EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Environment - Non Weather Related; Human Factors; Procedure
Beginning the BLUZZ1 Arrival into MEM; we were cleared to descend from 36;000 to 30;000.  While descending; we encountered moderate wake turbulence twice from an MD-11 15 miles ahead.  The Captain as pilot monitoring requested a heading 10 degrees right to avoid the wake turbulence.  ATC re-cleared us direct BLUZZ when able; and to descend via the arrival.  I briefed that I follow the VPI (Vertical Path Indicator) as habit on ODP (Optimized Descent Profile) arrivals; and waited until the VPI carrot came alive to begin descent.  While we met BLUZZ below 23000; as soon as we crossed the fix the FMS messaged 'max grade unable next altitude.'  We advised ATC we were unable to cross the COPEN fix at 10000.  ATC handed us off to approach; who gave us a vector to join the approach to 18L.Distance from BLUZZ to COPEN is 9.7 NM.  We were unable to lose 13000 FT in that distance; and later realized the VPI guidance from the FMS guided properly to BLUZZ; but for some reason did not factor descent to COPEN.  Threat:  The moderate wake turbulence disconnected the autopilot and distracted us from the arrival. Errors:  I as pilot flying did not maintain situational awareness on the arrival and backup the FMS with mental math to descend to the first hard altitude of 10;000 ft.  I went along with the FMS guidance without making sure it was accurate.I will still descend using VPI guidance from the VNAV; but back it up with mental math verifying that we will hit all descend via windows and make the first hard Altitude.  I will no longer trust the FMS to give proper guidance; especially on arrivals that branch off multiple lateral paths from one fix; such as BLUZZ.  After reviewing the arrival; I realized an altitude of 23;000 works well for landing north transitions; but not landing south transitions.  I will focus instead on the first hard altitude fix on our arrivals; and make sure we are descending appropriately to hit all windows.
EMB-145LR First Officer reported failing to make a crossing restriction on the BLUZZ1 Arrival into MEM when they were distracted by a wake turbulence encounter in trail of an MD-11.