Something a bit more serious.
On Saturday night, two JMSDF SH-60K helicopters crashed at sea during a night ASW training exercise. The exercise involved three helicopters (including the two helicopters that crashed), seven ships, and one submarine. At around 22:38 local time, radio contact was lost with one of the helicopters, followed by picking up the emergency location beacon of that helicopter. Radio contact was lost with the other helicopter at 23:04.
Search and rescue efforts recovered one of the crew (found dead), with seven still missing. The helicopters each carried one pilot, one co-pilot, and two other aircrew. The flight recorders for both helicopters have been found, in close proximity to each other, which led to the assumption that they had collided. Other helicopter parts have also been found.
First, the "lost radio contact" timings were about 30 minutes apart, so readers not familiar with naval operations would wonder why the helicopters could have collided. This is because helicopters do not necessary keep talking to their mother ships. In tactical operations, radio silence is usually maintained because radio communications can be picked up by the enemy, and those radio waves can be used to pinpoint your location. The nature of anti-submarine warfare (ASW) also means that helicopters may need to hover close to the sea surface at times (when dipping their sonars). The curvature of the earth then makes them drop out of radar detection and line-of-sight communications (like UHF). What happens then is that, for safety, helicopters have to check in with their mother ships at certain time intervals. When a helicopter fails to check in a certain number of times, it triggers certain responses as it means the helicopter met with some issue. This means that the second helicopter probably collided with the first, and when it failed to check in with its mother ship, the mother ship declared that it had lost radio contact at 23:04 local time.
I also want to mention how challenging night training at sea can be. Having conducted many many night training exercises at sea, the low level of light (sometimes zero if there is no moonlight) makes it very hard to pick up things around you visually. This is also why we conduct night training, so that people learn how to be effective lookouts at night, how to orientate themselves in low light, and how to operate effectively even when there is little (or no) light. For a ship operating in two dimensions, it is challenging enough. I had my own share of near misses at sea. For aircraft operating in three dimensions, it becomes even more challenging. This is why there are so many rules in place to prevent mutual interference between units (air or sea) in the same area, so that they don't interfere with each other, or endanger each other. One of the most basic rule is separation, either vertical or horizontal. First, you avoid having two aircraft in the same area. That's lateral (horizontal) separation. If they really need to operate in the same area, then you separate them by height (vertical). Each aircraft would be assigned a height block to operate within, and there is a buffer between height blocks as an added safety measure.
Even with all these safety rules in place, accidents still happen. Sometimes, it was because the rules in place were not stringent enough, and then we revise those rules to prevent future accidents. Sometimes, it is due to other aggravating factors (such as fog, bad weather, etc.) that made an already-challenging situation into something much more impossible. It could also be hardware issues (for example, an altimeter failure can cause the pilot to fly in the wrong height block). That is why accidents are investigated to understand their root cause(s). Procedures and rules are then revised to prevent future occurrences.
For the accident this time, I hope they eventually discover the root cause and make the necessary changes. Meanwhile, I pray that they find the seven missing crew members. Both are difficult tasks, since the accident happened out in open sea, with a depth of around 5,500m. Salvaging anything from the seabed is going to be a tremendous task.
