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Summary
On 16 August 2005, flight WCW 708 took off from Tocumen (MPTO) international airport, Panama, at 05:59 UTC bound for «Le Lamentin Fort de France» (TFFF) international airport, Martinique, in instrument meteorological conditions. At half-distance, there was an area of stratocumulus type cloud formation with heavy precipitation. The aircraft was airworthy and had no mechanical defects. Once it had reached flight level 330, the aircraft’s speed began to decay until it reached stall speed. The aircraft then went into a stall and continued to lose altitude until it struck the ground, in a flat area defined with an altitude of 119 feet above sea level, near the village of Machiques, State of Zulia, Venezuela.
CONCLUSIONS (EXTRACTS)
The use of the anti-icing system caused a drop in the proportion of engine pressure ratio (EPR) that, given the performance conditions linked to the inappropriate configuration of the autothrust system in EPR Limit Cruise mode, affected the aircraft’s energy state, by causing a progressive loss of speed. Consequently, the aircraft was flying behind the power curve, which meant that the thrust required for the aircraft to maintain its speed was greater than that which it was producing.
The facts gathered show that the speed indications were not correctly monitored and, consequently, that the continuous loss of speed was not identified, at the time that the energy drop-off was occurring, leading the aircraft to flying behind the power curve with a high angle of attack.
The crew identified that a decrease in aircraft performance had been reached that required descending to flight level 310. While the aircraft was descending through flight level 317, the engines suffered a loss of thrust and at the same time the stick shaker activated one second before the stall warning.
At the moment the stall warning activated, the horizontal stabilizer trim began to increase its pitch-up action in a progressive manner until it reached the pitch-up stop.
None of the appropriate and necessary actions were taken in order to recover the aircraft’s energy state, the crew’s attention being focused on the engine instrument displays, even when the co-pilot said that he had identified the stall.
CAUSAL FACTOR:
The aerodynamic and performance conditions meant that the aircraft reached the critical condition that led to the stall situation. Subsequently, the crew’s resource management (CRM) and decision-making throughout the crisis were inappropriate. This situation was generated by the following factors:
Inadequate situational and environmental awareness, which meant that the crew were not fully aware of the situation in terms of aircraft performance and behaviour.
The lack of effective communication between the members of the flight crew which, during the decision-making process, reduced the chances of choosing appropriate and well–adapted alternatives and of setting priorities that corresponded to the actions to be taken in a critical or emergency situation (high altitude stall situation).
It must be said that the cause of the accident is linked to the absence of appropriate actions to prevent the aircraft from going into a stall situation, and, when the emergency situation occurred, and until impact with the ground, inappropriate setting of priorities in carrying out procedures. Subsequently, actions were taken that were outside the limits and parameters established in the manufacturer’s performance manual, along with inappropriate flight planning with no consideration for the meteorological aspects, in addition to the crew’s incorrect and late interpretation of the drop in the aircraft’s energy state. Thus, in terms of classification, the available facts lead to the conclusion that «human factors» were the cause of this accident.
The JIAAC Commission issued ten safety recommendations in its final report: seven to the aviation authorities, one to the aircraft manufacturer Boeing and two to the manufacturers of Flight Data Recorders.