DCA24LA330

A partial loss of engine power due to bird ingestion in the No. 1 (left) engine, which resulted in the activation of the load reduction device to prevent vibration. The load reduction device activation resulted in smoke and fumes entering the cockpit.

During initial climbout shortly after takeoff, Southwest Airlines flight 554 struck and ingested a bird into its No. 1 (left) engine, resulting in damage to the left engine fan blades and a partial loss of engine power. The airplane began to “shake violently with a distinct loss of thrust” in the left engine. The engine master caution activated, and the captain reported that he heard the fire bell sound. The captain called for the Engine Fire or Engine Severe Damage or Separation checklist on the Quick Reference Card (QRC). According to the captain, after the first officer (FO) started the checklist, the cockpit began to fill with “acrid white smoke.” The FO called out “masks,” the pilots donned their masks, and they resumed performance of the checklist. The flight crew declared an emergency to air traffic control and requested airport rescue and firefighting (ARFF) in preparation for the flight’s return to the departure airport. The flight crew notified the cabin crew and passengers about the emergency. The captain later reported that, due to the smoke, his instrument panel was difficult to see and that he thought he might need to fly the airplane by solely using the heads-up guidance system. However, the captain stated that the smoke began to rapidly dissipate after the FO pulled the engine fire switch. After flight 554 landed and came to a full stop, ARFF personnel inspected the airplane before the flight crew taxied to the assigned gate. The passengers deplaned normally, and no injuries were reported. Postaccident examination found that the smoke in the cockpit was a result of the activation of the No. 1 engine’s load reduction device (LRD) after the bird ingestion. LRD activation is designed to reduce the severity of the vibration transmitted into the airframe by disconnecting the left engine’s fan blades from the turbomachinery. When the LRD activated, tubes supplying oil to the engine sump became dislodged and the flange from the sump area opened, allowing engine oil to enter the core compressor upstream of the pneumatic bleed ports that supply bleed air to the cabin and cockpit. The oil was exposed to high temperatures and resulted in smoke and fumes that were then fed into the cockpit. About 15 seconds after the bird ingestion, the left engine’s core speed (N2) was below 62% rpm, which would have de-energized the engine’s running relay and subsequently closed the pressure regulating shutoff valve (PRSOV). Following the closure of the PRSOV, which was the point of access into the cockpit, the smoke and fumes would have quickly dissipated. Considering that both crewmembers described the airplane as shaking following the bird ingestion, the captain’s decision to begin the Engine Fire or Engine Severe Damage or Separation checklist was appropriate (one of the conditions for using the checklist was airframe vibrations). Although the crew did not report performing the Smoke, Fire or Fumes checklist, the first officer stating “masks” accomplished two of the three memory items by donning their one-piece oxygen masks. Postincident review of this checklist found that it instructed pilots to turn off various switches, including the RECIRC FAN switches at step 9. It is not until step 11 that the checklist instructs that if the smoke or fumes become the greatest threat, pilots should reference another checklist. It is likely that the incident flight crew would have performed the Smoke, Fire or Fumes checklist first if they had not experienced severe airframe vibration following the bird ingestion. Boeing released a flight crew operations manual (FCOM) bulletin on February 9, 2024, that described the results of the bird ingestion in this incident and the actions a flight crew should take if they experience a similar incident. Boeing also updated the system description in the Boeing 737-8 FCOM on November 15, 2024, and the Quick Reference Handbook (QRH) on November 30, 2024, to include engine failure with smoke or fumes in the flight deck or cabin as a condition to trigger reference to the Engine Fire or Engine Severe Damage or Separation QRC. Although the NTSB found no clear evidence of significant toxic or irritant exposure to the flight crew resulting from the LRD activation on the incident flight, such an event may pose a toxicological risk. There are insufficient data to reliably determine the nature and magnitude of such risk, especially at what is expected to be limited exposure duration. It is reasonable to consider the potential for irritant effects on the pilots among the threats to the immediate safety of the flight in an LRD-related smoke event.

According to the FAA, there have been “about 292,000 reported wildlife strikes with civil aircraft between 1990 and 2023. In 2023, reported bird strikes occurred at 780 U.S. airports.” Of note, the “Wildlife Strike Database” indicated that in 2023 there were 19,400 strikes that occurred at 713 U.S. airports. Over half of the bird strikes occurred between July and October with over 30 percent of the bird strikes occurring during the take-off run and initial climb. The database entry associated with the incident flight reported the species of bird struck as a bald eagle. Title 14 Code of Federal Regulation Part 139.337 provides regulatory guidance for airports to alleviate wildlife hazards. A letter dated February 8, 2024, from the New Orleans Wildlife Control Coordinator to the FAA Airport Safety and Standards Division stated that MSY had completed a review and evaluation of their Wildlife Hazard Management Plan (WHMP) and they believed that the section that referred to eagle permits provided the best overall consideration for eagle hazards and mitigation that the law provides for the harassment of such a species. Boeing released an FCOM bulletin on February 9, 2024, that described the results of the bird ingestion in the MSY incident and the actions a flight crew should take if they experience a similar incident. Boeing also updated the system description in the Boeing 737-8 FCOM on November 15, 2024, and the QRH on November 30, 2024, to include engine failure with smoke or fumes in the flight deck or cabin as a condition to trigger reference to the Engine Fire or Engine Severe Damage or Separation QRC. In addition, on February 14, 2024, Southwest Airlines issued a Read Before Fly brief to its pilots describing the event and incorporating Boeing’s updates from its FCOM bulletin. The brief indicated that section 5.5.4 Engine Failure or Shutdown in the aircraft operating manual would be updated to indicate that if smoke enters the flight deck or cabin, flight crews should accomplish the Engine Fire or Engine Severe Damage or Separation steps of the QRC. The NTSB is aware that CFM International, in collaboration with Boeing, has begun work on an engine software design update that they anticipate completing in the first quarter of 2026. The update will mitigate the presence of smoke or fumes in the cockpit or airplane cabin by closing the PRSOV when the LRD activates. This update will be entirely software-based and made available through a service bulletin upon certification. The NTSB is also aware the FAA convened a corrective action review board in November 2024 to evaluate the potential for smoke in the cockpit and cabin resulting from LRD activation; the corrective action review board determined the issue did not warrant immediate action and that any corrective action would be taken through the usual regulatory process. As a result of findings during this investigation, on June 18, 2025, the NTSB issued Safety Recommendations A-25-10 through -14. The airplane was equipped with two CFM International LEAP-1B engines, which incorporate an LRD designed to minimize aircraft and engine damage during a significant fan imbalance. The design was intended to enable the fan to be mechanically disconnected from the turbomachinery, thus reducing the severity of the vibration that is transmitted into the airframe. LRD devices are a mechanical design feature and do not require any pilot intervention (see figure 1). Figure 1. The location of the LRD on the LEAP-1B engine. (Source: CFM) Postincident examination found that the No. 1 engine LRD was activated in this event, causing tubes supplying oil to the engine sump to become dislodged and the flange from the sump area to open. The open flange allowed oil to enter the core compressor upstream of the pneumatic bleed ports that supply bleed air to the cabin and cockpit. The oil was exposed to high temperatures and resulted in smoke and fumes that were then fed into the cockpit. Each engine has a PRSOV that, when closed, prevents bleed air from entering the airplane (see figure 2). Pulling the engine fire switch, causes the PRSOV to automatically close. Figure 2. Simplified engine bleed air diagram with PRSOV depicted. (Image Copyright © Boeing. Reprinted with permission.) Postincident examination of the airplane found damage to the left engine fan blades consistent with a bird ingestion (see figure 3). Figure 3. Close-up photo of damage to the left engine. (Source: Southwest Airlines) The NTSB conducted a study to evaluate the potential for toxic and irritant effects of smoke entering the cockpit or cabin after activation of the LRD. Because there was no direct measurable evidence of the chemical composition of the smoke or the concentrations of chemicals in the cockpit air over time during the incident, and because there was no practical experimental approach by which to reliably determine the chemical composition of the smoke or the concentrations of chemicals in the cockpit or cabin air, the study was limited to characterizing the incident exposure from available information, and to examining the potential toxicity of future LRD-related smoke events from a theoretical perspective. The study found no evidence that the captain or first officer experienced impairing irritant or toxic symptoms of smoke exposure during the incident flight. After the flight, no adverse health effects of smoke exposure were conclusively identified for either pilot, although the captain experienced some incompletely characterized respiratory symptoms in the months following the flight. The Engine Fire or Engine Severe Damage or Separation checklist, current at the time of the event, in the Boeing 737-8 QRH stated the following: Condition: One or more of these occur: • Engine fire warning • Airframe vibrations with abnormal engine indications • Engine separation 1. Autothrottle (if engaged) .......... Disengage 2. Thrust lever (affected engine) ...... Confirm ........ Close 3. Engine start lever (affected engine) ...... Confirm ...... CUTOFF 4. Engine fire switch (affected engine) ...... Confirm ........ Pull To manually unlock the engine fire switch, press the override and pull. 5. If the engine fire switch or ENG OVERHEAT light is illuminated: Engine fire switch ...... Rotate to the stop and hold for 1 second If after 30 seconds the engine fire switch or ENG OVERHEAT light stays illuminated: Engine fire switch ...... Rotate to the other stop and hold for 1 second 6. Choose one: - High airframe vibration occurs and continues after the engine is shut down: Without delay, reduce airspeed and descend to a safe altitude which results in an acceptable vibration level. Note: If high vibration returns and further airspeed reduction and descent are not practical, increasing airspeed may reduce the vibration. o Go to step 7 - High airframe vibration does not occur or does not continue after the engine is shut down: o Go to step 7 7. ISOLATION VALVE switch .......... CLOSE 8. PACK switch (affected side) .......... OFF This step causes the operating pack to regulate to high flow in flight with the flaps up. 9. APU BLEED air switch .......... OFF 10. Choose one: - APU is available for start: APU .......... START When APU is running: APU GEN switch (affected side) .......... ON o Go to step 14 - APU is not available: o Go to step 11 11. Advise the Cabin Crew that the cabin lighting will be extinguished, but passenger reading lights will continue to work. 12. CAB/UTIL switch .......... OFF 13. IFE/PASS SEAT switch .......... OFF 14. Balance fuel as needed. 15. Transponder mode selector .......... TA This step prevents climb commands which can exceed single engine performance capability. 16. ISOLATION VALVE switch (after the fire has been extinguished) .......... AUTO This step ensures bleed air is available t