A single engine air tanker (SEAT) struck a powerline while on final approach for a water drop on a fire in northern Idaho. At the time the pilot was not aware of the strike but after making the drop noticed that there was some damage to the left wing. The accident occurred July 28, 2016.
You can read the entire Rapid Lesson Sharing report here. Below is an excerpt:
“…New Approach Brings SEAT Over an Undetected Powerline
The SEAT, based out of McCall, was dispatched to the fire near Kooskia, Idaho at 1529 hours. The line strike occurred on the SEAT’s second load delivered to the fire. The first load was split and applied on two different runs prior to a Lead Plane arriving on scene.
On the second load, the SEAT was a little off of the line set by the Lead Plane and the SEAT Pilot was unsure of exactly where the Lead Plane wanted the drop. This prompted the SEAT Pilot to make a dry run.
At this point, the ATGS, who was circling overhead, instructed the Lead Plane to give the SEAT a target and let him work his own approach. The SEAT came back around in a fairly tight circle which created a different final approach than had previously been used. This new approach of the flight line brought the SEAT over a powerline that had not been identified prior to the strike. The Pilot identified the location of the known powerline across the draw and concentrated his attention on the approach as he was lining up for the drop.
Pilot Informs ATGS He Might Have Hit Something
The angle of the bank caused the nose and the right wing of the plane to create a blind spot, obscuring Power Pole 2 from view. The angle of the sun and the dark color of the powerlines would have made them basically invisible against the backdrop of the terrain. The Pilot was unaware of the strike at the time it occurred with the only indication being a brief sound that was not part of the “normal” sounds experienced in the aircraft. The flight was bumpy due to turbulent air that is normal on hot summer days in canyon country. Following the successful drop, the Pilot informed ATGS that he might have hit something.
Pilot Notices Vortex Generators Missing from Left Wing
The Pilot flew back over the drop area and confirmed that the known powerline was still intact. He did not locate the poles from the line that had been struck. As he was heading back to the dip location, he looked out at his left wing and realized that numerous vortex generators were missing. The vortex generators are glued on the wing and have been known to come off in flight, but normally only under extreme cold or hot weather conditions. Normal flight is not affected by missing vortex generators. Their purpose is to add stability, lift, and performance during dipping and dropping maneuvers. All controls of the aircraft were functioning normally.
At this time, it had not been established that a wire strike had, in fact, occurred. The Pilot was initially going to return to the dip site for another load when the ATGS recommended that the SEAT fly to the Lewiston Air Tanker Base to check for possible damage (56 miles with crash/rescue services). The Pilot informed ATGS that he was returning to base at McCall (83 miles without crash/rescue services).
The wire strike was first confirmed when the Pilot was on the ground in McCall and was able to see the black marks from the wire on the wing. At this time, the Tanker Base Manager in McCall alerted Dispatch to notify personnel on the fire that a wire had been struck and of the potential for hot wires on the ground…”