There were a streak of helicopters falling down of Japanese defense force in 2015. One of OH6, Cayuse, crashed in Kagoshima, a southern part of Japan on 12 February 2015. Thereafter, one of OH1, Ninja, fell down in Wakayama, a middle part of Japan on 17 February in the same year. It is statistically rare for the military helicopter to go down in this streak and the defense force decided to restrain its use until they can conclude a cause.
However, the similar helicopter, OHD-1 dropped down on 6 April in Miyagi, a northern part of Japan. There were three military helicopters down in this two months, which is impossible statistically as an accidental coincidence. Especially, the last two events happened under a severe surveillance after the first crash, which is more impossible. If something improbable happens, it is more like a result of the deliberation especially when it is a streak of events.
These events were highly likely caused by the electromagnetic wave, particularly for the latter two downs. Generally speaking, it is possible for the wave to cause all three crashes, but it is often the case that the perpetrators avail the first event as a trigger and create similar events thereafter to exaggerate their capability. In this way, the event causes more fear than it really is, which makes politicians hesitant to restrict the radiowave technology.
In these cases, the first one might be a result of the true accident and the latter two downs were caused by the criminal intention. At the same time, the latter fell down in the same way, though the former was not.
The most presumable causes were a bird strike manipulated by the electromagnetic wave. The helicopter often flies low with a low speed, which makes it an easy target for its manipulation. I saw many times the bird was controlled by the electromagnetic wave, dated back to 1993, which implies this manipulation should be well advanced nowadays.
If the perpetrator manipulates the bird flying toward a suction port of the engine, which should be swallowed in to fail its function. As a result, the helicopter makes an emergency landing with auto rotation. There is no destructive phenomenon occurs to it, which falls down slowly with slowing rotor. If there is no protection against the bird strike and if it just has one engine, the accident is more easily caused.
The latter two accidents were exactly like this, falling down due to the engine trouble from relatively lower height. Furthermore, this is more likely driven by the bird strike controlled by the electromagnetic wave, but there is no 100% sureness. This is absolutely not a result of accidental coincidence, highly likely deliberately caused externally.