The piʿʿēl stem expresses the bringing about of a state. The object of the piʿʿēl verb’s action “suffers the effect” of the action; i.e., it is put into a state by the action. In the sentence “Bob flies the plane,” the direct object [plane] is put into the state of flight by the subject of the verb [Bob]. See GKC §52; J.-M. §52; BHRG §16.4; IBHS §24.