During a recent routine Document 10 Inspection on a Citation 525A (CitationJet 2), technicians noticed a raised portion of B2 Sealant at the lower skin to bulkhead seam. Upon removal of the sealant, exfoliation corrosion was found.

This is a common area for corrosion to form as it is located at the lowest point in the aircraft, where moisture can accumulate. To compound the issue, the aft air conditioner evaporator is mounted directly over that location.

In order to remove and replace the seal cup, flight control cable tensions have to be broken and re-tensioned and rigged, and the Engine control cables removed. The process takes approximately 200 hours to remove and replace the assembly.

The Seal Cup Assembly is a machined aluminum plate that mounts on the lower center portion of the Aft Pressure Bulkhead. It acts as a structural reinforcement of the lower bulkhead skin as well as a “pass-through” for all of the flight control (elevator, rudder, and trim) and engine Teleflex control cables.

The aircraft that seem to be most affected by this are the CJ2 and CJ3 models. The severity of the aforementioned repair cannot be overstressed.

At this time, Textron Engineering allows no structural remedy other than complete removal and replacement.

West Star Aviation – ALN has performed five such repairs in the past two years. The aircraft affected are notably operated in coastal environments. The seal cup for both aircraft carries a similar part number and can come drilled or un-drilled upon request.