Ryan NAVION A N4911K accident near Torrington, Wyoming

Probable cause

The carburetor’s failure to meet its operating limits at the low range, which resulted in a loss of engine power when the pilot reduced power for landing.

NTSB analysis

The pilot reported that he leaned the mixture while en route, but could not find the peak performance. He set the mixture control to what he thought it was appropriate for 5,000 to 6,000 feet altitude. As he entered the landing pattern at his destination, he lowered the landing gear and prepared for landing. As he reduced the throttle position, the engine lost all power, and the descent rate increased. The pilot determined that the airplane would not glide to a runway and maneuvered to an open area. The airplane touched down hard, and the landing gear collapsed. The airplane sustained substantial damage to the firewall and fuselage. Postaccident examination of the airframe and engine revealed no mechanical malfunctions or failures that would have precluded normal operation. The carburetor was removed and connected to a test cell. The unit was found out of limits at the low end of its operating range. Thus, with the fuel mixture leaned and a subsequent reduction in the power for landing, a temporary disruption of the fuel flow caused the engine to sputter and lose power.

Text from the NTSB. Open the NTSB docket for WPR11LA346 for the full record.