On March 4, 2026, about 1648 eastern standard time, a Cessna 551, N228MH, was substantially damaged when it was involved in an accident near Opa-locka, Florida. The two pilots and three passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 post-maintenance test-flight. The test-flight was conducted due to an avionics upgrade. The pilot-in-command (PIC) reported that the takeoff and enroute portion of the approximate 45-minute local instrument flight rules flight was uneventful. During the return to the departure airport, on an instrument landing system (ILS) approach, the PIC was flying and the second-in-command (SIC) extended the landing gear. The flight crew noted that the right main landing gear (RMLG) red cockpit indication light remained illuminated, and a warning horn sounded when full flap extension was selected. Additionally, the SIC could visually see from his seat that the RMLG was slightly misaligned. The PIC performed a missed approach and received extended vectors for a second ILS approach to allow extra time to troubleshoot the anomaly. The flight crew performed the quick reference handbook (QRH) “Landing Gear Will Not Extend.” procedure, which included activation of the blow-down bottle, but the red landing gear indication light remained illuminated. The second ILS approach terminated in a low approach with tower personnel stating that the landing gear appeared extended. The PIC performed a go-around and a visual approach for landing. The flight crew confirmed that all QRH items were completed and landed on a runway with emergency vehicles standing by. During the landing, the left main landing gear touched down, and about 2 seconds later, the right main landing gear gradually collapsed. The airplane came to rest upright on the runway and sustained substantial damage to the right wing. Several days later, following the airplane’s recovery to a hangar, an FAA inspector witnessed landing gear extension and retraction tests. Three tests were conducted. In each case, the nose landing gear and left main landing gear retracted and extended normally. The RMLG retracted normally but only extended to about a 45° position. The RMLG actuator was retained for further examination.