Helicopter pilot reports encountering severe turbulence at 4000 ft approaching las from the east. En...

Narrative:

Pilot and medical crew responded to local hospital for a medical flight to a hospital in las vegas. Weather was forecast to be better than 12;000 ft and 6 miles visibility for the flight to and from las vegas. There was no mountain obscuration but turbulence was forecast from 12;000 ft to 24;000 ft. Enroute to las vegas; ceilings once came down to approximately 2000 ft but the lights of las vegas were still visible reflecting off the cloud base in the distance so the horizontal visibility was good. We flew in and out of light rain once or twice and I had already made the decision to wait until daylight for the return trip. About 15 minutes out we experienced moderate turbulence at 5500 ft when we were crossing the colorado river. Winds were expected to increase as a low pressure was approaching the southwest. However; nothing greater than winds in the high 'teens were expected near the end of our flight. We started a gradual descent to a VFR reporting point for the class B airspace of las vegas. ATIS was already received and I was preparing a voice call to tower when the nose of the aircraft pitched up rapidly and started and uncommanded roll to the right. That was quickly followed by a nose pitch down and I could sense the aircraft moving laterally to the right. Our altitude was approximately 4000 ft MSL or 1500 ft AGL. Pretty much from day one of flight training; unusual attitude recovery has been roll wings level and raise or lower the nose to the horizon. Once this was accomplished; I heard an alert tone and noticed the 'check instr' light on. During that evolution the collective was pulled and the engine received an over torque; although; I don't remember the event of pulling the collective. I believe that it was arresting the sink rate during the turbulence that the over torque occurred. The total time of the event was probably 5-6 seconds and the aircraft felt uncontrollable the whole time. After the occurrence; all engine and flight parameters were normal except for the exceedance on the torque gauge. Our intended landing site was changed from the hospital to the airport because of its closer proximity and possibility of maintenance for the aircraft. After the medical crew completed the transport via ground; we stayed at the las vegas airport until maintenance and transportation could be arranged.

Original NASA ASRS Text

Title: Helicopter pilot reports encountering severe turbulence at 4000 FT approaching LAS from the east. Encounter resulted in momentary loss of control; and engine over-torque.

Narrative: Pilot and medical crew responded to local hospital for a medical flight to a hospital in Las Vegas. Weather was forecast to be better than 12;000 FT and 6 miles visibility for the flight to and from Las Vegas. There was no mountain obscuration but turbulence was forecast from 12;000 FT to 24;000 FT. Enroute to Las Vegas; ceilings once came down to approximately 2000 FT but the lights of Las Vegas were still visible reflecting off the cloud base in the distance so the horizontal visibility was good. We flew in and out of light rain once or twice and I had already made the decision to wait until daylight for the return trip. About 15 minutes out we experienced moderate turbulence at 5500 FT when we were crossing the Colorado River. Winds were expected to increase as a low pressure was approaching the southwest. However; nothing greater than winds in the high 'teens were expected near the end of our flight. We started a gradual descent to a VFR reporting point for the Class B airspace of Las Vegas. ATIS was already received and I was preparing a voice call to Tower when the nose of the aircraft pitched up rapidly and started and uncommanded roll to the right. That was quickly followed by a nose pitch down and I could sense the aircraft moving laterally to the right. Our altitude was approximately 4000 FT MSL or 1500 FT AGL. Pretty much from day one of flight training; unusual attitude recovery has been roll wings level and raise or lower the nose to the horizon. Once this was accomplished; I heard an alert tone and noticed the 'Check Instr' light on. During that evolution the collective was pulled and the engine received an over torque; although; I don't remember the event of pulling the collective. I believe that it was arresting the sink rate during the turbulence that the over torque occurred. The total time of the event was probably 5-6 seconds and the aircraft felt uncontrollable the whole time. After the occurrence; all engine and flight parameters were normal except for the exceedance on the torque gauge. Our intended landing site was changed from the hospital to the airport because of its closer proximity and possibility of maintenance for the aircraft. After the medical crew completed the transport via ground; we stayed at the Las Vegas airport until maintenance and transportation could be arranged.

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.

Attributes
ACN	866021
Time
Date	200912
Local Time Of Day	0001-0600
Place
Locale Reference	LAS.Airport
State Reference	NV
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	Bell Helicopter Textron Undifferentiated or Other Model
Operating Under FAR Part	Part 135
Flight Phase	Descent
Component
Aircraft Component	Turbine Engine
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Commercial
Events
Anomaly	Aircraft Equipment Problem Less Severe Inflight Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Weather / Turbulence

Helicopter pilot reports encountering severe turbulence at 4000 ft approaching las from the east. Encounter resulted in momentary loss of control; and engine over-torque.