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Summary

Summary

On 11 November, 1998, VH-LPI, a Saab 340A turbo-propeller aircraft was enroute between Albury, NSW and Melbourne, Victoria on a scheduled public transport service. The aircraft was operating in instrument meteorological conditions and had accumulated a deposit of ice on the wings and windscreen wipers. The crew interpreted this ice deposit as being less than that required for them to activate the de-ice systems on the wing leading edges, in accordance with the aircraft flight manual procedures. As the aircraft approached Melbourne the crew were instructed to enter a holding pattern at Eildon Weir. The crew acknowledged this instruction and reduced power in order to slow the aircraft to the holding pattern airspeed. The crew subsequently allowed the airspeed to fall below the target speed of 154 knots, and despite remedial action, did not regain the target speed.

Shortly after the aircraft entered the holding pattern it suffered an aerodynamic stall and rolled approximately 126 degrees to the left and pitched nose down to approximately 35 degrees. The crew regained control after approximately 10 seconds. The aircraft lost 2,300 ft of altitude. The crew was not provided with a stall warning prior to the stall.

The investigation found that despite being certified to all required certification standards at the time, the Saab 340 aircraft can suffer from an aerodynamic stall whilst operating in icing conditions without the required warnings being provided to flight crew. This problem had been highlighted when the aircraft was introduced to operations in Canada and as a result a modified stall warning system was mandated for aircraft operated in Canada. This modification was not fitted to other Saab 340 aircraft worldwide.

The investigation also found a number of other occurrences involving Saab 340 aircraft where little or no stall warning had been provided to the crew while operating in icing conditions. Deficiencies were found in the operator's manuals, procedures and training.

During the course of the investigation, a number of recommendations were made in 1998 and 1999 concerning flight in icing conditions and modifications to the Saab 340 stall warning system. The completion of the investigation and finalisation of the report were the result of extensive consultation with the aircraft manufacturer and certification authorities.

 
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