 The Il-1 used the same principle of a stress-bearing armored shell to protect the engine and pilot as did the Il-2, but protection was increased by moving the oil cooler and radiator inside the shell, cooled by wing-root ducts that exhausted through an armored slot on the underside.The landing gear retracted aft and the wheels rotated to lie flat within the wings.The two VYa-23 cannon were carried over from the Il-2, but they were its only gun armament.