# NTSB CEN09LA526: Thrush S2R-T660, N660RB, Worthington, MN, August 16, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 16, 2009, 17:30 local (22:30 UTC) - Place: Worthington, MN - Coordinates: 43.652221, -95.572219 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=43.6522&lon=-95.5722&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 29, 2009 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA-MSP-FSDO - NTSB case key (mKey): 74532 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN09LA526 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74532/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74532 - Page: https://openairdocs.org/ntsb/CEN09LA526 ## Probable cause A fatigue failure of the elevator push-pull rod which resulted in the pilot's inability to control the aircraft's pitch attitude while landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Flight control system: elevator control system](https://openairdocs.org/ntsb-findings/01022730): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [All aircraft, 74 cases](https://openairdocs.org/ntsb-findings/01022730/cases.md) - [Performance/control parameters: pitch control](https://openairdocs.org/ntsb-findings/01062022): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [All aircraft, 526 cases](https://openairdocs.org/ntsb-findings/01062022/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Landing-flare/touchdown: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Landing-flare/touchdown: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported he heard and felt a “loud pop” at the end of a spray run and realized he did not have elevator control. The pilot controlled the pitch attitude using power and elevator trim as he flew back to an airport to land. The pilot decided to land at a higher than normal airspeed so he could maintain control of the airplane. The airplane bounced twice during the landing. During the second runway impact, the main gear collapsed. The airplane slid approximately 200 feet and veered off the right side of the runway prior to coming to rest and sustained substantial damage to the right wing. A post accident examination of the airplane revealed the elevator push-pull rod was fractured through the first full thread of the threaded shaft adjacent to the conical section. The remaining threaded section of the rod was threaded into the monoball spherical bearing fitting. A metallurgical examination revealed a fatigue fracture that initiated from both sides of the threaded shank on the rod end. Examination of the monoball bearing revealed several dents in the metallic bearing shield. The shape, size, and location of the dents and the deformation of the bearing shield were consistent with over-travel contact by the boss on the monoball bearing. ## Factual narrative On August 16, 2009, at 1730 central daylight time, a Thrush Aircraft S2R-T660, N660RB, experienced a loss of elevator control and collided with the runway during a forced landing on runway 29 (5,506 feet by 100 feet, asphalt) at the Worthington Municipal Airport (OTG), Worthington, Minnesota. The pilot was not injured. The airplane sustained substantial damage to the right wing. The aerial application flight was being operated under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from OTG at 1630. The pilot reported he heard and felt a “loud pop” at the end of a spray run and realized he did not have elevator control. The airplane continued to climb and lose airspeed, and at an altitude of about 500 feet, it started to nose over. The pilot was able to level the wings and he added power to raise the nose. The pilot continued to control the pitch attitude of the airplane by adjusting engine power and elevator trim as he flew back to the airport to land. The pilot reported that the airplane became less controllable as the airspeed decreased, so he decided to land at a higher than normal airspeed. He reported that the airplane bounced when it touched down and he was not able to control the pitch attitude with the trim as it was ineffective due to the slow airspeed. The airplane bounced a second time, gaining about 30 to 40 feet in altitude. The pilot reported he closed the throttle and the airplane impacted hard on the runway, collapsing the main landing gear. The airplane slid approximately 200 feet and veered off the right side of the runway prior to coming to rest. A post accident examination of the airplane revealed the elevator push-pull rod had fractured. The fractured rod was examined by the Safety Board's Materials Laboratory. This examination revealed rod fractured at the first full thread of the threaded shaft adjacent to the conical section. The remaining threaded section of the rod was threaded into the monoball spherical bearing fitting. A fatigue fracture initiated initiated from both sides of the threaded shank on the rod end. The fatigue propagated from both sides of the cross section of the shank. Examination of the monoball bearing revealed several dents in the metallic bearing shield. The shape, size, and location of the dents and the deformation of the bearing shield were consistent with over-travel contact by the boss on the monoball bearing in at least three directions. ## Aircraft - Registration: N660RB (not matched to a registry record) - Reported make and model: THRUSH AIRCRAFT INC S2R-T660 - Category: Airplane - Serial number: T660-114DC - Airframe hours: 556 - Engines: P&W CANADA PT6A-65AG 1300 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Boardman Air Service LLC, doing business as Boardman Aerial Spraying, Inc. - Registered owner: Boardman Air Service LLC - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, April 1, 2009, 52 hours before - Departed: OTG, Worthington, MN - Destination: OTG, Worthington, MN - Airport: OTG, Worthington Municipal Airport, runway 29, 5,506 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review February 9, 2008; seat: front; flight hours: 7,448 total, 502 in this make and model, 7,248 as pilot in command, 146 in the last 90 days, 146 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 12 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 46 °F - Altimeter: 29.94 inHg - Observed at: OTG ## 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 20090816048979A](https://openairdocs.org/incident/20090816048979A), Aug 16, 2009: Thrush Airc S2R-T660, Worthington, MN, Substantial damage. Pilot reported that while spraying third field, after making pass to look for obstructions, he heard a loud pop and realized he had no elevator control. He was… ## Docket (2 files) The files NTSB released with the investigation on October 22, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74532. 1.4 MB in all. - Materials Laboratory 15 - Factual Report 09-069 (item 1, .PDF, 618 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40319378&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2009-069-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 759 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40320165&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.