Fuel Tanks

Aircraft had been inactive and hangared for approximately six months. While trying to troubleshoot a fuel quantity indication problem, a fuel sample revealed contamination, which was sent for analysis. While awaiting results, tanks were drained and an anti-bacterial fuel additive was added before they were refilled.

Editorial Staff

Sunday, April 23, 2017 at 12:00 AM ET

Verified

Key Takeaways:

Aircraft experienced various structural and mechanical integrity issues within their fuel systems, including corrosion at sump drains, fatigue cracks at filler necks due to tank movement, and deteriorating fuel sender floats.
Significant contamination problems were identified, such as a large cloth rag left in a fuel tank during manufacturing that caused fuel pressure anomalies.
Biological contamination from mold, yeast, and bacteria was found in fuel tanks, particularly after periods of inactivity, proving difficult to eradicate with standard additives.

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Aeronca 15AC Sedan
Corrosion At Sump Drain

During routine inspection, corrosion was found adjacent to the fuel sump drain in the weld heat affected zone. Corrosion pitting caused leak. No fire danger. Metal fuel tanks installed IAW STC SA82CH.
Part total time: Unknown

Cessna Model 172M Skyhawk
Cracked Filler Neck

Anti-chafe rubber strips unbonded from mounting straps, loosening tension on tank. Tank movement in wing cavity caused a fatigue crack where filler neck was welded to tank since filler is screwed to structural upper wing skin. There was a fuel leak when tank was filled.
Part total time: 4581.0 hours