# NTSB SEA03LA160: Hughes 269C-1, N61442, Scappoose, OR, July 29, 2003 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: July 29, 2003, 16:30 local (23:30 UTC) - Place: Scappoose, OR - Coordinates: 45.770557, -122.861946 - Nearby events: https://openairdocs.org/map.md?lat=45.7706&lon=-122.8619&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report March 2, 2004 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 57593 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA03LA160 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/57593/pdf - Page: https://openairdocs.org/ntsb/SEA03LA160 ## Probable cause The helicopter encountering a ground resonance condition following a failure to maintain hovering flight. Contributing factors to the accident included the pilot's failure to maintain rotor RPM and the high pressure state of the landing gear shock absorbing dampers. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Altitude deviation,uncontrolled, hover - rotor rpm - not maintained, pilot in command (contributing factor) - Airframe/component/system failure/malfunction, standing - idling rotors - ground resonance - encountered, pilot in command (cause) - landing gear,main gear shock absorbing strut - high pressure (contributing factor) ## Analysis The pilot initiated the flight at maximum gross weight. After picking the helicopter up to a hover and stabilizing RPM, the RPM began to dip. Unable to recover RPM, the helicopter settled to the ground and subsequently encountered a ground resonance condition. After closing the throttle and lowering the collective, the helicopter began to shudder and turned 45 degrees to the left before the ground resonance condition subsided. The pilot was successful in his attempt to pick the helicopter up again to a hover, stabilizing engine RPM, coming to a stable hover, and sustaining rotor RPM during a left pedal turn. While attempting forward flight from this position the helicopter's RPM dipped again, resulting in the pilot having to set the helicopter down again. The aircraft entered ground resonance a second time, this time worse than the first, resulting in the helicopter being shook apart around the pilot and his passenger. Post-accident tests indicated that all four landing gear dampers, having failed a load stroke test, were set too hard, resulting in a ground resonance condition being encountered after a landing due to reduced rotor RPM. ## Factual narrative On July 29, 2003, approximately 1630 Pacific daylight time, a Hughes 269C-1 helicopter, N61442, was substantially damaged after impacting terrain while hovering at the Scappoose Industrial Airpark, Scappoose, Oregon. The commercial pilot and his sole passenger sustained minor injuries. The helicopter was registered to and operated by Hillsboro Aviation, Hillsboro, Oregon. Visual meteorological conditions prevailed for the 14 CFR Part 91 personal flight, and a flight plan was not filed. The flight was originating at the time of the accident, and its destination was the Portland-Hillsboro Airport, Hillsboro, Oregon. In a telephone interview with the NTSB investigator-in-charge (IIC), and according to the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the pilot reported that he initiated the flight at maximum gross weight and had not experienced any problems with the helicopter that day. The pilot stated that after boarding his passenger and checking his gauges, he "picked the helicopter up" and was stabilizing the RPM when he noticed that they started to "dip". The pilot reported that because he wasn't able to maintain RPM, the aircraft settled to the ground and subsequently encountered a ground resonance condition. The pilot stated that he then lowered collective and closed the throttle, but the helicopter continued to shake and turned about 45 degrees to the left. The pilot related that after the helicopter stopped shaking, he checked his gauges again and determined that he could attempt another takeoff. After lifting the aircraft off the ground a second time, he was able to stabilize the RPM in a hover. The pilot stated that he then initiated a left pedal turn, but when he attempted to fly forward he observed the rotor RPM dipping again, requiring him to land the helicopter a second time. The pilot reported that after the helicopter settled to the ground, he again lowered collective and rolled off throttle; however, the aircraft entered into a ground resonance condition again, this time worse than the first. The pilot further stated that, unable to get the helicopter out of ground resonance, "...it "shook itself apart around us." An FAA inspector, who traveled to the accident site, reported substantial damage to the mounts that retain the gearbox. The inspector also reported the main rotor blades had struck the top of the cabin and the tail boom. On August 20, 2003, subsequent to an examination of aircraft component parts, Schweizer Aircraft Corporation reported that all four of the aircraft's landing gear dampers were load stoke tested. Results of the examination indicated that the dampers failed the test, exceeding the specified load to reach the full compression point and higher than specified at the intermediate point. The dampers were not in compliance with specifications, being set too hard. Damage to the aircraft revealed that a ground resonance condition was encountered during landing with reduced rotor RPM. ## Aircraft - Registration: [N61442](https://openairdocs.org/deregistered/N61442-2003-10-27), registration cancelled 2003-10-27, S/N 0002, built 1995 (OpenAirDocs) - Reported make and model: Hughes 269C-1 - Registry model: [Schweizer 269C-1](https://openairdocs.org/model/schweizer-269c-1) (registry code 8059504) (OpenAirDocs) - Registry engine: [Lycoming HO-360 series](https://openairdocs.org/engine/lycoming-ho-360-series) (registry code 41513, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 0002 - Airframe hours: 3724.7 - Engines: Lycoming HO-360 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Hillsboro Aviation Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 17, 2003, 38 hours before - Departed: SBP, Scappoose, OR - Destination: HIO, Hillsboro, OR - Airport: SPB, Scappoose Industrial Airpark ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 26; injuries: minor; commercial; medical: class 3, valid medical--no waivers/lim.; last flight review February 7, 2003; seat: right; flight hours: 200 total, 187 in this make and model, 125 as pilot in command, 12 in the last 90 days, 6 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 350° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 99 °F, dew point 50 °F - Altimeter: 29.87 inHg - Observed at: PKX ## 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 20030729016659A](https://openairdocs.org/incident/20030729016659A), Jul 29, 2003: Hughes 269C1, Scappoose, OR, Substantial damage. (-23) Pilot attempted to depart from Scappoose, OR airport with 15 gallons of fuel and one pax on board. The pilot was unable to sustain hover flight due to a… 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.