WestJet Boeing 737 Landing Gear Collapse Investigation in St Maarten

Anatomy of a Landing Gear Failure: TSB Investigates WestJet Incident in St. Maarten

On September 7, 2025, a routine landing for a WestJet Boeing 737-800 at the scenic Princess Juliana International Airport in St. Maarten took an unexpected turn. The aircraft, arriving from Toronto with 157 passengers and 6 crew members, experienced a significant mechanical failure during its landing on Runway 10. The right main landing gear collapsed, causing the aircraft’s right engine to strike the runway surface. The event led to substantial damage to the aircraft and a prompt, controlled evacuation of everyone on board.

In the world of aviation safety, what happens after an incident is just as critical as the event itself. Under international aviation protocols, the St. Maarten Civil Aviation Authority delegated the complex task of investigation to the Transportation Safety Board of Canada (TSB). The TSB, working in close collaboration with American counterparts like the National Transportation Safety Board (NTSB) and the Federal Aviation Administration (FAA), as well as with Boeing and WestJet, immediately began to piece together the sequence of events. One of the first, and most crucial, findings from the flight data recorder was clear: this was not a hard landing, immediately shifting the focus from operational factors to the mechanical integrity of the aircraft.

This incident does not exist in a vacuum. As investigators delve deeper, the focus has narrowed to a specific, critical component known as the aft trunnion pin. This piece of hardware has been implicated in previous landing gear failures on other Boeing 737 aircraft. The TSB’s investigation, therefore, carries implications that extend beyond a single flight, touching upon maintenance procedures and the lifecycle management of one of the world’s most common commercial aircraft.

The Incident and Initial Findings

The moments following the gear collapse were a testament to crew training and procedural discipline. With the aircraft disabled on the runway, the crew initiated a planned evacuation. Passengers and crew exited the aircraft using the emergency slides on the left side, away from the damaged right side. The evacuation was swift and orderly, resulting in only one reported minor injury sustained during the process. No injuries were reported as a direct result of the landing gear failure itself, a positive outcome in a challenging situation.

The Fractured Pin: A Critical Clue

Once the site was secured, TSB investigators began a meticulous examination of the aircraft. Their attention was quickly drawn to the failed right main landing gear, where they discovered that the aft trunnion pin had fractured. This pin is a crucial structural component that secures the landing gear assembly to the wing, designed to withstand immense forces during takeoff and landing. Its failure is a significant structural event.

The two fractured portions of the pin were carefully recovered from the site and transported to the TSB’s Engineering Laboratory in Ottawa. There, they will undergo detailed metallurgical and forensic analysis to determine the precise cause of the fracture. This examination will look for evidence of fatigue, stress corrosion, or manufacturing defects, providing a scientific basis for understanding why the component failed when it did.

The TSB also noted a key piece of the aircraft’s history: the right main landing gear assembly had undergone a complete overhaul in 2016. While this is a standard procedure for aircraft components, the date and details of this maintenance work will undoubtedly form a key part of the ongoing investigation as the team builds a complete picture of the component’s service life.

The initial review of the flight data recorder data indicates that this was not a hard landing event. This finding directs the investigation away from operational factors and squarely towards the aircraft’s mechanical integrity.

A Pattern of Failures: The Aft Trunnion Pin in Focus

Standard investigative practice involves looking for patterns, and the TSB is currently reviewing previous occurrences involving aft trunnion pin fractures on Boeing 737 aircraft. This line of inquiry is particularly relevant, as the NTSB has investigated at least two similar incidents in recent years, both of which point to a potential systemic issue related to maintenance procedures rather than a design flaw.

Historical Precedents and Maintenance Links

In August 2023, an Alaska Airlines Boeing 737-800 experienced a landing gear collapse. The subsequent NTSB investigation found that the left main landing gear’s aft trunnion pin had fractured due to a fatigue crack. The probable cause was determined to be “excessive grinding” during a maintenance overhaul, a procedure that inadvertently introduced heat damage and created the conditions for the crack to develop and propagate over time.

This was not an isolated case. A similar incident in December 2019 involving a United Airlines Boeing 737-800 was also traced back to a fractured aft trunnion pin. Once again, the NTSB investigation concluded that a fatigue crack had formed due to “excessive grinding” during an overhaul. These repeated findings highlight the critical importance of adhering to precise, validated procedures during the complex process of refurbishing major aircraft components.

These historical cases provide a crucial context for the WestJet investigation. They suggest that the focus will likely be on the maintenance, repair, and overhaul (MRO) history of the component. Landing gear assemblies are periodically removed from aircraft and completely disassembled, inspected, repaired, and reassembled by specialized facilities. The NTSB’s findings in the Alaska and United cases show that even minor deviations from approved procedures in this highly technical process can introduce latent defects that may not become apparent for years, ultimately leading to in-flight failures.

Conclusion: Awaiting the Final Report

The investigation into the WestJet landing in St. Maarten is a clear example of the methodical, evidence-based approach that defines modern aviation safety. The key facts established so far are that the incident was not caused by a hard landing, but by the fracture of the right main gear’s aft trunnion pin. This specific component has a documented history of failure in other Boeing 737-800s, with previous investigations pointing to improper maintenance during overhauls as the root cause.

The TSB’s final report, which will be released after the completion of the laboratory analysis and a full review of all evidence, will provide the definitive cause of this specific incident. Its findings will be closely watched by airlines, MRO facilities, and regulators worldwide. Depending on the outcome, it could lead to revised maintenance protocols or airworthiness directives to prevent similar occurrences, reinforcing the continuous cycle of learning and improvement that makes air travel one of the safest forms of transportation.

FAQ

Question: What happened to the WestJet flight in St. Maarten?
Answer: On September 7, 2025, the aircraft’s right main landing gear collapsed upon landing at Princess Juliana International Airport. The investigation has focused on a fractured component in the gear assembly known as the aft trunnion pin.

Question: Was the incident caused by a hard landing?
Answer: No. The Transportation Safety Board of Canada (TSB) analyzed the flight data recorder and stated that the event was not a hard landing.

Question: Have similar incidents happened before?
Answer: Yes, the U.S. National Transportation Safety Board (NTSB) has investigated similar landing gear collapses on other Boeing 737-800 aircraft. In those cases, the cause was traced to fatigue cracks in the aft trunnion pin, which were attributed to improper maintenance procedures during overhaul.

Question: Were there any serious injuries?
Answer: No injuries were reported from the gear collapse itself. A planned evacuation was conducted, during which one minor injury was reported.

Sources

• Transportation Safety Board of Canada (TSB)