NTSB Factual Report

On December 30, 2004, approximately 1300 mountain standard time, an Aerostar 601 airplane, N601DF, was destroyed after impacting terrain following a loss of engine power during initial climb near Hamilton, Montana. The certificated commercial pilot, the sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the personal flight, which was conducted in accordance with 14 CFR Part 91, and a flight plan was not filed. The flight was originating at the time of the accident, with the destination being the Stevensville Airport (32S), Stevensville, Montana.

In a telephone interview with the NTSB investigator-in-charge (IIC), the pilot stated that "almost immediately" after taking off on Runway 34 he retracted the landing gear, then noticed the left engine beginning to lose power as the airplane began to drift to the left. The pilot stated that because he was less than 100 feet above the ground, he didn't have time to "feather" the propeller. The airplane impacted up slopping terrain in a left wing low attitude, sliding to a stop and coming to rest in an upright position. The pilot reported that after he turned the master switch off and exited the aircraft, he noticed a fire starting to break out, which subsequently consumed the left side of the airplane.

A Federal Aviation Administration (FAA) airworthiness inspector, who traveled to the accident site, reported that the left engine's propeller blades were bent almost straight back, indicating minimum engine power at impact, while the right engine's propellers revealed signatures consistent with the engine generating full power. The aircraft was subsequently moved to a secure facility at the Stevensville Airport for further examination.

On January 20, 2005, an FAA airworthiness inspector, assisted by a certificated airframe and powerplant mechanic, conducted an examination of the aircraft's left engine. The examination revealed the engine, equipped with two Ray Jay turbochargers, sustained thermal damage due to a post crash fire. The oil lines feeding the turbochargers sustained thermal damage; however, the fittings were intact and no obstructions were noted. The wastegates were in the open position and moved freely. The intake hose on the left turbocharger was removed. There was no foreign object damage observed and the impeller was found to turn freely. When examined, the right turbocharger impeller would not turn, but no foreign object damage was noted. At this point the right turbocharger was removed for further examination.

The right hand mounted turbocharger exhibited no evidence of thermal or impact damage. The center section of the turbocharger was checked for restrictions and none were found, and the exhaust side of the turbocharger revealed no damage to the housing or the impeller. The impeller was frozen in the center section and would not turn. The intake impeller was then removed from the shaft and the drive shaft was tapped out of the center section. The center of the drive shaft was observed to be discolored (black and blue) with round marks evenly spaced around the shaft that matched the oil holes found on the bearings. Indications of grooving and scraping from a lack of lubrication to the bearings and drive shaft was observed. The oil holes located in the bearings positioned in the center section of the turbocharger were clear of obstructions.

Maintenance records revealed that on January 25, 2000, the left engine's right turbocharger was replaced and new oil lines installed. Recorded data also indicates that on March 28, 2004, both of the engine's turbochargers were replaced with overhauled ones. The recorded time on both left and right turbochargers at the time of the accident was 24.3 hours.

The type certificate data sheet lists the takeoff manifold pressure at 29.9 inches for the engine with turbocharger installed. A normally aspirated IO-520 engine puts out approximately 24.5 inches at takeoff, a difference of 5.4 inches of manifold pressure at takeoff power.

The pilot reported that there were no mechanical anomalies with the aircraft prior to takeoff which would have prevented normal operations.

.

NTSB Probable Cause

A partial loss of engine power due to the lack of lubrication and subsequent failure of the left engine's right turbocharger for undetermined reasons, and subsequent forced landing after takeoff. A factor was the unsuitable terrain for the forced landing.