WPR23FA302

The Skycrane flight crew’s decision to enter the Fire Traffic Area’s 7-nm NOCOM ring at an altitude significantly above their maximum cleared altitude, which resulted in their need for an aggressive descent into congested airspace and subsequent failure to see and avoid the 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.

Skycrane Pilot in command (PIC) Siller Helicopters, Inc. hired the PIC in April, 2017. The pilot’s last flight review was completed on April 27, 2023. His last proficiency check for currency under CAL FIRE contract rules (pilot carding) was completed on May, 3, 2023, by the United States Forest Service (USFS). Skycrane Second in command (SIC) Siller Helicopters, Inc. hired the SIC in June, 2023. The pilot’s last flight review was completed on April 27, 2023. His last proficiency check for currency under CAL FIRE contract rules (pilot carding) was completed on June 24, 2023, by the USFS. Bell 407 PIC Air Shasta Rotor & Wing Inc. hired the PIC in February, 2018. The pilot’s last flight review was completed on April 27, 2023. His last proficiency check for currency under CAL FIRE contract rules (pilot carding) was completed on June 20, 2023, by the USFS. The Bell 407 pilot’s autopsy was performed by a forensic pathologist from Riverside County Sheriff’s Office, Office of the Coroner, Perris, California. According to the pilot’s autopsy report and associated death investigation documentation, his cause of death was blunt trauma and his manner of death was accident. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological tests on specimens recovered from the pilot. The pilot’s postmortem toxicological testing detected no drugs of abuse and detected Cetirizine, an over-the counter antihistamine commonly used to treat allergy symptoms, in the blood and liver. Cetirizine often carries a warning that users may experience drowsiness and should be careful when driving a motor vehicle or operating machinery. Data on sedation and psychomotor impairment from cetirizine are mixed, with some studies finding some sedating and impairing effects. The FAA states that pilots should wait 48 hours after using cetirizine before flying, to allow time for the drug to be cleared from circulation. On August 6, 2023, about 1844 Pacific daylight time, a Bell 407, N555AS, and a Sikorsky S-64, N4037S, collided mid-air near Cabazon, California. The Bell was destroyed and the pilot and two qualified non-crewmembers were fatally injured. The Sikorsky sustained minor damage and the pilot and copilot were not injured. Both helicopters were operated as public-use firefighting aircraft. Before their respective flights, each flight crew was briefed on their mission. The Bell 407 was tasked as a Helicopter Coordinator (HLCO) training flight while the Sikorsky Skycrane was dispatched to support fire operations. The Skycrane received their dispatch instructions about 15 minutes before their departure. Review of the communication recording from within the Skycrane shows that the recording started at 0:00 lapse time (refer to figure 1). Figure 1. Recorded ADS-B data with select communications annotated. At 01:18, the Bell 407 made a call to Hemet Base Victor Dispatch (Hemet Tower) requesting a bearing and distance to the fire. ADS-B data revealed that the Bell 407 departed from HMT about 1834 (02:37) and traveled north-northeast for about 2 nm then maneuvered to the north. HMT was about 3.5 miles from the edge of the FTA’s 12-nm Initial Communication Ring. The ADS-B flight track of the Bell 407 could not be correlated with the positioning of the Skyrcrane, which was based on CVR audio. At 04:17, the Skycrane PIC initiated a 10-sec conversation with the SIC stating the Bell 407 was “going too” [to support the incident] and was either an HLCO or a training platform. The Skycrane crew continued their checklist; at 06:14, the crew simultaneously made separate radio calls and the PIC transmitted on the Hemet Common Traffic Advisory Frequency and the SIC contacted Hemet Tower of their impending departure. ADS-B data showed that the Skycrane departed HMT about 3 minutes after the Bell; the Skycrane maneuvered to the northeast and, at 07:25, crossed a solar farm about 0.5 nm northeast of HMT. At 08:41, the Skycrane crew started an internal discussion that the first preferred call into the fire incident should be on the Air Tactics frequency. At 09:46, a broadcast from ATGS can be heard providing instructions for a tanker fire drop. At 10:47, in an internal conversation, the SIC told the PIC that they were about 10 nm from Cabazon. ADS-B data showed that the Skycrane was about 2,650 ft msl. At 11:23, the Bell 407, while in a left circling maneuver, reported to ATGS that they were 8 miles west of the fire at 4,300 ft msl. At 11:28, ATGS provided an altimeter setting of 29.96 and cleared the Bell 407 into the FTA with a maximum altitude of 2,500 ft msl. ATGS also informed the Bell 407 that ATGS was at 4,500 ft, with one tanker at 3,500 ft, and that there were multiple hazards. ADS-B showed that the Bell 407 initiated a steep descent to meet the 2,500 ft maximum altitude restriction and leveled off to about 2,500 ft about 2 miles inside the 7 nm (NOCOM) ring. At 11:42, the Skycrane PIC requested their clearance into the FTA on the ATGS frequency, stating, “Cabazon Air Attack, helitanker 37S checking in just inside 7 miles, err, uh, eight miles, rather.” At 11:56, the SIC broadcasted on a Victor frequency, “Cabazon Air Attack helitanker 37S, 7 miles south inbound.” At 12:08, the Skycrane SIC stated to the PIC that they tried to get their clearance from ATGS. At 12:33, ATGS broadcasted the Skycrane’s clearance into the FTA, stating, “and 37S altimeter 29.96, 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 when you get on the scene.” At 12:37, the Skycrane SIC points to the left, and the time on his watch read 18:34 local; the PIC initiated a left turn at 4,000 ft. ADS-B data showed that they were 6 nm from the fire incident and a mile into the FTA. At 12:45, the Skycrane acknowledged their clearance into the FTA. At 13:10, the Skycrane’s altimeter needle is seen climbing through 4,150 ft. About 13:23, the altimeter read 4,200 ft and the heading was 020°. About 13:34, the altimeter read 4,300 ft with the same heading. At 13:41, the altimeter read 4,200 ft. At 13:48, ATGS contacted the Bell 407 and the Skycrane. At 13:49, the Skycrane initiated a descent at 1,000 fpm, through 4,100 ft. At 13:53, the Skycrane had a descent rate of 2,500 fpm and the altitude was crossing 4,000 ft. At 13:57, the Skycrane had a descent rate of 2,800 fpm and was crossing 3,900 ft. Also, at 13:53 and 13:57, respectively, the Skycrane and Bell 407 both acknowledged ATGS’s request for their attention to receive further instruction. This is the last transmission recording heard from the Bell 407. At 13:58, ATGS responded back to both helicopters and stated, “Ok, you have high tension power lines just south of the incident paralyzing…paralleling in front of the road and you got windmills off the east, those’ll be your hazards.” At 14:11, the Skycrane acknowledged ATGS and simultaneously descended at 3,000 fpm through 3,550 ft msl. At 14:22, the Skycrane continued its descent at 2,900 fpm through 3,350 ft. At 14:50, the Skycrane initiated a descending right turn at 2,000 fpm passing through 3,000 ft at 95 knots indicated. At 15:03, the Skycrane crew scanned the instrument gauges and configured the water tanks. At 15:06, the Skycrane continued its descent at 2,000 fpm, through 2,600 ft, at 100 knots. At 15:16, the Skycrane descended at 1,800 fpm through 2,550 ft at 100 knots. At 15:20, the Skycrane descended at 1,500 fpm through 2,500 ft at 100 knots. At 15:23, the Skycrane descended at 1,500 fpm through 2,450 ft at 100 knots. The recording showed that the right side collective control moved down, up, and then down again while the cyclic moved right and aft, before it swung back to a neutral position. Immediately after, the SIC asked, “oh …what was that?” At 15:25, the PIC asked if the Bell 40