TAM A332 over Atlantic on Sep 2nd 2013, turbulence injures 15

Last Update: May 18, 2018 / 17:22:24 GMT/Zulu time

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Incident Facts

Date of incident
Sep 2, 2013

Classification
Accident

Cause
Turbulence

Airline
TAM Linhas Aereas

Flight number
JJ-8065

Departure
Madrid, Spain

Destination
Sao Paulo Guarulhos, Brazil

Aircraft Registration
PT-MVL

Aircraft Type
Airbus A330-200

ICAO Type Designator
A332

A TAM Linhas Aereas Airbus A330-200, registration PT-MVL performing flight JJ-8065 (dep Sep 1st) from Madrid,SP (Spain) to Sao Paulo Guarulhos,SP (Brazil) with 168 passengers and 16 crew, was enroute at FL400 over the Atlantic just south of the equator and about 250nm northeast of Fortaleza,CE (Brazil) when the aircraft encountered turbulence causing injuries to 15 occupants. The crew decided to divert to Fortaleza,CE (Brazil) for a safe landing on runway 13 about 45 minutes later. The injured were taken to hospitals.

The airline confirmed 12 passengers and crew received injuries, all but two could be discharged from hospital care a short time later, 2 remain in hospital care for observation. The flight is estimated to continue after about 12 hours on the ground in Fortaleza after a replacement crew has been flown to Fortaleza.

Passengers reported many on board were asleep when the aircraft jolted causing every loose item and unstrapped human to hit the cabin ceiling.

On Sep 11th 2013 the BEA reported in their weekly bulletin, 12 passengers and 2 crew received minor injuries, one more cabin crew member received serious injuries (broken arm).

On May 18th 2018 Brazil's CENIPA released their final report concluding the probable contributing factors causing the accident were:

- Control skills – undetermined.

The limits of the device entry and the Attack Protection Angle have been exceeded, causing the autopilot to disengage. According to FDR data, the pilot attempted to counteract the effects of the turbulence, with Sidestick applications opposed to the aircraft's attitude changes, which may have contributed to increase the effects caused by turbulence.

- Adverse meteorological conditions – a contributor.

The prevailing meteorology constituted a critical factor for the event, with characteristics of intense vertical currents of air, great variation of intensity and direction that were provoked directly by the intense and fast convective process of development of the CB cell. It was located at a horizontal distance, less than 20 NM and with cloud tops at approximately 3,000 ft. below the flown route.

- Other – undetermined.

- Radar TILT Adjustment - undetermined.

The adjustment of the radar control panel to a range of 80 NM (PF / PNF) with a TILT of -1° and the absence of reflectivity in the upper section of the turbulence dome at the time of the accident may have corroborated for the entry of the aircraft into a region of severe turbulence.

CENIPA reported one flight attendant and two passengers received serious injuries, 2 flight attendants and 10 passengers received minor injuries.

A SIGMET had been issued prior to departure of the aircraft indicating thunderstorms raising up to FL450 in the accident area. However, the windchart predicted northeasterly winds at 15-20 knots discarding the possibility of severe turbulence. Moderate convective activity was forecast for the ITCZ Intertropical Convergence Zone.

CENIPA analysed:

During the cruise phase over the Atlantic, at 0254 a.m. (UTC), keeping the FL400, on the UN741 airfield, near the NANIK position, suddenly the aircraft was submitted to severe turbulence, with presence of Santelmo fire and hail noise, without any indication of any adverse formation on the radar screen.

Twelve passengers and three crew members were injured, but one flight attendant and two passengers suffered serious injuries.

Both the crew member and the passengers who suffered serious injuries were not wearing seat belts. The injured crewman was standing, working in the galley area during the incident.

The "wear belts" light was not ON during the turbulence, since, according to the crew, at the time of the event, there was no indication of bad weather either on the radar navigation display or on the visual observation of the route.

Nevertheless, both in the initial speech of the flight attendants and in the other warnings posted during the flight, the crew warned that the belts should be buckled while the passengers were seated.

In the analysis of the FDR flight data, it was possible to verify that the aircraft faced a region of turbulence, being recorded that, in a certain moment, it was submitted to a vertical load factor that varied between +1.9 G and -0.3 G, corresponding to a variation of 2.2 G in two seconds.

In that same time, an intense variation in the climb rate of up to + 4.601 ft. / min could be observed, causing the aircraft to release the FL 400 and reach FL 409. The aircraft was also submitted, for about 5 seconds, to a strong vertical air current that varied between +2,000 ft. / min (down-wind) and - 9,300 ft. / min (up-wind).

This substantial variation in Vertical Acceleration, seen on board when the passengers and the flight attendant were thrown against the upper inside part of the aircraft, was the cause of serious injuries suffered by some of the occupants of the aircraft, since they were not buckled.

According to the FDR, there was a disengagement of the autopilot during the occurrence. This disengagement, considered as involuntary, occurred due to the overcoming of the limits established for Sidestick input and by factors related to the Angle of Attack Protection. After 6 seconds, the PF re-engaged the autopilot.

The FDR revealed that the turbulence lasted for about 1 minute and 37 seconds, with a maximum intensity in a period of 15 seconds.

With respect to the weather data CENIPA analysed:

Airbus indicated that maintaining an adequate radar adjustment was associated with a negative TILT and a ground return at the top of the ND. To do so, it recommended a TILT of -3.5° for a range of 80NM and a TILT of -1.5° for a range of 160NM (Figure 12).

The airline, in turn, although it did not recommend what the ideal TILT for the selected range would be, indicated that the maintenance of an adequate radar adjustment was associated, in addition to the ground return at the top of the ND, to a permanent scanning of the meteorological conditions by means of a TILT change (Figure 14).

Considering that, according to the FDR, the range of the two pilots (PF and PNF) was set to 80NM and that the TILT selected was -1°. It could be inferred that this configuration of the on-board radar did not allow the detection of the CB cloud that was forming at the lower levels (FL 370) of the aircraft (Figure 13).

In order for the cloud to be noted at a distance that would allow the diversion, the ideal TILT, for a range of 80NM, according to the Airbus Flight Operations Briefing Notes, would be -3.5 ° (Figure 12).

At high altitudes, cloud cells may have ice crystals, which provide low reflectivity to the radar (higher reflectivities are present in the lower and middle levels, where water is present in the liquid state).

In this context, an inadequate TILT of the radar could lead to a scan only in the top position of the cloud (where ice crystals predominate), which could lead to a scan of the less reflective part of the bad weather cell, causing it to be underestimated or undetected.

In this sense, and considering that no adverse weather formations were detected or visualized on the radar screen at the time of the accident, it can be deduced that the aircraft would be flying over a cumulonimbus cloud, at FL 400. Its top was estimated in FL 370, in the development / maturity phase, as highlighted in the CPTEC satellite images (Figure 6).

From this, it can be concluded that the following factors may have contributed to the aircraft entering an area of heavy turbulence without any indication in the ND of the weather radar.

- The TILT (1° DN) was not with an ideal angle for the selected range (80NM);

- The aircraft flew over a region subjected to severe turbulence, known as turbulence dome, located above the visible top of a storm formation, of low radar reflexivity and without cloudiness;

- The aircraft did not keep a vertical separation of 5,000ft and a lateral of 20NM from a CB cloud formation, with a top above 35,000ft.

- The cloudiness with more significant humidity (with reasonable reflectivity) was approximately 3,000ft below the aircraft;

- The aircraft would be flying over a cumulonimbus cloud, at FL 400 with its top estimated in FL 370, in the development / maturity phase;
- There was no adequate use of the services provided by Flight Watch to allow the SIGMET message to be known, which alerted to the existence of thunderstorms with top at FL450.
Incident Facts

Date of incident
Sep 2, 2013

Classification
Accident

Cause
Turbulence

Airline
TAM Linhas Aereas

Flight number
JJ-8065

Departure
Madrid, Spain

Destination
Sao Paulo Guarulhos, Brazil

Aircraft Registration
PT-MVL

Aircraft Type
Airbus A330-200

ICAO Type Designator
A332

This article is published under license from Avherald.com. © of text by Avherald.com.
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