The engine was used in combat — the R-1300-1A and -1B in the A model North American T-28 Trojan and the R-1300-3, -3A, -3C and -3D in the Sikorsky H-19 Chickasaw. The R-1300-1B was used to power the Ayres Thrush. The R1300-4 and -4A were used in the N class blimp; 50 of these variants were produced by AVCO.[2]