Radio Nav Systems RQ - Mode C XPDR???
Reading the AIP for a bit of study got me talking to a very knowledgeable LAME (E, I & R) friend.
He mentioned something about ATC directing a Go Around (Missed Approach) if, whilst making a GNSS Approach and not yet "visual", they lost the aircraft's Mode C readout. My mate said it was due to some earlier GPS receivers which took barometric aiding readings from the encoder attached to the altimeter (a now discontinued practice).
I cannot find any reference in the AIP (Book) which specifies that Mode C is required for a specific approach. (Sure it's required for flight in Radar CTA generally but I'm referring to a failure in flight.)
Any body out there know what he was referring to and able to back it up with a Reference?
FRQ CB