Russian Accident Fuels Concerns
In November, a Grand Caravan was on approach to Domodedovo International Airport in Moscow when it dove to the ground from almost 5,000 feet. The difference with this flight was that Russian air regs required the Caravan to carry both cockpit voice and flight data recorders and investigators have been able to piece together the final moments of the flight in disturbing detail. The pilot reported "light" icing to Moscow tower (the CVR records the two pilots talking between themselves about "severe" icing) as they leveled off near their assigned altitude of 4,900 feet. The data recorder shows the airspeed dropping to 102 knots (the spec sheet stall speed is 61 knots) before the aircraft stalls and spirals earthward (hitting speeds of 226 knots in the dive). The POH establishes a minimum speed of 105 knots during icing conditions but the NTSB says, for now, that's cutting it too close. In its recommendations, the board notes that the Moscow Caravan dropped only three knots below the minimum speed before "departing controlled flight." It says it's imperative the FAA figure out just what the safe speed in icing is for the Caravan, but, in the meantime, a conservative minimum speed of 120 knots "is critical for the continued safe flight of the Cessna 208 in icing conditions." The report also notes that the Russian Caravan was on autopilot until it automatically disconnected when the plane fell out of control. Had the pilots been flying manually, the letter suggests, they might have felt the impending stall in the controls. It's therefore recommending the autopilot be switched off in icing conditions.