ASN Wikibase Occurrence # 197098
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| Date: | Wednesday 2 August 2017 |
| Time: | 07:20 |
| Type: | Sikorsky S-97 Raider |
| Owner/operator: | Sikorsky Aircraft Corp. |
| Registration: | N971SK |
| MSN: | 0001 |
| Year of manufacture: | 2014 |
| Total airframe hrs: | 104 hours |
| Engine model: | General Electric YT706-GE-700R |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | William P Gwinn Airport, Palm Beach County, FL -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Test |
| Departure airport: | Jupiter, FL (06FA) |
| Jupiter, FL (06FA) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The airline transport pilot of the experimental, fly-by-wire-equipped helicopter was taxiing to the runway for a test flight. During the taxi, he had commanded a high collective pitch and a slight forward cyclic pitch stick, and the helicopter was light on its wheels; as a result, the flight control computer transitioned from ground mode to flight mode. The slight forward pitch stick in combination with flight control mode resulted in a nose down pitch rate. The pilot took corrective action, inputting aft cyclic stick. The initial pitch axis correction led to a small initial left roll. The pilot countered the small left roll rate with an appropriate magnitude right stick input. In conjunction with the right stick input, the pilot raised the collective to increase the helicopter's altitude. The helicopter’s right roll response to the right stick input was larger than expected, and the pilot countered with a large left stick input. The helicopter’s left roll response was also larger than expected. The helicopter bank angles quickly increased, and the pilot rapidly lowered the collective to land the helicopter. The rapid left and right rolls resulted in upper and lower rotor contact, which damaged all rotor blades. The investigation determined that the larger-than-expected roll response to the pilot’s cyclic stick input was the unintended result of a flight control system design change that resulted in an increase in cyclic stick sensitivity in the roll axis during the transition from ground control mode to flight mode.
Probable Cause: A design change in the helicopter's fly-by-wire control system that resulted in an increase in the sensitivity of the cyclic stick while transitioning from ground to flight mode, magnifying the pilot's control inputs, which resulted in unintentional over control in the roll axis, upper and lower main rotor contact, and damage to the rotor blades.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N971SK
Location
Media:
#OTD 2017 A design change in the FBW control system magnified the pilot's inputs, resulting in unintentional over control in roll and so the main rotor tips struck the ground. https://t.co/4YkMikFrf3 #accident #flighttest #aviationsafety #flightsafety pic.twitter.com/4yB9Eki8N6
— Aerossurance (@Aerossurance) August 2, 2023
#Sikorsky S-97 incident https://t.co/GKjhyttnYO #flightsafety
— Aerossurance (@Aerossurance) 2 août 2017
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 02-Aug-2017 21:58 | Iceman 29 | Added |
| 02-Aug-2017 22:26 | Aerossurance | Updated [Aircraft type, Location, Embed code] |
| 03-Aug-2017 05:28 | Aerossurance | Updated [Time] |
| 03-Aug-2017 10:47 | Iceman 29 | Updated [Registration, Source, Embed code] |
| 11-Sep-2017 17:57 | Aerossurance | Updated [Time, Registration, Cn, Location, Phase, Departure airport, Destination airport, Source, Damage, Narrative] |
| 11-Sep-2017 18:01 | Aerossurance | Updated [Location, Narrative] |
| 11-Sep-2017 21:18 | Aerossurance | Updated [Source, Narrative] |
| 01-May-2019 15:43 | Aerossurance | Updated [Source, Narrative] |
| 15-Jul-2019 18:03 | ASN Update Bot | Updated [Time, Cn, Operator, Nature, Departure airport, Destination airport, Source, Embed code, Narrative, Accident report, ] |
| 15-Jul-2019 18:36 | harro | Updated [Nature, Source, Embed code, Narrative, Accident report, ] |
| 15-Jul-2019 18:36 | harro | Updated [Operator] |
| 02-Aug-2023 07:27 | Aerossurance | Updated [[Operator]] |
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