Hi Mitsu,
>HoHun, altitude lever is supercharger lever. that lever is in the same position as supercharger lever of other planes. Ki-44-II had 2 speed supercharger engine as well.
I think it's a different lever from the supercharger gear:
"7. Close the altitude lever. (supercharger control?)
8. Check whether the primary speed selector lever and the flap (illegible - T.N.) lowering device are engaged."
Point 7 sounds to me like referring to the filter bypass ("closed"), while point 8 seems to refer to the supercharger ("primary speed selector lever ... engaged" = first gear selected and engaged).
This interpretation also matches the description under "Descending":
"3. Close the altitude lever. (Supercharger control?)"
Of course, it could be that the Japanese original is less ambigous - I'm going to have to rely on your expertise there :-)
Regards,
Henning (HoHun)