Naysa AT72 near Tenerife on Mar 22nd 2015, turbulence injures 3

Last Update: November 12, 2015 / 14:15:52 GMT/Zulu time

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Incident Facts

Date of incident
Mar 22, 2015

Classification
Accident

Cause
Turbulence

Airline
Naysa

Flight number
NT-190

Departure
Tenerife Norte, Spain

Destination
Las Palmas, Spain

Aircraft Registration
EC-KGJ

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

A Naysa Avions de Transport Regional ATR-72-212A, registration EC-KGJ performing flight NT-190 from Tenerife Norte,CI to Las Palmas,CI (Spain) with 48 passengers and 4 crew, had just reached cruise level FL130 when the aircraft encountered turbulence causing three occupants to receive injuries. The aircraft continued to Las Palmas for a safe landing about 29 minutes after departure.

On Apr 8th 2015 Spain's CIAIAC reported that one passenger received serious, two cabin crew minor injuries when the aircraft encountered turbulence at FL130 about 15 minutes into the flight, all three people were standing at the time of the occurrence. The occurrence is being investigated by the CIAIAC.

On Apr 21st 2015 the French BEA reported in their weekly bulletin, that 3 occupants received serious injuries, the aircraft sustained substantial damage. The Spanish CIAIAC is investigating the accident.

On Nov 12th 2015 Spain's CIAIAC released their final report in Spanish concluding the probable cause of the accident was:

The accident occurred as result of the onset of convective turbulence producing a vertical acceleration of +2.54G. The turbulence could not be foreseen by the crew.

Contributing factors were:

- The operator's use of significant weather maps which did not show turbulence and icing in the area of the accident
- The stable atmosphere and smooth flight in the 7 minutes prior to the turbulence encounter
- The limitations of weather radar unable to detect certain atmospheric phenomens, e.g. turbulence

The CIAIAC reported that the while climbing through the usual cruise levels of 090 and 100 the crew observed cloud at those levels and decided to continue the climb until clear of cloud, which occurred at FL130. The aircraft subsequently encountered smooth flight for 7 minutes, the fasten seat belt sign was switched off about 2 minutes after levelling off (and 5 minutes prior to the accident). Then a sudden turbulence encounter produced a vertical acceleration of +2.54G throwing three people (both flight attendants and a passenger), who were standing, onto the floor causing injuries to the three.

The aircraft sustained no damage, the vertical acceleration exceeded limits specified by the aircraft manufacturer and required a structural inspection of the aircraft, which however did not find any issues.

The CIAIAC analysed that in accordance with inter-insular flights meteorologic charts were available showing significant weather between ground and FL150. Those maps, affecting four Naysa flights that day, showed the islands of Tenerife and Gran Canaria in an area of showers, storms, multiple layers of cloud, moderate to severe turbulence and icing with cumulonimbus and cumulus congestus cloud of large vertical extension.

Maps of medium to high altitude, available to the crew, were coherent though with differences, the maps were more favourable showing halves of both islands each in the clear and the other halves, being affected by adverse conditions, would improve during the day. The line separating the area of non-adverse weather and adverse weather went right through the location of the accident.

The medium level map identified an area of adverse weather enroute from Tenerife but showed Gran Canaria in the clear and did not indicate turbulence in the area of the accident, which might cause the crew to be less vigilant.

The CIAIAC analysed that forecasts are forecasts and a certain uncertainty remains, whether the prognosis turns into reality or not. "Despite all these potential factors it must be taken into account that the forecasts are an essential part of flight because they warn the crew of possible risks along the flight."

The CIAIAC analysed that once the flight is airborne the crew had two major sources of assessment of weather: visual observation and weather radar. During a fully developed night and no moonlight, as in this case, there is lack of contrast due to black in black. While lightning activity might provide a glimpse cloud cover without electrical activity could not be detected. Once the crew had climbed above cloud they were able to see the stars however. Hence the main source of weather information had to be the weather radar. The investigation was not able to retrieve reliable data about how the weather radar was used, the cockpit voice recorder also did not record references by either pilot to the weather radar. Crew testimony indicated that they had no observation alerting them to a possible significant weather.

The weather radar has limitations. The radar installed in EC-KGJ did not detect turbulences, however was capable of detecting rain. It is essential therefore to operate the radar continuously changing the proper scope and orientation of the antenna in order to achieve a compromise between the details in front of the aircraft and phenoma further into the distance.

The flight data recorder revealed that within 4 seconds after the turbulence encounter an ice build up was detected. This activation must have been associated with the presence of cloud. The indication activates only if a certain thickness of ice accreation is exceeded, the ice therefore must have started to accrete prior to the turbulence encounter. The ice warning continued for 3:40 minutes.

The CIAIAC analysed that another aircraft flying behind EC-KGJ did follow at an offset but did not deviate around the weather and passed the accident area in very close distance.

The CIAIAC analysed that the CVR showed the crew was continuously monitoring their flight and working all required checklists with proper task distribution amongst the crew. Following the accident the crew consistently collected information about the state of the injured and relayed the status to Air Traffic Control in order to have assistance available as soon as possible, ATC handled the flight with priority and ensured that proper assistance was available at Gran Canaria Airport when the aircraft arrived.
Incident Facts

Date of incident
Mar 22, 2015

Classification
Accident

Cause
Turbulence

Airline
Naysa

Flight number
NT-190

Departure
Tenerife Norte, Spain

Destination
Las Palmas, Spain

Aircraft Registration
EC-KGJ

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

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