Yeah, the harbor entrance to Halifax is wide but there is only a narrow deep water channel to navigate so we always needed a pilot supervise the sailor manning the helm.
This post was edited by Kittigate at March 28, 2020 8:40 PM MDT
Yes sometimes if there is difficult manoeuvres to get a large vessel in or out of Port but usually to help guide the huge ships tying up alongside and departing.
Most commercial ships now use enormous diesel-engines, either driving the screws directly or via a generator and electric motors; and a long-established way to start those is by injecting a blast of compressed-air into the cylinders to start the engine turning.
A lot of warships have gas-turbine engines, and those are spun up electrically.