Amateur-built GLASTAR GS-1 N513GC accident near Columbus, Indiana

Probable cause

Slippage in the engine clutch and gear reduction module and a resultant uncommanded movement of the propeller blades into reverse thrust.

NTSB analysis

Family members and friends reported that, 2 years before the accident, the experimental, amateur-built airplane had experienced a serious in-flight engine problem. Since that time, the pilot had been repairing the engine and propeller system, and the accident flight was the airplane's first flight following the reported engine problem.

The pilot-rated passenger reported that, just after departing for a short local flight and turning the airplane to enter the downwind leg of the airport traffic pattern, the pilot informed him that there was a problem and that they needed to return to the airport. He added that the pilot began working "frantically on an electric switch for the propeller" while the engine was "screaming" but that the airplane continued descending. The airplane struck a tree and then impacted a house. An explosion and a postimpact fire immediately ensued, which consumed most of the airplane and the house. The pilot and passenger were able to exit the burning wreckage without assistance.

An examination of the engine clutch and gear reduction module found some metal contamination and a nonstandard displacement of the sprag clutch elements, and these issues likely resulted in clutch slippage, which can lead to the uncommanded movement of the propeller blades. The propeller blades were observed to be in about 5 degrees of reverse pitch, which would result in a substantial loss of glide capability.

Text from the NTSB. Open the NTSB docket for CEN13LA433 for the full record.