N8830Q – BOEING 737-8 – 2023-12-20 NTSB Accident Report

HISTORY OF FLIGHTOn December 20, 2023, about 1414 central standard time, Southwest Airlines flight 554, a Boeing 737-8 airplane, N8830Q, was departing from the Louis Armstrong New Orleans International Airport (MSY), Kenner, Louisiana, when a bird ingestion occurred in the No. 1 engine during the initial climbout. The flight crew returned to the airport. None of the 139 occupants aboard the airplane were injured, and the airplane sustained minor damage. The regularly scheduled passenger flight was operating under the provisions of Title 14 Code of Federal Regulations (CFR) Part 121 from MSY to Tampa International Airport (TPA), Tampa, Florida. Visual meteorological conditions prevailed for the flight.

The captain was the pilot flying for the incident flight, and the FO was the pilot monitoring. The flight crew reported that, after an uneventful takeoff and while climbing through about 1,000 ft, the FO heard the captain say “bird,” which was followed immediately by a “thump” on the left side of the airplane. 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 QRC. According to the captain, after the FO started the checklist, the flight deck began to fill with “acrid white smoke.” The FO stated that he could not clearly see the captain. 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 asked ARFF to roll the trucks in preparation for the airplane’s return to MSY. The captain stated that visibility in the cockpit was restricted and that he could see nothing beyond the FO, who was holding the Quick Reference Handbook (QRH). The captain also stated that 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. The captain further stated that, after the engine fire switch had been pulled (by the FO), the smoke began to rapidly dissipate.

The flight crew notified the flight attendants about the emergency and made a public address announcement to notify the passengers that fire trucks would be meeting the airplane. After landing at the airport, the airplane came to a full stop on the arrival runway, and ARFF inspected the airplane before the flight crew taxied the airplane to the assigned gate under its own power. The passengers deplaned normally, and no injuries were reported.

Data from the airplane’s digital flight data recorder was sent to the NTSB’s Vehicle Recorder Laboratory in Washington, DC, for analysis. The data showed that, after takeoff, while the airplane was climbing through about 600 ft, both the left and right engine fan speed (N1) values were about 83% rpm. About 2 seconds later, the left engine’s N1 decreased to 75% rpm. Subsequently, the airborne vibration monitor began to increase, and the left engine’s oil tank quantity began to decrease from 16.25 quarts. 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 PRSOV. About 28 seconds later, the left engine’s N1 stabilized at 6% rpm with an oil tank quantity of 3.5 quarts. AIRCRAFT INFORMATIONThe 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.) AIRPORT INFORMATIONThe 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.) ADDITIONAL INFORMATIONAccording 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. DAMAGE TO AIRCRAFTPostincident 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) MEDICAL AND PATHOLOGICAL INFORMATIONThe 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 to...