How does the application of foam differ from that of water in an aircraft fire?

The application of foam in aircraft fires serves distinct and essential functions that differ significantly from those of water. Foam is specifically designed to smother the fire and prevent re-ignition by forming a blanket over the fuel. This blanket not only cools the flames but also deprives the fire of oxygen, effectively suffocating it. On the other hand, while water can cool the flames, its primary role is thermoregulation, lowering the temperature and potentially controlling the fire. However, water does not provide the same level of protection against re-ignition as foam does.

In the context of aircraft fires, where fuels can be aviation-generated and volatile, the unique properties of foam make it far more effective in mitigating the risks associated with flammable liquids. Water may not be suitable for all types of fires, particularly those involving flammable liquids or fuels, as it can sometimes spread the fire.

Foam's ability to coat and isolate fuels, thus preventing a resurgence of flames, makes it the preferred choice for combating aircraft fires, especially where the risk of re-ignition is a concern. This highlights why foam is favored over water in these scenarios.