On 28 January 2019, at 1908 Eastern Daylight-saving Time, a Sikorsky S-64E Skycrane, registered N173AC and operated by Erickson Inc., collided with water at Wood Creek Dam, Victoria. The collision occurred following an approach to the dam to fill an external tank with water for firebombing operations. All the crew exited the aircraft and swam to shore. One crewmember was seriously injured and two were uninjured. The aircraft was substantially damaged.
The ATSB found that the approach path to the dam was incrementally shortened over the course of the days’ operation. It is likely that the final tight approach path was at the upper margins of allowable speed and angle of bank, requiring a steep flare that contributed to the aircraft entering vortex ring state on approach.
Furthermore, the shape of the dam and surrounds of the site reduced the opportunity for recovery, and the aircraft impacted the water. The carriage of additional crew increased the risk of injury, while training for emergencies directly supported the crew’s survival.
Erickson Inc. advised that the following safety action was taken in response to this occurrence:
- vortex ring state avoidance and recovery was to be emphasised in future training and checking
- a policy preventing non-essential personnel from being aboard during firefighting operations had been introduced.
In addition, the organisation that facilitated operation of the United States‑registered Skycrane during Australian firebombing operations, Kestrel Aviation, advised that the following safety action was also undertaken:
- It was reiterated to pilots that, though aircrew work in close partnership and cooperation with aerial attack supervisors (AAS), AAS instructions are advisory. The pilot in command retains full authority to make decisions to ensure the safety of the aircraft and management support was available if escalation was required.
- Kestrel Aviation increased the frequency of contact with Erickson Inc. crews to provide safety management support, and reduce operational pressure.
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 an operation has deviated from earlier versions and re-evaluating elements if they appear less stable.
Helicopters excel in confined areas, yet are vulnerable when operating within them. Periodic reassessment of confined areas, and approach and departure profiles, should be done throughout the duration of an operation. Both supervising parties and operating crews are well-positioned to do this.
The ATSB has previously emphasised the importance of Helicopter Underwater Escape Training (HUET) for all over-water helicopter operators. This accident demonstrates the value of HUET in saving lives.
Following an accident, it is common to overlook the need to unplug one’s helmet. 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.
Here is two fantastic videos explaining on Vortex Ring State!
HUET is Helicopter Underwater Escape Training - Basically how to get out of a helicopter when you go into the water