France A343 at Bogota on Aug 18th 2017, windshear during rotation for takeoff

Last Update: December 6, 2019 / 16:13:38 GMT/Zulu time

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Incident Facts

Date of incident
Aug 18, 2017

Classification
Report

Airline
Air France

Flight number
AF-681

Aircraft Registration
F-GLZO

Aircraft Type
Airbus A340-300

ICAO Type Designator
A343

An Air France Airbus A340-300, registration F-GLZO performing flight AF-681 from Bogota (Colombia) to Paris Charles de Gaulle (France) with 219 passengers and 10 crew, was accelerating for takeoff from Bogota's runway 13R, before the takeoff roll the runway anemometer showed winds from 211 degrees at 1 knots. During the takeoff roll the winds changed to a head wind component of about 13 knots. At 138 KIAS the captain began to rotate the aircraft for takeoff, when the winds changed to a tail wind component of 12 knots, the IAS reduced by 6 knots. The aircraft became airborne, after lift off the winds further changed to a 25 knots tail wind component and a downdraft component of 4 knots, while the IAS reduced to 128 KIAS. Six seconds after the main gear left the ground a windshear aural warning occurred three times, a red WINDSHEAR warning from the FMGEC was displayed on the primary flight displays for 15 seconds. The captain held the pitch attitude between 11 and 13 degrees, the aircraft remained stabled at 5 feet AGL, the captain increased nose up inputs until Alpha Prot activated for 4 seconds. The tailwind component then began to decrease, the IAS began to increase and the aircraft began to climb again crossing the runway end at 58 feet AGL and the subsequent climb profile had the aircraft pass all obstacles with sufficient margin. 21 seconds after becoming airborne the windshear warning stopped at 193 feet AGL, a pitch of 13 degrees nose up. 5 seconds later, at 258 feet AGL, the IAS increased through 145 KIAS, which had been computed as V2. The aircraft climbed without further incident, the crew reported the windshear to ATC (this report prompted the next crew to wait for 3 minutes before commencing their takeoff) and continued to Paris without further incident.

The BEA released their final report, however, did not release a formal conclusion of their investigation report but following lessons learned from the occurrence:

Management of risk of windshear at take-off: prevention-oriented strategy

Windshear, a headwind component changing to a tailwind component, associated with a downdraft wind gradient, as was the case in the event, results in a reduction in the air speed and lift. When such a phenomenon occurs shortly before or shortly after the rotation, the associated risks are the loss of control or collision with obstacles.

During this event, once the aeroplane had entered the windshear, as the thrust was already set to TOGA, the crew had little means available to them to restore safety margins and could only act on the aeroplane’s pitch to prevent both stalling and collision with the ground or obstacles. In this case, the flight envelope protections, notably in angle of attack, leave the crew the possibility of applying a stick input up to full nose up deflection if necessary (refer to the procedure described in section 2.6).

The possible actions to limit the risks identified above therefore mainly take place before the aeroplane enters the windshear.

Assessment of windshear risk at Bogotá El Dorado airport

There are no statistics produced by the local authorities on the number of windshear occurrences per year at Bogotá El Dorado airport. At this airport, take-offs by long-haul aeroplanes often occur at the performance limit which may compound the consequences of a windshear at take-off. In addition, this airport is not equipped with equipment to detect these phenomena which are associated with multiple risks as described above. A statistical study of the windshear at Bogotá El Dorado airport would make it possible to decide if means are to be implemented to limit these risks.

Consequently, the BEA recommends that:

- the Civil Aviation Authority of Colombia (Unidad Administrativa Especial de Aeronáutica Civil) assess the number of windshears per year at Bogotá El Dorado airport, their strength and the conditions conducive to their appearance. [Recommendation FRAN 2019-035]

€- the Civil Aviation Authority of Colombia assess, according to the results of the abovementioned study, the relevance of equipping Bogotá El Dorado airport with systems designed to detect these phenomena and warn the air traffic control of them. [Recommendation FRAN 2019-0036]

Wind data provided to crews by air traffic control

The crew’s flight file did not contain any message indicating the presence of windshear. In addition, the Predictive Warning System (PWS) did not detect the windshear despite its strength, its location on the aeroplane’s axis and the presence of rainfall. The crew therefore mainly relied on the information transmitted by the air traffic controllers for assessing the risk at the time of take-off.

The controllers had wind data at the four runway thresholds but did not give this to the crew in the take-off clearance. More generally, this information is not systematically communicated. The investigation showed that this data, indicating a continuing difference in wind speed and direction between thresholds 13 and thresholds 31, at the time of the event, was the only data which could have warned of a windshear risk.

Following this serious incident, Air France issued an operational directive with a COMPANY NOTAM requiring crews to ask the controller for the wind at the two thresholds of the runway used and to take into account the most unfavourable wind before take-off. This NOTAM was inserted in all the flight files to Bogotá on 25 August 2017, six days after the serious incident. In addition, the Air France crews now have the wind measured at the four runway thresholds in the cockpit via their PILOTPAD. This data could benefit all the operators operating at this airport.

Consequently, the BEA recommends that:

€- the Civil Aviation Authority of Colombia (Unidad Administrativa Especial de Aeronáutica Civil) ensure that a procedure is set up by the Bogotá air traffic control unit with the aim of supplying crews, in the take-off clearances, with the wind measured at the two thresholds of the runway in service when the weather situation is such that windshear is likely (in particular in the presence of storms, towering cumulus or cumulonimbus close to the airport) and that the Bogotá airport aeronautical information warns operators of the risk associated with these particular situations. [Recommendation FRAN 2019-037]

Communication language with air traffic control

During the event, only the exchanges between the air traffic control and the crew of the Air France flight were in English, all the others were in Spanish. The ontroller asked Spanishspeaking crews several times for information on the weather situation encountered during the take-off.

Likewise, the controller cleared several crews for take-off shortly before the Air France flight and gave them the latest wind information each time. This information, transmitted in Spanish, could have been of interest to the crew of this serious incident.

Even if these exchanges did not mention the presence of windshear, the crew of the Air France flight did not have access to the information exchanged with the air traffic controller about the weather situation and the sequencing of the departures, which limited the crew’s situational awareness.
Incident Facts

Date of incident
Aug 18, 2017

Classification
Report

Airline
Air France

Flight number
AF-681

Aircraft Registration
F-GLZO

Aircraft Type
Airbus A340-300

ICAO Type Designator
A343

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