A pilot's escape from a submerged and inverted UH-1H in January 2020 has promtped the Australian Transport Safety Bureau (ATSB) to highlight the potential benefits of Emergency Breathing Systems (EBS).
Huey VH-ONZ was filling a bucket from Ben Boyd Reservoir to help on a fire near Eden when the engine failed due to a lack of oil to the two main bearing at the front. The aircraft descended into the dam and rolled inverted when the cabin filled with water.
The pilot was able to escape by punching out the window in the right sliding door after finding a small pocket of air to breathe.
VH-ONZ was not fitted with EBS and was not required to be.
“Research into helicopter overwater accident survival consistently reports drowning as the leading cause of fatalities, due to the inability of the occupant to hold their breath long enough to escape,” said ATSB Chief Commissioner Angus Mitchell.
“In this accident, the pilot found an air pocket in the cabin, which enabled the escape time to extend beyond the initial breath-hold time. While it could not be determined if the pilot would have drowned without the air pocket, it would have increased that likelihood.
“Although the pilot was able to successfully escape from underwater after finding the air pocket, an emergency breathing system would have reduced the risk of drowning.”
The pilot had conducted a number of helicopter underwater escape training (HUET) courses, a condition of the operator’s contract with the NSW Rural Fire Service. At interview, the pilot told ATSB investigators they "would have been dead without HUET".
However, the pilot had not completed the EBS portions of the HUET courses as EBS equipment had not been introduced into their operation.
"Helicopter underwater escape training provides a learning environment for the essential skills of maintaining orientation, location, and operation of exits,” said Mitchell.
“However, extended breath-hold may be necessary for problem-solving and physical effort during an underwater escape, such as dealing with snagging hazards, obstructions, or inoperative exits that require an alternative escape route, as in this accident.
“In these scenarios an EBS can afford the pilot sufficient time to perform the escape actions without an air pocket and therefore reduce the risk of drowning.”
Following the accident, the pilot acquired a compressed air EBS and intends to conduct the EBS elements of future HUET courses.
The ATSB investigation was not able to determine why the oil supply to the two main bearings was interrupted.
The full report is on the ATSB website.