CEN22LA283

The pilot reported that the amphibious airplane’s engine gradually lost partial power shortly after takeoff and he was unable to maintain altitude. He performed a forced landing in a field with the retractable landing gear in the retracted position. After touchdown on the hull, as the airplane slowed, the right wing settled to the ground and the right-wing sponson struck the ground. The airplane incurred substantial damage to the right wing and fuselage during the forced landing. Postaccident examination of the airplane revealed that the fiberglass fuel tanks of the airplane had debris and deterioration. The resin used in construction of the fuel tanks was not compatible with automotive gasoline. The pilot/owner had never used automotive gasoline but could not attest to what previous owners had used. Further examination did not reveal any other preimpact anomalies with the engine that would have precluded normal operations. Although there was a potential for carburetor icing at glide power, based on the available evidence and that the airplane was taking off at the time of the accident, the engine likely lost power due to fuel starvation caused by debris obstructing the fuel outlet port of the fuel tank.

On June 24, 2022, about 0848 central daylight time, an Osprey II airplane, N10236, was substantially damaged when it was involved in an accident near Bulverde, Texas. There were no injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the airplane was not fueled on the day of the accident and had last been fueled a week before. The fuel tanks were about ½ full with about 6 gallons in each of the 2 tanks. He sampled the fuel tanks and observed no contaminants. The engine start and run-up were normal, and he proceeded to runway 16 at the Bulverde Airpark (1TT8) for takeoff. The engine operated normally during the takeoff roll. Shortly after rotation, the engine sounded quieter, and the rpms fluctuated between 2,300 - 2,500 rpm. An engine speed of 2,600 rpm was normal for takeoff. He retracted the landing gear, which helped the climb a little, but the engine power continued to deteriorate. No engine roughness was felt at this time. The airplane was placed at the best angle for climb, about 70 mph. As the airplane cleared the 35-ft-tall trees at the end of the runway, the engine rpm was about 2,100 - 2,300 rpm and some roughness was now felt. The airplane would not climb, and the pilot selected a field and landed the airplane with the retractable landing gear in the retracted position. Before touchdown, the mixture was leaned to shutoff and the throttle was closed. After touchdown on the hull, as the airplane slowed, the right wing settled to the ground and the right-wing sponson struck the ground. The airplane incurred substantial to the right wing and fuselage during the forced landing. Postaccident examination of the airplane revealed that the fiberglass fuel tanks contained a considerable amount of contamination and the resin system appeared to be deteriorating. The resin system used in construction was believed to be polyester resin, which was not compatible with automotive fuel. The pilot/owner was not the original builder and had only used 100 low lead aviation gasoline since purchasing the airplane, but he could not say if previous owners had used automotive gasoline. The baffling in the tanks prevented visual inspection with the tanks mounted in the airplane and removal was not possible, requiring disassembly of the wings. The pilot noted that when he first purchased the airplane the gascolator had debris and after the accident it had some debris in it as well. Examination of the engine confirmed compression on all cylinders. Although ignition was not verified during the examination, the pilot reported that during the accident flight the engine never stopped running, indicating that the ignition system was operating during the event. The air temperature about the time of the accident was 80° F and the dew point was 70° F. The Federal Aviation Administration’s Carburetor Icing Probability Graph indicates that, under those conditions, the airplane encountered a seriousrisk of carburetor icing at glide power.