# NTSB ATL07LA066: Szybowcowy Zaklad Do SZD-36A, N6SZ, Sylacauga, AL, March 31, 2007 - Type: NTSB accident investigation - Classification: Accident · Fatal · Limited investigation · Final report - Date: March 31, 2007, 15:30 local (20:30 UTC) - Place: Sylacauga, AL - Coordinates: 33.169723, -86.303337 - Nearby events: https://openairdocs.org/map.md?lat=33.1697&lon=-86.3033&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report July 30, 2008 - Report: Approved by Office Director - Parties: FAA/FSDO - NTSB case key (mKey): 65521 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL07LA066 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65521/pdf - Page: https://openairdocs.org/ntsb/ATL07LA066 ## Probable cause The pilot's improper installation of the left wing attachment pin, which allowed it to disengage during cruise flight, resulting in wing separation. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - maintenance,installation - improper, pilot in command (cause) - wing,wing attachment bolt - disengaged - In flight collision with terrain/water, descent - uncontrolled - terrain condition - ravine ## Analysis Witnesses stated that the glider had been airborne for about 30 minutes when they observed both wings fold up, and the glider descend out of control until impacting into a rock quarry. The wings were located about 1/2-mile north of the impact crater on the upper rim of the quarry. Examination of the wreckage revealed that during assembly, the lower attach pin had failed to enter the lower attachment hole on the left wing. The misalignment allowed the pin to rest on the top surface of the left wing attach lug in a clamping action. Examination of the mechanism that actuates the movement of both pins found that there had been two tabs located above the center pivot, and these two tabs were not found. Examination of the area where the two tabs were missing disclosed that these tabs had been missing for an extended period of time, as the upward motion of the mechanism (center pivot) had machined into the surface above where the upper tabs should have been located. The misalignment of the attach pin in the lower attachment hole allowed the left wing to move upwards to about 45 degrees and separate. ## Factual narrative On March 31, 2007, at 1530 central daylight time, an amateur-built experimental Szybowcowy Zakland DO, SZD-36A glider, N6SZ, registered to a private individual, was substantially damaged when both wings failed and separated from the glider during a personal flight in Sylacauga, Alabama. The private pilot received fatal injuries. Visual meteorological conditions prevailed for the flight, which departed Merkel Field Sylacauga Municipal Airport (SCD) Sylacauga, Alabama, about 1500. No flight plan was filed for the local flight conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the pilot's brother, they had trucked the glider from Birmingham, Alabama, to Sylacauga, to fly around in the local area. The brother of the pilot stated that he assisted the pilot in assembling the glider prior to the flight. Witnesses stated that the glider had been airborne for about 30 minutes when they observed both wings fold up, and the glider descend out of control until impacting into a rock quarry, about 2 miles south of SCD. The tow plane pilot stated that he towed the glider to altitude and released it. He added that the last time he saw the glider, it was about 1500 feet above the ground. He said he did not observe the breakup, but did see the wings fluttering through the air towards the quarry. The tow plane pilot circled the area looking for the fuselage but could not find it. Witnesses working in the quarry stated that they initially heard what sounded like a "rocket," looked up and saw the fuselage descending at a very fast rate. The fuselage impacted in the bottom of the quarry, and the wings "floated" down like leaves from a tree and impacted "several minutes" after the fuselage impacted. The workers located the glider in a small impact area. Examination of the fuselage by a Federal Aviation Administration (FAA) inspector found it substantially damaged. Debris from the fuselage was scattered approximately 10 feet forward of the impact crater with the majority of the fuselage remaining in the crater. The wings were located about 1/2 mile north of the impact crater on the upper rim of the quarry. Examination of the wing attachments found that the lower attachment lugs had disengaged, allowing the wing to move upwards 45degrees, breaking the left upper wing attach lug. The examination revealed that during assembly, the lower attach pin had failed to enter the lower attachment hole on the left wing. The misalignment allowed the pin to rest on the top surface of the left wing attach lug in a clamping action. The upper wing attachment pin was found to be properly installed. Examination of the mechanism that actuates the movement of both pins found that there had been two tabs located above the center pivot, these two tabs were not found. No autopsy or toxicology was performed on the pilot. A review of the glider's logbooks by an FAA inspector found that the annual condition inspection was performed on June 22, 2006, at a total time of 537 hours. Total glider time was estimated at 556 hours with the pilot's logbook entries. Review of the pilot's logbook revealed that he had an estimated 685 hours of total time in powered aircraft and 36 hours of glider experience. ## Aircraft - Registration: [N6SZ](https://openairdocs.org/deregistered/N6SZ-2017-06-21), registration cancelled 2017-06-21, S/N W813, built 1977 (OpenAirDocs) - Reported make and model: Szybowcowy Zaklad DO SZD-36A - Registry model: [Szybowcowy Zaklad Doswiadczaln SZD-36-A](https://openairdocs.org/model/szybowcowy-zaklad-doswiadczaln-szd-36-a) (registry code 8821636) (OpenAirDocs) - Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs) - Category: Glider - Serial number: W813 - Airframe hours: 556 - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Robert Obrian Wallace - Registered owner: Donald R. Tawzer - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, June 1, 2006, 19 hours before - Departed: SCD, Sylacauga, AL - Destination: SCD, Sylacauga, AL - Airport: KSCD, Merkel Field Sylacauga Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 65; injuries: fatal; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; seat: single; flight hours: 685 total, 36 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 150° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 61 °F - Altimeter: 30.03 inHg - Observed at: EET ## 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 20070331012949A](https://openairdocs.org/incident/20070331012949A), Mar 31, 2007: Szd SZD36A, Sylacauga, AL, Destroyed, 1 fatal. (-23) Both wings separated from the aircraft during a personal/proficiency flight in an unpowered glider at the Sylacauga, Alabama airport (scd). Subsequently,… 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.