The National Transportation Safety Board (NTSB) has determined that improper installation of a critical landing gear component caused a Cessna Citation CJ4's right main landing gear to collapse during landing rollout in September, marking the latest in a concerning series of business jet landing gear failures linked to maintenance errors.

The NTSB's final report, released today, concludes that the right main landing gear trunnion pin was not properly seated during installation, allowing it to work free during the landing sequence. The trunnion pin failure occurred on September 25, 2025, when Citation CJ4 N361MB, a nearly new 2021 aircraft operated by Baton Rouge-based Pacifia LLC, landed on Runway 31 at Baton Rouge Metropolitan Airport.

According to the investigation, the right main gear penetrated the wing structure after the brakes were applied following touchdown. The aircraft, which had accumulated only 33 flight hours since new, remained inoperable on the runway until approximately 11:30 p.m. local time while recovery operations were conducted. No injuries were reported among the occupants.

Critical Component Failure

Trunnion pins serve as pivot points that secure landing gear assemblies to an aircraft's wing structure, bearing substantial loads during landing and takeoff operations. The NTSB found that the pin on N361MB's right main gear was not advanced far enough forward to allow proper retention by the locking mechanism.

"The pin must be fully seated to align retention holes and allow the securing bolt to pass through," explained one investigator familiar with Citation landing gear systems. Without proper alignment, the retention system cannot function as designed, leaving the landing gear assembly vulnerable to separation under operational loads.

The failure mode mirrors recent high-profile landing gear incidents involving business jets, though the Citation CJ4 and Learjet families employ different landing gear designs. In October, the NTSB issued urgent safety recommendations for approximately 1,883 Learjet aircraft following a fatal February 2025 accident in Scottsdale, Arizona, where a Learjet 35A's left main landing gear detached during landing rollout.

Maintenance-Related Concerns

The Citation CJ4 incident highlights ongoing challenges in the business aviation maintenance sector, particularly regarding complex mechanical assemblies where proper installation procedures are critical but verification can be difficult.

Aviation safety experts note that trunnion pin installations typically occur during landing gear overhauls, gear replacements, or certain inspection procedures. The components are often located in confined spaces with limited visibility, making verification of proper installation challenging even for experienced technicians.

"These are not routine line maintenance items," said one maintenance facility manager who spoke anonymously. "When you're in there working on landing gear, everything has to be done precisely according to the manual, with proper tooling and verification."

The NTSB report did not identify which maintenance facility performed the work or when the trunnion pin was last installed on the accident aircraft. N361MB was enrolled in Textron Aviation's TAP Blue engine program and ProParts airframe support program at the time of the incident.

Industry Response

Textron Aviation, manufacturer of the Citation CJ4, has not issued public statements regarding the incident or announced any fleet-wide inspection requirements. The company's Citation CJ4 Gen2 entered service in 2020 and represents one of the manufacturer's most popular light jet models, with a typical list price approaching $10 million.

The aircraft features a Collins Pro Line 21 integrated avionics suite and is powered by Williams FJ44-4A engines. With a range of approximately 2,100 nautical miles and cruise speeds around 450 knots, the CJ4 competes directly with aircraft like the Embraer Phenom 300 and Pilatus PC-24 in the light jet category.

Industry observers note that while landing gear issues remain relatively rare in modern business jets, the consequences of failures can be severe. Beyond the safety implications, gear collapses typically result in substantial structural damage requiring extensive repairs that can ground aircraft for months.

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Broader Safety Picture

The Citation CJ4 incident comes amid heightened scrutiny of business jet landing gear systems following the fatal Scottsdale Learjet accident. In that case, investigators determined the retaining bolt securing the aft trunnion pin had been installed but failed to pass through the pin itself, leaving the gear insecurely attached despite appearing normal during inspections.

The NTSB subsequently urged the FAA to mandate inspections of 10 Learjet models and recommended that Bombardier revise maintenance procedures to include mandatory visual verification of proper trunnion pin and retaining bolt positioning. However, the FAA has not yet issued an airworthiness directive making such inspections mandatory.

According to manufacturer data, only about 12% of affected Learjet aircraft had completed the recommended inspections as of late October, despite the NTSB characterising the issue as an urgent safety concern.

Moving Forward

The NTSB's findings on the Citation CJ4 incident underscore the critical importance of proper maintenance procedures and verification protocols for complex mechanical systems. While the investigation did not result in new safety recommendations specific to the Citation fleet, the report serves as a reminder of the potential consequences when proper installation procedures are not followed.

For Citation CJ4 operators, the incident highlights the importance of ensuring all maintenance is performed by qualified technicians using proper procedures and tooling, with thorough verification of work completed. The aircraft type has an otherwise strong safety record, with this incident representing an isolated maintenance-related failure rather than a systemic design flaw.

The FAA continues to review the NTSB's broader recommendations regarding business jet landing gear inspections and maintenance procedures, though no timeline has been announced for potential regulatory action.

The NTSB final report on accident N361MB is available through the agency's public docket system. The investigation file includes detailed photographs of the failed components and a maintenance documentation review.

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