MIA07LA036 · Cessna 182Q

During cruise flight, a Cessna 182Q seaplane experienced an engine compartment in-flight fire followed by a total loss of engine power. A successful forced landing to a lake was completed, and the fire was extinguished by a local fire department. Heat damage was noted to the firewall and structural members just aft of the firewall on the bottom of the fuselage. Examination of the engine compartment revealed a 10.00-inch long fire-sleeved, steel braided, flexible fuel line (the pressure return from the fuel control unit to the engine-driven fuel pump) had chafed against an electrical cable approximately 5 inches from where the fuel line attached to the engine-driven fuel pump. The chafing had created a hole in the fuel line and worn away the insulation from the wire which resulted in the in-flight fire, and ultimately the loss of engine power. The airplane was modified by a mechanic 2 years 4 months and 11 days earlier by installing a dimensionally larger engine and modifying the firewall per a Supplemental Type Certificate (STC). The engine provided to the mechanic came from the STC holder with the 10.00-inch fuel line installed, though this line was originally 8.25 inches in length when the STC was approved by the Federal Aviation Administration (FAA) Aircraft Certification Office (ACO). Prior to STC approval, personnel from the ACO inspected a modified airplane and drawings submitted by the STC submitter; however the drawings only depicted modifications and not previously installed lines, hoses, etc. The mechanic who modified the airplane with the larger engine reported that postaccident, he inspected five similar airplanes and found two had chafing of the same electrical cable, but against different fuel lines. He also stated the area where the fracture fuel line was located was "tight."

Verbatim NTSB analysis and probable cause from the NTSB dataset