An ionic conduction device 10 of the kind including a tri-layer 11 including an electrolytic membrane 12 having a pair of opposed surfaces 13, 14, and a gas permeable electrode 15, 16 in contact with each opposed surface 13, 14, has a first gas flow path 2...

The method involves sensing air flow rates individually in each of air bleed lines (11a,12a,13a) from engines (11,12,13) with respective flow rate sensors (S1-S3). The air flow rates are compared to air bleed lines to derive flow matching signals (30b,31b,...