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A blade outer air seal in a gas turbine engine, the BOAS includes a plurality of ring segments secured to a blade ring carrier. An impingement ring forms a pressure vessel within the blade ring carrier and includes a first group of impingement holes positioned over the middle of the blade tip. The r

A blade outer air seal in a gas turbine engine, the BOAS includes a plurality of ring segments secured to a blade ring carrier. An impingement ring forms a pressure vessel within the blade ring carrier and includes a first group of impingement holes positioned over the middle of the blade tip. The ring segments each include a plurality of stiffener ribs forming a plurality of leading edge pockets, trailing edge pocket and middle pockets each with pin fins to enhance the heat transfer effect. A metering plate is secured over the stiffener ribs to form closed pockets over the edge pockets while leaving the middle pockets open. A second group of impingement holes are formed in the metering plate over the edge pockets. Pressurized cooling air supplied to the pressure vessel first passes through the first group of impingement holes and is discharged directly over the middle pockets. The cooling air then flows through the second group of impingement holes and into the closed edge pockets, and then out discharge holes arranged along the leading and trailing edges of the ring segment. The individual pockets can have the impingement holes of varying sizes in order to regulate the amount of cooling air that flows into the specific pocket.

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I claim: 1. A blade outer air seal for a gas turbine engine comprising: a blade ring carrier having a cooling air feed hole to supply cooling air to a blade ring air seal; a ring segment held in place by the blade ring carrier and forming the blade outer air seal with a tip of a turbine blade; the

I claim: 1. A blade outer air seal for a gas turbine engine comprising: a blade ring carrier having a cooling air feed hole to supply cooling air to a blade ring air seal; a ring segment held in place by the blade ring carrier and forming the blade outer air seal with a tip of a turbine blade; the ring segment having a plurality of pockets formed by stiffener ribs and including at least one leading edge pocket, at least one middle pocket, and at least one trailing edge pocket; a metering plate secured to the stiffener ribs and forming closed pockets on leading and trailing edges and forming an open pocket on the middle pocket; an impingement ring secured between the cooling air feed hole and the metering plate, the impingement ring having a first group of impingement holes positioned over the middle pocket; and, the metering plate including a plurality of second groups of impingement holes positioned over the edge pockets. 2. The blade outer air seal of claim 1, and further comprising: the leading edge and trailing edge pockets and the middle pocket include pin fins extending from a floor of the pocket to enhance the backside convection of the pockets. 3. The blade outer air seal of claim 2, and further comprising: the pins fins each have a diameter of around 0.1 inches and a height of around 0.1 inches. 4. The blade outer air seal of claim 2, and further comprising: the pins fins have a density pattern of greater than 50%. 5. The blade outer air seal of claim 2, and further comprising: the pin fins have a height substantially equal to the floor thickness of the ring carrier. 6. The blade outer air seal of claim 1, and further comprising: a height of the stiffener ribs is around four times the diameter of the second group of impingement holes. 7. The blade outer air seal of claim 6, and further comprising: a plurality of impingement pockets formed by the stiffener ribs, the pockets each including pin fins to enhance the heat transfer rate from the metal to the cooling air; and, the pin fins have a height substantially equal to the floor thickness of the ring carrier. 8. The blade outer air seal of claim 1, and further comprising: the floor of the pockets in the ring segment is a thin wall; pin fins extend from the floor wall in each of the pockets; and, the height of the pin fins is substantially equal to the thickness of the floor of the ring carrier. 9. The blade outer air seal of claim 1, and further comprising: at least one metering and diffusion slot arranged along the leading edge side of the ring segment and in fluid communication with the leading edge pocket to discharge the cooling air from the pocket into the hot gas flow. 10. The blade outer air seal of claim 9, and further comprising: at least one exit hole arranged along the trailing edge side of the ring segment and in fluid communication with the trailing edge pocket to discharge the cooling air from the pocket. 11. The blade outer air seal of claim 2, and further comprising: the middle pocket is located over the middle of the blade tip where the hottest gas flow leakage occurs. 12. The blade outer air seal of claim 2, and further comprising: a plurality of the pockets forming a grid of pockets extending in both the leading to trailing edge direction and the circumferential direction of the ring segment. 13. The blade outer air seal of claim 12, and further comprising: the impingement holes in the metering plate are varying in size from pocket to pocket to vary the impingement cooling over the ring segment. 14. The blade outer air seal of claim 2, and further comprising: the first group of impingement holes in the impingement ring is positioned directly over the middle pocket to provide impingement cooling in the middle pocket. 15. A process for cooling a blade outer air ring of a gas turbine engine comprising the steps of: feeding pressurized cooling air into a pressure vessel of a blade ring carrier; metering cooling air from the pressure vessel through a first group of impingement holes positioned over a center pocket of the blade outer air seal ring segment; re-directing the impingement air from a middle pocket through a plurality of second impingement holes into pockets on the leading edge and trailing edge sides of the ring segment; and, discharging the cooling air from the edge pockets through holes in the ring segment. 16. The process for cooling a blade outer air ring of claim 15, and further comprising the step of: varying the impingement cooling air flow through the second impingement holes to vary the amount of cooling in the pockets. 17. The process for cooling a blade outer air ring of claim 15, and further comprising the step of: discharging the cooling air from the leading edge pocket through a plurality of metering and diffusion slots in a direction toward the blade tip. 18. A blade outer air seal ring segment for use in a gas turbine engine, the ring segment comprising: the ring segment having hooks to secure the ring segment to a blade ring carrier; a floor with an outer surface for application of a thermal barrier coating; a plurality of stiffener ribs forming impingement pockets; each pocket having a plurality of pin fins extending from the floor; a height of the pin fins is substantially equal to a thickness of the thin wall floor; the stiffener ribs form a plurality of middle pockets located over the hottest portion of a blade tip in the engine; the stiffener ribs form a plurality of leading edge pockets and a plurality of trailing edge pockets; a metering plate secured to the stiffener ribs, the metering plate having an opening above the middle pockets such that the middle pockets are not metered with cooling air; and, the metering plate enclosing the leading and trailing edge pockets and having a plurality of impingement holes over the edge pockets. 19. The blade outer air seal ring segment of claim 18, and further comprising: The height of the stiffener ribs is at least four times the diameter of the impingement holes. 20. The blade outer air seal ring segment of claim 18, and further comprising: The leading edge pockets each include at least one metering and diffusion cooling hole to discharge cooling air from the leading edge pocket; and, The trailing edge pockets each include at least one exit cooling hole to discharge the cooling air from the trailing edge pocket. 21. The blade outer air seal ring segment of claim 18, and further comprising: A thermal barrier coating applied to the outer surface of the ring segment floor. 22. The blade outer air seal ring segment of claim 18, and further comprising: The pin fins have a diameter of about 0.1 inches and a height of about 0.1 inches. 23. The blade outer air seal ring segment of claim 18, and further comprising: the LE pockets and the TE pockets and the middle pockets are without film cooling holes that discharge onto an inner surface of the BOAS.