Issues Discovered With Fuel Return Lines That Pass Through Anti-Icing Fluid Tanks

The FAA has issued an SAIB tied to possible corrosion of the fuel return lines that pass through the Tecalemit Kilfrost-Sheepbridge-Stokes (TKS) deicing fluid tank/s; and softening of the sealant used in the TKS tank/s on Cirrus Design Corporation (CDC) Model SR22 airplanes, serial numbers 2334, 2420, 2438 through 3691, equipped with ice protection, and Model SR22T airplanes, serial numbers 0001 through 0556, equipped with ice protection.

This SAIB results from two field notifications of blue fuel staining on the underside of the wing near the TKS fluid tank vent. In both cases it was determined that a fuel return line passing through the TKS tank had pin holes due to corrosion. The pin holes allowed fuel (under low pressure) into the TKS tank, which then floated on top of the TKS fluid. Once the tank was full of fluid, the additional fuel was effectively vented overboard through the TKS vent.

During compliance to the original release of the service bulletin, it was found that, not only was the fuel return line corroding due to interaction with the TKS fluid, but the TKS tank sealant itself was becoming soft after long term exposure to the TKS fluid. Revision R2 of the service bulletin calls for replacement and sealing of the return fuel line. This revision (R2) also replaces the TKS tank sealant with one that will not soften after long term exposure to TKS fluid.

The FAA recommend that all CDC model airplanes, specified in the introduction above, complete Cirrus service bulletin number SB 2X-28-11 R2, revised August 2, 2013. In addition, we request feedback from owners and operators as to the condition of the fuel line and the TKS tank sealant discovered during the accomplishment of the service bulletin.

(SR22 pictured in file photo)

FMI: SAIB