, which has worked with the FAA on the Leap-1B LRD issue, said last year it would review other variants.
The NTSB’s move comes seven months after the FAA determined the proposed CFM and Boeing software change and interim guidance was enough to mitigate risks posed by the LRD. Industry reaction was mixed. Some operators and pilot groups agreed with the regulator. Others expressed concern at the risks of a compounded emergency that an LRD activation poses and wanted more immediate action.
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