Warning placard intended to cut Dash 8 overspeed hazard

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Canadian regulators have ordered operators of Bombardier Dash 8 turboprops to place warning labels in the cockpit to guard against accidental propeller overspeed.

The order is aimed at preventing pilots from unintentionally moving the throttle levers on some Dash 8s below the flight-idle position, which carries the risk of overspeed and damage to the engines.

Norwegian investigators attributed a serious February 2006 incident, involving a near total power loss on a Wideroe Dash 8-100, to such inadvertent action by the crew. The aircraft suffered overspeed in both engines, severely damaging one of them.

Investigation into the fatal crash, in Papua New Guinea, of an Airlines PNG Dash 8-100 in October 2011 also cited the simultaneous overspeed of both propellers, before the flight crew shut down both engines.

Transport Canada says it will mandate a lock-out modification being developed by Bombardier, which will prevent pilots pulling the throttle levers into the wrong setting during flight.

But until then it is ordering interim action to mitigate the risk, stating that operators must comply with a Bombardier service bulletin covering installation of a warning label in the cockpit.

Transport Canada says the measure must be carried out on Dash 8-100 to -300 aircraft within 400 flight hours or 60 days.

Swedish authorities ordered the installation of a manually-operated stop mechanism on the Saab 340 turboprop in 1995, after a warning placard failed to prevent a similar throttle-lever incident and subsequent engine flame-out.