# NTSB WPR18LA129: Gulfstream AM Corp Comm Div 695A, N79PH, Bishop, CA, April 26, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: April 26, 2018, 12:55 local (19:55 UTC) - Place: Bishop, CA - Coordinates: 37.373054, -118.363609 - Nearby events: https://openairdocs.org/map.md?lat=37.3731&lon=-118.3636&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 97146 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18LA129 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97146/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97146 - Page: https://openairdocs.org/ntsb/WPR18LA129 ## Probable cause 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear attach sec](https://openairdocs.org/ntsb-findings/01023211): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Gulfstream AM Corp Comm Div 695A, 1 case](https://openairdocs.org/ntsb-findings/01023211/cases.md?model=3970411), [All aircraft, 66 cases](https://openairdocs.org/ntsb-findings/01023211/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Gulfstream AM Corp Comm Div 695A, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=3970411), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Gulfstream AM Corp Comm Div 695A, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=3970411), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis 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. ## Factual narrative 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 dimensionsthan that on the upper fracture surface. ## Aircraft - Registration: [N79PH](https://openairdocs.org/aircraft/N79PH), registered now, S/N 96029 (OpenAirDocs) - Reported make and model: GULFSTREAM AM CORP COMM DIV 695A (A) - Registry model: [Gulfstream AM Corp Comm Div 695A](https://openairdocs.org/model/gulfstream-am-corp-comm-div-695a) (registry code 3970411) (OpenAirDocs) - Registry engine: [AiResearch TPE331 series](https://openairdocs.org/engine/airesearch-tpe331-series) (registry code 01514, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 96029 - Year built: 1982 - Airframe hours: 7666 - Engines: Airesearch TPE331 turbo prop; Airesearch TPE331 turbo prop - Damage: Substantial damage - Flight: Business, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 1, 2017, 102 hours before - Departed: CNO, Chino, CA - Destination: BIH, Bishop, CA - Airport: BIH, Bishop, runway 12, 7,498 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review September 15, 2017; seat: left; restraint: 3-point; flight hours: 10,636 total, 77 in this make and model, 10,466 as pilot in command, 67 in the last 90 days, 47 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 170° at 13 knots, gusting 18 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 41 °F - Altimeter: 29.97 inHg - Observed at: BIH ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20180426000309A](https://openairdocs.org/incident/20180426000309A), Apr 26, 2018: Gulfstream Am Corp Comm Div 695A, Bishop, CA, Substantial damage. N79PH a turbo commander experienced a collasped left main gear during landing on runway 12 at Bishop California airport (bih). Aircraft skidded to a stop on… ## Docket (5 files) The files NTSB released with the investigation on March 25, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97146. 21.3 MB in all. - Materials laboratory factual report (item 1, PDF, 17 pages, 25 photos, 7.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=7366089&FileExtension=pdf&FileName=18-103%20-%20Materials%20Lab%20Factual%20Report%20(WPR18LA129)-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 10 pages, 7.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11968044&FileExtension=pdf&FileName=NTSB%20accident%20report%20form_Redacted-Rel.pdf - Release of wreckage and return of parts forms (item 3, PDF, 3 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11967878&FileExtension=pdf&FileName=NTSB%20Retention-Release%20and%20Return%20of%20Parts%20forms_Redacted-Rel.pdf - Evidence control form (item 4, PDF, 1 page, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11968805&FileExtension=pdf&FileName=Evidence%20Control%20Form_redacted-Rel.pdf - Photo array of airplane at accident site (item 5, PDF, 4 pages, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11969900&FileExtension=pdf&FileName=Photo%20array%20of%20airplane%20at%20accident%20site-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.