Narrative:

A C172 was cleared for take off on runway 29R; departing IFR and turning to a 350 assigned heading. At the time; the field was below basic VFR minimums. A helicopter called and reported airborne off a nearby hospital; approximately 3 miles northwest of the airport; requesting transition southeast bound towards downtown. I advised the helicopter that the field was 'below basic VFR minimums; say intentions.' the helicopter requested SVFR clearance; and I advised 'unable due to IFR traffic in the airspace.' I believe the pilot responded that he would exit the airspace to the north. I then began exchanging traffic between the helicopter and the C172; and if I recall the C172 was about 3 miles south of the helicopter climbing through 6;100 MSL. The helicopter; I believe; appeared at 5;800 MSL indicated; airborne off the hospital and may have started heading south then east. Both the C172 and the helicopter responded to their traffic advisories and mentioned having either TCAS or traffic advisory equipment of some kind on both their respective aircraft. Additionally; the C172 was already above the helicopter and climbing while I expected the helicopter to remain low level due to the low ceiling and visibility - thus; though I could not ensure separation between the aircraft; I did not fear there was imminent danger of a collision. Since the reported weather was below basic VFR minimums; I could not visually observe the aircraft and did not have a means to ensure separation as required per 7110.65 ch. 7; and its associated references. When I determined the helicopter was no a factor; I switched the C172 to departure. Once the C172 was climbing out of 7;500 and clearing the class D airspace; I determined I could then provide the separation required and issued a SVFR clearance (per our LOA and SOP) to the helicopter; approving his request to continue southeast bound towards downtown. This was the first time I encountered this kind of situation; with an air ambulance helicopter reporting already airborne at a location off-airport while the field was below basic VFR minimums. Because the pilot was already airborne in the airspace; with conflicting IFR traffic nearby; I felt my duty priority at the time was to ensure that both pilots were aware of each other; so that they could take action to ensure that they did not become a conflict for each other. The presence of traffic advisory equipment in both aircraft was a definite benefit to safety. I also felt it was inappropriate to issue control instructions to the helicopter; since I was unable to issue an appropriate SVFR clearance. In this situation; I felt that the pilot in command of the helicopter was in the best position to determine whether it would be safest to continue flying (especially if a critical patient was aboard or needed transport); or return to the hospital until an appropriate SVFR clearance could be issued. To prevent this kind of occurrence in the future; I believe it is critical for flight crews operating from the hospitals within our airspace to ensure they have current weather information prior to departing. In this instance; I believe the ATIS message was current for at least 15 minutes prior; reflecting that the field was below basic VFR. However; I understand that it may be difficult to receive the ATIS transmission while sitting on the pad; and it may also not be possible to establish communications on tower frequency while off-airport; prior to becoming airborne. However; using a cell phone to receive our ATIS may be an option when weather is near/below basic VFR minimums; as well as calling the tower cab on the phone immediately prior to departure to coordinate if SVFR operations are possible.

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Original NASA ASRS Text

Title: Tower Controller described a loss of legal separation when a helicopter departed a hospital within Class D airspace during IFR conditions without clearance; conflicting with a previously cleared IFR departure.

Narrative: A C172 was cleared for take off on Runway 29R; departing IFR and turning to a 350 assigned heading. At the time; the field was below basic VFR minimums. A helicopter called and reported airborne off a nearby hospital; approximately 3 miles northwest of the airport; requesting transition southeast bound towards downtown. I advised the helicopter that the field was 'below basic VFR minimums; say intentions.' The helicopter requested SVFR clearance; and I advised 'unable due to IFR traffic in the airspace.' I believe the pilot responded that he would exit the airspace to the north. I then began exchanging traffic between the helicopter and the C172; and if I recall the C172 was about 3 miles south of the helicopter climbing through 6;100 MSL. The helicopter; I believe; appeared at 5;800 MSL indicated; airborne off the hospital and may have started heading south then east. Both the C172 and the helicopter responded to their traffic advisories and mentioned having either TCAS or traffic advisory equipment of some kind on both their respective aircraft. Additionally; the C172 was already above the helicopter and climbing while I expected the helicopter to remain low level due to the low ceiling and visibility - thus; though I could not ensure separation between the aircraft; I did not fear there was imminent danger of a collision. Since the reported weather was below basic VFR minimums; I could not visually observe the aircraft and did not have a means to ensure separation as required per 7110.65 Ch. 7; and its associated references. When I determined the helicopter was no a factor; I switched the C172 to Departure. Once the C172 was climbing out of 7;500 and clearing the Class D airspace; I determined I could then provide the separation required and issued a SVFR clearance (per our LOA and SOP) to the helicopter; approving his request to continue southeast bound towards downtown. This was the first time I encountered this kind of situation; with an Air Ambulance helicopter reporting already airborne at a location off-airport while the field was below basic VFR minimums. Because the pilot was already airborne in the airspace; with conflicting IFR traffic nearby; I felt my duty priority at the time was to ensure that both pilots were aware of each other; so that they could take action to ensure that they did not become a conflict for each other. The presence of traffic advisory equipment in both aircraft was a definite benefit to safety. I also felt it was inappropriate to issue control instructions to the helicopter; since I was unable to issue an appropriate SVFR clearance. In this situation; I felt that the pilot in command of the helicopter was in the best position to determine whether it would be safest to continue flying (especially if a critical patient was aboard or needed transport); or return to the hospital until an appropriate SVFR clearance could be issued. To prevent this kind of occurrence in the future; I believe it is critical for flight crews operating from the hospitals within our airspace to ensure they have current weather information prior to departing. In this instance; I believe the ATIS message was current for at least 15 minutes prior; reflecting that the field was below basic VFR. However; I understand that it may be difficult to receive the ATIS transmission while sitting on the pad; and it may also not be possible to establish communications on Tower frequency while off-airport; prior to becoming airborne. However; using a cell phone to receive our ATIS may be an option when weather is near/below basic VFR minimums; as well as calling the Tower Cab on the phone immediately prior to departure to coordinate if SVFR operations are possible.

Data retrieved from NASA's ASRS site as of April 2012 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.