N992BCDji AGRAS T40

On April 1, 2016, about 1720 central daylight time, an experimental, amateur-built Gill Lancair IV-P Propjet airplane, N992BC, was substantially damaged during landing on runway 33 (7,203 feet by 100 feet, asphalt) when the nose landing gear collapsed resulting in a runway excursion at the Addison Airport (ADS), Addison, Texas. The pilot was not injured. The airplane was registered to N992BC Properties LLC and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was operated on an instrument flight rules flight plan. The flight originated from the Georgetown Municipal Airport (GTU), Georgetown, Texas, about 0930.The pilot reported that on his initial approach to runway 33, a gusty wind condition caused the airplane to "balloon" on short final and he elected to execute a go-around. On the second approach, the airplane touched down "just left" of the runway centerline, about 1,000 feet from the approach threshold. However, when the pilot placed the propeller into beta, the nose landing gear collapsed. He was unable to maintain directional control and the airplane subsequently departed the right side of the runway. He "felt a loud bang" after the airplane had exited the runway pavement. He noted that the left landing gear strut had failed above the wheel and the strut dug into the ground before the airplane came to rest.

Video footage from cameras positioned at the approach end of the runway was provided by airport management. The airplane initially touched down on the right main landing gear, followed by the left main landing gear. The right main wheel appeared to leave the pavement momentarily before settling back down. Shortly afterward, the nose landing gear collapsed. The airplane subsequently veered to the right and departed the runway pavement. The airplane continued to travel through the grass area adjacent to the runway and rotated abruptly to the right immediately before coming to rest.

Federal Aviation Administration (FAA) inspectors identified runway propeller strike and tire skid marks attributable to the accident airplane. A line of propeller strike marks began at the runway number markings, about 10 feet left of the centerline, and appeared to initially parallel the runway centerline. Small fiberglass fragments were located near the strike marks. Shortly afterward, the strike marks began tracking toward the right side of the runway. The strike marks were joined by a set of three tire skid marks. The center mark was defined by two uniform marks consistent with being formed by the edges of the tire. This mark was collocated with the propeller strike marks and was continuous until it reached the right side of the runway pavement. The left and right tire skid marks were also continuous to the edge of the runway pavement; however, they were lighter/more faint and narrower than the center skid mark. The skid marks continued as ruts in the adjacent grass area and led to the accident site.

A postaccident examination of the airplane landing gear system by FAA inspectors did not identify any anomalies consistent with a preimpact failure or malfunction. The nose landing gear was collapsed/retracted. The left main landing gear strut had separated near the wheel assembly; the fracture surface appeared consistent with an overstress failure. The right main landing gear remained extended and appeared intact. The nose landing gear doors, lower engine cowling, and both wings were damaged. The nose landing gear strut, wheel assembly, support structure, extension/retraction linkage and hydraulic actuator appeared to be intact. The actuator did not exhibit any evidence of leakage.

Normal extension and retraction of the nose landing gear is provided by a hydraulic actuator. Landing gear extension begins when the pilot moves the cockpit landing gear handle to the down position, which directs hydraulic fluid to the extension side of the actuators. A pressure switch is incorporated into the system in order to maintain hydraulic system pressure. Once the nose landing gear is fully extended, the over-center linkage is intended to react the operating loads and to keep the nose landing gear in the down position until retraction is commanded by the pilot. Within its capability, the hydraulic actuator will resist movement of the over-center linkage provided the hydraulic system is operating normally. The emergency extension gas strut will also provide this function, within the limits of its capability.