I took a high speed 1200 fps video of a Spektrum DX9 RC transmitter next to a Trex 500 that it was controlling with DS510 servos, focusing on the transmitter's stick and the trex 500's swash plate.
The transmitter stick was then held back and then let go to see how long it took for the swash movement. Each frame of the video is under a millisecond of time (0.83) and it is displaying at 30 fps. What is interesting is I stepped through the frames one by one and it appears to take about 57 frames from the time the stick was let go to the time the swashplate started to move which equals about 47.5 milliseconds. I was actually surprised by that because I expected it to be about 22 milliseconds because the frame rate is set to 22ms. Spektrum's DX7 and Futaba's 12z transmitter showed the same tx to swash latency.