An aircraft ground support equipment, GSE, unit for externally accessing video data from an aircraft video surveillance system, AVSS. The GSE unit constitutes a back-up AC power supply for the aircraft's AVSS and comprises a power output connector for connecting a power cable to a ground connection panel on the outside of the aircraft. AC power is supplied either by a rechargeable battery through a converter, or by mains power plugged into the GSE unit. A power source selection switch is switched to route either battery power or external power to the aircraft dependent on factors including battery status, presence of power at the external power connector and presence of power in the aircraft. Video data from the AVSS can thus be streamed out, even in the absence of aircraft power, for example to a portable personal computer.