Citation I/SP (C501)
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types
Air Traffic Control Issued New Clearance
ATC Equipment / Nav Facility / Buildings; Human Factors
HTS had transitioned to a full CENRAP operation approximately 30 minutes prior to the event for TECH-OPS. CENRAP provides severely limited RADAR coverage below 020 in the HTS/HTW vicinity. HTW is located 5 miles northeast of HTS. In addition; a SCT-BKN020 cloud base apparently had been developing. A C501 was south of HTS descending northbound expecting a visual approach Runway 30. An SR22 called airborne off the HTW Airport requesting a southbound IFR clearance. He was maintaining VFR level at 015 unable to climb due to the cloud base. Because of his low altitude I was unable to ascertain the position of a SR22. I then suggested that the SR22 fly an east or southeasterly heading until I could RADAR identify him in order to stay away from the Runway 30 final that the C501 was rapidly approaching. At this time; the C501 stated that he would be unable to accept the visual approach to Runway 30 due to the clouds. He then requested a visual approach to the opposite Runway 12 as this end of the airport was without the cloud base. Coordination with Local Control was then completed. I then asked the SR22 to give me an updated position report from HTW He stated that he was now inexplicably west of HTW. I then suggested he fly a northbound heading in order to stay away from the Runway 12 final that the C501 was now approaching. A few minutes later; the SR22's squawk code was observed approximately 15 miles east-northeast of HTS at 015 about 2-3 miles from a complex of large antennas. I immediately took action to RADAR identify; turn and issue an IFR clearance to the aircraft. Given the position reports from the pilot; I did not expect the aircraft to be near that location! This event definitely has reminded me of the specific limitations of working with CENRAP. The unexpected cloud base hampered operations unexpectedly as did the inaccurate/confusing pilot position reports given. I could have transitioned back to normal RADAR for a short time in order to locate the SR22 and issue his IFR clearance. In hindsight; because of the low clouds; I think this would have been the appropriate solution.
HTS TRACON Controller described a MVA event when trying to identify a VFR aircraft operating at low altitudes due to low ceiling. The reporter listed CENRAP equipment/operations as a contributing factor.