NTSB Factual Report

On September 2, 2017, about 0948 Pacific daylight time, a Leonardo (formerly AugustaWestland Philadelphia) AW139 helicopter, N304FD, sustained substantial damage after impacting trees while conducting aerial firefighting operations in a residential area in Tujunga, California. The pilot and crewmember sustained no injuries. The helicopter was registered to the City of Los Angeles and was operated by the Los Angeles Fire Department as a public use visual flight rules aerial firefighting flight, operating as Fire 4. Visual meteorological conditions with moderate smoke were present in the area at the time of the accident and flight following procedures were utilized by the operator. The helicopter departed from the Van Nuys Airport, Van Nuys, California about 0815 to conduct the aerial firefighting operations for the day.

The operator reported that the helicopter was in support of the La Tuna wildfire, that was spreading throughout the Verdugo Mountains. The helicopter was tasked with structure protection for a residential complex on a ridgeline, about one half mile northeast of Interstate 210, known as the Foothill Freeway. The pilot was stationed in the right seat, and a helicopter pilot crewmember, who was not type rated in the AW139 model, was stationed in the left seat. The helicopter was operating with several other firefighting helicopters, which were all supporting the structure protection for the residential complex via water drops. The team of helicopters were operating out of the Green Verdugo helispot, which is located next to the Green Verdugo reservoir about 2 miles northwest of the residential complex.

Once on station, the pilot performed a high reconnaissance orbit over the residential complex, with the intent of conducting a water drop from the south to the north. During the high reconnaissance, the pilot noted the prevailing wind, the smoke conditions, the ground obstructions, and his intended approach and departure route for the water drop. The pilot reported the wind condition was variable and originated from the east.

When the pilot was flying from south to north to drop the water in a descending profile, about 100 feet above the trees and about 40 knots, and about 200 feet away from the residential complex, the helicopter began an uncommanded yaw to the right and the vertical descent increased. The pilot released the water and the helicopter continued to yaw to the right and descend rapidly. The pilot reported he had little positive control of the helicopter. The crewmember verbally called out the trees located on the left side of the helicopter. The main rotor blades impacted a eucalyptus tree, following with the tailboom and tail rotor system impacting a pine tree. After the tree impacts, the uncommanded yaw appeared to decrease and the pilot regained control of the helicopter. The pilot departed from the residential complex area by initiating a climbing turn to the northwest and initiated a mayday call. The pilot flew about 1 mile north, and made a landing at a school athletic field without further incident.

The helicopter was equipped with a Simplex Aerospace model 326 GII aerial firefighting belly-mounted tank that has the capability to hold 450 gallons of water via a supplemental type certificate.

The pilot reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

The helicopter sustained substantial damage to the left stabilizer, the right stabilizer, and the tailboom. The heliocopter was secured and is pending transportation to the manufacturer's repair station for a comprehensive damage assessment.

The cockpit voice recordings, the flight data recordings, the terrain awareness and warning system data, and the flight tracking system data were secured for future download of the various data parameters.