Citation Excel (C560XL)
Maintenance Airframe; Maintenance Powerplant
Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Manuals; Incorrect / Not Installed / Unavailable Part; Human Factors; Aircraft
Working with Aircraft Maintenance Technician (AMT) 'Y' in ZZZ. This was a repeat write-up; three or four times. AMT Z and I had worked [same aircraft] two weeks prior. We found the right wing anti-ice control valve leaking at [forward] clamp. Crew reported a whirling sound coming from the right side leading edge wing root area during flight. The sound started a couple of minutes after selecting right wing anti-ice 'on'. The sound went away as soon as the right wing anti-ice was selected 'off'.  We gained access to the right wing anti-ice plumbing and performed leak checks. First problem: Noted bleed air leaking at the tee fitting where it connects to the inboard leading edge. Upon disassembly it was noted that the O-ring in the leaking connection were of a different size than the ones in the non-leaking connection. The Illustrated Parts Catalog (IPC) shows the same part number seal in all three connections.Second problem: Looking thru the access panel in the inboard leading edge towards the wing tip I could see there was damage to the heat blanket at the connector where the inboard and outboard come together. We removed the inboard leading edge for a closer examination. We found more heat blanket damage and found the O-ring for the outboard leading edge was missing; causing metal to metal contact. This metal to metal contact damaged the bell connection to the outboard leading edge. The other O-ring was compromised and its bell connection was damaged as well. [Recommend] technicians need to pay closer attention to the IPC and ensure the O-ring they are installing belongs in that position. Double check to ensure there is a seal in the component before installation especially if it cannot be leak checked after installation.
Reporter stated he works for a Fractional Jet Operator. He and an older Mechanic with years of experience; do a lot of field trips troubleshooting various aircraft that have recurrent write-ups. They had previously worked on the same Cessna CE-560XL and replaced a leaking clamp at the Right-Hand (R/H) Wing Anti-Ice Control Valve two weeks earlier.  Later however; subsequent flight crew write-ups for a swirling sound heard in the cabin; associated with the cycling of the R/H Wing Anti-Ice Control Valve; led them to do a more extensive checking of the right wing leading edge pneumatic anti-ice metal ducting. That's when they found an incorrect and smaller O-ring; a missing O-ring and a deteriorated O-ring along the different sections of ducting. The O-rings are not your typical black rubber type of O-rings. They are orange-red colored to indicate use for the intense; high heat of the pneumatic bleed air going through the leading edge ducting. The O-rings are difficult to install on the metal ducting and connecting (joining) the inboard and outboard sections are equally as difficult. No lubricant is allowed to be used except for water; due to concerns for lubricant fire that may be initiated by the high heat. Reporter stated the Heat Blankets are installed between the hot pneumatic anti-ice ducting and wing fuel tanks at the forward spar area. The blankets are actually a barrier insulating material with a crinkled aluminum surface that reflects pneumatic heat away from the fuel tanks. Damage to the heat blankets was especially noticeable at the Interconnect tube that is used to join the inboard and outboard aluminum ducts in the leading edge. The O-ring seals continue to be an issue on the CE-560XL's.
An Aircraft Maintenance Technician (AMT) describes the progressive troubleshooting that he and another Technician applied to locate the cause of a whirling sound coming from the Right-Hand (R/H) Leading Edge Anti-Ice ducts on a Cessna CE-560XLS aircraft. Damage also found to Heat Blankets used to protect the fuel tanks from excessive duct heat was caused by missing; undersized and deteriorated orange colored O-Rings at pneumatic duct connections.