MD-11
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 50; Flight Crew Total 10000; Flight Crew Type 1500
Situational Awareness; Communication Breakdown
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport
Aircraft; Human Factors; Procedure
I was the First Officer from ZZZ to ZZZ1. During the takeoff role the Captain stated 80 kts.  I was monitoring my PFD and I only had 50 kts indicated airspeed.  I then looked over at the Captains PFD and saw he was above 100 kts at this time.  I made the decision to continue all airspeed call outs from his PFD; and once airborne the Captain called for positive rate; gear up.  Once I placed the handle in the UP position; my PFD was unreadable and several EICAS messages displayed.  The Captain lost his flight director; the auto throttles disengaged and he was flying raw data at this point in time.  We were entering ZZZZZ airspace with dozens of TCAS traffic symbols on our NAV display.  I asked the Captain if he wanted to make the turn to follow the SID or [advise ATC] and ask for vectors.  At this time we did not know what the problem was other than my PFD was unreliable and we had multiple EICAS alerts.  The Captain said to [advise ATC] and ask for radar vectors; which I did.  We then climbed up to 4000 ft and the Captain ask to retract the flaps.  The Captain called for the jump seater who was a MD 11 Captain to come up on the flight deck and assist me in running the QRH procedures.  At this point we assumed we had an air speed unreliable issue and treated the [situation] as such. After completing the QRH checklists and isolating the First Officers CADC; the Captain had his flight director back and we requested vectors for the ILS runway XXL; and returned to ZZZ.  I informed the company via the ACARS 'Divert' icon we were returning to ZZZ; I requested landing data; and we briefed the approached.  I asked ATC to provide ground speed readouts until touchdown as a backup and crosscheck to our aircraft information.  The landing was uneventful and we taxied back to the ramp.
First Officer reported that CADC2 failed on takeoff; resulting in loss off Air Data.  The crew returned to the departure airport.