25th of September 2025, RTFM, Blog #755
With a crew of two, a Cessna 525C Citation CJ4 was operating a positioning flight from Pensacola Regional Airport (Florida, USA) to Baton Rouge (Louisiana, USA).
While climbing through approximately 10,000 feet, the crew felt a bump from the rear of the aircraft, which they initially thought was something falling from the toilet. After both crewmembers looked back into the cabin, it became obvious that this was not the case. The crew then observed that the right-hand main landing gear unsafe (red) indication was illuminated.
The emergency/abnormal checklist for "Landing Gear Won't Retract" was consulted, resulting in a three-green indication, confirming that all landing gear were down and locked. It was decided to continue the flight to Baton Rouge with the landing gear in the extended position.
The remainder of the flight continued without any additional problems.
ATC cleared the aircraft to land on Runway 31, where it touched down approximately 300 feet beyond the aiming point. The speed brakes and ground spoilers were deployed, resulting in an amber SPEEDBRAKE/GROUNDSPOILER CAS message. This coincided with the right wing dropping and the aircraft pulling to the right. The crew was able to stop the aircraft within the confines of the runway.
Damage to the aircraft was substantial. The right wingtip suffered abrasion damage, and the right main landing gear had punctured the wing
The National Transportation Safety Board (NTSB) was alerted, and an investigation into the accident was launched. A post-accident examination revealed that the aft main landing gear trunnion pin for the right main landing gear had not been properly installed during recent maintenance. The pin had not been installed far enough to allow the retaining roll pin to engage and secure the trunnion pin.
Maintenance records revealed that work on the right-hand main landing gear, including the trunnion pin, had been completed only 2.9 flight hours before the accident.
The manufacturer's Aircraft Maintenance Manual (AMM) states that maintenance personnel must ensure that the aft end of the trunnion pin is at least 2.0 inches (50.8 mm) forward of the aft spar fitting to verify proper installation.
The Civil Aviation Accident and Incident Investigation Commission (CIAIAC) of Spain investigated a similar accident that occurred on 4 May 2018, as documented in CIAIAC Report A-012/2018. As a result of that investigation, the aircraft manufacturer issued Mandatory Service Letter SL525C-32-12, requiring an inspection of the aft main landing gear trunnion pins to verify correct installation. Click on the PDF file below to access the service letter.
The NTSB determined that the probable cause(s) of this accident was:
The improper installation of the trunnion pin, which resulted in a failure of the right main landing gear. Contributing to the accident was the failure of maintenance personnel to follow the aircraft manufacturer’s maintenance procedures.
The NTSB report (with access to the NTSB Docket) which served as source for this blog can be accessed by clicking on the .pdf file below;
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