Originally Posted by
WE992
Ascot is used by All RAF transport aircraft when route flying. RR1000 series, Bae146. RR2000 series KC-30, RR4000 series being the A400M, RR5000 series C-130 and RR6000 series C-17. KC30s use Madras and Tartan call signs when tanking in the UK. 400 sometimes use Comet call signs when undertaking tactical flying with C-130s using Jigsaw.
RAF fast jets often use the Ascot call sign when in transit overseas when accompanied by KC-30. The ASCOT call sign dates back to the days of RAF Air Support Command, standing for Air Support Command Operation Task.
RRR1xxx callsigns are also used by 32 Sqn's Agusta. RRR7xxx is used by the Sentinels, Shadows and RC-135s.
I assume that by "KC-30" you mean the Voyagers, which also use RRR9xxx (possibly dependent on the mission).