I.on [美 ɑn, ɔn, 英 ɒn]介词on often appears as the second element of certain verb structures in English (count on, lay on, sign on, etc). For translations, see the relevant verb entry (count, lay, sign, etc).
In newer models of constant-speed propellers, oil is pumped through the propeller shaft to push on a piston which drives the mechanism to change pitch.