Tip clearance control for turbine blades

A carrier segment of a carrier section for circumscribing an array of circumferentially spaced turbine blades of a gas turbine engine, the blades being disposed radially inwardly of a turbine casing, the carrier segment comprising:

• a first impingement carrier wall disposed radially inwardly of the turbine casing and radially outwardly of the turbine blades, the first impingement carrier wall including a first aperture for passage of air,
• a second impingement carrier wall disposed radially inwardly of the first impingement carrier wall and radially outwardly of the turbine blades, the second impingement carrier wall including a second aperture for passage of air,
• an extension section extending axially, relative to a longitudinal axis of the engine, from the first impingement carrier wall,
• a first intermediate chamber disposed between the first impingement carrier wall and the turbine casing,
• a second intermediate chamber disposed between the first impingement carrier wall and the second impingement carrier wall, a carrier wall aperture being disposed in an axially forward wall defining the second intermediate chamber for passage of air into the second intermediate chamber,
• a third intermediate chamber disposed between the extension section and the turbine casing, and
• a support disposed between the first intermediate chamber and the third intermediate chamber such that the support separates the first intermediate chamber and the third intermediate chamber, the support being connected to the turbine casing and supporting the carrier segment,
• wherein an extension section aperture is disposed between the first intermediate chamber and the third intermediate chamber for passage of air, and
• wherein the extension section includes a third aperture for passage of air into the third intermediate chamber.