A firefighting crew have credited their training for enabling them to swim to safety through fuel contaminated water when their Sikorsky S-64E Skycrane crashed into a dam.
An ATSB report has detailed how the team weren’t able to see anything underwater, but remembered drills from their helicopter underwater escape training – waiting until the last moment to draw breath and not unbuckling their harnesses until the Skycrane’s movement had ceased.
One crew member sustained a knee injury but the other two were uninjured in the incident that took place on 28 January 2019 at Wood Creek Dam, Victoria.
The Accident Transport Safety Bureau’s director of transport safety, Stuart Macleod, emphasised the importance of thorough preparation, saying, “In the wake of a separate, sadly fatal, accident the ATSB released a Safety Advisory Notice highlighting the importance of HUET regular training. This accident demonstrates the value of that training in saving lives.”
The two pilots and one engineer, from Canada and the US, were tackling the Thomson Catchment Complex fires in Victoria’s Yarra Ranges National Park when they returned to Wood Creek Dam to fill their tank.
All three crew members were highly experienced, and twice during the day had utilised the same location to fill their tank using a pond snorkel.
On the day’s third visit, while descending with a nose-high attitude, the helicopter’s tail struck the water, which then submerged and resulted in the tail rotor breaking off.
The helicopter then spun rapidly and its main rotor blades separated as they hit the water.
The right cockpit door separated from the fuselage, and the helicopter came to rest on its left side, submerging the cockpit.
The crew recall that they couldn’t see anything underwater, and that jet fuel contamination was present.
Each recalled the rehearsed drills from their helicopter underwater escape training and identified their harnesses and nearest exit to orientate themselves.
They all waited until the last moment to draw a breath and did not unbuckle or attempt to exit the helicopter until motion had stopped.
All three crew successfully exited the aircraft, inflated their life jackets, and swam to shore. The aircraft was badly damaged.
Macleod noted that accident highlighted another survivability consideration, as neither pilot unplugged their helmet. However, the extension cords from the aircraft to the helmet plug allowed the plug to release, preventing the helmets from snaring them.
“Following an accident, it is common for air crew to overlook the need to unplug their helmet,” he said. “Using a good quality extension cable that will maintain the integrity of communications and release under tension in the event of an emergency can also save lives.”
The ATSB investigation into the accident established that, over the course of the day’s operation, the helicopter’s approach path to the dam was incrementally shortened. The length of the final approach was considerably shorter than earlier approaches.
ATSB investigators determined that it was likely that the final tight approach path was at the upper margins of allowable speed and angle of bank. This would have required a steep flare on arrival and likely resulted in the rapid onset of vortex ring state.
“When performing aerial work, it is easy to accept incremental changes that gradually reduce margins. While these changes often increase efficiency, it is worth checking how much a sequence has deviated from earlier versions and re-evaluating elements if they appear less stable,” Macleod said.
“Helicopters excel in confined areas, but are vulnerable when operating within them. In this case, the shape of the dam and surrounds of the site reduced the opportunity for recovery. Periodic reassessment of confined areas, and approach and departure profiles, should be done throughout the duration of an operation.”
You can read the full report here.