Definition
A system that sprays a mixture of water and methanol into the induction system of a reciprocating engine, or into the compressor or combustion section of a turbine engine, to increase power output during takeoff or other high-demand operations. The water cools the charge, allowing higher manifold pressures or turbine temperatures without detonation or overheating, while the methanol prevents the water from freezing and adds a small amount of fuel value.
Plain English
A way to give an engine a short burst of extra power by spraying a water-and-methanol mix into it. The water cools things down so the engine can be pushed harder, and the methanol stops the water from freezing.
Context Anchor
Seen in engine operating procedures, takeoff performance planning, and checklist items for aircraft equipped with water/methanol injection systems.
Derivation
W/M stands for Water/Methanol. Methanol is a type of alcohol (wood alcohol) that mixes with water and resists freezing. The slash in W/M simply means the two fluids are combined in one mixture.
Why Pilots Care
Allows greater power without engine damage from overheating or detonation while protecting the cylinders during critical phases of flight.
Grounding Statement
The water helps absorb heat, and the methanol helps the mixture work in cold conditions and can also add some burnable energy.
Intuition Check
W/M injection is not normal fuel injection. It is an added water/methanol system used only when the aircraft’s engine procedure calls for it.
Example Sentence 1
The crew armed W/M injection before takeoff to get the rated power needed for the heavy load and short runway.
Example Sentence 2
Low fluid in the W/M injection tank must be corrected before any high-power flight.