The Australian Taxation Office released Interpretative Decision ID 2006/314 in which it states that the size of a helicopter makes it large enough to constitute a permanent establishment.
The Interpretative Decision considers a situation where a helicopter, which is able to transport 15 to 18 passengers, is leased by a Norwegian company, without any other presence in Australia, to an Australian resident to be used to transport workers within Australia.
The Australian Taxation Office concludes that since the helicopter is almost 20 meters long, its size is "substantial" in absolute terms. As the helicopter is "equipment" in a broader meaning, it will constitute "substantial equipment" and therefore a PE for the purposes of Art. 5(4)(b) of the tax treaty between Australia and Norway.