I’ve just been reading an AOPA article that gave the rough rule of thumb that for every 2% below max weight, you should reduce your manoeuvre speed by 1%. That got me thinking about the new RAAus 750kg class G. Let’s say that you want the extra load capacity because your favourite travelling companion gets a bit annoyed when you limit them to 10kg luggage in a 600kg plane, so you decide to splash out and go to the bigger class. So far, so good. However…
However, most of the time, you’re not carrying a big load. In fact, you’re carrying just yourself and 30L fuel. For the purposes of this discussion, let’s imagine that amounts to 460kg, and that the published Va of the plane is 115kt. For a 600kg plane, that brings your ‘real’ Va down to 101kt, but for a 750kg plane, it drops to 92kt. That makes for pretty slow going in a supposedly fast aircraft.
Now, I know that I’ve made some wild assumptions regarding the similarity of two aircraft designed for different max weights, but taking as an example ICP’s Ventura (newish big sister to the wonderful Sav) which is available in three max weights with similar specs (after taking different engine powers into account), perhaps the assumptions are not so wild after all?
The question is, what’s wrong with my analysis, or is moving up to a heavier aircraft a bad idea if you mostly just tootle around?