An investigation into a May 29 incident that injured three wildland firefighters in New Mexico highlights the risks that helicopter water drops can pose to ground crews, and the fact that such incidents are occurring more frequently than many people realize.

According to a newly published facilitated learning analysis (FLA) by the U.S. Forest Service and Bureau of Land Management, U.S. wildland firefighting agencies are averaging one serious injury from water drops every 12 to 14 months. Recent events suggest that this estimate may actually be low and the frequency of water drop injuries could be increasing.

Even moderate amounts of water dropped from overhead aircraft can topple burnt trees and break off branches, creating hazards for firefighters on the ground. In the case of the largest firefighting helicopters, which the Forest Service classifies as Type 1, the force of the water release alone can be enough to cause injury.

That’s what happened in the recent event in New Mexico, when three members of the Vale Interagency Hotshot crew were struck by water dropped from a Sikorsky CH-54 Skycrane operated by Helicopter Transport Services (HTS). Skycranes equipped for aerial firefighting can carry as much as 2,600 gallons (around 9,800 liters) of water in their tanks, although the exact amount of water released in any drop varies.

The FLA illustrates how communication issues and a high tempo of operations can lead to problems regardless of the experience and skill level of the people involved. It also warns against normalizing events in which firefighters on the ground are sprayed by water, even when no injury occurs.

The May 29 incident took place on the Hermits Peak/Calf Canyon Fire northwest of Las Vegas, New Mexico. Three hotshot crews were assigned to work an edge of the fire in a remote, hard-to-access location at an elevation of around 9,400 feet (2,865 meters).

The terrain was described in the FLA as “extremely challenging,” with steep slopes covered by “suitcase-sized” boulders. Winds were forecast to increase throughout the day, reaching red flag warning conditions by the afternoon.

Work on the line began early, with a single firefighter from the Stanislaus Hotshots directing two HTS Skycranes to cool off the edge of the fire in advance of the crews’ arrival. According to the FLA, the helicopters were initially making direct cross-slope approaches along the fire line, but as winds became erratic and strong, they started dropping downhill and into the wind instead.

As hotshot crews began entering the area, several firefighters noticed, but did not verbalize, how unusually fast the helicopter turnarounds were: reportedly just one to three minutes between drops. Direction of the helicopters was handed off twice, first to the Silver State Hotshots, then to the Vale crew.

The heavy canopy impeded visibility for both ground crews and pilots. Although a red target panel was placed on the ground to direct the drops, drone footage taken after the fact shows that the panel was almost impossible to see from the air. One of the pilots recalled confusion with some drop cycles because the ground contact described the target being “out your right door” when it was actually on the left.

Some drops sprayed firefighters with water, but the pilots weren’t informed of the full extent of the soaking because of radio handoffs between the ground crews. Meanwhile, these handoffs weren’t necessarily obvious to the pilots, one of whom said, “I always thought I was talking to the same person; the voices sounded the same.”

On one of the last two drops before the Skycranes returned to base for fuel, the water hit three Vale crewmembers who were scrambling across a boulder field. The firefighter who sustained the most severe injuries — including skull fractures to the face and a broken kneecap — was carrying a saw and braced for the impact by dropping to one knee.

“I don’t remember the water hitting me or my face hitting the saw,” the sawyer told investigators. “I remember it being hard to breath. By the end of the drop, I was out of breath . . . I was gasping for air when the water stopped hitting me.” Other crewmembers in the vicinity described seeing their colleagues disappear in a wall of water and dust. The pilots were not aware that people were hit and were not told about the incident until later.

The FLA contains a number of recommendations for improving air-to-ground and ground-to-air communication, emphasizing the need to “over-communicate” during transitions. It notes that the phrase “the line is clear” can mean different things to pilots and ground crews, and will vary depending on the type of helicopter and its load capacity, the visibility of the line from the air, and other situational factors.

Additionally, “ground resources need to communicate with the pilot about being sprayed by water, immediately, every time, and provide time to adjust the approach before the next drop,” the FLA asserts. “Resist normalizing ‘brace and hit’ as something that people ‘just get used to’ in typical operations.”

The report cites many similar events over the past decade in which ground crews were injured or killed by water or retardant drops from helicopters or airtankers. Notably, just one month after the Hermits Peak incident, another Type 1 helicopter — a Boeing CH-47D — inadvertently dropped water on a four-person engine crew in California, knocking them to the ground and toppling a tree on them.

Three firefighters were struck in the back and arms, while the fourth sustained a head injury and severe concussion. In that incident as well, no attempt was made to immediately contact the pilots, who made several more water drops in the area and were not informed of the injuries until the following day.

The Wildland Fire Lessons Learned Center and SAFECOM aviation safety reporting system document at least three other helicopter water drop incidents in the past three years that resulted in injuries. But that list is not comprehensive.

Not included, for example, is an October 2020 incident on the Zogg Fire near Redding, California. The San Francisco Chronicle reported that three inmate firefighters were injured, one critically, when a water drop from a Skycrane helicopter caused a smoldering tree to fall on them.