Pilot Debrief

BOEING 767-300 near Ni'ihau, HI — 2011-02-10

Final reportWPR11LA139
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Date
2011-02-10
Location
Ni'ihau, HI, USA
Airport
PHNL
Aircraft
BOEING 767-300
Registration
JA603J
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Descent

Probable cause

An encounter with unanticipated convectively induced windshear and turbulence during descent.

NTSB narrative

As the airplane descended from about 38,000 feet, the flight crew observed that they had a tailwind of between 60 and 70 knots and that cumulonimbus clouds were ahead of the airplane. Descending through 34,668 feet, the tailwind suddenly decreased and the indicated speed of the airplane quickly increased. The captain activated the speed brakes and disengaged the autopilot. Subsequently, the airplane began to slow. As the captain was slowly retarding the speed brakes, the airplane started to climb and the captain slowly lowered the nose of the airplane. The digital flight data recorder revealed that over a 30-second period the airplane’s vertical acceleration decreased to 0.75 g, then increased to 2.33 g, decreased to 0.05 g, then stabilized at 0.9 g (normal). During the event, one passenger broke her femur; two cabin attendants and four passengers received minor injuries. The airplane was not damaged. Convective activity was located immediately west of where the event occurred, likely blocking the wind flow and causing a wave-like disturbance downstream of the storms, which would result in unanticipated convectively induced turbulence. Since the event occurred in clear air downstream of the cumulonimbus clouds, the airplane likely encountered an undulating turbulence under a strong temperature inversion and strong windshear. The turbulence was not predicted by weather forecasters.

Analysis

Primary failure mode
Environmental
First missed decision gate
Avoiding descent through areas with predicted turbulence could have prevented injuries.

NTSB coding

Evidence available

  • FDR / data
  • 12 docket documents
View NTSB final reportView NTSB docket

Docket documents12

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BOEING 767-300 near Ni'ihau, HI — 2011-02-10 · Pilot Debrief