When a line breaks in an hydraulic system, a fine mist of oil sprays all over everything in sight and the oil pressure drops almost instantaneously to zero. Oil is always under very high pressure (1,200 pounds per square inch or "PS1"), and because of this, a leak can be dangerous insofar as hydraulic oil is flammable. When the oil in the lines is exhausted, the system can no longer function until the line is repaired, the lost oil replaced and the lines bled of air bubbles. If such a leak should occur while at sea, the most likely place for it to happen, it would deprive a vessel of the use of its stabilizers when they are most needed and repairs probably couldn't be made until it had returned to port.

A pneumatic system is very different. First of all, the pressure on the lines of a pneumatic system is very low (only 120 PSI), and because of this, the likelihood of a break in the system is quite small.

Secondly, if a break in the lines should occur, only clean, dry air would escape. This would pose no threat of fire in the engine compartment and would not cover the surroundings with oil that would have to be cleaned up at a cost of much time and trouble.

Third, if the break in the line was not too large, an pneumatic system would continue to function at some degree of efficiency until the break could be repaired. This is so because there is an infinite supply of air available at the intake of the compressor and because of the low pressure required by the system. An oil powered system, on the other hand, requires continuously high pressure so operate. The reason why a pneumatic system can continue operating with a leak in the lines and an hydraulic system cannot, is that air is compressible and oil is not. Air pressure is such that pressure can be directed not only to the air leak, but also to the components activating the fins. In the case of oil pressure, once the pressure drops, the system is in capacitated.

To summarize, a pneumatic system is clearly more reliable than a hydraulic system because the low pressure requirements of the pneumatic system create fewer problems, and because a leak in the pneumatic system neither disables the system nor creates substantial difficulties thereafter.