Unmistakeable yes, but I certainly wouldn't call it howling. Droning maybe, but not howling. I used to love hearing the sound of ACZ (the Augusta Airways mail plane) fading into the distance as it headed north every weekend on the (then) World's Longest Mail Run.
Desert Flower, didn't you like the drone of the chieftain as it headed north every weekend as well? I enjoyed having a cuppa tea and biscuit in your donga after refuelling.
Sorry for the thread drift. Memory nostalgia overcame me.