# NTSB FTW97LA349: AS+ AC-4B, N3021, Sundance, WY, September 14, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 14, 1997, 17:45 local (23:45 UTC) - Place: Sundance, WY - Coordinates: 44.400672, -104.370018 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.4007&lon=-104.3700&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 26, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 20345 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW97LA349 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20345/pdf - Page: https://openairdocs.org/ntsb/FTW97LA349 ## Probable cause improper planning/decision by the pilot, which led to a snag and sudden slack in the tow rope, and necessitated an aborted launch (emergency landing) after initial liftoff. This in turn led to an inadvertent stall, a wing drop, and the left wing tip dragging the ground. A factor relating to the accident was: the restricted movement of the tow rope after it became snagged on the crop stubble. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Dragged wing,rotor,pod,float or tail/skid, takeoff - aborted - terrain condition - open field - terrain condition - crop (contributing factor) - planning/decision - improper, pilot in command (cause) - glider launch/tow equipment - movement restricted (contributing factor) - aborted takeoff - initiated, pilot in command - stall - inadvertent, pilot in command (cause) ## Analysis A glider launch was being conducted, using a vehicle tow and a mechanical advantage/pulley arrangement. During the launch, the tow rope became snagged on vegetation (alfalfa crop stuble), then slack developed in the tow rope as the rope came loose from the stuble. When slack was taken up, it 'jerked' the glider, which pitched up. The pilot released the tow rope, but the glider settled (stall) and rolled approximately 25 degrees left wing down. The wing contacted the ground, and the glider spun around and came to rest facing backwards. This resulted in substantial damage to the wings and fuselage. ## Factual narrative On September 14, 1997, at 1745 mountain daylight time, an AS + LTD model AC-4 glider, N3021, settled after an auto launch, struck one wing tip on the ground, and crashed on the Canfield Ranch, 10 miles southwest of Sundance, Wyoming. The certified flight instructor pilot was not injured and the glider sustained substantial damage. Visual meteorological conditions existed and no flight plan was filed for this personal flight conducted under Title 14 CFR Part 91. The flight was originating at the time of the accident. According to the attached pilot statement and a telephone interview with the pilot, this was the fourth flight of the day, all of which used a vehicle tow pulley system for launch. The mechanical advantage of this system was 3 to 1, the same as used on the third launch and the wind was a right quartering head wind estimated to be 5 to 7 knots. The pilot said that during the tow, the rope became entangled in some alfalfa stubble. When it came loose from the stubble some slack occurred. When the slack was taken up it caused the tow rope to "jerk" the glider, which then pitched up. Altitude at the time was about one wing span, according to the pilot, and about 800 feet into the takeoff run. The pilot said he released the tow and attempted to set up for a landing; however, the left wing dropped and the glider struck the ground with the left wing in about a 25 degree left wing down attitude. The glider reversed heading and came to rest approximately 900 feet from where the takeoff had started. (See attached narrative and drawing). Substantial damage was done to the fuselage and both wings. ## Aircraft - Registration: [N3021](https://openairdocs.org/aircraft/N3021), registered now, S/N 023 (OpenAirDocs) - Reported make and model: AS+ Ltd AC-4B - Registry model: [AS+ AC 4](https://openairdocs.org/model/as-plus-ac-4) (registry code 05628R1) (OpenAirDocs) - Category: Glider - Serial number: 23 - Airframe hours: 8 - Engines: unknown - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Gary W. Hewett - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, July 20, 1997, 4 hours before - Airport: Private Strip, runway 22, 2,200 × 500 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; airline transport, flight instructor; airplane ratings: single-engine sea, multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: center; flight hours: 4,551 total, 3 in this make and model, 2,836 as pilot in command, 4 in the last 90 days, 3 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 43 °F - Altimeter: 29.00 inHg - Observed at: GCC, 47 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 19970914047149A](https://openairdocs.org/incident/19970914047149A), Sep 14, 1997: Sundance, WY, Substantial damage. (-16) Glider launch system failed to propel aircraft into flight, pilot released tow cable to maintain aircraft control and avoid injury. 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.