EMB ERJ 170/175 ER/LR
Maintenance Airframe; Maintenance Apprentice; Maintenance Powerplant
Maintenance Technician 20
Communication Breakdown; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Flight Crew Diverted; General Maintenance Action
Chart Or Publication; Procedure; MEL; Human Factors; Aircraft
Discrepancy showed both forward coffee makers inop. I had used MEL to defer no-water at the coffee makers. I had confirmed there was water at the Forward lav so the lav would stay in service. I did not see any errors in the paperwork.I learned that Aircraft X was the aircraft that had frozen flight controls due to a water leak. [Later]; it became clear to me that had Fault Isolation Manual (FIM) 38-11-00-810 been completed and if there was a water leak it may [have] been discovered preventing the inflight emergency. At the time I completed the MEL I was unaware that potable water could cause a flight control problem.  On the date I placed the potable water on MEL; I was not aware of the possibility of the Potable Water System leaking and freezing causing stiffness of aileron cables. Changing the MEL to require an inspection for leaks if there is no water in the forward monuments [lavatories] may increase awareness and prevent a future occurrence.
Reporter stated the potable water supply manifold has separate lines (hoses) that go to the Forward lav and Galley. The water lines are held together using a Wiggins Fitting type coupling with O-rings and a clam shell type clamp to secure the hose connections. Sections of the water lines run under the Forward cargo pit floor and are subject to freezing in cold weather whenever the cargo door is opened. The belief is the Wiggins Fitting froze; popping the O-rings allowing water to leak under the Forward Galley. The water leak filled some of the bays under the Forward cargo pit flooring and froze. Reporter stated that at least one half set of Aileron cables also run under the cargo floor in the same area the water had leaked down into. The same ERJ-175 aircraft reporter had previously deferred the coffee makers on due to lack of water; experienced two incidences of aileron stiffness and excessive force required to move the control yoke for aileron control. Pilots had to actuate the Disconnect Handle to separate the Left and Right forward torque tubes to get aileron control due to one side of the aileron cables had frozen at a pulley in the belly and would not move. Reportedly; there has not been any movement to provide a connection in the MELs for Line Maintenance Technicians about galley water and flight controls freezing. There is however a reference for checking the Potable water lines under the lavs using FIM 38-11-00-810; when Lavatory water is not available prior to deferring the lav water.
A Line Aircraft Maintenance Technician (AMT) states that aileron flight control cables had frozen on an ERJ-175 aircraft after he had deferred a Forward Galley coffee maker for lack of water. Technician noted the lack of any information in the MEL about deferring coffee makers and the possibility of flight controls freezing needs to be addressed.