Bishop, CA, USA
N79PH
GULFSTREAM AM CORP COMM DIV 695A
The pilot reported that before touching down on the runway with a 13-kt 50° right crosswind, the landing gear were down with the three green landing gear lights illuminated. After touching down and beginning the ground roll, the airplane pulled slightly to the left, the left wing dropped, and the airplane started to pull harder to the left. The pilot corrected with right rudder and brake, as well as reverse power on the right engine. The left wing dropped further, and the airplane pulled harder to the left before coming to rest about 10 ft from the left edge of the runway. The left main landing gear had collapsed, which resulted in substantial damage to the fuselage. Postaccident examination revealed that the left main landing gear upper arm forging failed from fatigue cracking. The largest fatigue crack appeared to have initiated along multiple sites along scratch-like features on the outside surface of the arm. These cracks grew inward under spectrum loads until the loads from the accident landing could not be withstood by the remaining cross section, causing the part to fracture in overstress.
On April 26, 2018, about 1255 Pacific daylight time, a Gulfstream AM CORP COMM DIV 695A airplane, N79PH, was substantially damaged when it was involved in an accident near Bishop, California. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 business flight. The flight was landing at Bishop Airport (BIH), Bishop, California. The pilot reported that he chose to land on runway 12, as the reported wind was from 170° at 13 kts with gusts to 20 kts, that the landing gear were down with the three green landing gear lights illuminated. He said he touched down using a typical crosswind landing technique, touching first with the right main landing gear followed by the left main landing gear, holding the nose gear off the ground, and bringing the power levers into ground idle. The pilot stated that as he lowered the nose and began the ground roll, the airplane started pulling slightly to the left, and the left wing then dropped as if the left main tire had gone flat. The pilot said the airplane began to pull harder to the left, so he applied additional right rudder, right brake, and reverse power on the right engine. The left wing dropped further, and he heard metal scraping sounds. The airplane pulled harder to the left before coming to a stop, and the pilot shut down both engines. The airplane came to rest about 10 ft from the left edge of the runway, oriented in line with the runway heading. The left main landing gear had collapsed, which resulted in substantial damage to the fuselage. Examination of selected left main landing gear components revealed that the upper arm forging had fractured in two places. Regarding the upper fracture surfaces from the arm forging, most of each mating fracture surface exhibited a rough texture and dull luster, with shear lips on three of the edges. The fracture surface exhibited river patterns that fanned outward in the middle of the fracture surface. The river patterns exhibited an orientation consistent with having emanated from a thumbnail-shaped crack on the upper side. Further examination of the largest thumbnail crack revealed fatigue striations consistent with fatigue crack propagation. The striations were not uniformly spaced, consistent with spectrum loading. Smaller thumbnail cracks on the fracture surface also exhibited fatigue striations. Along the fatigue crack initiation sites of the main fatigue crack, scratch-like features were present. On the outside arm surface, several cracks were present along scratch-like features. Outside of the fatigue regions, the remainder of the fracture surface exhibited dimple rupture and ductile tearing consistent with overstress fracture. The lower fracture surfaces also exhibited shear lips, rough texture, and dull luster. The river patterns were consistent with having emanated from the lower-facing outer surface. At this fracture edge, a thumbnail-shaped crack was observed that was smaller in dimensions than that on the upper fracture surface.
The failure of the left main landing gear upper arm forging due to fatigue cracking and subsequent overstress, which resulted in the collapse of the landing gear during the landing roll.
Source: NTSB Aviation Accident Database
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