Overview
A commercial certificated pilot departed on a cross-country flight in a float-equipped airplane under Title 14, CFR Part 91. About 15 minutes after takeoff, the engine began to lose power and then quit. The pilot executed a forced landing on a small lake, but the airplane collided with trees before touchdown.
Fuel Management and Indications
The pilot reported departing with 10 gallons of fuel and noted that the right wing fuel gauge was indicating 1/4 full. After landing, the right fuel gauge still indicated 1/4 full. The following day, the pilot drained the fuel tanks and discovered that both wing fuel tanks were empty. He eventually drained about 2 gallons of fuel from the fuel system.
Fuel Quantity Indicators
The left wing fuel indicator was an original float-type rod. The right wing tank quantity indicator had been installed in the airplane by a mechanic under a Supplemental Type Certificate (STC) about 4 months before the pilot purchased the airplane. This STC uses a "U"-shaped, clear segment of plastic tubing that functions as a visual column indicator (sight gauge) of the tank's fuel level.
Installation Issue
The installation instructions for the sight gauge include the installation of a length of fuel hose between the ends of the sight gauge and the fuel tank outlets. The length of the hose is not specified in the STC, only stating "as required." During a post-accident examination of the airplane by an FAA inspector, the pilot and a mechanic noted that they found an excessively long length of fuel hose between the lower sight gauge attach point and the lower fuel tank outlet. They stated that the length of hose was arched upward between the two points of attachment, allowing fuel to be trapped in the lower end of the sight gauge.