By Darren Shannon in Washington DC
All operators of Saab 340 series aircraft have been instructed by the US National Transportation Safety Board (NTSB) to adopt new operating standards during icing conditions.
In a recommendation, the safety board says the US Federal Aviation Administration should require all 340 pilots to maintain a minimum operating airspeed of 45% above stall speed (1.45 x VS) during icing encounters and exit from such conditions as soon as that performance level is unsustainable.
The NTSB also calls for the installation of modified stall protection logic in 340s certificated for flight into known icing conditions, and the installation of an icing detection system on all such aircraft.
"All operators of turbopropeller-driven aircraft [must] instruct pilots, except during intermittent periods of high workload, to disengage the autopilot and fly the aircraft manually when operating in icing conditions," adds the NTSB in its recommendation. The FAA should also convene a panel of specialists, including NASA, to determine if a requirement for the installation of low-airspeed alert systems in aircraft engaged in commercial operations under Part 121 and 135 regulations is feasible.