Accident Mitsubishi SH-60K 8443, Saturday 20 April 2024

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Date:	Saturday 20 April 2024
Time:	22:33 LT
Type:	Mitsubishi SH-60K
Owner/operator:	Japan Maritime Self-Defence Force
Registration:	8443
MSN:	5043
Fatalities:	Fatalities: 4 / Occupants: 4
Other fatalities:	0
Aircraft damage:	Destroyed
Location:	150 nm east of Torishima island, Izu Islands - Japan
Phase:	En route
Nature:	Military
Departure airport:	JS Kirisame, DD-104
Destination airport:	JS Kirisame, DD-104

Narrative:
Two Japan Maritime Self-Defence Force (JMSDF) Mitsubishi SH-60K's have crashed near Torishima island, Izu islands. They were excuting a night time anti-submarine warfare exercise and unit inspection with third SH-60K (8413), a JMSDF submarine and fleets at the time of the accident and both are belong to Fleet Air Wing 22, one is based at Omura Air Base (OMJ/RJDU; 8416) and the other at Komatsujima (RJOP; 8443). The first SH-60K, 8416 lost radio/radar contact at 22:38 LT and the ELT signal was received at one minute later. The second SH-60K was also found lost contact at 23:04 LT. Each helicopter carried four crew members. Search and rescue operations are being conducted. Just after the losses, some debris including rotor blades and helmets of the crew were found floated over the sea and the dead body of 8416's copilot has been retrieved. Remaining seven are still missing. The flight recorders of both SH-60Ks were recovered at close location each other. The cause of the accident is supposed to be a mid-air collision. The weather at the time was fine (7 oktas at 3000 feet, west wind at 11 knots, visibility 20 km with moon aged 11.4 days) and could not be a factor. The initial analysis of the FDRs was released 22nd April and there were no mecanical failure recorded. Both SH-60Ks seem to be collided head on each other.
On 11th June, the Ministar of Defence declared that all eight occupants of both SH-60Ks had been dead.
On 9th July, the final accident report was issued and the press release was opened. It says as follows: 8416 conducted a submarine search under the command of the 4th Escort Flotilla Commander, while 8443 conducted a search for the submarine under the command of Captain of JS Suzunami, DD-114. When a new search target appeared, each headed for the same target. 8443 flew in an almost straight line from the point about four minutes before the collision to the point of collision, and recognized the direction and distance of 8416 about two minutes before the collision. 8416 was making a clockwise turn while also using automatic flight. Although both aircraft were aware of each other's presence a few seconds before the collision, it appears that they did not sense the risk of a collision. There was no sign of either aircraft taking evasive action until the moment of collision.
On 20th July, it was announced that the wreckage of one helicopter was discovered at the ocean floor 5500 meters under the sea surface by Deep Tow, an unmanned deep ocean floor survey system operated by the Japan Agency for Marine-Earth Science and Technology, which was conducting a search at the request of the Ministry of Defense. The second SH-60K was located nearby the first one on 22nd July.
The main part of the wrickage of 8416 was salvaged on the night of 11th March 2025, and of 8443 on the next morning, along with some bodies of crew.

The cause of the accident:
In order to determine the cause of the accident, the factors that led to the accident were analyzed and examined in terms of environmental factors, equipment factors, management factors, human factors, aircraft operation factors, and command and control factors. No environmental factors, equipment factors, management factors, or human factors that could have led to the accident were found. Some aircraft operation factors and command and control factors were found to have led to the accident.
(1) Inadequate lookout procedures
A) Although both aircraft were aware of each other's presence, no evasive maneuvers were taken until the moment of collision, which may have led to a misjudgment of the distance of the other aircraft at night, when it is difficult to grasp the visual distance.
B) In both aircraft, there was insufficient reporting of visually identified targets to the captain, sharing of information among the onboard crew, and instructions from the captain to accurately grasp the targets' movements, and the lookout reporting procedures and response to grasping the targets' movements were insufficient.
C) While Aircraft 8416 was circling clockwise using its automatic flight controls, there was insufficient vigilance against the approach of Aircraft 8443, and Aircraft 8443 also was insufficiently vigilant against the flight path of Aircraft 8416.
(2) Insufficient advanced management in a complex operational environment
A) The Commander of 4th Escort Flotilla 4 did not clearly communicate to Captain of JS Suzunami his intention to send Aircraft 8416 under his command to search for the target, and Captain of JS Suzunami did not clearly communicate to the Commander of Escort Flotilla 4 that he was sending Aircraft 8443 under his command to search for the same target.
B) The Commander of Escort Flotilla 4, who was in overall command of the naval battle, did not fully grasp the overall situation of the three aircraft in flight at the time, including Aircraft 8413 and Aircraft 8443 under Captain of JS Suzunami's command. Furthermore, they did not supervise the coordination between the two aircraft, 8416 and 8443, or take any other action such as instructing advanced control.
C) Under these circumstances, the Commander of the 4th Escort Flotilla, Captain of JS Suzunami, 8416, and 8443 all recognized that the two aircraft were searching for the same target, the order of searches between the two aircraft, and the relative positions of the two aircraft, but they did not establish advanced separation.

Sources:

Revision history:

Date/time Contributor Updates

20-Apr-2024 19:55 gerard57 Added

20-Apr-2024 20:16 gerard57 Updated [Aircraft type, ]

20-Apr-2024 20:23 RobertMB Updated [Operator, Source, Narrative, ]

21-Apr-2024 05:46 isamuel Updated [Time, Location, Source, Narrative, ]

21-Apr-2024 12:28 isamuel Updated [Time, Registration, Cn, Location, Source, Narrative, ]

22-Apr-2024 18:04 isamuel Updated [Source, Narrative, ]

23-Apr-2024 09:09 isamuel Updated [Source, Narrative, ]

24-Apr-2024 15:54 isamuel Updated [Location, Source, ]

26-Apr-2024 17:06 isamuel Updated [Source, ]

27-Apr-2024 16:46 isamuel Updated [Source, Narrative, ]

02-May-2024 15:01 isamuel Updated [Source, ]

11-Jun-2024 05:36 isamuel Updated [Total fatalities, Source, Narrative, ]

09-Jul-2024 05:37 isamuel Updated [Time, Departure airport, Destination airport, Source, Narrative, ]

21-Jul-2024 08:01 isamuel Updated [Source, Narrative, ]

23-Jul-2024 09:02 isamuel Updated [Source, Narrative, ]

13-Mar-2025 06:23 isamuel Updated [Source, Narrative, ]

Date/time	Contributor	Updates
20-Apr-2024 19:55	gerard57	Added
20-Apr-2024 20:16	gerard57	Updated [Aircraft type, ]
20-Apr-2024 20:23	RobertMB	Updated [Operator, Source, Narrative, ]
21-Apr-2024 05:46	isamuel	Updated [Time, Location, Source, Narrative, ]
21-Apr-2024 12:28	isamuel	Updated [Time, Registration, Cn, Location, Source, Narrative, ]
22-Apr-2024 18:04	isamuel	Updated [Source, Narrative, ]
23-Apr-2024 09:09	isamuel	Updated [Source, Narrative, ]
24-Apr-2024 15:54	isamuel	Updated [Location, Source, ]
26-Apr-2024 17:06	isamuel	Updated [Source, ]
27-Apr-2024 16:46	isamuel	Updated [Source, Narrative, ]
02-May-2024 15:01	isamuel	Updated [Source, ]
11-Jun-2024 05:36	isamuel	Updated [Total fatalities, Source, Narrative, ]
09-Jul-2024 05:37	isamuel	Updated [Time, Departure airport, Destination airport, Source, Narrative, ]
21-Jul-2024 08:01	isamuel	Updated [Source, Narrative, ]
23-Jul-2024 09:02	isamuel	Updated [Source, Narrative, ]
13-Mar-2025 06:23	isamuel	Updated [Source, Narrative, ]

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