BACKGROUND:
Fuel leaks occur due to sealant aging, temperature changes, and mechanical stress on the structure.
The most common causes of leaks:
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Structural stress: Wing twisting caused by turbulence or hard landings disrupts the sealing layers at the corners of the tanks and near the bulkheads.
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Sealant degradation: Over time, the original sealant naturally degrades (becoming brittle and cracking), leading to leaks around rivet rows and access panels.
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Improper service: A common cause is an unprofessional previous repair or the use of unsuitable sealants that are incompatible with the fuel or the tank’s original material.
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Loose rivets and fasteners: For example, filling necks very often crack when the tank is filled improperly. Another common point of damage is the tank outlets or their mountings.
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Degraded seals: For example, under the drain valve or on fittings.
REPAIR PROCEDURE (RESEALANT):
We perform our repairs using certified procedures, which include:
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Diagnosis and preparation: Identification of the leak location via a pressure test. This is followed by thorough removal of old sealant and contaminants. We use gentle chemical methods (e.g., PolyGone) combined with precise mechanical cleaning to ensure the base material (aluminum alloy) remains undamaged.
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Surface Treatment: Thorough degreasing and surface activation to ensure maximum adhesion of the new sealant.
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Sealant Application: Application of aerospace-grade polysulfide sealants (e.g., PR-1440 grade or as specified by the manufacturer). We perform complete “fillet seals” (seals in corners) and “cap seals” (sealing over rivet heads) to prevent future leaks.
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Curing inspection: The process takes place in several stages with precisely defined curing times, culminating in a final pressure leak test.
RECOMMENDATIONS:
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Prompt Action:
Blue stains on the wing or the smell of fuel are clear signs that action is needed. A neglected leak will always worsen due to vibrations and temperature cycles. Pay special attention to the upper surface of the wings (negative pressure on the suction side of the wing can cause fuel to be sucked out during flight or lead to engine failure). A leaky fuel tank can also allow water to enter the tank. -
Long-term solution: Re-sealing is an investment in the aircraft’s value and safety. If you plan to own the aircraft for the long term, a complete resealing is more effective than repeated spot repairs.