PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Commercial; Flight Crew Glider
Flight Crew Last 90 Days 7; Flight Crew Total 345; Flight Crew Type 4
Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
I was inbound for landing at ZZZ arriving from the south in position for a 45 degree entry into left traffic for Runway XX; the runway in use. I was in two-way communication with the ZZZ Airport Control Tower from the time I was 10 miles out. Tower requested me to report left downwind abeam. At that time; a single engine piston aircraft was departing Runway XX and was on upwind for an east bound departure and a CRJ-700 commercial flight was established on left downwind for landing on Runway XX. A Cessna 182 was maneuvering from the west for a practice RNAV approach and initially requested Runway XY. Tower rejected their request because Runway XX was in use and because of the volume of traffic. The C-182 then requested and received a practice approach for Runway XX. I had all three aircraft in sight. Myself; the departing aircraft on upwind; the arriving CRJ; and the C-182 were in two-way communication with the Tower. At about 3.5 miles from the airport and just completing my descent to traffic pattern altitude (8000' MSL); I observed the unidentified piston twin aircraft at my 11 o'clock and above me within the distances specified above.  I immediately took evasive action by initiating a descent and slight turn to the right. The unidentified aircraft was within the ZZZ Class D airspace and as far as I could tell was not in communication with the Tower. I then entered the left downwind for Runway XX; made my position report to the Tower and landed uneventfully.
PA-28 Pilot reported a NMAC event in landing traffic pattern with an unidentified twin aircraft in class D airspace.