Originally Posted by
Flying Binghi
...and TCAS is generally found in two pilot aircraft. .
Notwithstanding that TCAS is also fitted to most modern SPIFR equipped helicopters.
Unfortunately, from what has been found already, it appears that the pilots of both aircraft were probably completely unaware of the other's close presence.
From personal experience, small helicopters such as the Gimbal Cabrio offer a very small profile and are very difficult to see, especially from behind.