N7849YPiper PA-30 · 1965

On April 3, 2011, about 1300 mountain daylight time, a Piper PA-30, N7849Y, experienced an intermittent loss of left engine power during initial climb from the Sierra Blanca Regional Airport (SRR), Ruidoso, New Mexico. The airline transport pilot subsequently executed a forced landing and neither he nor the passenger was injured. The airplane sustained substantial damage to the fuselage and both wings. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the cross-country flight destined for the Eagle's Nest Estates Airport (2TS6), Midlothian, Texas.

According to the pilot, around 200-feet above ground level (AGL), the airplane's left engine began operating intermittently with reduced power. The pilot added that because of the partial loss of engine power, along with high density altitude, turbulence, and wind shear, he was unable to maintain altitude. The airplane collided with the airport's perimeter fence and the left wing struck a tree. Subsequently, the airplane impacted the ground and came to rest in an upright position in a field adjacent to the airport.

Logbook entries provided to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), documented previous occurrences where the left engine experienced partial power loss. An entry dated December 11, 2009, reported that the left engine would not reach expected static RPM and that it ran "rough." The fuel flow divider was removed, cleaned, and reinstalled. The engine would then reach expected static RPM and was returned to service. An entry on February 2, 2010, stated that the airplane was landed due to a "rough' running left engine. Following the discovery of fuel contamination, the fuel system was flushed and the engine returned to service.

An airframe and powerplant mechanic (A&P), with an inspection authorization (IA), examined both engines. Engine continuity was established through each engine and the magnetos produced spark when rotated. A differential cylinder compression test was performed on each cylinder. The right engine cylinders ranged from 65 to 72 PSI over 80 PSI and the left engine cylinders ranged from 62 to 68 PSI over 80 PSI. Both inlet air filters, along with the fuel servo inlet screens, were found to be unobstructed. The mechanic reported that no abnormalities were noted that would have prevented either engine from producing power.

The airplane's weight at the time of the accident was calculated to be approximately 231 pounds below the maximum gross weight of 3,600 pounds. In addition, the center of gravity (CG) was calculated to be within limits. Per the pilot operating handbook (POH), the service ceiling for the airplane was listed as 18,600 feet density altitude and the single-engine service ceiling as 5,800 feet density altitude. The calculated density altitude around the time of the accident was 9,040 feet.

At 1315, the automated weather observing system at SRR reported, wind from 230 degrees at 37 knots with gust to 46 knots, 10 miles visibility, clear of clouds, temperature 68 degrees Fahrenheit, dew point 16 degrees Fahrenheit, and a barometric pressure setting of 29.86 inches of Mercury.

The reason for the left engine's intermittent loss of power could not be determined.