Definition
A method of temporarily increasing the power output of a reciprocating or turbine engine by spraying a metered mixture of water (often blended with alcohol or methanol as an antifreeze) into the induction system or combustion chamber. The water absorbs heat as it vaporizes, cooling the charge air and allowing the engine to run at higher manifold pressures or turbine inlet temperatures without detonation or thermal damage, producing a short-term boost in power.
Plain English
Spraying water into the engine to cool the incoming air so the engine can safely produce more power for a short time, usually during takeoff.
Context Anchor
Seen in engine operation, takeoff performance, and high-power procedures for some piston and turbine aircraft.
Derivation
Injection comes from a Latin root meaning “to throw in.” In aviation, it means forcing a measured fluid into a specific part of an engine system, not simply adding liquid loosely.
Why Pilots Care
It increases available takeoff power while protecting the engine from detonation and excessive cylinder-head temperatures.
Intuition Check
Water injection is not used to put out a fire inside the engine. It is a controlled engine-power system that helps keep the engine’s internal air charge cooler during high-power operation.
Example Sentence 1
The pilot of the heavily loaded aircraft armed the water injection system before takeoff to ensure full rated power was available.
Example Sentence 2
Preflight checks include verifying the water injection tank is full for the planned high-density-altitude departure.