USA The U.S. Forest Service has released a 90-page Learning Review about the March 30, 2015 crash of a helicopter that occurred during prescribed fire operations on a National Forest in Mississippi approximately 20 miles north of Gulfport. The accident took the lives of Forest Service employee Steve Cobb, contract pilot Brandon Ricks, and seriously injured another Forest Service employee on detail from Montana.
The helicopter was igniting a prescribed fire by using a plastic sphere dispenser (PSD), a device that drops small balls that burst into flame after they land on the ground. Steve Cobb was serving as the Firing Boss [FIRB] and the detailed employee was operating the PSD out of the right-rear door.
According to the pilots personal flight logbooks, he had accumulated 6,471 total hours of flight experience, about 6,300 hours of which were in the accident helicopter make and model. The owner estimated that the pilot had accrued 22 additional flight hours in the 90 days that preceded the accident.
Before the flight the engine on the helicopter failed to start on the first try, but the second attempt was successful. Later over the prescribed fire the aircraft made about 12 passes over the project and had been over the fire for about an hour when the crash occurred.
Below is an excerpt from the USFS report:
The PSD operator recalled they were flying along 25-to-30 feet above the highest tree things were going really well, and they were nearly through the first bag of balls when he heard two alarm warning buzzers go off simultaneously or nearly so,16 followed immediately by the pilot stating, We lost power, and FIRB saying, Were going in; were going in.
The PSD operator swung his right leg over the PSD machine and back inside the helicopter, just as he had practiced in his head when he envisioned this scenario. He didnt want his leg broken or trapped under the helicopter if it were to roll on its side. As he tightened his lap belt and pushed his back against the seat, hands on his knees in the crash position, he felt the helicopter tip backwards and to the right slightly. The PSD operator believed the pilot initiated this position purposefully, possibly as part of an autorotation. The descent through the tree canopy was not violent, and the helicopter slipped through the trees tail first. The impact with the ground was abrupt. The PSD operator felt the lap belt catch him; the impact knocked the wind out of him.
The PSD operator remembers the helicopter coming to rest more or less upright, and it was quiet. The PSD operator could hear breathing over the intercom system and crackling as the balls they had just dropped began to establish fire. He thought to himself, Im still alive! He unbuckled the lap belt and unhooked the gunner straps tether from the helicopter, then reached forward to jostle the pilot, yelling at the pilot and FIRB, We gotta get outta here. He exited the helicopter from the right side and once on the ground, moved towards the front of the aircraft. He yelled again, We gotta go, calling each by name while realizing they were unconscious and that he wouldnt be able to move them with his injuries.19 As it was, he was having difficulty breathing and standing up. He now heard the roar of the fire that had grown from small individual spots of fire to a wall of flames surrounding them; he knew it was time to move.
He turned and faced the wall of flames and thought, I just survived a helicopter crash; I am going to live. He recounted, I started walking, through the wall of flames 10-to-15 feet thick, then all the glowing ashes on the other side and residual heat hands over my face and screaming into my hands and saying, Dont fall, dont fall everything was glowing and I just kept going I could feel myself burning the watchband melting on my wrist. The PSD operator walked approximately 900 feet in a westerly direction to reach the 415A road and the western edge of the burn unit sometime between 1448 and 1451.
After a while he was found by firefighters and was eventually transported by ground ambulance to a waiting air ambulance which flew him to the University of Southern Alabama Hospital in Mobile, Alabama. His injuries included fractures of two cervical and two lumbar vertebrae, left ocular and left side ribs; and intestinal and hernia tears.
The National Transportation Safety Board concluded the helicopter experienced a loss of engine power for reasons that could not be determined. The helicopter did not catch fire when it hit the ground, but it was soon ignited by the spreading prescribed fire, hampering the NTSB investigation.
The USFS Learning Review emphasized several issues related to the accident not necessarily causes, but items for discussion. One was the decision to ignite the project from a helicopter rather than from the ground.
The primary purpose for utilizing helicopters for aerial ignition in this region is to mitigate the exposure of ground resources to the hazards of hand-lighting units. For Unit 1459, like most units on the De Soto Ranger District, a combination of the vegetation, terrain, and fire behavior make hand-lighting units inefficient and hazardous. Flame lengths of greater than four feet combined with difficult walking conditions raise a red flag for a burn boss concerning firefighter safety. Plants such as palmetto (Serenoa repens), gallberry (Llex spp.), ti-ti (Cyrilla racemiflora), and smilax (Smilax spp.) when combined with needles from longleaf, slash, and Loblolly pines can create flame lengths in excess of 10 feet with as little as a two-to-three year accumulation of dead material. These species are also very difficult to traverse. Smilax vines can ensnare firefighters and drip torches and stop them in their tracks. This area also still has some large dead fuel concentrations as a result of Hurricane Katrina. In these areas people working in the woods may encounter downed timber that can stop heavy equipment from forward progress.
Using an airborne resource for igniting the fire rather than personnel on the ground does not eliminate risk. It transfers it.
Another issue was the required flight characteristics of a helicopter while igniting a fire with a PSD. An air tanker when dropping retardant has to fly low and slow to be effective. Similarly, with the current versions of the PSD, a helicopters recommended speed should not exceed 50 mph (43 knots), while the preferred altitude is 300 feet above ground level (AGL).
Hovering out of ground effect (HOGE) is the typical flight profile.
The last data from the helicopter provided by the Automated Flight Following (AFF) before the crash indicated it was at 132 feet AGL and traveling at 43 knots.
From the report:
It is clear how organizational processes influenced the acceptance of risk. As a result, risk assessments did not consider the flight profile, as it was already determined that low/slow was necessary in order to accomplish the work. The fact that the recommendations for airspeed and altitude were heavily influenced by the capability of the PSD likely influenced a gradual decay over time of the options and decision space for the pilot to maintain optimal combinations of airspeed and altitude. The fact that this is a successful tool available for conducting prescribed burn operations, sets the stage to justify its use, rather than to prompt the agency to look at better options or technology.
The acknowledgement of these flight conditions in agency guides likely affects the deliberate acceptance of a low and slow profile as necessary for the accomplishment of the mission. A low/slow flight profile makes sense because it is suggested within written procedure. Over a period of time (4+ decades), confidence and acceptability of the flight parameters strengthens with each successful mission, along with a slight departure from the awareness of the hazards associated with the flight profiles. This is a demonstration of how the production goals creep into mission planning to dominate the protection goals without recognition of such. In this case, all required policy was followed and personnel were conducting their work within the operational norms set up by agency policy and culture.
The Learning Review has numerous recommendations, including modifying the existing PSD machines to enable the helicopter to fly higher and faster. Another is to invent a new method of aerial ignition, again to mitigate the low and slow flight profile.