ERA25LA091

The pilot reported that, after a normal landing, the pilot heard a “pop” followed by a leaning tendency to the right that he attempted to correct with flight control inputs. He could not arrest the right turn, and the airplane departed the right side of the runway and came to a stop, upright, in the grass. The right wing and right stabilator sustained substantial damage. The right main landing gear spring separated during the landing roll. Metallurgical examination of the spring revealed evidence of chloride intergranular stress-corrosion cracking that progressed into fatigue over time. The examination also found evidence of the spring being reworked after manufacture, with grinding marks perpendicular to the lengthwise direction of the part (contrary to manufacturer-approved procedures), areas of missing paint, and corrosion pitting. The operator reported that the spring had not been removed or reworked since they purchased the airplane more than 25 years before the accident.

On January 5, 2025, about 1700 eastern standard time, a Helio HT-295 airplane, N18JC, was substantially damaged when it was involved in an accident near Marion, Ohio. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. The pilot reported that he was en route from Buffalo Niagara International Airport (BUF), Buffalo, New York, to Coleman A. Young Municipal Airport (DET), Detroit, Michigan, when he elected to divert to Marion Municipal Airport (MNN), Marion, Ohio, due to deteriorating weather conditions. He prepared for a visual straight-in approach to runway 31. After a normal landing, the pilot heard a “pop” followed by a leaning tendency to the right that he attempted to correct with flight control inputs. He could not arrest the right turn, and the airplane departed the right side of the runway and came to a stop, upright, in the grass. He secured the airplane, and he was met by first responders. FAA inspectors responded to the accident site and examined the wreckage. The left wing and left stabilator sustained substantial damage. The right main landing gear spring separated at the fuselage connection point. The inspectors removed the spring section that remained inside the fuselage and secured the outboard section of the spring. The fractured gear spring parts were sent to the NTSB Materials Laboratory for further examination. The examination revealed that the spring fractured at the upper, inboard end of the spring between the inboard attachment hole and the outboard support bracket. The fracture was located about 4.5-4.75 inches away from the inboard end of the spring. The examination revealed evidence of chloride intergranular stress-corrosion cracking. After the crack grew over time, the dominant fracture mechanism turned to fatigue. Beyond the fatigue boundary, the fracture area showed evidence of ductile overstress failure. The gear spring was found to be consistent with Cessna part number 0741001-8 main landing gear spring, reportedly used on the Helio HT-295. The leg also showed indications of rework after manufacture. The corners of the leg had chamfers with variable width and geometry. The chamfer surface had grinding marks that were perpendicular (traverse) to the lengthwise direction of the leg. There were also areas of missing paint and corrosion pitting. According to Cessna Specification CSPS026, grinding of the main landing gear spring in the longitudinal direction is permitted; however, no transverse grinding is permitted on either edges or flats. The operator reported that there were no aircraft logbook entries showing removal or reworking of the main landing gear since they purchase it in September 1998.