What happened
During a scheduled competency flight, an FAA inspector was accompanying a pilot in a seaplane as part of a training session. While returning to the departure airport, the aircraft descended to 1,000 feet. After contacting the control tower for landing instructions and receiving a right base approach assignment, the engines began producing loud, irregular, and unusual noises. The pilot declared an emergency, notifying the tower that the left engine was malfunctioning while the aircraft was located two miles south of the field.
During the emergency, the inspector noted fluctuations in engine RPM and manifold pressure. Due to her rudder pedals being stowed, she was unable to use the dead foot, dead engine method to identify the specific failing engine. The pilot indicated an intention to land in a nearby body of water. Before the flight concluded, the aircraft struck a tree and a canal bank, eventually coming to rest upside down in the canal. There were 0 fatalities reported in the provided text.
Findings
Post-crash investigations of the airframe and flight controls showed no signs of mechanical failure or malfunction prior to the impact. However, inspections of the left propeller revealed it had not been feathered. Technical examination of the engines identified that the No. 6 front forward spark plug ignition lead had become disconnected, and the coupling for the No. 4 spark plug was unscrewed, leaving the carbon wire exposed.
When the left engine was tested in a cell, it reached rated and takeoff power, but a magneto check revealed a 125 rpm drop, which exceeded the limits specified in the overhaul manual. The right engine also showed a 75 rpm drop during testing. Additionally, an investigation into the inspector's credentials revealed she was not Event Based Current (EBC) for the fourth quarter, violating FAA requirements for performing flight certification duties. While the inspector's supervisor believed they had received authorization from the FAA Southern Region to proceed, the Southern Region stated they had not approved any operation outside of standard regulatory parameters.