# NTSB WPR15LA129: Cessna 310Q, N7770Q, St. George, UT, March 21, 2015 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 20, 2015, 19:00 local (Mar 21, 2015, 01:00 UTC) - Place: St. George, UT - Coordinates: 37.091667, -113.592781 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.0917&lon=-113.5928&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 June 25, 2019 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 90902 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR15LA129 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90902/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90902 - Page: https://openairdocs.org/ntsb/WPR15LA129 ## Probable cause Failure of the left main landing gear lower adjusting bolt due to overstress, which resulted in the left main landing gear collapse during landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Cessna 310Q, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2074242), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/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: [Cessna 310Q, 3 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=2074242), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Cessna 310Q, 2 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=2074242), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The commercial pilot reported that he completed three takeoffs and landings before departing the area to practice in-flight maneuvers, after which he reentered the traffic pattern for landing. With normal landing gear indications in the cockpit, the pilot landed the airplane normally and uneventfully. During the landing roll, the left wing lowered more than normal, and the engine propellers and left wingtip impacted the runway surface; subsequently, the airplane slid to the left and exited the runway surface. The airplane sustained substantial damage to the left aileron. Postaccident examination revealed that the lower adjusting bolt on the left main landing gear was fracture separated. Both fracture surfaces exhibited fractographic features consistent with overstress fracture due to tensile and cantilever bending loads applied to the tie-rod end fitting. No indications of preexisting cracking were observed. The airplane's last annual inspection was completed on the day of the accident, during which the left and right main landing gear side brace bolts and bushings were replaced and a gear retraction test was satisfactory. According to the manufacturer, the area where the fracture occurred is where a mechanic would place a spring scale to measure the down lock force. This area is one of two main fracture locations when the down lock is improperly adjusted. The investigation could not determine if the bolt fractured as a result of overstress from the landing sequence, an improper adjustment of the bolt, or a combination of the two. ## Factual narrative On March 20, 2015, about 1900 mountain daylight time, a Cessna 310Q airplane, N7770Q, experienced a left main gear collapse during the landing roll at St. George Regional Airport (SGU), St. George, Utah. The commercial pilot and one passenger were not injured; the airplane sustained substantial damage to the left aileron. The airplane was registered to, and operated by, the pilot as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed SGU about 1800. The pilot reported that the purpose of this flight was to regain currency after the airplane had been in maintenance for an extended period of time. During the flight, three takeoff and landings were completed before the pilot departed the traffic pattern to practice inflight maneuvers. After finishing the maneuvers, he reentered the traffic pattern for landing. With normal landing gear indications in the cockpit, the pilot landed the airplane normally and uneventfully. During the landing roll, the left wing lowered more than normal; subsequently, the engine propellers and wingtip impacted the runway surface. The airplane slowly slid to the left and exited the runway surface. A postaccident examination conducted by a Federal Aviation Administration Inspector revealed that the lower adjusting bolt on the left main landing gear was fracture separated. High quality photos of the fracture surfaces were sent to the National Transportation Safety Board (NTSB) Materials Laboratory for further examination. The NTSB Materials Laboratory specialist reported that both fracture surfaces exhibited fractographic features consistent with overstress fracture due to tensile and cantilever bending loads applied to the tie-rod end fitting. No indications of preexisting cracking was observed. Review of maintenance logbooks revealed the last annual inspection was completed the same day as the accident. During the inspection, the left and right landing gear side brace bolts and bushings were replaced, and a gear retraction test was satisfactory. According to a Cessna Representative, the area of the fracture is where a mechanic would place the spring scale to measure the down lock force. This area is one of two main fracture locations when the down lock is improperly adjusted. ## Aircraft - Registration: [N7770Q](https://openairdocs.org/deregistered/N7770Q-2018-05-31), registration cancelled 2018-05-31, S/N 310Q0270, built 1971 (OpenAirDocs) - Reported make and model: CESSNA 310Q - Registry model: [Cessna 310Q](https://openairdocs.org/model/cessna-310q) (registry code 2074242) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 310Q0270 - Year built: 1971 - Airframe hours: 8704 - Engines: CONT MOTOR IO-470 SERIES 260 horsepower reciprocating; CONT MOTOR IO-470 SERIES 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 20, 2015, 2 hours before - Departed: SGU, St. George, UT - Destination: SGU, St. George, UT - Airport: SGU, St George Regional Airport, runway 19, 9,300 × 150 ft, asphalt - Equipment: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review December 14, 2013; seat: left; restraint: 3-point; flight hours: 1,071 total, 199 in this make and model, 950 as pilot in command, 5 in the last 90 days, 1 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 240° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 18 °F - Altimeter: 30.05 inHg - Observed at: KSGU, 1 nm away ## Docket (6 files) The files NTSB released with the investigation on April 30, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90902. 1.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 676 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462322&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Record of Email - FAA Regarding Airplane Examination (item 2, .PDF, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462324&FileExtension=.PDF&FileName=Record%20of%20Email%20-%20FAA%20Regarding%20Airplane%20Examination-Master.PDF - Materials Laboratory Examination Observations (item 3, .PDF, 157 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462326&FileExtension=.PDF&FileName=Materials%20Laboratory%20Examination%20Observations-Master.PDF - Record of Email - NTSB Materials Laboratory Follow Up (item 4, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462328&FileExtension=.PDF&FileName=Record%20of%20Email%20-%20NTSB%20Materials%20Laboratory%20Follow%20Up-Master.PDF - Maintenance Records (item 5, .PDF, 83 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462330&FileExtension=.PDF&FileName=Maintenance%20Records-Master.PDF - Record of Email - Cessna Representative (item 6, .PDF, 87 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40472849&FileExtension=.PDF&FileName=Record%20of%20Email%20-%20Cessna%20Representative-Master.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.