The private pilot conducted a 20-minute local flight in the Eros 1600, an experimental, amateur-built airplane, after installing a new ignition coil on the two-stroke, two-cylinder engine.
He then returned to the airport in Lebanon, Tennessee, where he landed the airplane, back-taxied on the runway, and initiated a second takeoff.
Witnesses reported that, shortly after takeoff, the plane experienced a total loss of engine power.
The airplane entered a left turn back toward the runway, then subsequently turned “sharply” left and descended to the ground. The pilot died in the crash.
Examination of the airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Examination of the engine revealed that the front spark plug was burnt white, consistent with exposure to high temperatures or an excessively lean carburetor calibration. Although both front and aft carburetor adaptors exhibited degradation, the front cylinder adaptor exhibited significantly more damage and cracking compared to that of the aft cylinder.
This likely resulted in additional air being ingested by the front carburetor, which subsequently resulted in a leaner fuel/air mixture in that cylinder.
In addition, the front cylinder piston exhibited a hole about 1 centimeter in diameter, consistent with detonation/preignition.
Records located in the pilot’s hangar indicated that he was servicing the engine with a fuel/oil ratio of 40:1, rather than the manufacturer-recommended ratio of 50:1.
It is likely that the use of an improper fuel/oil ratio resulted in carbon deposits in the front cylinder.
Combined with the effects of the lean fuel/air mixture as a result of the degraded carburetor adaptors, the engine was susceptible to the development of detonation and/or preignition, which subsequently resulted in the development of a hole in the front cylinder piston head.
As a result, the engine experienced a total loss of power, to which the pilot responded by attempting to turn back to the airport at low altitude. During the turn, he allowed the airplane’s airspeed to decay and exceeded its critical angle of attack, which resulted in an aerodynamic stall and collision with terrain.
Probable cause: A failure of the front cylinder piston due to the pilot’s improper maintenance, which resulted in a total loss of engine power after takeoff. Contributing to the accident was the pilot’s decision to return to the runway at low altitude following the loss of engine power, and his failure to maintain adequate airspeed during the turn, which resulted in the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall.
NTSB Identification: ERA16FA084
This January 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.