A noisy environment dominated by low frequency noise can often be improved through the use of active noise control. This situation arises naturally in propeller aircraft where the propellers induce periodic low frequency noise inside the cabin. The overall interior sound pressure level inside a turboprop aircraft is typically rather high, and the passenger flight comfort could be improved considerably if this level was significantly reduced. This paper discusses the behaviour and robustness of a narrowband twin--reference feedforward active noise and vibration control system in a SAAB 340 mock-up. The resulting sound pressure level were recorded and is presented as the narrowband attenuation versus time. The spatial distribution of the sound pressure level is also presented. The results show that the twin-reference controller exhibits good performance with respect to attenuation and robustness for both stationary and non-stationary conditions.