What happened
During the landing phase, the flight crew of a Boeing 737 (registration not provided) experienced a failure of the nose landing gear extension. After attempting to lower the gear without receiving a down indication, the crew performed a low-approach, during which air traffic control personnel confirmed that the nose landing gear remained retracted.
The crew climbed to 6,000 feet and contacted maintenance to troubleshoot the issue. Despite following emergency checklists and attempting a manual extension of the nose landing gear, the crew was unable to resolve the problem. Consequently, the aircraft executed a landing on runway 14R with the main landing gear extended but the nose landing gear in the up position, resulting in aircraft damage.
The investigation
An examination of the aircraft revealed that the spray deflector center link had fractured and the right-hand urethane deflector was displaced. The deflector had rotated aft and was no longer within its proper track inside the wheel well. When the crew attempted to lower the nose landing gear, this deflector impinged on the wheel well structure, physically preventing the gear from extending.
Components of the spray deflector were sent to the NTSB Materials Laboratory for analysis. The center deflector assembly showed fractures along three separate lines where the right side attaches. Specifically, the aft right side of the center defulating was fractured through the bolt holes and the vertical and horizontal plate members. Magnified optical examinations of the fracture faces revealed rough, crystalline matte gray surfaces, which are consistent with overstress separations in cast aluminum alloys. No evidence of porosity, corrosion, or preexisting cracking was found. Testing confirmed the material was the specified cast aluminum alloy C355 with a hardness of 101 HB, consistent with required heat treatment specifications.