I have come across some flying with Hughes 500s at Boeing Field when someone was using a strobe to track the rotors as part of the maintenance. I figured that would be a one off but another time I was there, the same thing happened – this time with a 369. I would have loved to have been onboard when this was being done to see how the tracing of the blades looks in flight when the strobe is flashing. I imagine it would be quite an interesting engineering thing to see.