Accident Overview
On May 18, 2023, about 1800 mountain daylight time, a Luscombe 8E, registration N2515K, was substantially damaged when it was involved in an accident at the Cortez Municipal Airport (CEZ), Cortez, Colorado. The pilot and the flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Events Leading to Accident
The airplane was recently purchased by the pilot and delivered to CEZ by the flight instructor. After delivery, the pair conducted flights over several days to familiarize the pilot with the airplane. According to the pilot, during the accident flight he conducted several landings without incident. The final takeoff and landing were conducted with the flight instructor manipulating the airplane’s flight controls. The pilot described the final landing as “very hard.” The flight instructor reported that he landed on the runway centerline and as the airplane was rolling out, the right main landing gear collapsed. He noted that the right seat position, where he was seated, did not have brakes installed. During the landing, the right main landing gear collapsed, and the airplane’s left wing was substantially damaged.
Landing Gear Failure Analysis
The failed right main landing gear was examined by the National Transportation Safety Board Materials Laboratory. Examination revealed corrosion on the inside of the main landing gear tube in the area where it was welded to the wheel axle. The corrosion progressively thinned the leg tube walls over time and caused pitting and microcracking on the tube interior. The combination of missing material, pitting, and microcracks led to an overstress fracture of the leg at this location on the final landing, which subsequently led to two other overstress fractures. The tube thickness near the fracture had thinned from 0.040 inches to 0.025 inches.
Maintenance History and FAA Advisories
On June 5, 2017, the Federal Aviation Administration (FAA) issued a special airworthiness information bulletin (SAIB), CE-17-14, to alert operators of several models of JGS Properties LLC and Luscombe airplanes, including the model 8E, of a need for inspection to detect and correct corrosion inside the main landing gear legs. According to the bulletin, internal surface treatment and regular inspection of the lower legs may help mitigate corrosion-related gear failures. Compliance with an FAA SAIB is not mandatory for 14 CFR Part 91 operations.
The FAA recommended that owners and operators follow the inspection procedures outlined in The Don Luscombe Aviation History Foundation Service Recommendation No. 4, dated Jan. 22, 1996, which provided instructions for installing a drain hole in the lower portion of the leg, performing repetitive inspections of the gear legs for corrosion, and cleaning and sealing the gear legs’ internal surfaces. The accident airplane did not appear to have a drain hole in this portion of the lower leg. The FAA also urged using X-ray or ultrasound inspection methods on the leg-to-axle joint to detect internal rust during initial or follow-on inspections.
Limited maintenance records were available during the investigation; however, the most recent annual inspection entry did not indicate that the landing gear were inspected for corrosion. The fractured main landing gear did not have drain holes as noted in the service recommendation.