AN SMA ALMOST LANDED ON TOP OF ANOTHER SMA AT AN UNCTLED ARPT.

Narrative

AT PM05 HRS; SMA X CALLED HEBER VALLEY UNICOM; RPTED A POS 8 MI TO THE W OF THE ARPT; ANNOUNCED INTENTION TO LAND AND REQUESTED TA'S. UNICOM RESPONDED WITH WX AND ACTIVE RWY AND WHEN REQUESTED IF THERE WAS TFC IN THE PATTERN; REPLIED NEGATIVE. AT PM12; SMA X ANNOUNCED A 3 MI LONG FINAL FOR RWY 21 AT HEBER; FULL STOP. AT PM14; SMA X WAS 200 FT PAST THE NUMBERS FOR RWY 21; 55 KIAS; ABOUT 20 FT OFF THE GND WHEN SMA Y; A LCL HEBER SMA OWNED AND OPERATED BY THE FLYING SVC; FLEW OVERHEAD; APPROX 15- 20 FT VERT SEPARATION AND LANDED IN FRONT OF SMA X. BOTH ACFT MADE UNEVENTFUL LNDGS. SMA X PROCEEDED TO THE RAMP. SMA Y CONTINUED TO THE END OF THE RWY; BACK-TAXIED AND EXECUTED ANOTHER TKOF AS IF HE HAD NOT NOTICED ANYTHING PECULIAR. 15 MINS AFTER THE OCCURRENCE; SMA Y TAXIED TO THE RAMP. BOTH MYSELF AND MY ATP RATED PAX MADE INQUIRIES AS TO WHAT THE OTHER ACFT HAD OBSERVED. THE PLT OF SMA Y WAS A LCL CFI GIVING INSTRUCTION TO A LCL STUDENT. THE CFI SAID HE HADN'T NOTICED A THING AND WAS FLABBERGASTED THAT HE HAD ALMOST LANDED ON TOP OF ANOTHER ACFT. HE CLAIMED HE HAD BEEN LISTENING TO UNICOM AND HAD BEEN MAKING POS RPTS ALTHOUGH NONE HAD BEEN HEARD BY UNICOM OR BY SMA X. THE LCL FBO COMMENTED THAT THESE KINDS OF THINGS HAPPEN ALL THE TIME AND WE SHOULDN'T BE SO UPSET. POSSIBLY THE LCL CFI HAD HIS RADIO TURNED DOWN A LITTLE TOO MUCH AND MAYBE HE WAS A LITTLE DISTRACTED BY HIS STUDENT BUT 'YOU KNOW THESE KIND OF THINGS HAPPEN AND ANYWAY THIS IS UNCTLED AIRSPACE AND RADIOS AREN'T REQUIRED AROUND HERE.' IN CONSIDERING THE CHAIN OF EVENTS; I CONCLUDE THAT SMA Y WAS NOT BROADCASTING POS; EITHER BECAUSE HIS RADIO WAS OFF; TURNED DOWN; OR ON WRONG FREQ. FOR THIS REASON UNICOM DID NOT KNOW HE WAS IN THE PATTERN. POSSIBLY HE HAD JUST RETURNED FROM THE PRACTICE AREA. SMA X CHOSE TO MAKE A STRAIGHT IN APCH TO LNDG RATHER THAN FLY OVER THE RWY MID-FIELD AND ENTER A DOWNWIND PATTERN BECAUSE UNICOM HAD ANNOUNCED THE PATTERN WAS CLR. SMA X IS A WHITE AIRPLANE WITH GREEN SIDE STRIPING. WITH SNOW ON THE GND IT WOULD BE DIFFICULT TO SEE FROM OVERHEAD UNTIL IT WAS OVER THE RWY. THE PLT OF SMA Y OBVIOUSLY MADE THE ERRONEOUS CONCLUSION HE HAD THE ARPT TO HIMSELF AND THEREFORE LOWERED HIS VIGILANCE.