The first U.S. airborne early warning aircraft were the carrier based Grumman TBM-3W Avenger, followed by the Douglas AD-3W, -4W, and -5W Skyraider and the Grumman AF-2W Guardian (not to be confused with the AGR ships of the same name); though the Skyraiders and Guardians were built in large numbers, none were very successful as they were too small to function as a full CIC, and all were used more often in the ASW role. While the latter carrier-compatible Sikorsky HR2S-1W helicopter had room for a full CIC it also failed, largely due to excessive vibration, slow speed, and cost.