Airfoil platform impingement cooling

A gas turbine, engine comprising:

• a compressor,
• a combustor receiving compressed air from the compressor,
• a series of turbine vanes for directing combustor gases from the combustor to a turbine rotor, each of the turbine vane having a radially inner platform having a gas path side, a back side opposite the gas path side, and an airfoil extending radially from the gas path side of the radially inner platform, the radially inner platform having an overhanging portion projecting axially downwardly beyond a trailing edge of the airfoil, the radially inner platform having a mounting flange depending radially inwardly from the back side of the radially inner platform,
• the turbine vanes and the turbine rotor defining therebetween a vane/rotor cavity, in use, the turbine rotor imparting a swirl to the air in the vane/rotor cavity, and
• a source of air for purging the vane/rotor cavity, said source of air including a plenum located radially inwardly of the radially inner platform, said plenum being in fluid flow communication with said vane/rotor cavity through at least one impingement hole defined through said mounting flange, said at least one impingement hole having an axis intersecting the overhanging portion so as to direct an impingement jet from the plenum onto the back side of the overhanging portion rearwardly of the trailing edge of the airfoil of the vane.