The last message from the pilot was a manualsignal at 11pm local time, in which he said he was flying through an area of black, electrically charged clouds with violent winds and lightning.
The first indication is that Tuesday afternoon's crash occurred after the metro system staff had switched to manual scheduling following a signal failure.
暗示星期二下午这场事故发生的第一个信号就是，地铁系统员工在信号指示失败后立刻转为手动操作。
3
Pulse counter with manual reset and electric output signal.