No Mixture Control in Hurricane MkIIb

[martinistripes]

I've just started learning this aircraft to eventually play a campaign with it. One thing puzzling me is, in the aircraft guide it says it has manual mixture control. However, when I try to adjust it in a quick mission I get no indication it's changed (with on-screen text). I'm set at full realism and running the latest version. Am I missing something?

Prop pitch, radiator and supercharger settings work as normal.