Dead reckoning means figuring out where you are on the basis of
past performance. 2D RNAV systems like the KNS80 usually only use one
co-located VOR and DME to work out position so “the system is not receiving
information from one VOR and one DME” represents normal operation and “the
system is receiving information from one VOR and two DMEs” would be wrong.
Systems like this don’t often take a TAS input because they are fitted to
little aeroplanes which don’t have ADCs or TAS computers so “the system is receiving
TAS information from the Air Data Computer” is wrong. “The system is receiving
information from only one VOR” suggests only bearing information is available
which means there is not enough data for a simultaneous fix and, if the RNAV
system has a DR capability, this is when it might be used.