# NTSB DFW07CA186: Eurocopter Deutschland BK117, N911R, Slaton, TX, August 20, 2007 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: August 20, 2007, 09:30 local (15:30 UTC) - Place: Slaton, TX - Coordinates: 33.489444, -101.650833 - Nearby events: https://openairdocs.org/map.md?lat=33.4894&lon=-101.6508&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report October 31, 2007 - Report: Approved by Office Director - Parties: Lubbock, Texas - NTSB case key (mKey): 66475 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DFW07CA186 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/66475/pdf - Page: https://openairdocs.org/ntsb/DFW07CA186 ## Probable cause The pilot's failure to maintain control of the hovering helicopter and the flight instructor's improper supervision of the flight. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with object, hover - in ground effect - terrain condition - congested/confined area - aircraft control - not maintained, copilot/second pilot (cause) - terrain condition - grass - object - tree(s) - supervision - improper, pilot in command(cfi) (cause) ## Analysis The helicopter drifted backwards during a confined area operations training and the tail rotor blades struck tree branches while hovering over tall grass. The 11,330 hour flight instructor and the 16,800 hour pilot receiving instruction reported that they were both familiar with the training area being used, the flight was properly briefed, and they had both worked together as a crew in the past. The crew reported that the pilot performed a high recon of the landing area, noting the surface winds, approach and departure paths, and the conditions of the landing zone. The approach was planned to terminate at a hover. The grass at the landing zone is normally less than a foot long; however, due to the record rainfall this year, the grass was 3-to-4 feet tall. Both pilots underestimated the effects of prolonged hovering over tall grass. The tall-waving grass disoriented the pilot and allowed the helicopter to drift into the trees. The flight instructor was clearing the left side of the helicopter during the approach and hover, but was unable to react in time to take the flight controls to stop the drift. The flight crew immediately landed the helicopter in the confined area when they felt a vibration from the tail rotor. The helicopter was recovered to the operator's maintenance facility for damage assessment. Examination of the helicopter by the flight crew, the operator, and the FAA inspector, confirmed that both tail rotor blades were destroyed, the mounting bolts for the tail rotor 90 degree box were damaged or broken, and the tail fin gearbox mounting spar was also damaged. ## Factual narrative The helicopter drifted backwards during a confined area operations training and the tail rotor blades struck tree branches while hovering over tall grass. The 11,330 hour flight instructor and the 16,800 hour pilot receiving instruction reported that they were both familiar with the training area being used, the flight was properly briefed, and they had both worked together as a crew in the past. The crew reported that the pilot performed a high recon of the landing area, noting the surface winds, approach and departure paths, and the conditions of the landing zone. The approach was planned to terminate at a hover. The grass at the landing zone is normally less than a foot long; however, due to the record rainfall this year, the grass was 3-to-4 feet tall. Both pilots underestimated the effects of prolonged hovering over tall grass. The tall-waving grass disoriented the pilot and allowed the helicopter to drift into the trees. The flight instructor was clearing the left side of the helicopter during the approach and hover, but was unable to react in time to take the flight controls to stop the drift. The flight crew immediately landed the helicopter in the confined area when they felt a vibration from the tail rotor. The helicopter was recovered to the operator's maintenance facility for damage assessment. Examination of the helicopter by the flight crew, the operator, and the FAA inspector, confirmed that both tail rotor blades were destroyed, the mounting bolts for the tail rotor 90 degree box were damaged or broken, and the tail fin gearbox mounting spar was also damaged. ## Aircraft - Registration: N911R (not matched to a registry record) - Reported make and model: Eurocopter Deutschland BK117 - Category: Helicopter - Serial number: 7502 - Airframe hours: 11456 - Engines: Turbomeca Ariel 1E2 734 horsepower turbo shaft; Turbomeca Ariel 1E2 734 horsepower turbo shaft - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Covenant Health System, dba AeroCare, doing business as AeroCare - Registered owner: Covenant Health System - Airworthiness certificate: Standard, Transport - Last inspection: AAIP, July 1, 2007 - Departed: F49, SLATON, TX - Destination: LBB, LUBBOCK, TX - Flight plan: Company VFR - Airport: LBB, Lubbock Intl ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 35; injuries: none; airline transport; instrument ratings: helicopter; medical: class 2, with waivers/limitations; seat: left; flight hours: 11,300 total, 3,648 in this make and model, 10,600 as pilot in command, 105 in the last 90 days, 35 in the last 30 days, 1 in the last 24 hours - Co-pilot; age 56; injuries: none; flight instructor, commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, with waivers/limitations; last flight review August 1, 2006; seat: right; flight hours: 16,800 total, 2,510 in this make and model, 14,900 as pilot in command, 1 in the last 90 days, 1 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 66 °F - Altimeter: 29.94 inHg - Observed at: KLBB, 13 nm away 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.