After requesting icebreaker assistance, a ship must maintain continuous radio watch, and keep the icebreaker informed of any change in her ETA at the position where escorting is to commence. The channel When an icebreaker is breaking a channel through large heavy floes at slow speed, the channel will be about 30-40 per cent wider than the beam of the icebreaker. If, however, the ice is of a type which can be broken by the stern wave of the icebreaker proceeding at high speed, the width of the channel may be as much as three times the icebreaker's beam. In the channel there may be pieces of ice and small floes which the icebreaker has broken off the floes at the sides of the channel. These may greatly reduce the speed of a ship following the icebreaker, or may even block the channel.
Rams sometimes project into the channel from old ice.
A ship unable to keep off the ice should request the icebreaker to widen the channel. But in the narrow channel left by an icebreaker in heavy ice, rams are less likely to be encountered. Distance between ships The Master of the icebreaker decides on the minimum and maximum distances that a ship should keep from the icebreaker. The minimum distance is determined by the distance the ship requires to come to a complete stop after reversing her engines from full ahead to full astern. The maximum distance depends on the ice conditions and the distance the channel will remain open in the wake of the icebreaker.