Navion Navion A N4106K accident near Livermore, California

Probable cause

The improper installation of the gascolator fuel inlet line and hose clamp connection, which resulted in the total loss of engine power.

NTSB analysis

The airplane had an annual inspection and new wingtip fuel tanks installed about 6 months before the accident. The accident flight was the first flight since the maintenance. The pilot completed a normal runup inspection and the engine developed full power during takeoff. However, at an altitude of approximately 500 ft above ground level (agl), as the pilot turned onto the crosswind leg of the traffic pattern, the engine began to surge and lose power. As the pilot reduced the power for landing on the downwind leg, the engine lost total power. When the pilot realized the airplane would not make it to the runway, he prepared for a landing on the grass area parallel to the runway. The airplane touched down and the left wing impacted concrete blocks.

A postaccident examination of the engine revealed a leaking gascolator fuel inlet line caused by a loose hose clamp connection on the fuel line from the fuel selector to the gascolator. The loose connection allowed a large amount of air to be introduced into the fuel line going to the engine and fuel pumps, which caused the engine to surge and eventually lose power.

The examination also revealed several maintenance discrepancies. The leaking fuel inlet line was made of rubber instead of aluminum tubing, and the fuel selector's connection was improper. Additionally, the wingtip fuel tank installation revealed several inconsistencies with the installation, such as loose clamps and improper hardware installed. These discrepancies were an indication of improper recent maintenance.

Text from the NTSB. Open the NTSB docket for WPR21LA072 for the full record.