Assembly (100, 400, 600) in an aircraft, comprising: - an outer tubular portion (106, 406, 606) that is centred on a central line and delimits an inner space (110, 410, 610), - an inner tubular portion (108, 408, 608) that is mounted coaxially with the outer tubular portion (106, 406, 606) and inside the outer tubular portion (106, 406, 606), wherein the inner tubular portion (108, 408, 608) contains a fluid exhibiting a temperature referred to as "second temperature", - a fluid jacket (102, 402, 602) that is mounted coaxially with the outer tubular portion (106, 406, 606) and inside the inner tubular portion (108, 408, 608), wherein the fluid jacket (102, 402, 602) contains a fluid exhibiting a temperature referred to as "first temperature" and wherein the first temperature is different from the second temperature, characterized in that said assembly (100, 400, 600) also comprises: - a plurality of groups of at least four thermal flow sensors, wherein, for each group, the sensors of said group are fixed on the inner surface of the outer tubular portion (106, 406, 606) or on the outer surface of the inner tubular portion (108, 408, 608) or on the inner surface of the inner tubular portion (108, 408, 608) and overall in one and the same plane perpendicular to the central line, and wherein, in each group, the sensors of said group are distributed angularly about the central line, and - a control unit which, for each group, receives the data from each sensor of said group and which, on the basis of these data, determines a warning level that relates to said assembly (100, 400, 600), the control unit having: - collecting means which are intended to collect, for each group of sensors, the value that relates to the thermal flow passing through each sensor of said group at a time 't' and is transmitted by said sensor, - first calculation means which are intended to calculate, for each group, a so-called "group" average, which is the average of the values thus collected for said group, - second calculation means which are intended, for each group and for each sensor of said group, to calculate the difference between the value of said sensor and the group average and the ratio between this difference and the group average, and - classification means which are intended, for each group and for each sensor of said group, to classify the warning level of said sensor into a category depending on the ratio thus calculated for said sensor. - an outer tubular portion (106, 406, 606) that is centred on a central line and delimits an inner space (110, 410, 610), - an inner tubular portion (108, 408, 608) that is mounted coaxially with the outer tubular portion (106, 406, 606) and inside the outer tubular portion (106, 406, 606), wherein the inner tubular portion (108, 408, 608) contains a fluid exhibiting a temperature referred to as "second temperature", - a fluid jacket (102, 402, 602) that is mounted coaxially with the outer tubular portion (106, 406, 606) and inside the inner tubular portion (108, 408, 608), wherein the fluid jacket (102, 402, 602) contains a fluid exhibiting a temperature referred to as "first temperature" and wherein the first temperature is different from the second temperature, - a plurality of groups of at least four thermal flow sensors, wherein, for each group, the sensors of said group are fixed on the inner surface of the outer tubular portion (106, 406, 606) or on the outer surface of the inner tubular portion (108, 408, 608) or on the inner surface of the inner tubular portion (108, 408, 608) and overall in one and the same plane perpendicular to the central line, and wherein, in each group, the sensors of said group are distributed angularly about the central line, and - a control unit which, for each group, receives the data from each sensor of said group and which, on the basis of these data, determines a warning level that relates to said assembly (100, 400, 600), the control unit having: - collecting means which are intended to collect, for each group of sensors, the value that relates to the thermal flow passing through each sensor of said group at a time 't' and is transmitted by said sensor, - first calculation means which are intended to calculate, for each group, a so-called "group" average, which is the average of the values thus collected for said group, - second calculation means which are intended, for each group and for each sensor of said group, to calculate the difference between the value of said sensor and the group average and the ratio between this difference and the group average, and - classification means which are intended, for each group and for each sensor of said group, to classify the warning level of said sensor into a category depending on the ratio thus calculated for said sensor. - collecting means which are intended to collect, for each group of sensors, the value that relates to the thermal flow passing through each sensor of said group at a time 't' and is transmitted by said sensor, - first calculation means which are intended to calculate, for each group, a so-called "group" average, which is the average of the values thus collected for said group, - second calculation means which are intended, for each group and for each sensor of said group, to calculate the difference between the value of said sensor and the group average and the ratio between this difference and the group average, and - classification means which are intended, for each group and for each sensor of said group, to classify the warning level of said sensor into a category depending on the ratio thus calculated for said sensor.