Miscommunication between pilots, a ramp agent and a de-icing truck driver led to an accident that caused "significant" damage to the horizontal stabiliser and elevator of a Piedmont Airlines Dash 8 Q100 (N839EX) at the Tri-State airport in Huntington, West Virginia on 16 January, according to a US National Transportation Safety Board preliminary report.
The pilots of Piedmont flight 4117, operating as US Airways Express from Tri-State to Charlotte with 36 passengers and crew on board, had taxied out short distance from the gate for de-icing before departure as part of a new off-gate de-icing procedure at the airport.
Several miscues then took place, according to the NTSB. An agent walking with the aircraft to verify its wing had cleared nearby obstacles during the taxi, gave a thumbs-up signal to the pilots that the aircraft was clear. The de-icing team, operating a vehicle with a boom used to spray de-icing fluid on the aircraft, mistook the agent's thumbs-up as approval to approach the aircraft from behind the left wing and begin spraying.
Meanwhile the pilots radioed the agent who earlier had coordinated the off-ramp de-icing procedure with the de-icing team and asked if the aircraft was in the correct location to receive the spray. That agent, now back inside the airport working the radios, assumed the Q100 was still at the gate, told the pilots to taxi "50 feet or so and stop", the NTSB said.
"The flight crew initiated taxiing and almost immediately felt a bump, then stopped," the report stated. "After 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 struck the boom arm."
No one was injured in the incident.