20120116000849A

A piedmont flight 4117, in aircraft N839EX, struck a deicing truck boom with the left horizontal stabilizer, elevator and elevator trim tab, while taxiing on the hts ramp. The flight was an originator and the flight crew preflight identified frost on the aircraft that required deicing. There was no active precipitation at the time. The hts station had recently changed from deicing on the gate to off-gate deicing, but did not have a designated or specific location identified. Before the aircraft left the gate, the captain and the ramp agent agreed that the pilot would taxi out with one engine, and leave the engine in feather while the vendor (Huntington jet center) conducted the deicing. The ramp agent then walked to the deice vehicle and conveyed the agreement, to which the vendor personnel agreed, and the ramp agent then went back to the aircraft to confirm for the captain that his plan was ok with the vendor. They also spoke about where to go on the ramp for deicing, but there the statements vary somewhat. The ramp agent said he told the captain to taxi out in front of gate 2 (aircraft was parked at gate 3), and the captain said he was told to just taxi out there in a non-specific manner. After the aircraft started #1 engine, one agent pulled the chocks and then went inside to station operations to man the radio while the second agent marshaled the aircraft out of the gate 1 parking area. An agent doing the marshalling then stood by the wing to ensure sufficient clearance, and gave a thumbs up to the flight crew to signal that they were clear of the equipment. After the aircraft taxied approximately 50 – 70 feet, and were basically positioned in front of gate 2, the captain stopped and asked the first officer (fo) to call station operations and clarify where they were to go for the deicing. The fo did so and spoke with the 1st ramp agent who was working the radio in a location in which he could not see the aircraft and did not realize the aircraft had left the gate. The agent told the crew to just taxi 50' or so and stop. Without the flight crew's knowledge, the vendor deicing team, having mistaken the 2nd agent's thumbs up signal as the signal that deicing could begin, moved into a position behind the #1 wing and in front of the left horizontal tail when the aircraft first stopped, and started spraying the rear of the aircraft. Having received guidance from station operations to move 50', the flight crew initiated taxi and almost immediately felt a bump, then stopped. Seeing the aircraft start to move, the bucket operator yelled to the driver to back up and tried to lower the boom, but the aircraft tail struck and rode over the peak of the boom arm.