Narrative:

I was proceeding with a passenger on an IFR flight plan at 27;000 ft; in a cessna 414 which is a pressurized turbo charged twin engine aircraft. We encountered isolated cell buildups. We proceeded to pass between cells with little or no precipitation or turbulence. Continuing eastward; center advised of the cell build ups [ahead] and advised that most of the traffic was getting through [to the] north. Upon reaching the area of buildups; the cells were clear on my GPS xm weather. We proceeded to fly in an area that appeared to have little or no buildup activity. As we entered IMC conditions; apparently the intakes on both engines became blocked by ice buildup. There was no ice on the wings or windshield. When I continued the instrument scan after concentrating on my flight path between the cells; I noticed my manifold pressure dropping in both engines; I immediately adjusted the mixture and power to see if that would make a difference; [and] the autopilot was continuing to hold our altitude. After dealing with the failed engines; I noticed the airspeed dropping dramatically. I advised center that both engines were out and that I would be descending. As the emergency descent continued we were inadvertently entering the heavy part of the cell buildups. I continued the descent at approximately 2;000 FPM; and was having a great deal of difficulty controlling the aircraft and dealing with limited avionics. I had previously installed an electric artificial horizon which became the most dependable instrument. In an effort to keep the wings level and keep the airspeed at a level to avoid over stressing the aircraft the plane continued to bank to the left; most likely causing further penetration into the thunderstorm. We encountered heavy rain; lightning; hail; and severe turbulence. Both engines slowly came back on around 11;000; as I chose not to feather the props and complete a shut down since we had plenty of altitude. We remained in the thunderstorm for approximately 15 more minutes. As we exited the storm; I amended my clearance to [a nearby airport] to pick up additional fuel to continue to our destination. En route to [destination]; I had to readjust the trim tabs; check the auto pilot and other systems of the aircraft. Upon arrival; the only visible damage to the aircraft was paint that had been worn off by the hail on the wing roots; engine cowls and nose. There were no injuries.

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Original NASA ASRS Text

Title: A Cessna 414 pilot reported intake ice and resultant loss of both engines despite the XM weather display showing no precipitation.

Narrative: I was proceeding with a passenger on an IFR flight plan at 27;000 FT; in a Cessna 414 which is a pressurized turbo charged twin engine aircraft. We encountered isolated cell buildups. We proceeded to pass between cells with little or no precipitation or turbulence. Continuing eastward; Center advised of the cell build ups [ahead] and advised that most of the traffic was getting through [to the] north. Upon reaching the area of buildups; the cells were clear on my GPS XM weather. We proceeded to fly in an area that appeared to have little or no buildup activity. As we entered IMC conditions; apparently the intakes on both engines became blocked by ice buildup. There was no ice on the wings or windshield. When I continued the instrument scan after concentrating on my flight path between the cells; I noticed my manifold pressure dropping in both engines; I immediately adjusted the mixture and power to see if that would make a difference; [and] the autopilot was continuing to hold our altitude. After dealing with the failed engines; I noticed the airspeed dropping dramatically. I advised Center that both engines were out and that I would be descending. As the emergency descent continued we were inadvertently entering the heavy part of the cell buildups. I continued the descent at approximately 2;000 FPM; and was having a great deal of difficulty controlling the aircraft and dealing with limited avionics. I had previously installed an electric artificial horizon which became the most dependable instrument. In an effort to keep the wings level and keep the airspeed at a level to avoid over stressing the aircraft the plane continued to bank to the left; most likely causing further penetration into the thunderstorm. We encountered heavy rain; lightning; hail; and severe turbulence. Both engines slowly came back on around 11;000; as I chose not to feather the props and complete a shut down since we had plenty of altitude. We remained in the thunderstorm for approximately 15 more minutes. As we exited the storm; I amended my clearance to [a nearby airport] to pick up additional fuel to continue to our destination. En route to [destination]; I had to readjust the trim tabs; check the auto pilot and other systems of the aircraft. Upon arrival; the only visible damage to the aircraft was paint that had been worn off by the hail on the wing roots; engine cowls and nose. There were no injuries.

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.