Date: 201407
Local time of day: 1201-1800
Location: DEN.Airport, CO
Flight conditions: VMC
Aircraft: EMB ERJ 190/195 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Aircraft component: Rudder Control System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Maintenance Action; General Release Refused / Aircraft Not Accepted
Contributing factors: Logbook Entry; Manuals; Procedure; Aircraft; Company Policy; Human Factors
Primary problem: Ambiguous

Narrative: During post-flight inspection in DEN; my First Officer discovered what appeared to be a missing seal on the vertical stabilizer just forward of the rudder. I entered the discrepancy into the aircraft logbook and contacted Maintenance Control. The responding Mechanic said that it could be deferred according to Maintenance Control.After about a thirty minute delay; he returned to the aircraft with the logbook. I reviewed the entry and it appeared to be properly signed off with a 200 flight cycle limitation on the item. I saw no reason to not accept the aircraft; so we departed on our scheduled flight. The flight was uneventful and we arrived at our destination about 20 minutes late. After deplaning; I spoke with some of our Maintenance people and learned that the airplane was in fact; not legal for flight and was grounded. They already knew this before I arrived. I had unknowingly accepted and flown a non-airworthy aircraft. I can only suspect that the aircraft was signed off in order for me to accept the aircraft and complete my flight. The 'complete the flight at all cost' mentality at this company flies in the face of the so-called 'safety first' mantra. I am extremely angry and frustrated to think that a non-airworthy airplane may have been signed off solely for the purpose of me completing my flight and getting the aircraft back to a Maintenance base. This is simply not the way I or any other professional aviator conducts our business.


Second narrative: Upon arrival at our destination we were greeted by an outbound crew clearly upset and pointing at the tail section. What they had learned prior to us arriving was that this aircraft was supposed to be grounded as the sealant section was missing 100% of its section rather than only 50%; which was what the MEL had called for. With this news my Captain and I promptly made contact with the local mechanics who also seemed extremely upset with what had been done in DEN with this write up. The general consensus was the notion that DEN Maintenance may have not wanted to deal with it there and just wanted to dispatch the plane out to its destination to be dealt with there. Whatever the reason may be; we were given a green light to take an aircraft that was not legal per the MEL. Unacceptable!


Synopsis: An EMB-190 may have been dispatched with a deferred maintenance item for a missing vertical stabilizer aerodynamic seal section.  Confusion centered over whether 50% of the entire seal could be missing or only 50% of an individual section of the entire seal.