Tanker · Center of Gravity, Surge, and Outage
You bring a partly loaded tanker to a stop on an icy street. What can the liquid inside do as you stop?
Explanation
Liquid in a partly filled tank keeps moving after the vehicle has slowed, running fore and aft, and every time the wave reaches an end of the tank it shoves the vehicle whichever way the wave happens to be running, which on a slick surface is enough to move a truck that has already stopped out into an intersection. This is why surge is a stopping problem and not only a cornering one: the load has momentum of its own, and it does not finish moving when the wheels do. The mechanism and the icy-intersection consequence are manual teaching; 49 CFR 383.119(a) makes the causes, prevention, and effects of cargo surge on vehicle handling a required knowledge area for this endorsement without describing how surge works. The wrong options each assume the liquid is well behaved, settling the instant the vehicle stops, adding grip rather than taking it, or being confined to one axis when the closed ends of the tank are exactly what the fore and aft wave strikes.
Source: 49 CFR 383.119(a)
Related Center of Gravity, Surge, and Outage questions
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