C172 PLT HAS A CLOSE ENCOUNTER WITH ANOTHER ACFT AT GTU; AN UNCONTROLLED ARPT.

Narrative

I WAS GIVING COMPLEX AIRPLANE TRAFFIC PATTERN TRAINING TO MY STUDENT; WHO WAS FLYING THE ACFT. THE TFC PATTER HAD BEEN QUIET BUT TWO ACFT CALLED AT ABOUT THE SAME TIME STATING THAT THEY WERE INBOUND ON THE GPS RWY 36 APCH AT GEORGETOWN. MY STUDENT AND I WERE PRACTICING LNDGS ON RWY 36. WE COMPLETED ANOTHER LNDG ON THE RWY AND MONITORED THE CTAF FOR THE INBOUND TFC ON THE GPS APCH. THERE WERE TWO ACFT (A BEECH DUCHESS AND AN RV-4) CONDUCTING THEIR RUN-UPS AT THE RWY. THE FIRST ACFT ON THE GPS APCH WAS A DIAMOND STAR AND ANNOUNCED THAT HE WAS NOW ON A 2 MI FINAL. FROM THE CTAF IT SEEMED THAT THERE WAS A CESSNA 400 SERIES ON THE APCH BEHIND THE DIAMOND. WE WERE NOW UPWIND AND I PRETTY MUCH ASSUMED THAT THE DIAMOND WOULD NOT BE A FACTOR. AT THIS TIME A KING AIR ANNOUNCED THAT HE WAS ENTERING THE DOWNWIND FOR RWY 36. TURNING CROSSWIND I SPOTTED THE KING AIR AND NOW WANTED TO GET A VISUAL ON THE DIAMOND AND THE TWIN CESSNA. ON DOWNWIND I SAW THE DIAMOND TOUCH DOWN ON THE RWY AND NOTICED THAT THE TWIN CESSNA WAS ON VERY SHORT FINAL. I GOT THE ATTENTION OF MY STUDENT TO SEE HOW THE TWIN CESSNA DOUCHED DOWN ABOUT 1000 FT BEHIND THE DIAMOND (STILL ROLLING OUT) WITH LOCKED BRAKES THAT GENERATED A LOT OF SMOKE. THE KING AIR WAS NOW ON BASE AND I ANNOUNCED ON THE CTAF THAT WE WOULD EXTEND OUR DOWNWIND SO THAT THE ACFT WAITING TO TAKE OFF COULD DO SO. THE KING AIR PLT TOLD ME THAT THERE WAS SOMEBODY ON LONG FINAL ON THE GPS APCH. I THOUGHT THAT HE WAS TALKING ABOUT THE INCIDENT THAT HAD JUST HAPPENED. WE EVENTUALLY TURNED A 3 MILE BASE WHEN I SPOTTED THE BONANZA DIRECTLY IN FRONT OF US AT OUR ALT; ON VERY LONG FINAL. I ANNOUNCED THAT WE WOULD CONTINUE OUR DOWNWIND NOW FOR THIS TFC AND WE FINALLY EXTENDED IT OUT TO ABOUT 4 MILES. IT HAS BECOME SOMEWHAT COMMON AT THIS ARPT FOR PLTS TO TRY TO AVOID THE PATTERN BY USING THE GPS APPROACHES; BUT THIS IS THE FIRST TIME THAT I HAVE SEE THREE ACFT WITHIN A SPACE OF 5 MILES TRYING TO USE THIS TRICK.