J3 Cub
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 25; Flight Crew Total 1990; Flight Crew Type 350
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
While training a student pilot in ground reference maneuvers and lazy eights; we suffered a complete loss of power. engine restart procedures were executed and were unsuccessful. Our area of operation is in a humid coastal area. We are well versed in the use of carb heat and many times it is on for most of the flight. It was on continually this day. The area that we use for this training has many good hay meadows and pastures to complete a forced landing. Our landing was very good and we were able to land our Piper j3 with no damage or injuries whatsoever. We used less than 1/2 of the field to execute the forced landing.After the landing and securing the aircraft it was noticed that we had several areas below the carburetor where fuel was continually dripping out of the airbox in substantial amounts. We assumed the carb float was stuck and flooded the engine out.After disassembly of the Stromberg carburetor in the shop we found a good amount of small gray beads and flakes in the float bowl that could be easily crushed into a powder. one of these beads was lodged in the carburetor main fuel jet cutting off the fuel flow to the carburetor venturi. In maintenance during the [previous] annual the carburetor fuel bowl plug was removed and the fuel that was captured was visually inspected for contaminates. There were none. during an inspection of the disassembled carburetor after the forced landing it was found that this drain is not the lowest point in the fuel bowl and the only way to really be sure that all of these contaminates are out is to disassemble the carburetor. We also checked the carb fuel screen and it was clean. The gascolator had a small amount of what appeared to be rust and aluminum flakes in it but not enough to cause any issue. We purchased a lead test kit and tested the gray particles from the float bowl. They were found to be lead. We have been running nothing but locally sourced 100LL fuel for the past year. This event seemed to be a big enough deal that it was worth sharing to possibly prevent others from suffering a forced landing due to a similar issue.
J3 Instructor reported that contaminated fuel resulted in a loss of engine power followed by a forced landing.