The Australian Transport Safety Bureau (ATSB) has recommended that Saab modifies the stall warning system on the Saab 340 fleet to provide sufficient warning of an impending stall during icing conditions, writes Emma Kelly.
The recommendation follows publication of the ATSB's report on a "serious incident" involving a Saab 340B in June 2002, when the crew did not receive a stall warning and lost control because of low airspeed and airframe icing when the aircraft was on autopilot. Control was lost at 3,810ft (1,150m) and the aircraft descended to 112ft above ground level before control was regained. The ATSB found that the aircraft can stall before activation of the stall warning system if there is ice on the wing and noted reports of similar incidents involving the type.
Saab 340s in Canada - uniquely - are required to have a manually selected ice stall warning option, but this simply raises the airspeed at which stall warning is given if the crew notice that the aircraft is in icing conditions and activate it.
The 340's certificating authority, the Swedish civil aviation administration, says it will study the report with Saab to see if any clarification to the icing section in the aircraft's operating manual is needed. But the authority's Ingmar Hedblom, certification manager for the 340, says the problem exists for all aircraft types in icing conditions, and it does not plan to make any further recommendations to the European Aviation Safety Agency.
Aviation authorities from Brazil and the USA have issued an emergency airworthiness directive requiring all operators of Embraer ERJ-145 family aircraft to inspect aft rudder control rods before further flight. This follows an aborted take-off by an American Eagle ERJ-135 because of a failure of both upper and lower control rods.
Source: Flight International
