Points well taken on the nitro availability Europe, and other parts of the world. I've heard from numerous European flyers on this website who have asserted that practically no one in Europe uses nitro in their fuel and heard no one contradict such assertion... so I'm just going by what I've heard. I stand corrected.
As far as it's function is concerned, I stand by my belief that the main function of nitro is to make tuning easier. It DOES add power by adding oxygen to the combustion process, which enables the engine to burn more fuel. The ratio (by weight) of nitro to air going through a running engine is roughly 1.6:1. This is in sharp contrast to:
Methanol's 6:1 ratio
E85's 10:1 ratio
10% ethanol gasoline's (the BS we're practically forced to buy in the US, don't get me started on that subject) 14:1 ratio
Pure gasoline's 15:1 ratio
Since the engine can guzzle down more fuel containing nitro, the needle settings become somewhat less sensitive to their settings.
Nitro DOES allow a glow engine to make more power...by simply enabling the engine to burn more methanol by oxygenating the combustion process. You're getting more power by burning more fuel. No real magic or mystery there. One could obtain a similar power increase by going from, say, a .40 engine to a .46 engine (which may be made in the same size case) and burning cheaper nitro-free fuel.
Anyhow, I did see about a 500rpm drop in power when switching to nitro-free fuel in my ASP .46, something I hardly noticed at all in my 4 star 40. IMO most flyers (whether they realize it/would admit or not)would be more likely to notice that their engine is a bit easier to tune that they would that their engine is making a hair less power. Just my opinion. Peace