Narrative:

While returning to base from a patient transfer I encountered reduced ceilings enroute. The ceiling was consistent at about 2000 feet AGL. There was rising terrain ahead. I selected an altitude that would allow me to cross the high ground an equal distance from the terrain and the ceiling. The terrain was not level; as I crossed the apex of the pass the terrain alerting system in the aircraft announced minimums several times. My focus was outside the aircraft but when I did glance at the radar altitude I noted that I had gone below 500 feet AGL several times. This terrain crossing lasted a few minutes. I could have minimized the number of terrain alerts but chose to stay in a stable flight profile. The visibility was very good and the illumination from cultural lighting was more than sufficient to identify obstacles and prevent CFIT. I am required to maintain 500 AGL at night per the fars. My decision to stay an equal distance from the clouds and the terrain put me below minimums. I felt that the greatest risk during this portion of the flight was an inadvertent IMC (iimc) event. Based on the visibility and the illumination I felt that a lower altitude guaranteeing cloud clearance was the most conservative approach.landing the aircraft was always an option. What I did not want to do was climb the aircraft closer to the clouds to satisfy the system. The risk was an iimc event; the terrain and obstacles were clearly illuminated. Since night vision goggles (nvg) are in such wide use today there should be a change that allows pilots to fly at lower altitudes with nvgs. We are able to reduce our weather minimums but not our in route minimum altitude.

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Original NASA ASRS Text

Title: A helicopter pilot reported difficulty maintaining the FAR required altitude above terrain due to a lowering weather ceiling and rising terrain.

Narrative: While returning to base from a patient transfer I encountered reduced ceilings enroute. The ceiling was consistent at about 2000 feet AGL. There was rising terrain ahead. I selected an altitude that would allow me to cross the high ground an equal distance from the terrain and the ceiling. The terrain was not level; as I crossed the apex of the pass the terrain alerting system in the aircraft announced minimums several times. My focus was outside the aircraft but when I did glance at the radar altitude I noted that I had gone below 500 feet AGL several times. This terrain crossing lasted a few minutes. I could have minimized the number of terrain alerts but chose to stay in a stable flight profile. The visibility was very good and the illumination from cultural lighting was more than sufficient to identify obstacles and prevent CFIT. I am required to maintain 500 AGL at night per the FARs. My decision to stay an equal distance from the clouds and the terrain put me below minimums. I felt that the greatest risk during this portion of the flight was an Inadvertent IMC (IIMC) event. Based on the visibility and the illumination I felt that a lower altitude guaranteeing cloud clearance was the most conservative approach.Landing the aircraft was always an option. What I did not want to do was climb the aircraft closer to the clouds to satisfy the system. The risk was an IIMC event; the terrain and obstacles were clearly illuminated. Since Night Vision Goggles (NVG) are in such wide use today there should be a change that allows pilots to fly at lower altitudes with NVGs. We are able to reduce our weather minimums but not our in route minimum altitude.

Data retrieved from NASA's ASRS site 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.