# NTSB WPR18LA170: Schweizer 269C, N557DC, Las Vegas, NV, June 13, 2018 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: June 13, 2018, 10:59 local (17:59 UTC) - Place: Las Vegas, NV - Coordinates: 36.210556, -115.194442 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.2106&lon=-115.1944&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Defining event: [Standing-engine(s) operating: Ground resonance](https://openairdocs.org/ntsb-events/232) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - SAIBs cited in the narratives: [SAIB SW-17-29](https://openairdocs.org/saib/SW-17-29) (OpenAirDocs) - NTSB case key (mKey): 97479 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18LA170 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97479/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97479 - Page: https://openairdocs.org/ntsb/WPR18LA170 ## Probable cause The pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Action: incorrect action selection](https://openairdocs.org/ntsb-findings/02041010): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Schweizer 269C, 1 case](https://openairdocs.org/ntsb-findings/02041010/cases.md?model=8059502), [All aircraft, 397 cases](https://openairdocs.org/ntsb-findings/02041010/cases.md) - [Knowledge: knowledge of procedures](https://openairdocs.org/ntsb-findings/02032010): Personnel issues › Experience/knowledge · Pilot (probable cause); cases with it: [Schweizer 269C, 1 case](https://openairdocs.org/ntsb-findings/02032010/cases.md?model=8059502), [All aircraft, 41 cases](https://openairdocs.org/ntsb-findings/02032010/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Schweizer 269C, 8 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=8059502), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Standing-engine(s) operating: Ground resonance](https://openairdocs.org/ntsb-events/232) (defining event); cases with it: [Schweizer 269C, 6 cases](https://openairdocs.org/ntsb-events/232/sequence.md?model=8059502), [All aircraft, 21 cases](https://openairdocs.org/ntsb-events/232/sequence.md) ## Analysis The pilot was preparing to depart in the helicopter on a local flight. He stated that he powered up the helicopter and that, with the engine/rotor rpm at the “very bottom of [the] green range” and the helicopter still on the ground, the helicopter began to vibrate. The vibrations worsened, and in response to the ground resonance, he lowered the collective and rolled off the throttle to abort the takeoff. The vibrations increased in severity and lasted about 20 seconds. The main rotor and engine then shut down, and the helicopter had rotated about 45° to the left. A nearby witness stated that the helicopter was shaking and that it never came to full power or left the ground. Postaccident examination of the helicopter, including the landing gear dampers, skid attachments, and main rotor blade dampers, revealed no anomalies that would have precluded normal operation. Further, the main rotor dampers were tested about 7 flight hours before the accident flight with no anomalies noted. The Federal Aviation Administration’s (FAA) Helicopter Flying Handbook (FAA-H-8083-21A) stated the following about ground resonance: "If the rpm is low, the only corrective action to stop ground resonance is to close the throttle immediately and fully lower the collective to place the blades in low pitch. If the rpm is in the normal operating range, fly the helicopter off the ground." However, this guidance for ground resonance corrective action was listed in the same paragraph after discussion of hard contact with the ground and when one other landing gear strikes the surface. Although the pilot noted that the engine/rotor rpm was at the very bottom of the green range, the rpm was still in the normal operating range; his decision to lower the collective instead of taking off led to increased (and/or continued) ground resonance vibrations and the subsequent substantial damage to the fuselage. ## Factual narrative On June 13, 2018, about 1059 Pacific daylight time, a Schweizer 269C helicopter, N557DC, was substantially damaged when it was involved in an accident near Las Vegas, Nevada. The pilot sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot was departing North Las Vegas Airport (VGT), Las Vegas, Nevada, destined for Perkins Field Airport (U08), Overton, Nevada. According to the pilot, he started the engine and, after performing startup and preflight checks, increased the engine/rotor rpm; the helicopter had not yet become light on the skids. He stated that, with the engine/rotor rpm at the “very bottom of [the] green range,” the helicopter began to vibrate while still on the ground. The vibrations initially seemed normal but then worsened. He stated that the helicopter was not yet at the point where he would proceed to hover, which he said would have included getting the helicopter light on the skids, lifting gradually, and having the engine/rotor rpm at the top half of the range. In response to the ground resonance, he lowered the collective and rolled off the throttle to abort the takeoff. The vibrations increased in severity and lasted about 20 seconds. The main rotor and engine then stopped, and the helicopter had rotated about 45° to the left. A nearby witness stated that the helicopter was shaking, with the main rotor blades “flopping up and down.” He said it never came to full power or left the ground and that the helicopter “destroyed itself.” Postaccident examination of the helicopter revealed substantial damage to the fuselage. Examination of the airframe revealed no anomalies or evidence of preimpact mechanical failure that would have precluded normal operation. Flight control continuity was established to the main rotor and tail rotor blades. All of the landing gear dampers were examined and tested within the specified pressure/charge range. No anomalies were observed on the skid attachments. Two main rotor dampers were separated from the main rotor blades and remained attached to the mast; visual examination revealed no anomalies. The attached main rotor damper was removed from the main rotor blade and was examined and tested with no anomalies noted. All of the main rotor blade dampers had been tested about 7 flight hours before the accident and met the specified criteria. Compliance was documented with a special airworthiness information bulletin on landing gear damper inspections (SAIB SW-17-29). The Federal Aviation Administration’s (FAA) Helicopter Flying Handbook in effect at the time of the accident (FAA-H-8083-21A), Chapter 11, Helicopter Emergencies and Hazards, stated the following regarding ground resonance: "If the rpm is low, the only corrective action to stop ground resonance is to close the throttle immediately and fully lower the collective to place the blades in low pitch. If the rpm is in the normal operating range, fly the helicopter off theground." This ground resonance corrective action guidance was listed in the same paragraph after discussion of hard contact with the ground and when one other landing gear strikes the surface. The pilot stated that there are no procedures in the pilot’s operating handbook for the helicopter make/model for dealing with ground resonance on startup and that his training focused on ground resonance during the transition from flight to hover and as the result of skid-to-ground hard contact. The pilot further stated that the FAA guidance in the Helicopter Flying Handbook was focused on ground resonance occurring on skid-to-ground hard contact when the helicopter was already in the air. He also cited the guidance in the handbook regarding corrective action when rpm was low of lowering the collective and closing the throttle. The pilot stated that he had not anticipated that ground resonance could develop so easily without lifting the helicopter. ## Aircraft - Registration: [N557DC](https://openairdocs.org/aircraft/N557DC), registered now, S/N S1630, built 1993 (OpenAirDocs) - Reported make and model: SCHWEIZER 269C (UNDESIGNAT) - Registry model: [Schweizer 269C](https://openairdocs.org/model/schweizer-269c) (registry code 8059502) (OpenAirDocs) - Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: S1630 - Year built: 1993 - Airframe hours: 5208.4 - Engines: Lycoming HIO-360-D1A 190 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 4, 2018 - Departed: VGT, Las Vegas, NV - Destination: U08, OVERTON, NV - Flight plan: VFR - Airport: VGT, North Las Vegas - Equipment: Handheld GPS, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; injuries: minor; private; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review May 9, 2017; seat: left; restraint: 4-point; flight hours: 1,120.9 total, 72 in this make and model, 970.5 as pilot in command, 3.7 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 97 °F, dew point 28 °F - Altimeter: 29.81 inHg - Observed at: KGVT ## 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 20180613007719A](https://openairdocs.org/incident/20180613007719A), Jun 13, 2018: Schweizer 269C, North Las Vegas, NV, Substantial damage. On June 13, 2018 at approximately 1146 PST, at North Las Vegas airport (kvgt), a 1993 Schweizer 269C sustained substantial damage due to ground resonance. The… ## Other investigations on N557DC (1) 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. - [NTSB CHI98LA021](https://openairdocs.org/ntsb/CHI98LA021), Oct 15, 1997: Schweizer 269C (N557DC), Grand Forks, ND, substantial damage. Probable cause: the pilot's inadequate preflight planning which resulted in a low fuel state, and his inability to see the wire which the helicopter contacted. Factors associated to the accident were the… ## Docket (6 files) The files NTSB released with the investigation on February 22, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97479. 13.8 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 9.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299745&FileExtension=pdf&FileName=2018-07-15%20NTSB%206210%20Final_Redacted-Rel.pdf - Airframe examination report (item 2, PDF, 3 pages, 330 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299434&FileExtension=pdf&FileName=WPR18LA170%20Airframe%20Examination-Rel.pdf - Record of email (item 3, PDF, 1 page, 28 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299180&FileExtension=pdf&FileName=Record%20of%20Email%20WPR18LA170-Rel.pdf - FAA helicopter flying handbook excerpts (item 4, PDF, 3 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299041&FileExtension=pdf&FileName=FAA%20Helicopter%20Flying%20Handbook%20Excerpts-Rel.pdf - Logbook excerpt (item 5, PDF, 1 page, 746 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299335&FileExtension=pdf&FileName=Logbook%20Exceprt_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=8299620&FileExtension=pdf&FileName=Wreckage%20Release%20Form_Redacted-Rel.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.