Failure to redistribute passengers on an Airbus A320 led the aircraft to strike its tail on take-off from Verona, Italian investigation agency the ANSV has found.
The Bulgarian-registered twinjet (LZ-BHC) had been operating a wet-lease service from Hurghada in Egypt to Rome Fiumicino via Verona on 1 September 2009.
Eighty-seven Rome-bound passengers were seated mainly aft on departure from Hurghada, while 77 Verona-bound passengers occupied the forward cabins.
Baggage had been loaded with a similar layout in the hold, which meant that the aircraft's centre of gravity shifted rearwards, outside the operating envelope limit, once passengers and luggage were offloaded in Verona.
Despite the captain's receiving and approving a trim sheet that detailed a "considerably different" seating arrangement for the transit passengers heading for Rome, ANSV says this redistribution "was not detected or not considered" by the captain.
"Passengers remained in the same seats they had occupied in the previous flight," it said. As soon as the thrust levers were advanced to the flex position for take-off, the A320 began an uncommanded early rotation, hitting and damaging its rear fuselage.
It lifted off at 113kt (209km/h) and a stall warning immediately followed. Flight control had degraded, said the ANSV, to alternate and direct law. The "extensive" structural damage to the jet had compromised the pressurised area and the crew, having received a pressurisation system warning, returned to Verona.
The ANSV said the incident highlights the vulnerability, particularly of charter flights operating onward sectors, to undetected changes in mass balance and is recommending that a "positive check" procedure be implemented to ensure necessary loading changes are carried out.