Self-metering impingement plate

An impingement apparatus, comprising:

• a chamber defined by sides forming the chamber,
• a plurality of impingement holes located on only one side of the chamber, which are able to act as a plurality of flow passages for a coolant fluid to pass from the chamber through the plurality of impingement holes to impinge of a surface to be cooled,
• one or more metering holes located on at least two sides of the chamber and not located on the side on which the impingement holes are located, said one or more metering holes are positioned upstream from said plurality of impingement holes and are able to act as one or more flow passages for the coolant fluid to pass from an exterior coolant fluid source into the chamber,
• wherein the pressure created by the coolant fluid inside the chamber is lower than the pressure of the exterior coolant fluid source before entering the chamber through the one or more metering holes.