The Fourier transform is the main processing step applied to data collected from the Square Kilometre Array (SKA) receivers. The requirement is to compute a Fourier transform of 2 19 real byte samples in real-time, while minimizing the power consumption. We address this challenge by optimizing a FFT implementation for execution on the Kalray MPPA manycore processor. Although this processor delivers high floating-point performances, we use fixed-point number representations in order to reduce the memory consumption and the I/O bandwidth. The result is an execution time of 1,07ms per FFT, including data transfers. This enables to use only two first-generation MPPA chips per flow of data coming from the receivers, for a total power consumption of 17.4W.