Two Boeing 737 MAX aircraft experienced smoke in the cabin due to malfunctioning Load Alleviation Reduction Devices (LRDs). The LRDs, which reduce stress on the horizontal stabilizer during ground operations, generated excessive heat in these instances, causing their internal components to overheat and smoke. This issue did not affect the aircraft's ability to fly and the smoke was quickly dissipated after landing. Boeing issued a service bulletin alerting airlines to the potential problem and advising inspections and potential replacements of affected LRD components.
This YouTube video, titled "Smoke in the cabin of two 737 MAX caused by Load Reduction Device system [video]," discusses two separate incidents involving Boeing 737 MAX aircraft where smoke entered the cabin, ultimately attributed to a malfunction within the Load Alleviation Reduction Device (LARD) system. The LARD, also known as the Load Alleviation System (LAS), is designed to reduce stress on the aircraft's structure during ground operations, primarily by managing the deployment and retraction of the spoilers on the wings. The video explains that the LARD utilizes electric motors, housed within the wheel well, to actuate the spoiler mechanisms. These motors contain brushes and commutators, components which, under certain conditions, can produce dust and debris.
The video posits that in these two specific incidents, excessive wear or malfunction within the LARD motor assemblies led to the generation of an abnormal amount of this dust. Due to the proximity of the LARD system components to the air conditioning packs, which draw air from outside the aircraft and circulate it into the cabin, this dust was ingested into the air conditioning system. The contaminated air was then distributed throughout the cabin, resulting in the reported smoke or haze. While the video emphasizes that the incidents did not involve fire or combustion, the presence of the particulate matter created a concerning smoky atmosphere within the passenger cabin. The video underscores the importance of proper maintenance and inspection of the LARD system to prevent the recurrence of such events, and highlights the potential implications for passenger safety and comfort. It also suggests a potential design flaw, where debris from normal LARD operation could be ingested into the air conditioning system, even without a significant malfunction. The video uses visuals and diagrams to explain the location and function of the LARD system, the airflow path within the aircraft, and the potential points of contamination.
Summary of Comments ( 27 )
https://news.ycombinator.com/item?id=42994590
Several Hacker News commenters discuss potential contributing factors to the 737 MAX's Load Alleviation Device (LAD) issues highlighted in the video. Some suggest inadequate testing and certification processes, pointing to Boeing's potential cost-cutting measures as a root cause. Others highlight the complexity of the LAD system and the difficulty of predicting all possible failure modes. A few commenters propose alternate theories, such as manufacturing defects or maintenance issues, as potential contributors. The overall sentiment reflects concern over the thoroughness of the 737 MAX's safety assessments and the potential for similar issues in other aircraft. Some also criticize the video itself, finding its explanation of the LAD system's contribution unclear and potentially misleading.
The Hacker News post titled "Smoke in the cabin of two 737 MAX caused by Load Reduction Device system [video]" has generated several comments discussing the linked YouTube video about incidents involving the Boeing 737 MAX's Load Alleviation Reduction Device (LRD).
Several commenters discuss the technical aspects of the LRD system and its potential to generate smoke. One commenter explains how the LRD functions by using hydraulic actuators to offload stress on the horizontal stabilizer during high-speed flight, and points out that these actuators can leak, potentially leading to smoke in the cabin. They further elaborate on how the hydraulic fluid used in these systems is inherently flammable and that even small leaks can atomize the fluid, creating a fine mist which can ignite or simply appear as smoke.
Another commenter questions the adequacy of the investigation and wonders if the FAA truly understands the root cause of the issue. They speculate about the possibility of other contributing factors and the implications for the safety of the 737 MAX. This concern is echoed by another commenter who questions the thoroughness of Boeing's response and the FAA's oversight.
There is some debate about the severity of the incidents. One commenter downplays the events, suggesting that the amount of smoke reported is not necessarily indicative of a major problem. However, other commenters counter this by arguing that any smoke in the cabin is a serious safety concern and requires thorough investigation. They emphasize the importance of passenger safety and the need for transparency from both Boeing and the FAA.
A few commenters express broader concerns about the 737 MAX's design and history, referencing the previous grounding of the aircraft due to the MCAS issues. They see these LRD incidents as further evidence of underlying problems with the aircraft and question whether enough has been done to address them.
Finally, some commenters offer additional information about the LRD system, including its purpose and how it operates in different flight regimes. These comments help to provide context and a deeper understanding of the technical details involved in the incidents. One such commenter highlights the specific type of hydraulic fluid used and its properties related to flammability.
Overall, the comments reflect a mixture of technical analysis, concern for safety, and skepticism about the handling of the issue by Boeing and the FAA. While some commenters downplay the severity of the incidents, others express serious concerns about the potential risks and call for greater transparency and investigation.