THE maximum take‐off thrust available from the Pegasus engine is limited, particularly at the higher ambient temperatures, by the turbine blade temperature. As this temperature cannot reliably be measured, the operating limits are determined by jet pipe temperature. To enable the engine speed and hence thrust to be increased for take‐off, water is sprayed into the combustion chamber to keep the blade temperature down to an acceptable level. The water flow rate for the required turbine temperature reduction has been established and qualified in the engine Type Approval Test. The quantity of water carried is sufficient for and appropriate to the particular operational role of the aircraft.