We suggest an innovative architecture for an efficient energy generator devoted to the powering of a wireless sensor network deployed for Aircraft Health Monitoring. This battery-free generator captures energy from its environment (transient thermal gradients as a main source, and vibrations as a secondary source allowing early biasing of the generator) and stores this energy in ultracapacitors. In this way, this multi-source architecture benefits from the synergy between energy scavenging and harvesting: vibrations bring low but early and permanent energy. They also contribute to energy harvesting during cruise while thermal gradients have vanished. The use of active diodes and of a very low bias current of 10nA/branch allow achieving ultra-low power consumption, experimentally demonstrated on two different CMOS technologies. It is also proven that enough energy could be delivered to power the functions of a wireless sensor node.