Pilots of a Bombardier Dash 8-300 had initiated a steep descent into Kabul as a precautionary defensive measure before the turboprop landed hard, suffering substantial damage.
The aircraft, operated by the US Department of State, had been approaching runway 29 at the Afghan capital, in visual conditions, on 17 October last year.
To counter potential threats in the airport vicinity the crew initiated a "random steep approach" with a flap 35 landing configuration, in accordance with the operator's procedures, says the US National Transportation Safety Board.
The pilots reduced engine power to idle and this was "not increased" prior to touchdown, the inquiry adds, the torque remaining "at or near zero" for the final 5min of the approach.
Flight-data recorder information shows the aircraft descended at 2,000ft/min before reducing to 1,500ft/min just before landing. It touched down hard, at 2.7g, with a nose-up pitch of 8°, exceeding the threshold for a tailstrike.
It sustained buckling and cracking of frames and stringers as its aft fuselage hit the runway. While the turboprop (N800AW) was damaged, the six occupants - three crew and three passengers - were not injured.
Investigators state that the crew had disengaged the ground-proximity warning system to avoid nuisance alerts during the steep approach, but point out that they would otherwise have been expected and "unlikely" to have prompted corrective action.