Grumman CP-121 Tracker RCAFRCAF Canadian Navy Grumman CP 121 S 2 Tracker airplane model. The first flight of the prototype S 2 was 4 December 1952, and production deliveries started in 1953. A total of 1,342 aircraft were eventually built in 16 configurations. The major configurations included the S 2 Tracker, the C 1 Trader, and the E 1B Tracer. Testing of the various versions and configurations of the aircraft continued here at Patuxent River from the early 1950's through the