NOS APCH CHARTS. MEANING OF 10 MI RING.

Narrative

TODAY I GOT INTO A DISCUSSION WITH SOME OF MY FELLOW CTLRS CONCERNING NOS APCH PLATES AND ALTS TO FLY. THE DISCUSSION DEALT WITH THE 10 NM DISTANCE CIRCLE ON NOS INST APCH PLATES; AND WHAT IT MEANS. OUR DISCUSSION CTRED ON THE NDB RWY 4 APCH TO BOLTON ARPT (2I4) HERE IN COLUMBUS; OHIO. ALL OF MY FELLOW CTLRS THAT I SPOKE WITH INSISTED THAT THE 'REMAIN WITHIN 10 NM' NOTATION ON THE NOS APCH PLATE PROFILE VIEW IS COINCIDENT WITH THE '10 NM DISTANCE CIRCLE' ON THE PLAN VIEW. IN OTHER WORDS; THEY INSIST; AS IN 2I4'S NDB RWY 4 APCH; THAT THE PLT IS SAFE TO FLY AT 2700 FT -- ANYWHERE -- WITHIN THAT 10 NM CIRCLE. WHILE I AGREE THAT IT IS SAFE TO FLY AT THAT ALT IN THIS PARTICULAR CASE; I DISAGREED; SAYING THAT THE '10 NM DISTANCE CIRCLE' SHOULD NOT BE RELIED UPON FOR SAFE ALT INFO. I INSISTED THAT IT IS NOT DESIGNED FOR THIS PURPOSE. WHILE I FEEL CERTAIN ABOUT THIS; I'M AT A LOSS TO FIND ANYTHING DEFINITIVE ON THE PURPOSE OF THAT '10 NM DISTANCE CIRCLE.' WHAT PURPOSE DOES IT SERVE ON THE NOS CHARTS? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ATP 210 SPECIALIST STATED THE MEANING OF THE 10 MI RING WAS NOTHING MORE THAN SHOWING INFO CONTAINED IN THE RING IS DRAWN TO SCALE. THIS INFO IS CONTAINED IN SPEC BOOK NOT READILY AVAILABLE TO PUBLIC. RPTR WAS CALLED AND INFORMED.