Skyhawk 172/Cutlass 172
Air Traffic Control Fully Certified
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Human Factors; Procedure
Marginal VFR weather; Runway 31 was the active. There is no RADAR coverage from the surface to around 1;000 FT at the Tower; which uses the ZZZ1 RADAR site for the STARS display; and no RADAR coverage from the surface to around 2;500 FT for the Approach Control which uses the ZZZ2 RADAR site. The Tower uses different colored plastic chips to differentiate between IFR and VFR aircraft. The Ground Control/Flight Data position was conducting training and had received a Remove Strips on an arriving C172 and removed the red IFR chip from the Local Control board and replaced it with a clear VFR chip. Several minutes later; Approach verbally coordinated the C172 as an NDB approach to Runway 13 in accordance with the Letter of Agreement. Since many aircraft do practice approaches VFR I; as Local Controller; incorrectly assumed that the C172 was VFR on the approach. At the same time I was starting to recover several other aircraft that were having difficulty with lowering clouds to the north and west. Several minutes later Approach used automated methods to coordinate a King Air on a RNAV approach to Runway 31. As the aircraft got closer; it became necessary to circle the C172 to Runway 31; but as I assumed he was VFR; I failed to coordinate the circle with Approach. Since Approach has such poor RADAR coverage in the area they were not able to know the C172's position and had to break the King Air off his approach. Ideally we should have RADAR coverage to the surface. In the meantime; I would like more training on the STARS display; tailored to this particular situation; especially the data tags on IFR aircraft. An overall review of both STARS and FDIO information for all our controllers would not be amiss either. Additionally the facility SOP should be changed so that the Ground Control/Flight Data controller doesn't make changes to the Local Control chip board beyond handing the Local controller the chips for aircraft taxiing to the runway and let the Local controller handle his own inbound chips.
Local Controller described a loss of separation event when the IFR vs. VFR status of an aircraft was confused; the reporter recommending changes to local procedures to re-emphasize flight plan status to Local Control.