Basicly , the type 24 is the type 18. Just the difference was the engine. Type 18 powered with the M-62 engine while the Type 24 by the M-62 or M-63. Type 18 had the WISZ - 6A variable prop and Type 24 AV-1 or VV-1 . Type 24 got more rounded prop spinner and doors for accessing of the cockpit on both sides of the fuselage.. The Type 18 had the door on the port side only.
The Type 29 was modified Type 24 with M-63 engine. Instead of two SzKAS MGs installed there was one 12,7mm Bieresin UBS heavy MG mounted at the bottom of the fuselage. Additionally there were attached RS-82 launchers and racks for external fuel tanks or 100 kg of bombs. In the Summer of 1941 Type 29 was modified to carry RS-136 rocket missiles