Tway B738 near Tokyo on May 2nd 2019, turbulence injures flight attendant

Last Update: October 28, 2020 / 14:01:36 GMT/Zulu time

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Photo of t'way Airlines HL8021, Boeing 737-800 — t'way Airlines HL8021, Boeing 737-800 (Photo credit: contri / Flickr / License: CC by-sa)

Incident Facts

Date of incident
May 2, 2019

Classification
Accident

Cause
Turbulence injures flight attendant

Airline
t'way Airlines

Flight number
TW-201

Departure
Seoul, South Korea

Destination
Tokyo Narita, Japan

Aircraft Registration
HL8021

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

Airport
Narita International Airport, Tokyo

Airport ICAO Code
RJAA

A Tway Airlines Boeing 737-800, registration HL8021 performing flight TW-201 from Seoul (South Korea) to Tokyo Narita (Japan), was descending towards Tokyo about 60nm north of Tokyo's Narita Airport when the aircraft encountered turbulence. The aircraft continued to Tokyo and landed on runway 16L without further incident. A flight attendant needed to be taken to hospital.

Japan's TSB reported the flight attendant sustained a serious injury (fractured right ankle) and opened an investigation.

In 2020 Japan's TSB released their final report concluding the probable cause of the accident was:

In this accident, it is highly probable that the Aircraft was shaken by severe atmospheric disturbance it encountered during the descent, which caused Flight Attendant A who was ensuring safety in the cabin to lose her balance after feeling like floating and fall down severely backward, which resulted in her injury in the right ankle.

The JTSB described the sequence of events:

While the Aircraft was descending to Narita International Airport at FL 200, the PIC rang the chimes three times in accordance with FOM*3 and let four flight attendants begin preparing for the landing. Then, because the PIC visually recognized a belt of thin cloud ahead at around FL180, he, considering safety of the passengers, rang the chimes once and illuminated seat belt sign to inform flight attendants that light turbulence was predicted. Then, the Aircraft passed through the thin cloud. While passing through the thin cloud, the PIC and the FO felt not only a slight shaking but also the shaking that was much bigger than the average level they had expected.

At that time, flight attendants were ensuring safety in the cabin by confirming that the passengers fastened their seat belts. Because two flight attendants in the forward area of the cabin were taking care of with passengers who were in lavatory, a flight attendant covering the right aft area (hereinafter referred to as “Flight Attendant A”) was ensuring safety from aft galley to around the 10th row in the forward zone. When Flight Attendant A was near the 23rd row in the midst of returning to her seat, the Aircraft suddenly shook severely. After Flight Attendant A felt like floating by the shaking, she lost her balance and severely fell down backward. Flight Attendant A attempted to regain her feet promptly thereafter, however, she was unable to put some muscle due to a strong pain in her right ankle and took an empty seat (25D) in the aft (see Figure 2). There was no indication of echo on airborne weather radar or no turbulence information by PIREP. The descent was being
performed by autopilot.

Because Flight Attendant A the pain in the right ankle that was so severe with a significant swelling as to be unable to move, she judged that she was unable to continue her duties and decided to keep seated until the landing.

The Aircraft landed at Narita International Airport at around 10:15.

After the landing, Flight Attendant A was diagnosed at the hospital as right tibia and distal end of fibula fractured.

According to FDR records of the Aircraft from 09:57:12 until 09:57:14, roll angle changed in the range from 15.3 degrees to the left to 3.7 degrees to the right , and at the same time, vertical acceleration speed instantaneously changed in the range from +0.685G to +2.308G. Lateral acceleration speed at this time changed by 0.048G in the left direction and 0.074G in the right direction. Simultaneously, changes in longitudinal acceleration speed and air speed were also recorded. (See Figure 3)

This accident occurred at around 09:57 on May 2, 2019, at FL160 over Hitachiota City, Ibaraki Prefecture (36° 43’ 15’’ N, 140° 29’ 24’’ E).

The JTSB analysed:

(1) Shaking of the Aircraft

The shaking of the Aircraft at the time of the accident was to correspond to instantaneous changes in vertical acceleration speed and lateral acceleration speed during the period from 09:57:12 until 09:57:14 recorded in FDR, and it is highly probable that the Aircraft was descending in the thin cloud at this time. It is highly probable that the shaking caused Flight Attendant A who was ensuring safety in the cabin to lose her balance after feeling like floating and fall down severely backward, which resulted in her injury by an excessive force applied to the right ankle at that time.

(2) Meteorology

From domestic significant weather observation chart issued by the Japan Meteorological Agency, on the radar echo, from 5 mm or more to less than 10 mm precipitation per hour was observed near the accident site, and an hourly atmosphere analysis chart indicated Vertical Wind Shears near the accident site. It is probable that there might have occurred atmospheric disturbance near the accident site although there was no report of the PIREP regarding turbulence near the accident site within an hour before and after the accident.

(3) PIC’s Judgement on Meteorology It is probable that, even if the PIC predicted a chance to encounter a light turbulence, he did not expect to encounter a severe turbulence when passing the thin cloud, because meteorological data confirmed prior to the departure, the display of on-board weather radar and PIREP did not indicate turbulence along the flight route that might affect the flight.

When visually recognized the thin cloud, the PIC, considering safety of the passengers, notified the flight attendants by the seat belt fastening chimes that a light turbulence was predicted; however, it is probable that the atmospheric disturbance bigger than the flight crew had expected generated along the flight route.

Metars:
RJAA 020300Z 15005KT 120V190 9999 -SHRA FEW013 FEW020CB SCT025 BKN070 17/14 Q1005 TEMPO 3000 TSRA BR FEW008 BKN012 FEW020CB=
RJAA 020230Z 18005KT 150V220 9999 SHRA FEW013 SCT020 BKN070 18/13 Q1005 TEMPO 3000 TSRA BR FEW008 BKN012 FEW020CB=
RJAA 020200Z 17005KT 140V220 9999 -SHRA FEW013 SCT020 BKN050 18/14 Q1005 TEMPO 3000 TSRA BR FEW008 BKN012 FEW020CB RMK 1CU013 3CU020 7SC050 A2969=
RJAA 020130Z 17006KT 140V200 9999 -SHRA FEW013 SCT020 BKN050 18/14 Q1005 NOSIG=
RJAA 020100Z 23003KT 180V260 9999 FEW013 BKN050 18/14 Q1005 NOSIG=
RJAA 020030Z 21003KT 160V270 9999 FEW015 BKN040 17/14 Q1005 NOSIG=
RJAA 020000Z 19004KT 150V230 9999 FEW010 BKN040 17/15 Q1005 NOSIG=
RJAA 012330Z 20005KT 170V240 9999 FEW010 SCT040 BKN070 17/14 Q1004 NOSIG=
RJAA 012300Z 20005KT 170V230 9999 FEW007 BKN070 16/14 Q1004 NOSIG=
RJAA 012230Z 20006KT 9999 FEW007 BKN070 16/14 Q1003 NOSIG=
RJAA 012200Z 22005KT 190V250 9999 FEW030 SCT040 BKN070 15/14 Q1003 NOSIG=