WPR23FA302 · Bell 407

Two helicopters collided in a Fire Traffic Area (FTA) during cruise flight while responding to a fire. Both helicopters were dispatched from Hemet-Ryan Airport (HMT), about 16 nm miles southwest of the fire. The first helicopter dispatched was a Bell 407, as an instructional Helicopter Coordinator platform, and the other was a Skycrane helitanker, dispatched to support water dropping operations. The Bell 407 and Skycrane were dispatched and departed about 3 minutes apart. The Bell 407 travelled north, skirting and staying west of the San Jacinto Mountain range between HMT and the fire, while the Skycrane travelled northeast over the western section of the mountain range. Both helicopters were operating under FTA procedures overseen by the California Department of Forestry and Fire Protection (CAL FIRE). According to CAL FIRE’s procedures, inbound aircraft were required to contact the Air Tactical Group Supervisor (ATGS) for permission to proceed into both the 12-nm Initial Communication Ring as well as the 7-nm No Communication (NOCOM) Ring of the FTA. Likely due to the mountainous terrain, neither helicopter was able to receive a clear radio signal from ATGS before entering the 12-nm ring. Instead, both helicopter crews decided to maneuver to have a better line of sight for radio transmission before reaching the 7-nm ring. Flight track data and communication recordings showed that the Bell 407 flight crew initiated a 360° turn to establish communication with ATGS before crossing the 7-nm ring. Shortly after, they descended and leveled off at the maximum assigned altitude of 2,500 ft msl, about 5 nm from the fire, where they stayed in level flight until the collision. The Skycrane’s flight crew attempted to contact ATGS before entering the 7-nm ring; however, they continued about 1 nm, or 30 seconds, into the 7-nm ring before ATGS provided their clearance. After providing the Skycrane’s call sign and the altimeter setting, ATGS stated, “you are cleared in 2,500 [ft] and below, air attack [ATGS] is at 4,500, one tanker at 3,500 [ft], and you have multiple hazards in the area. I [ATGS] will orient you once you get on the scene.” The crew of the Skycrane, already in the FTA at about 4,000 ft msl, then acknowledged the clearance before climbing to about 4,300 ft, likely to avoid terrain. After both helicopters were cleared into the FTA and to the fire, no further position reports by either helicopter were recorded. After climbing, the crew of the Skycrane then initiated a rapid descent after it overflew mountainous terrain to get to the maximum clearance altitude of 2,500 ft, which they reached 3 seconds before the collision; they were in a slight right descending turn during the impact about 2 nm west of the fire at 2,450 ft msl. According to NWCG guidelines, the Skycrane pilot should have advised ATGS that the aircraft could not comply with the altitude clearance and should have informed ATGS of their aggressive descent, which falls into the definition of a non-standard maneuver and constitutes communication to aerial supervision. Surveillance footage showed that the Bell 407 was in level flight when it was impacted by the Skycrane's right wheel and tire assembly. The impact was immediately followed by an explosion and the separation of the Bell 407’s tail boom, main rotor, mast, and transmission. The remaining portion of the fuselage continued in the direction of the Bell 407's flightpath until it impacted terrain. The Skycrane’s right main wheel and tire assembly were damaged by the Bell 407’s main rotor blade during the collision. Postaccident examination of the Bell 407 revealed that all major structural components of the helicopter were present within the wreckage debris path. Wreckage and impact signatures were consistent with a midair collision. Postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. All on-board communication and video recordings within the Bell 407 were destroyed by the post-crash fire. CAL FIRE procedures stated that if any part of the clearance could not be complied with, “the inbound aircraft will remain outside the NOCOM ring until an amended clearance is received and understood.” However, the Skycrane’s crew did not remain outside of the 7-nm ring, did not report to ATGS that they were unable to comply with the altitude restriction, and did not inform ATGS of their intention to rapidly descend and follow mountainous terrain until they reached the clearance altitude. Toxicology results indicated that the Bell pilot had used the antihistamine medication cetirizine. Although his cetirizine levels indicate a possibility that the Bell pilot may have been experiencing some associated impairing effects, the circumstances of the accident do not suggest that the pilot’s impairment contributed to the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset