An aeroengine comprising: a front casing and a nacelle casing located radially outwardly of the front casing a primary air circuit being defined between the front carter and the nacelle casing; a high-pressure compressor fed by said primary air; a secondary air circuit defined between the nacelle carter et an air sleeve located radially outwardly of the nacelle casing; at least one heat exchanger (28, 28') mounted in the primary air circuit upstream from the high-pressure compressor, said heat exchanger comprising a cold secondary circuit (28b, 28'b) and a hot primary circuit (28a, 28'a), said hot primary circuit being fed with air from said primary air circuit, and said cold secondary circuit being fed with air from the secondary air circuit, the inlet of the cold secondary circuit of the heat exchanger (28, 28') being connected to air intake means disposed in the secondary air circuit, symmetrically about the axis of said engine, and the outlet from the cold circuit of the heat exchanger being connected to means for reinjecting air into said secondary air circuit and disposed symmetrically about the axis of said engine; said engine being characterized in that the air intake means are constituted by open first ends (70a, 72b) of first pipes (70, 72) having second ends (70b, 72a) connected to said heat exchanger, and the air reinjection means are constituted by the open first ends of second pipes which second ends are connected to said heat exchanger, said open first ends (70a, 72b) being distributed angularly in regular manner relative to the axis of the engine and in that said heat exchanger (28, 28') is annular and presents the same axis of revolution as the engine. a front casing and a nacelle casing located radially outwardly of the front casing a primary air circuit being defined between the front carter and the nacelle casing; a high-pressure compressor fed by said primary air; a secondary air circuit defined between the nacelle carter et an air sleeve located radially outwardly of the nacelle casing; at least one heat exchanger (28, 28') mounted in the primary air circuit upstream from the high-pressure compressor, said heat exchanger comprising a cold secondary circuit (28b, 28'b) and a hot primary circuit (28a, 28'a), said hot primary circuit being fed with air from said primary air circuit, and said cold secondary circuit being fed with air from the secondary air circuit, the inlet of the cold secondary circuit of the heat exchanger (28, 28') being connected to air intake means disposed in the secondary air circuit, symmetrically about the axis of said engine, and the outlet from the cold circuit of the heat exchanger being connected to means for reinjecting air into said secondary air circuit and disposed symmetrically about the axis of said engine; said engine being characterized in that the air intake means are constituted by open first ends (70a, 72b) of first pipes (70, 72) having second ends (70b, 72a) connected to said heat exchanger, and the air reinjection means are constituted by the open first ends of second pipes which second ends are connected to said heat exchanger, said open first ends (70a, 72b) being distributed angularly in regular manner relative to the axis of the engine and in that said heat exchanger (28, 28') is annular and presents the same axis of revolution as the engine.