Date: 201811
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Seaplane or Amphibian
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Cruise
Aircraft component: Engine
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Rotorcraft; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Situational Awareness; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: Aircraft had; on previous flight a week earlier; been reported to lose RPM on last take off run. Spoke with mechanic who felt carburetor ice might have been likely cause. Fuel topped off; engine run up on shore; no trouble found. Aircraft launched with another pilot at the controls to test engine operation and wind conditions. Aircraft warmed up normally; step taxied normally; and took off with normal engine operations. Aircraft landed; taxied to pier; and I boarded in pilot's seat with second pilot occupying the rear seat. Performed preflight tests; step taxied to the end of the lake; and took off normally. Climbed to 1;500 feet MSL over lake with all indications (oil pressure; oil temperature; amperage; RPM) normal. With all checks normal; decision was made to transit to nearby lake to make two take offs and landings and return. Enroute at 1;500 feet about 10 miles out; engine began to lose RPM. Pushed full throttle without any effect; put on carb heat with no effect; [and] removed carb heat as aircraft descended. Turned towards golf course off left wing and lined up on a reasonably long fairway. In descent; cycled mags; retarded and advanced throttle; removed carb heat; all without effect; engine power in slow deterioration. Flared and touched down on fairway and slid to a stop without damage to the aircraft or significant damage to the fairway. Engine quit as aircraft slid to a stop. We exited aircraft and arranged for ride. Aircraft moved to side of fairway; disassembled; and removed to maintenance facility.Lessons learned - With report of prior power roll back; I should have stayed over [the departure lake] and done a longer maintenance check flight showing more caution with regards to the reported engine roll back. My (poor) assumption after 15-20 minutes total flying that engine was OK (it had been over the course of several flights since the annual inspection) and that carburetor ice was indeed the cause of the prior power roll back. The past normal operation of the aircraft influenced my decision to depart the safe area over the lake to transit to a different lake to reduce the noise impact of multiple operations. Had I been more cautious and stayed over [the departure lake] the loss of power would have been followed by a dead stick landing at [the departure lake] rather than off airport.On a positive note; discussions with the pilot not flying (influenced by the prior reported power anomaly) included conversations regarding suitable landing sites below and a routing that that was not direct; but maximized the time spent over favorable terrain. Further; when the engine power loss occurred; very little time was lost recognizing issue and going through emergency memory tasks; or deciding that a forced landing was imminent. I was able to quickly select a suitable landing site and concentrate on basic airmanship to make the short approach and land on the fairway. Good crew resource management occurred as the Pilot Not Flying actually called out the emergency memory items (or performed them); as I set up the approach. Verbal inputs were also received with advice on flare; touchdown and roll out. The off airport landing was avoidable had I not been influenced by mechanic suggestion of carb ice; and took a far more cautious and rigorous test series over [the departure lake]. Fortunately; that poor decision only resulted in the significant cost and inconvenience of an off airport recovery; but no physical damage or injuries.The positive lessons learned included the value of thinking in advance of potential landing sites in the situation; and taking a 'point to point' route vs. a 'direct' route; which maximized the time over benign and favorable terrain. Having a second Non-Flying Pilot taking care of emergency check list items and giving verbal coaching greatly enhanced the likelihood of a successful outcome.




Synopsis: Amphibious aircraft pilot reported a loss of engine power resulted in an off field landing.