Complex sentence: An initial attempt at the full scale test was scrubbed in late 1983 due to problems with the uplink connection to the 720, due to the fact that if the uplink failed the ground based pilot would no longer have control of the aircraft.
Split into simpler sentences: An initial attempt at the full scale test was scrubbed in late 1983 due to problems with the uplink connection to the 720. If this failed, the ground based pilot would no longer have control of the aircraft.