MD-11
Maintenance Powerplant; Maintenance Airframe
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors; Incorrect / Not Installed / Unavailable Part; Procedure; Chart Or Publication
I was called to the Number 2 Engine to perform RII [Inspection] on a fan blade replacement due to a tip curl.  I reviewed the paperwork; the part numbers; and witnessed the installation of the blades per the Aircraft Maintenance Manual (AMM).  The AMM required blades to be replaced in a matched pair 180 degrees out [opposite from each other]. The blades were identified and removed and then reinstalled at what we thought were exactly 180 out.  We visually identified the blade that was 180 degrees out from the damaged blade; and then counted the positions in the C1 disc root. At that time; the non-routine paperwork was short-signed and required an Engine Run for a Vibration Survey.  The Vibe Survey was performed on Day Shift and was signed-off as within limits.  According to the information I received; the blade was actually installed one position off from 180 degrees. Apparently the Blade Location was mistakenly placed; one spot out from the 180 degree mark. It may have happened when the adjacent blades were removed to allow for re-installation of the new blades.  We did not have access to the prior Blade Mapping Chart that was provided with the notification of this issue. [Recommend] providing knowledge of and easy access to the latest Fan Blade Mapping Chart.  This will help positively identify that blades and locations for removal and reinstallation; by verifying fan blade Serial Numbers (S/N) and location. Graveyard shift.
An Aircraft Maintenance employee was informed he had signed-off an RII Inspection for a fan blade replacement on Number 2 Engine of an MD-11 aircraft that was later found to be one spot out from the required 180 degree opposite position of a tip curl damaged fan blade. An Engine Run with a Vibration Survey was signed-off as within limits.