Regulations & Safety
NTSB Urges LEAP-1B Engine Fixes After Smoke Incidents
Safety alert issued for Boeing 737 MAX engines after bird strikes caused cockpit smoke via Load Reduction Device flaws. Software and design updates in progress.
On June 18, 2025, the National Transportation Safety Board (NTSB) issued an urgent safety recommendation concerning CFM International LEAP-1B engines. These engines, a cornerstone of modern commercial aviation, are used on Boeing 737 MAX aircraft and have logged over 1.5 million flight hours. The recommendation follows two serious incidents in which smoke entered the cockpit and cabin after bird strikes triggered a safety mechanism known as the Load Reduction Device (LRD).
The NTSB’s findings point to a potentially systemic issue in the design of the LRD, which, though intended to reduce engine damage during emergencies, can inadvertently allow hot oil to leak into the aircraft’s ventilation system. This has raised red flags across the aviation industry, prompting calls for immediate action from aircraft manufacturers, engine developers, and international aviation regulators.
Given the widespread use of LEAP engines across Airbus A320neo, Boeing 737 MAX, and COMAC C919 aircraft, the implications of this safety concern are far-reaching. This article delves into the technical background, incident analysis, and the broader impact of the NTSB’s recommendations on aviation safety and operations.
The Load Reduction Device (LRD) is a mechanical safety feature built into the LEAP-1B engine. It is designed to activate automatically during severe engine imbalances, such as those caused by fan blade failures or bird strikes. When triggered, the LRD decouples the fan from the engine core to minimize vibrations that could otherwise damage the airframe or engine mounts.
This system is a product of lessons learned from over a billion flight hours on the CFM56 engine family. Its primary goal is to enhance safety without requiring pilot intervention, especially during critical phases of flight like takeoff and landing. However, despite its safety-driven design, the LRD has introduced a new and unanticipated hazard.
Investigations revealed that LRD activation can dislodge oil-supply tubes or fracture engine sump flanges. This allows engine oil to enter areas of high temperature, where it vaporizes and is then carried into the aircraft’s ventilation system via bleed air ports, resulting in smoke in the cockpit and cabin.
“What was once considered a fail-safe mechanism now presents a potentially serious hazard under specific but foreseeable conditions,”, NTSB report, June 2025. Two Southwest Airlines flights in 2023 serve as case studies for the LRD-related smoke hazard. In December, Flight 554 departed from New Orleans when a bird strike led to LRD activation. Within seconds, thick white smoke filled the cockpit, impairing the pilot’s visibility. The crew managed to return safely, but the NTSB noted that the 10–15 second delay in manually shutting off the engine bleed valve was a critical vulnerability.
Earlier that year, in March, a similar incident occurred on Flight 392 departing from Havana. A bird strike on the right engine led to LRD activation and subsequent vapor fog entering the passenger cabin. Passengers reported a chemical-like odor and visible haze. The crew declared an emergency and returned without injuries, but the incident reinforced concerns about the LRD’s unintended consequences. Both incidents highlighted that while the LRD effectively mitigated engine damage, it introduced a new risk by enabling smoke to enter occupied areas of the aircraft. The NTSB emphasized that bird strikes are not rare, occurring roughly every 2,000 flights globally, and must be accounted for in engine safety systems.
The NTSB’s technical analysis found that oil leakage into the high-pressure compressor, where temperatures can exceed 500°F, results in rapid vaporization. This vapor is then distributed through the aircraft’s ventilation system, which draws bleed air from the engine. The system’s reliance on manual intervention to shut off the bleed valve poses a safety concern, particularly during high workload periods like takeoff.
CFM and Boeing have proposed a two-phase solution. The short-term fix involves a software update that automatically closes the bleed valve upon LRD activation. The long-term solution includes redesigning the oil-supply tube anchorage and sump sealing mechanisms to prevent displacement during LRD events.
These solutions aim to eliminate the delay in pilot response and reduce the likelihood of smoke entering the aircraft. However, implementation will require regulatory approval, certification, and fleet-wide retrofitting, which could be both time-consuming and costly.
Following the NTSB’s urgent recommendation, the Federal Aviation Administration (FAA), European Union Aviation Safety Agency (EASA), and the Civil Aviation Administration of China (CAAC) have been asked to evaluate the risk across all LEAP engine variants, including the LEAP-1A and LEAP-1C used on Airbus and COMAC aircraft, respectively.
Boeing has revised its Flight Crew Operations Manual (FCOM) and Quick Reference Handbook (QRH) to include new procedures for managing LRD-related smoke events. These revisions instruct pilots to immediately close the engine bleed valve and initiate emergency descent protocols if necessary.
Training simulators are being updated to include LRD-specific scenarios, and operators are being urged to brief flight crews on the new procedures. The NTSB stressed that awareness and preparedness are crucial, especially given that many pilots were previously unaware of the LRD’s potential to cause smoke ingress.
Retrofitting the existing fleet of over 1,200 Boeing 737 MAX aircraft with the proposed software update is estimated to cost $150,000 per engine, amounting to approximately $360 million. Additional downtime during modifications could cost airlines an estimated $1.2 million per day in lost utilization. Despite these costs, industry analysts suggest that proactive compliance with the NTSB’s recommendations may help mitigate reputational damage for both Boeing and CFM. The joint venture between GE Aerospace and Safran Aircraft Engines has committed to implementing the changes and supporting operators throughout the transition.
Beyond financial implications, the issue underscores the importance of comprehensive risk modeling in engine design. As aircraft systems become more complex, ensuring that safety features do not introduce new hazards is a critical challenge for manufacturers and regulators alike.
The LEAP engine’s LRD issue offers valuable lessons for future engine development. One potential area of innovation is the integration of real-time oil leak detection systems, which could provide early warnings before smoke enters the aircraft.
The incident also highlights the need for harmonized global regulations. As the aviation industry becomes increasingly interconnected, ensuring consistent safety standards across regions is essential. The International Civil Aviation Organization (ICAO) may play a key role in standardizing LRD-related procedures.
Looking ahead, resolving the LRD issue could set a new benchmark for fail-safe design in next-generation propulsion systems, including those powered by sustainable aviation fuels or hydrogen. The aviation industry must balance innovation with rigorous safety validation to maintain public trust and operational reliability.
The NTSB’s urgent recommendation concerning LEAP-1B engines marks a pivotal moment in aviation safety. While the LRD was designed to protect aircraft from structural damage, its unintended consequence, smoke ingress, revealed a critical vulnerability. The incidents involving Southwest Airlines flights underscore the importance of continuous monitoring, evaluation, and adaptation in aerospace engineering.
As regulatory agencies, manufacturers, and operators work together to address the issue, the aviation industry is reminded that even the most well-intentioned safety features require thorough testing under all plausible scenarios. The resolution of the LRD flaw will not only restore confidence in the LEAP engine family but also inform the design of future propulsion systems.
What is the Load Reduction Device (LRD)? Why is smoke entering the cockpit and cabin? What actions are being taken to resolve the issue? Sources: NTSB Press Release, NTSB Investigation Report, NTSB Docket DCA24LA330
Smoke Risk in LEAP-1B Engines: NTSB Issues Urgent Safety Recommendations
Understanding the Load Reduction Device and Its Risks
The Intended Function of the Load Reduction Device (LRD)
Case Studies: Southwest Airlines Incidents
Technical Analysis and Design Implications
Industry Response and Broader Implications
Regulatory and Manufacturer Actions
Economic and Operational Impact
Future Directions and Safety Innovations
Conclusion: A Turning Point in Engine Safety
FAQ
The LRD is a mechanical safety feature in LEAP engines that decouples the fan from the engine core during severe imbalances to reduce vibration and prevent structural damage.
When the LRD activates, it can dislodge oil-supply tubes, allowing oil to enter hot engine areas and vaporize. This vapor can then be circulated into the cockpit and cabin via the bleed air system.
Boeing and CFM are developing a software update to automatically close bleed valves upon LRD activation and are redesigning certain engine components. Regulatory agencies are evaluating similar risks in other LEAP engine variants.
Photo Credit: NTSB
Regulations & Safety
FAA Proposes Pilot Dashboard for AWOS and ASOS Outage Reports
The FAA seeks public comments on a Surface Weather Status Dashboard letting pilots report AWOS and ASOS outages directly.
The Federal Aviation Administration (FAA) is seeking public comments on a proposed Surface Weather Status Dashboard that will allow pilots and other National Airspace System (NAS) users to crowdsource reports of outages and erroneous data from automated airport weather systems.
Published in the Federal Register on October 6, 2026, the 30-day notice outlines an information collection initiative designed to improve real-time situational awareness. By integrating user-submitted trouble tickets directly into the agency’s maintenance workflow, the FAA aims to expedite repairs for critical weather infrastructure.
The new dashboard will be hosted on the existing FAA Aviation Weather Cameras website. The agency estimates that completing a report will take a user approximately one minute, with an anticipated volume of 1,825 reports submitted annually.
Once a pilot flags an issue with an Automated Weather Observing System (AWOS) or Automated Surface Observing System (ASOS), the data will undergo verification before entering the official maintenance queue.
“It is anticipated that the information collected will be used after verification to create reports that will trigger trouble tickets within the FAA’s Remote Monitoring and Logging System (RMLS) for corrective action to be taken by the responsible parties, such as technicians within the FAA, NOAA, and non-federal entities,” the FAA stated in its filing. The primary benefit for pilots in the air or during preflight planning is the rapid update of system status. According to the FAA, once a trouble ticket is logged in the RMLS, the Aviation Weather Cameras website will capture and display the real-time service status of the affected automated weather station within 30 minutes.
AWOS and ASOS installations are critical infrastructure for aviation safety. These automated stations provide continuous, real-time weather information, typically broadcast via radio frequency and distributed globally as Aviation Routine Weather Reports (METARs).
When these systems experience outages or transmit erroneous data, the operational impact can be severe. Pilots relying on accurate altimeter settings, visibility measurements, and cloud ceiling data may be forced to delay departures, divert to alternate airports, or cancel operations entirely.
The FAA noted that the data collected through the new dashboard will serve a dual purpose, facilitating immediate maintenance dispatch while also informing long-term infrastructure planning. The agency stated that because the collected information will be site-specific, it may be used to update future policy decisions regarding surface weather infrastructure, approvals, and audits.
The integration of the Surface Weather Status Dashboard into the FAA’s weather camera portal builds on a decades-long effort to improve weather visibility for pilots. The FAA Weather Camera Program originated in 1999 in Alaska, initially designed to give pilots operating under Visual Flight Rules (VFR) actual views of current weather conditions in remote, mountainous areas where weather reporting was sparse. Since its inception, the program has expanded to over 600 locations across the United States. The FAA credits the camera network with significantly reducing weather-related flight interruptions and accidents.
Recently, the FAA has been expanding its broader camera network by adding new locations and deploying Visual Weather Observation Systems. These newer installations combine high-resolution imagery with automated surface-weather sensors to provide a more comprehensive picture of airport conditions. The addition of the Surface Weather Status Dashboard is a congressionally mandated enhancement to this existing platform.
The regulatory process for the dashboard began earlier in the year. On May 11, 2026, the FAA published the initial 60-day comment period notice in the Federal Register to solicit industry feedback on the concept.
The October 6, 2026, publication serves as the 30-day notice, formally requesting approval from the Office of Management and Budget (OMB) for the information collection process.
Public comments on the proposal are due by November 5, 2026. Following the close of the comment period, the FAA will seek final clearance from the OMB to implement the data collection webform and launch the dashboard to the public.
We view the implementation of a crowdsourced reporting tool for AWOS and ASOS infrastructure as a pragmatic shift in how the FAA manages the National Airspace System. Historically, the agency has relied on automated self-reporting diagnostics or internal monitoring to detect sensor failures. However, pilots on the ground or on approach frequently identify discrepancies, such as a frozen precipitation gauge, a stuck wind direction sensor, or an uncalibrated altimeter setting, long before the system flags itself as degraded.
By formalizing a feedback loop that takes only a minute for a pilot to complete, the FAA is effectively deputizing thousands of daily airspace users as quality control inspectors. If the agency can consistently meet its stated goal of updating the public-facing service status within 30 minutes of a verified report, this dashboard will significantly reduce the latency between a localized weather system failure and the broader aviation community being alerted to the hazard.
Streamlining weather system maintenance
Operational impact of automated weather data
Evolution of the Weather Camera Program
Regulatory timeline and next steps
AirPro News analysis
Photo Credit: Stock – Canva
Regulations & Safety
FAA Proposes Special Conditions for HondaJet Echelon HA-480
FAA proposes a 1.67 pressure vessel safety factor for the Honda HA-480 to support high-altitude operations up to 47,000 feet.
The Federal Aviation Administration (FAA) has published a notice of proposed special conditions for the Honda Model HA-480, establishing stricter pressure vessel safety standards required for the light jet to operate at altitudes up to 47,000 feet.
Published in the Federal Register on October 5, 2026, the regulatory filing addresses a gap in current Title 14 of the Code of Federal Regulations (CFR) Part 23 airworthiness standards, which the agency considers inadequate for normal category airplanes operating above 41,000 feet. The proposed rules mandate a higher structural safety factor for the aircraft fuselage, marking a critical regulatory step toward the eventual type certification of the aircraft, which is marketed by Honda Aircraft Company LLC as the HondaJet Echelon.
The FAA notice outlines specific engineering thresholds required to ensure occupant safety in the event of a high-altitude depressurization. Under existing 14 CFR Part 23 regulations, safety standards are not fully defined for aircraft operating above 41,000 feet. Furthermore, specific depressurization criteria regarding occupant breathable air safety apply when an aircraft operates above 45,000 feet.
To bridge this regulatory gap for the HA-480, the FAA is requiring Honda Aircraft Company to design the fuselage structure, including all doors and windows, to withstand higher pressure differentials than standard Part 23 aircraft.
To ensure adequate pressure vessel strength, the FAA proposes a factor of 1.67 be applied to the maximum relief valve pressure level prescribed in § 23.2225(c)(3), rather than the 1.33 factor currently prescribed in that regulation. The agency noted in the filing that the proposed special conditions contain the additional safety standards considered necessary to establish a level of safety equivalent to existing airworthiness standards. The FAA is accepting public comments on the proposed special conditions until November 19, 2026.
Honda Aircraft Company, a wholly owned subsidiary of American Honda Motor Co., Inc. based in Greensboro, North Carolina, applied for an amendment to Type Certificate No. A00018AT on February 21, 2019. The application seeks to add the Model HA-480 to the existing certificate held by the Honda Model HA-420, commonly known as the HondaJet.
The manufacturer officially named the HA-480 program the HondaJet Echelon on October 16, 2023. While the HA-480 is a derivative of the HA-420 and retains the manufacturer’s signature Over-The-Wing Engine Mount (OTWEM) configuration, it features a substantially larger cabin designed to accommodate up to 11 passengers. The aircraft has a maximum takeoff weight of 17,550 pounds and a projected range of 2,625 nautical miles. Honda Aircraft Company is designing the HA-480 to be the first single-pilot certified light jet capable of nonstop transcontinental flight across the United States.
The publication of the FAA special conditions follows a recent manufacturing milestone and a concurrent schedule adjustment for the program. On September 15, 2026, Honda Aircraft Company announced the completion of the first wing structure for the HA-480 test unit at its Greensboro facility.
Alongside the manufacturing update, the company confirmed a delay in the program timeline. The targeted first flight of the HondaJet Echelon has been shifted from 2026 to 2028. Consequently, the expected type certification and first delivery dates have been moved from 2028 to 2031. In a press statement, the manufacturer attributed the delay to tier-one supplier-related schedule adjustments and ongoing development activities. We view the FAA’s proposed special conditions for the HA-480 as a standard but rigorous regulatory bridge for Part 23 aircraft pushing into performance envelopes traditionally occupied by Part 25 transport category jets. By mandating the 1.67 safety factor for the pressure vessel, the FAA is ensuring that the structural integrity of the HondaJet Echelon matches the severe physiological risks associated with a rapid depressurization event at 47,000 feet. This regulatory clarity, while demanding higher engineering tolerances and extensive testing from Honda Aircraft Company, provides a defined certification pathway for the program as it navigates recent supplier delays and targets its revised 2031 entry into service.
Regulatory requirements for high-altitude operations
HondaJet Echelon program development and timeline
AirPro News analysis
Photo Credit: HondaJet
Regulations & Safety
NASA Tests New Probes to Improve SLD Icing Certification Data
NASA Glenn completed supercooled large droplet icing tests in June 2026 to help validate tools for FAA Appendix O aircraft certification.
NASA researchers at the Glenn Research Center have completed a specialized testing campaign aimed at improving the aerospace industry’s ability to model and mitigate supercooled large droplet icing. The tests, conducted in June 2026 and detailed in an October 5 announcement, utilized advanced instrumentation to measure unusually large water droplets that pose a rare but persistent hazard to commercial aircraft.
The Subsonic Flight Demonstrator of SLD Instrumentation Test took place inside the agency’s historic Icing Research Tunnel in Cleveland, Ohio. According to the NASA press release, the initiative seeks to provide aircraft manufacturers with enhanced experimental data to validate engineering tools against the complex physics of supercooled large drops, which can bypass conventional ice protection systems.
Aircraft ice protection systems are typically designed to handle standard cloud conditions, which consist of water droplets ranging from 2 to 100 microns in diameter. For comparison, a human hair is approximately 70 microns wide. Supercooled large droplet (SLD) conditions represent a much rarer atmospheric phenomenon where droplets can reach up to 2,000 microns in diameter.
Supercooled water droplets remain in a liquid state at temperatures below 32 degrees Fahrenheit provided they do not encounter particles to crystallize around. When an aircraft flies through these conditions, the droplets freeze upon impact. While standard droplets freeze on the leading edges of wings and engine nacelles where thermal or pneumatic ice protection systems are located, the massive mass and momentum of SLD droplets cause them to splash and run back before freezing. This runback ice forms ridges behind the protected areas, severely disrupting airflow and degrading aerodynamic lift.
To better understand this hazard, NASA engineers utilized new Drop Sizing Probes during the June 8 to 11 testing window. These advanced sensors are capable of detecting and performing real-time analysis on droplets larger than 45 microns. Researchers are currently comparing the real-time probe data against a more laborious traditional technique that involves post-processing droplet size image data captured from the tunnel. By mating the new probe data with existing sensors that measure smaller drops, NASA aims to capture the complete droplet size spectrum.
The aviation industry relies on engineering tools to help design their aircraft. Current tools work well for typical clouds, but engineers have questions about how well they account for the physics of supercooled large drops. The push to understand and model SLD physics is rooted in aviation safety regulations enacted following a watershed accident in the 1990s. On October 31, 1994, American Eagle Flight 4184, an ATR 72, crashed in Roselawn, Indiana. The official investigation determined the accident was caused by an SLD icing encounter that formed a severe ice ridge behind the aircraft’s pneumatic de-icing boots, leading to an uncommanded roll and loss of control.
That accident prompted the Federal Aviation Administration (FAA) to introduce stringent new certification standards, codified as Appendix O to Part 25, which specifically address aircraft performance and ice protection in SLD conditions. While the aerospace industry possesses highly calibrated engineering tools for typical Appendix C icing conditions, accurately modeling the physics required for Appendix O certification remains a technical challenge. The data gathered in the Icing Research Tunnel is intended to bridge that gap for modern aircraft certification programs.
The recent test campaign marks a significant milestone for the Subsonic Flight Demonstrator (SFD) project, an initiative managed under NASA’s Research and Technology Mission Directorate aimed at developing technologies for next-generation, highly efficient aircraft.
The testing venue itself holds a central place in aviation history. NASA’s Icing Research Tunnel began operations on September 13, 1944, and has run continuously since, making it the longest-running and second-largest icing facility in the world. The agency notes that most ice protection technologies in use on commercial aircraft today were either developed or tested in this specific facility. Detailed analysis of the data collected during the June campaign is ongoing. NASA’s project team plans to share the finalized results and validated droplet size spectrums with the broader aerospace community once the post-processing and evaluation phases are complete.
The transition from Appendix C to Appendix O icing certification has historically presented a steep compliance challenge for aircraft manufacturers. Flight testing in known supercooled large droplet conditions is inherently dangerous, highly unpredictable, and difficult to schedule, forcing original equipment manufacturers to rely heavily on computational fluid dynamics and wind tunnel data. By refining the instrumentation used to measure these massive droplets, NASA is directly addressing a critical bottleneck in the certification process. If the agency’s new Drop Sizing Probes can reliably validate computational models for drops exceeding 45 microns, we expect manufacturers will face fewer late-stage design iterations and reduced flight-test risk when developing next-generation ice protection systems.
Advancing droplet measurement technology
The regulatory legacy of American Eagle Flight 4184
Next steps for the Subsonic Flight Demonstrator project
AirPro News analysis
Photo Credit: NASA
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