Korean Kamov Ka-32T Fire-Fighting Water Impact and Underwater Egress Fatal Accident (KFS HL9419)
On 1 December 2018, Korea Forest Service (KFS) Aviation Headquarters Kamov Ka-32T HL9419 impacted the Han River in Seoul, South Korea during an approach to uplift water for fire-fighting operations. An aircrewman was killed but the two pilots escaped with minor injuries.
The Accident Flight
The 11 t helicopter, based at Gimpo Airport on 15 minute stand-by, was equipped with a Simplex Model 326 Fire Attack 2972 litre external tank and dual snorkel system. It was tasked to put out a fire on Mount Youngchuk in eastern Seoul. The fire was reported at 10:42 and the helicopter was airborne at 10:55, arriving over the fire at 11:08. The fire was at the edge of the outer Seoul P-73B prohibited airspace. Tracer is authorised as a warning to unauthorised aircraft in P-73B whereas lethal force is authorised in P-73A. This therefore also required liaison with the RoKAF Master Control and Reporting Center (MCRC).
The crew were unable to identify a small reservoir, suggested by their control room, near Sahmyook University at 11.11. They then tried a site at Wangsukcheon at 11.15 but the water level was too low for the snorkels to work successfully.
The commander decided to proceed to the Han River, near the Gangdong Bridge. Visibility was good (>10 km), the wind was from the south-east at 2-3kts, and air temperature 7-8℃.
ARAIB explain that the KFS procedure for a water uplift is first to conduct a high and low level reconnaissance. This was not done, nor was there a briefing prior to the approach.
The KFS approach procedure is to pass through 100 ft at 50 km/h (25 knots) and at a decent rate below 2 m/s (400 fpm), as shown in this video.
The rate of descent during this approach was however 5.7 m/s (1120 fpm) at 100ft and although the rate of descent slowed, impact was still at 3.2 m/s (630 fpm).
The commander (5006 hours total time and 1182 on type) was Pilot Flying (PF) and the co-pilot (2223 hours total time and 1182 on type) was Pilot Monitoring (PM). However, investigators say that both flight crew were concentrating on radio communications, so they failed to recognise the excessive descent rate and proximity to the river’s surface. The radalt low height warning was set at 20 m and triggered 6 seconds before impact.
Underwater Escape – Survivability Issues
The aircraft was not equipped with an Emergency Flotation System (EFS). All the crew had completed Helicopter Underwater Escape Training (HUET). They were issued Switlik life jackets and had a 3000 psi HEED3 Compressed Air Emergency Breathing System (CA-EBS).
Both pilots were unable to activate their door release and both escaped through the right-hand bubble window that had been smashed by the right-hand mirror that was twisted backwards on impact. The c0-pilot initially struggled to release his harness, used his HEED bottle and escaped ‘towards the light’.
The investigators confirmed that scheduled maintenance jettison tests had been conducted previously and successfully passed within the activation force requirements. The ARAIB postulate that after the water impact the crew may have been confused at how the emergency door mechanism worked. The KA-32T does not seem to be equipped with push out windows, as is the norm for offshore helicopters to aid underwater escape.
The Seoul Fire Department were notified within 1 minute of the accident. The helicopter came to rest at a 45º angle, nose down in 5.8 m deep water.
The commander, who escaped with neither life jacket nor HEED bottle swam to shore and was rescued by firefighters. He initially claimed he had removed them to help swim, but they were later found on his office desk…
The co-pilot inflated his life jacket and remained with the wreckage and was rescued by a police boat.
The aircrewman failed to escape, though his HEEDS3 bottle was found in the wreckage with a pressure of 400 psi, implying it had been used. There was no sign of a door handle being activated. His unconscious body was recovered by fire service divers about 40 minutes after the accident. They noted that underwater visibility was <1.5 m.
During the descent approach, the flight crew concentrated on the radio calls, so they failed to recognise excessive descent speed and proximity to the surface.
They determined that the following were contributing factors:
1. Water uplift procedures such as location selection of water sources, high-altitude and low-altitude reconnaissance and stabilised flight were not implemented.
2. During the approach, the assignment of duties was not clearly implemented, with both flight crew focused on radio communication.
3. Failure to monitor information provided by the aircraft, such as low altitude warning and radio altimeter.
4. The crew’s emergency exit door opening method and escape training response capability were insufficient.
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