LEAP-1B Engine Aviation Propulsion (LEAP-1B) Engine Load Reduction Device (LRD) update
- Airbus has software logic (at least in some fleets) that, during a severe LRD vibration response, shuts off the affected sides Pressure Regulating and Shut-off Valve (PRSOV) automatically and immediately.
- Boeing are working on the software change to logic but have not had an emergency mandate YET. We were expecting that, but an urgent recommendation seems to be it.
Key Points
- The LRD prevents catastrophic engine failure—but its activation currently poses a smoke risk. The 737 Max’s left-side Leap supplies bleed air to the cockpit, a left engine LRD failure will cause that engine to pipe smoke into the cockpit. A right-engine LRD failure will cause the cabin to fill with smoke, as that turbofan supplies cabin air. The problem arises when the LRD mechanically severs the load path, oil supply tubes and sumps can be breached, introducing oil to the compressor airflow—and thus into the environmental control system that supplies air to the cabin and cockpit.
- Permanent resolution relies on engineering a faster-acting, automatic system to shut off bleed air when LRD triggers due to events like bird strikes.
- Certification of this fix is targeted for 2026, with all major aviation regulators and manufacturers closely involved in the rollout and interim risk management.
B737 Max Bleeds off considerations from American Airlines pilots:
- AA pilots take a risk-based view of each take -off and consider things like: Are there large birds probable on the departure flight path, Time of day / night, Departure conditions, Terrain etc.
- Crew Workload
- Smoke entry can occur rapidly (within seconds), often close to the ground during take-off or climb, leaving crews with little time to respond effectively.
- Standard emergency checklists were found to be ambiguous for this specific event, making the situation more challenging for pilots.
Interim Mitigations
- Revised Crew Procedures: Airlines have updated smoke/fire/engine failure checklists for pilots, instructing them to treat LRD activation with smoke as "severe engine damage"—including immediate engine shutdown and bleed air isolation.
- Flight Crew Training: Authorities and airlines have been urged to reinforce simulator and classroom training for handling LRD/smoke events.
Permanent Fix Underway
- Software Modification: A joint Boeing–CFM project is developing a software update for the engine's bleed air system. The update will rapidly close the pressure-regulating shutoff valve (PRSOV) if a bird strike or fan failure with LRD activation is detected. This is intended to prevent or sharply limit the amount of smoke entering the aircraft cabin or cockpit.
- The software fix is expected to be certified and implemented in 2026.
- Engineering Enhancements: Parallel to software improvements, CFM is developing durability upgrades to mitigate wear and durability issues more broadly in the LEAP engine series.
Regulatory Actions and Warnings
- The NTSB issued an urgent recommendation, and the FAA and EASA published safety bulletins, demanding immediate procedural changes and highlighting the need for permanent engineering solutions.
- The problem—and its interim and permanent solutions—affect the LEAP-1B (737 MAX); similar issues are being investigated for LEAP-1A (A320neo, C919) and -1C
- Mentour Pilot Youtube presentation