Incident Details
During the second leg of the day, the crew performed a normal departure. The captain, hand-flying, selected the landing gear up between 300 and 500 feet above ground level. Immediately, a red "doors" light illuminated on the front panel and an amber right main gear door light appeared on the second officer's panel. The crew attempted to lower the right main gear but were unsuccessful. The captain decided to return to the airport and land with the right main gear extended at approximately 15 degrees.
Examination Findings
Post-flight inspection of the right main landing gear revealed several abnormalities. The safety bar was bent downward about 20 degrees at the leading edge and 15 degrees at its midpoint. The inboard flanges of the safety bar had buckled just below the reinforced area. The inner gear door drive rod was bent aft about 15 degrees at the upper attachment fitting, and the tube had buckled and separated below the four attachment nuts. The outboard section of the clamshell gear door exhibited mechanical damage. Despite these issues, the door rods were not loose and were in good condition. A general inspection of the wheel well found no other damage. The up-lock hook showed no abnormal wear or movement marks and was properly adjusted. The actuator adjustor plate was properly installed.
Maintenance Actions
Delta maintenance technicians replaced the clamshell door halves and the drive rod. They serviced the strut, isolated the right main clamshell gear door, and cycled the gear. Subsequently, they cycled the right main wheel with the door, and finally cycled all landing gear together. All wheels and doors operated in proper sequence during the test cycles.
Metallurgical Analysis
Metallurgical examination of the safety plate found no cracks. The drive rod's fracture faces exhibited no fatigue crack arrest marks or corrosion; the fracture was a result of overstress.
Additional Observations
The interior side of the outer clamshell door was covered with a greasy black coating. A rectangular scuffmark, with its long axis parallel to the aircraft's longitudinal axis, was present in the center of the black area. The coating appeared pushed into a slight ridge along the outer edge of the scuffmark. A small piece of rubber was found under a rivet at the center of the scuffmark. When the tire and gear door were positioned as they would have been at rest, the tire did not contact the scuffmark. Fourier Transform Infrared Spectroscopy (FTIR) analysis of the rubber piece and samples from the tire and a chock showed they were all hydrocarbon compounds, but the technique could not differentiate between the samples. It could not be determined whether the scuffmark and rubber piece originated from runway debris or another rubber object.