Sikorsky S-97A N971SK

Summary

On 2 August 2017 at about 11:20 local time, a Sikorsky S-97A registered N971SK was involved in an accident near Jupiter, Florida, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

2 August 2017 at 11:20

Classification

Accident

Location

Jupiter, Florida, United States

Nearest airport

William P. Gwynn (06FA)

Coordinates

26.9081, -80.3283

Aircraft

Sikorsky S-97A

Registration

N971SK

Category

Helicopter

Year built

2014

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Flight Test

Phase of flight

Not recorded

Route

Jupiter → Jupiter

Aircraft damage

Substantial

Weather

VMC

Light

Dawn

NTSB number

ERA17LA263

2 people had minor injuries.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.