N488VGThiel George A JUST AIRCRAFT (HIGHL · 2013

The pilot of the experimental amateur built airplane reported that, after descending to a local river, he increased the throttle to add power and level off, but the engine did not respond. The engine lost total power, and he attempted an in-flight engine restart to no avail. The pilot initiated a landing to a nearby island in the river, however, during the landing, the airplane’s airspeed was fast, and braking was ineffective. The pilot turned the airplane to the right toward vegetation and subsequently impacted a sandbank. The airplane sustained substantial damage to the left-wing and the empennage.

A postaccident examination of the throttle control linkage revealed that the throttle control had separated at the throttle control pivot arm. The bolt, washer and nut which secured the cable to the throttle control pivot arm had backed out and were not located during the examination. Additionally, a bolt, bushing binding and nut were used to secure the throttle control pivot arm to a cross-member located between the throttle control cable and the carburetor cable binding. The return spring is designed to open the throttle to the fully open throttle position when the throttle control malfunctions. The torque on the nut that secured the pivot arm to the cross-member was excessive and consequently prevented the pivot arm from allowing the return spring to open the throttle.

The pilot of the tailwheel-equipped, experimental amateur built airplane, who was also an airframe and powerplant mechanic reported that, during approach to a sandbar, he side-slipped the airplane and the engine lost power because he was "too aggressive with the throttle and pulled it enough to bend the [carburetor] idle stop screw bracket." Because the engine was normally quiet, the airplane was sound proofed, and he used a noise-cancelling headset, he was unaware of the power loss until he attempted to add power, to no avail. He did not have enough time to restart the engine, so the airplane settled onto the water about 15 to 20 ft short of the sandbar. Subsequently, the airplane hydroplaned and came to rest on the sandbar inverted.

The pilot reported that the reason he was aggressive with the throttle was because of a lean mixture that tended to overheat the engine during takeoff or cruise on hot days.

Previously, he had attempted to mechanically enrichen the mixture by drilling holes in the fuel spray bar, but had drilled a hole "at the location where the engine wanted to idle", meaning that if the hole was open, the engine would idle high and if the hole was closed, the engine would "die." He added that it was not a problem unless he was trying to land short.

The airplane sustained substantial damage to the left wing lift strut, left wing, and rudder.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.

The Federal Aviation Administration (FAA) inspector reported that the pilot had modified the number and position of the last hole in the fuel spray bar. By doing so, the pilot was able to get the engine to "barely run" to perform short field landings. During the accident landing, it "must have cut off the flow of fuel enough to make the engine quit."