CEN14LA276

The pilot reported that, during cruise flight, the engine lost power and began running roughly. He applied carburetor heat, set the mixture control to full rich, attempted to switch fuel tanks, and cycled the ignition switch to test the magnetos, but the engine continued to run roughly at reduced power. During the subsequent forced landing, the tires sunk into soft soil, and the airplane then nosed over. The weather conditions when the power loss occurred were conducive to the accumulation of moderate carburetor icing at cruise and descent power settings. Formation of ice within the carburetor throat could have resulted in a richer fuel/air mixture that could have been further exacerbated by the pilot's application of carburetor heat and his setting of the mixture control to full rich. The airplane was recovered from the accident site and released before a postaccident examination could be conducted; therefore, other possible causes for the engine power loss could not be ruled out.

On June 3, 2014, about 1515 central daylight time, a Cessna 172N, N734BY, sustained substantial damage when it nosed over during a forced landing following a loss of engine power near North Padre Island, Texas. The pilot was not injured. The aircraft was registered to and operated by an individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The flight originated from the David Wayne Hooks Memorial Airport near Houston, Texas, and was destined for the Port Isabel-Cameron County Airport, Port Isabel, Texas. The pilot reported that the airplane had been in cruise flight at 8,500 feet above mean sea level (msl) when the engine began running rough. He stated that he suspected the engine roughness may have been due to carburetor ice, or a fuel-air mixture that was too lean so he applied carburetor heat and set the mixture control to full rich. The engine continued to run rough. The pilot stated that he then attempted to switch fuel tanks, and cycled the ignition switch to test the magnetos but the engine continued to run rough at reduced power. The pilot reported that the airplane had approximately twice the required amount of fuel for the flight. When all efforts to restore engine power failed, the pilot executed a forced landing on an island. During the landing, the tires sank into the soft sandy soil. Once the nose landing gear tire touched down, the tire sunk into the soft soil and the airplane nosed over. Weather conditions reported near the accident site included a surface temperature of 32 degrees Celsius and a dew point of 21 degrees Celsius. Radiosonde information obtained from the National Oceanic and Atmospheric Administration (NOAA) indicated that the temperature and dew point at the airplane's cruising altitude were about 17 degrees Celsius and 3 degrees Celsius respectively. According to a carburetor icing probability chart, the surface readings were in a range of susceptibility for light icing at cruise and descent power settings. The NOAA readings at altitude were in a range of susceptibility for moderate carburetor icing at cruise power settings and severe carburetor icing at descent power settings. An Aircraft Owners and Pilots Association flight training publication states: "When you apply carburetor heat to melt ice that has formed in the throat, or venturi, of the carburetor, you may notice that the engine begins to run even rougher. This happens because the fuel mixture, already enriched because the ice is choking off some of the induction air flow, is suddenly made even richer by the addition of hot air." The document further states that the mixture may have to be leaned to provide the engine with a burnable fuel/air mixture. Due to the location of the accident site, on-scene examination of the airplane was not possible. Due to miscommunication between interested parties, the airplane was releasedprior to an FAA or NTSB postaccident examination after it had been recovered from the accident site.