Early retraction of the landing-gear on a Polish-operated Antonov An-26 initiated the accident sequence which badly damaged the freighter on take-off from Tallinn, investigators have determined.
Estonia's Safety Investigation Bureau says the aircraft (SP-FDP) had started its take-off roll on Runway 08 but, a few seconds after reaching the V1 decision speed of 98kt (180km/h), banked to the right. Its starboard propeller struck the runway and the aircraft then slid on its fuselage underside for 1,228m (4,000ft) until coming to a halt.
The inquiry found the flying pilot began rotating the aircraft at 78kt which, it said, was "significantly below" the required airspeed.
It stated that the elevator moved up to the "high angle" of 17˚ before being eased back to 9.2˚, and the resulting pitch was probably enough to allow gear retraction through closure of the weight-on-wheels switch.
The navigator made a V1 call-out at 98kt and almost immediately afterwards the flight engineer called "retracting".
While the engineer said he had seen the pilot rotating the An-26, and claimed he clearly heard a "gear-up" command from the flying pilot, three other crew members did not confirm the call. The inquiry said the low-speed rotation, with large elevator movement, was "misleading" to the engineer.
The aircraft's operating manual states the gear retraction must not be commanded below 5m and the pilot said the gear-up command is normally given at a height of 50m.
"Based on the cockpit voice recordings and crew members' statements the flight engineer retracted the landing-gear without command from the flying pilot," says the inquiry report into the 25 August 2010 accident.
Operator Exin says it introduced a new procedure following the accident, under which the engineer keeps his right hand on the throttle until positive climb is established, then - after a clear command from the pilot - uses the same hand to activate gear retraction.
Only six months earlier, Russian investigators examining a near-identical accident involving a Yakutia passenger Antonov An-24 at Yakutsk also found that "mistaken perception" and the "illusion of flight" by an engineer had led to the wheels being retracted too early.