Amateur-built AIRCRAFT (HIGHL N488VG accident near Monroe, Washington

Probable cause

The pilot's improper engine modification and operation, which resulted in a total loss of engine power due to fuel starvation, and the pilot's failure to maintain an adequate approach path, which resulted in the airplane landing short of the runway.

NTSB analysis

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 that the engine then lost power because he was "too aggressive with the throttle and pulled it enough to bend the [carburetor] idle stop screw bracket." The engine was normally quiet, the airplane was sound proofed, and the pilot also used a noise-cancelling headset, which prevented him from being aware 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 then 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.

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 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."

That pilot reported that he had previously attempted to mechanically enrich 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.

Text from the NTSB. Open the NTSB docket for GAA19CA034 for the full record.