Narrative:

I was working the ground control position and observed this event on local west. The controller in charge was also observing and attempted to communicate instructions to the local controller; however; these suggestions went unused or were unwanted. Aircraft X; SR22; IFR; issued heading 230 and 2;000 ft; per LOA with approach control. Thirty seconds later; aircraft Y; MO20; called 6 miles south inbound. Mooney was instructed to enter right downwind to runway; and issued a beacon code and traffic departing on a 230 heading. Mooney was on a 1200 code and was 5 miles southwest of the field tracking a northeasterly course directly towards the path of the departing cirrus. Mooney was descending. Traffic was called to the cirrus with 'no joy.' moony finally entered the correct code and the position from the cirrus was approximately 2 miles. Cirrus was instructed to maintain 1;000 ft. Mooney was instructed to maintain 1;100 ft. The two aircraft had past each other by the time the mooney said he had the cirrus in sight. The cirrus was advised traffic no factor and switched to departure. I reminded the local controller in a loud tone to climb the cirrus to 2;000 ft. The local controller complied; the cirrus had not switched yet and received the climb instruction; [and] the MVA is 1;700 ft. No positive separation was being applied when several alternatives were available. This was a very dangerous situation that was completely preventable. Any type of positive control would have been preferable. Move the VFR mooney immediately. Using assigned altitudes below MVA that are only 100 ft apart is not approved separation. Certainly this was at a minimum; a 'traffic alert' situation to both aircraft.

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Original NASA ASRS Text

Title: Tower Controller described an unsafe event when the Local Controller used questionable altitude assignments to separate a VFR from an IFR aircraft.

Narrative: I was working the Ground Control position and observed this event on Local West. The CIC was also observing and attempted to communicate instructions to the Local Controller; however; these suggestions went unused or were unwanted. Aircraft X; SR22; IFR; issued heading 230 and 2;000 FT; per LOA with Approach Control. Thirty seconds later; Aircraft Y; MO20; called 6 miles south inbound. Mooney was instructed to enter right downwind to runway; and issued a beacon code and traffic departing on a 230 heading. Mooney was on a 1200 code and was 5 miles southwest of the field tracking a Northeasterly course directly towards the path of the departing Cirrus. Mooney was descending. Traffic was called to the Cirrus with 'no joy.' Moony finally entered the correct code and the position from the Cirrus was approximately 2 miles. Cirrus was instructed to maintain 1;000 FT. Mooney was instructed to maintain 1;100 FT. The two aircraft had past each other by the time the Mooney said he had the Cirrus in sight. The Cirrus was advised traffic no factor and switched to Departure. I reminded the Local Controller in a loud tone to climb the Cirrus to 2;000 FT. The Local Controller complied; the Cirrus had not switched yet and received the climb instruction; [and] the MVA is 1;700 FT. No positive separation was being applied when several alternatives were available. This was a very dangerous situation that was completely preventable. Any type of positive control would have been preferable. Move the VFR Mooney immediately. Using assigned altitudes below MVA that are only 100 FT apart is not approved separation. Certainly this was at a minimum; a 'Traffic Alert' situation to both aircraft.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.