# NTSB CEN15LA182: Air Tractor AT 400, N136DB, Levelland, TX, March 26, 2015 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: March 26, 2015, 14:55 local (19:55 UTC) - Place: Levelland, TX - Coordinates: 33.552501, -102.372497 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.5525&lon=-102.3725&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report July 23, 2015 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Air Tractor, FAA Flight Standards District Office - NTSB case key (mKey): 90947 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN15LA182 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90947/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90947 - Page: https://openairdocs.org/ntsb/CEN15LA182 ## Probable cause The in-flight separation of the left aileron's attachment hardware at the connection between the long aileron pushrod and the left aileron bellcrank. Contributing to the accident was maintenance personnel’s improper installation of, or failure to install, the left aileron attachment hardware. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Flight control system: aileron control system](https://openairdocs.org/ntsb-findings/01022710): Aircraft › Aircraft systems · Incorrect service/maintenance (probable cause); cases with it: [Air Tractor AT-400, 1 case](https://openairdocs.org/ntsb-findings/01022710/cases.md?model=0390202), [All aircraft, 45 cases](https://openairdocs.org/ntsb-findings/01022710/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Air Tractor AT-400, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=0390202), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Initial climb: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Air Tractor AT-400, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=0390202), [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: [Air Tractor AT-400, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=0390202), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Air Tractor AT-400, 5 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=0390202), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that, shortly after takeoff on a postmaintenance test flight, the flight controls felt "stiff." The pilot flew a traffic pattern and intended to conduct a precautionary landing on the runway. However, after the pilot turned the airplane to the final leg in the traffic pattern, the airplane started to roll left. While attempting to level the wings, the pilot observed the left aileron traveling up and down. During the landing, the airplane bounced twice, rolled left, and then cartwheeled. The airplane had undergone extensive maintenance throughout the year before the accident, and, during this maintenance, maintenance personnel reinstalled the ailerons. The accident flight was the first flight following this maintenance. A postaccident examination of the airplane revealed that the hardware that attached the long aileron pushrod to the aileron bellcrank was not present, and the hardware was not found at the accident site; therefore, it could not be determined whether new or existing hardware was installed during the recent maintenance. However, given that the flight control malfunction occurred immediately following the extensive maintenance, it is likely that maintenance personnel either did not install the attachment hardware at all or did not install it properly, either of which would have resulted in the loss of airplane control and subsequent impact with terrain. ## Factual narrative On March 26, 2015, about 1455 central daylight time, an Air Tractor Inc., AT-400 airplane, N136DB, was substantially damaged during a precautionary landing on runway 35 at the Levelland Municipal Airport (KLLN), Levelland, Texas. The commercial pilot was seriously injured. Visual meteorological conditions prevailed for the flight, which without a flight plan.. The airplane was registered to and operated by Devil Dusters Inc., under the provisions of 14 Code of Federal Regulations Part 91 as a post maintenance test flight. The local flight was originating at the time of the accident.According to the pilot, he was asked by HSI Turbine to "test fly" his airplane which they had just rebuilt. During a ground run of the engine an issue with the throttle linkage was found and corrected. The pilot conducted a preflight of the airplane and did not note any issues. After restarting the engine, the pilot went through his preflight checklist including verification that the flight controls were free and correct. The pilot did not discover any discrepancies during the preflight check and the takeoff roll was uneventful. As the airplane leveled out on the crosswind leg of the traffic pattern, the flight controls felt "stiff." The pilot elected to land the airplane and have the flight controls examined. During the downwind and crosswind legs of the pattern the flight controls continued to feel stiff. After turning to the final leg in the traffic pattern, the airplane started to roll to the left. The pilot attempted to level the wings at which time the flight controls "became loose" and the pilot observed the left aileron "flopping" up and down. The right aileron continued to work correctly. While trying to land on runway 35, the airplane bounced and rolled to the left. On the second bounce the pilot added power to try and regain control of the airplane. The airplane immediately rolled to the left and the left wing impacted the ground. The airplane cartwheeled and came to rest to the west of runway 35. The empennage, fuselage, and both wings were substantially damaged. According to the pilot, he had purchased the airplane as a "wreck" in Minnesota. It did not have an engine or propeller and had damage to the right wing and landing gear. He brought the airplane to HSI Turbine during the summer of 2014 to have it repaired. According to the owner of HSI Turbine, the right wing was sent to Air Tractor to be repaired. Several mechanics and mechanic's assistants worked on the airplane and during interviews, they recalled that it was a long project that they worked on sporadically over the winter and spring. All of the mechanics and assistants reported using the maintenance manuals provided by Air Tractor to guide all of their work. All of the mechanics and assistants reported using the existing hardware on the airplane to reinstall the wings and flight controls. One assistant recalled helping to remount the wings on the airplane and recalled that was in October orNovember of 2014. Another mechanic recalled installing the ailerons in January of 2015. The maintenance on the airplane was signed off on just prior to the accident flight. Work orders for the airplane, provided by HSI Turbines, indicated that "new hardware" had been used for the installation of the horizontal stabilizer, elevator, rudder, and wings. Specific work on the ailerons was not documented in the work orders provided. An inspector with the Federal Aviation Administration and an investigator with Air Tractor examined the wreckage of the airplane. Control continuity to the elevator and rudder was confirmed. Separation points were consistent with overload. Control continuity was established to the right aileron control. All of the hardware was installed correctly and separation points were consistent with impact forces and methods used to recover the wreckage from the accident site. Control continuity was established from the left aileron control, inboard to the long aileron pushrod. The hardware to connect the long aileron pushrod to the aileron bellcrank was not present. The mounting surface on the aileron pushrod was not damaged or elongated, consistent with the hardware not being present prior to the impact sequence. An examination of the remaining wreckage and accident site did not locate the missing hardware. According to the Air Tractor AT-400 Owner's Manual and Parts Manual, an AN24-19A clevis bolt and an AN364-428 nut should be used to connect the pushrod to the bellcrank. The hardware should be torqued between 30 and 40 inch pounds. ## Aircraft - Registration: [N136DB](https://openairdocs.org/deregistered/N136DB-2017-12-11), registration cancelled 2017-12-11, S/N 400-0504, built 1983 (OpenAirDocs) - Reported make and model: AIR TRACTOR INC AT 400 - Registry model: [Air Tractor AT-400](https://openairdocs.org/model/air-tractor-at-400) (registry code 0390202) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52034, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 400-0504 - Year built: 1983 - Airframe hours: 10680 - Engines: Pratt & Whittney PT6A 15AG 680 horsepower turbo prop - Damage: Substantial damage - Flight: Flight test, Part 91 - Operator: Devil Dusters Inc - Registered owner: Devil Dusters Inc - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, March 15, 2015, 0 hours before - Departed: KLLN, Levelland, TX - Destination: KLLN, Levelland, TX - Airport: KLLN, Levelland Municipal Airport, runway 35, 6,110 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: serious; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review July 14, 2014; seat: single; restraint: 4-point; flight hours: 15,792 total, 200 in this make and model, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 19 °F - Altimeter: 30.18 inHg - Observed at: KLBB, 28 nm away ## 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 20150326003819A](https://openairdocs.org/incident/20150326003819A), Mar 26, 2015: Air Tractor Inc AT-400, Levelland, TX, Destroyed. AT-402, N136DB was being rebuilt; the right wing was sent to the factory for rebuilding and a replacement engine was installed. This was the first flight after… ## Docket (6 files) The files NTSB released with the investigation on June 8, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90947. 3.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427480&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Record of Conversations - Mechanics (item 2, .PDF, 90 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427482&FileExtension=.PDF&FileName=Record%20of%20Conversations%20-%20Mechanics-Master.PDF - Air Tractor Wreckage Examination Report (item 3, .PDF, 557 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427484&FileExtension=.PDF&FileName=Air%20Tractor%20Wreckage%20Examination%20Report-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 4, .PDF, 93 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427485&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 5, .PDF, 203 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427486&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Photograph 1 – Main wreckage (Provided by the LBB FAA FSDO) (item 6, .PDF, 178 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427487&FileExtension=.PDF&FileName=Photograph%201%20%E2%80%93%20Main%20wreckage%20(Provided%20by%20the%20LBB%20FAA%20FSDO)%20%0D%0A-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.