AerialPro

Feature question on the Canon 5D Mark III. When does the camera produce NTSC video output? Is the output enabled whenever the camera is on, or only when actively recording video? I am setting up an aerial photography platform and am exploring options for a rig that will shoot not only stills and video but has an FPV downlink for easier operation. I need to know if I can use the 5D as my full time source for FPV video or if I need a secondary video camera to do this.