MGM Tower and TRACON Controllers described a uncertain separation event when an aircraft departed VFR when in fact the weather had changed to IFR conditions.
Synopsis
MGM Tower and TRACON Controllers described a uncertain separation event when an aircraft departed VFR when in fact the weather had changed to IFR conditions.
Narrative
Airport was reporting IFR conditions with 2-1/2 SM visibility. Tower visibility was not reported as it was probably more than 4 SM. Local Control scanned two departure strips; with the first one apparently being SVFR and the next one IFR. The rules on SVFR are somewhat vague and always the subject to interpretations; but the last one that I heard indicated that if an aircraft was operating under Special VFR in a Class Delta Surface Area; then it could be the only aircraft airborne in the CDSA. I think that is excessive; but that is the way I understand the last interpretation of the rules that I was briefed on. I called Local Control and asked if the aircraft was on a Special VFR clearance; and he replied that I was correct; although the tone in his voice suggested that he had forgotten that until I posed the question. The SVFR aircraft had been fanned left to a 210 degree heading off of Runway 28 and the subsequent IFR departure had been fanned right to 300 degrees. This was much more separation than would be required of two IFRs. The reported visibility was suspect as aircraft were reporting the field in sight from 7 or more miles away. I continued to work the two aircraft out of the Class D as it appeared to be an incredibly safe operation. Recommendation: review and simplify the ATC requirements for SVFR. They are overly restrictive in many situations.
Second reporter narrative
I was working in the Tower with all the positions combined (CIC; Local Control; Ground Control; Flight Data and Clearance Delivery). The visibility was 2 1/2 SM to the north of the airport because of a fog bank; but the visibility to the south of the airport was clear. Multiple aircraft were on the three frequencies (Local; Ground; and Clearance Delivery). When the PA28 initially called clearance delivery for a SVFR to the southwest; I told the pilot to stand-by because I had IFR aircraft with clearances and release times to taxi to Runway 28 for departure and there were IFR aircraft lined up on final for landing on Runway 28. When I was able to turn my attention to the PA28; I gave him a standard VFR clearance off of MGM; maintain VFR at or below 3;000; squawk code; and departure frequency. Once the pilot of the PA28 had the departure information; he requested to taxi to Runway 21 for a southwest bound departure. I taxied the PA28 to Runway 21 for departure. Once the PA28 was ready for departure; I cleared the aircraft for departure and once the aircraft was airborne; I switched it to Departure. After switching the aircraft to Departure; I realized the AWOS alarm was alarming and that was when I noticed the visibility was 2 1/2 SM and that the PA28 should have been given a SVFR clearance to depart MGM to the southwest.On most occasions; this time of the morning is very very slow so it warrants the Tower being combined. This just happened to be on of those rare occasions where there was a busy spurt! My recommendation would be to de-combine the Tower positions at a set time; in the morning.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.