Not many aircraft (other than special purpose homebuilts) actually achieve a
top speed:stall speed ratio of 4, much less a max cruise: stall speed ratio
of 4. Of course, some consider max cruise to be maximum speed at any (read
"low") altitude.

Examples:

Aircraft Top Speed:Stall Speed at gross
150 HP RV-3 4.1
180 HP RV-4 3.9
200 HP RV-8 3.8
160 HP RV-9 3.9
260 HP RV-10 3.3

The typical RV-3 that is going that fast is operating at well over the 2700
RPM where the engine is rated 150 HP.

The prototype GlaStar was designed and flown successfully with the O-240.


BJC

Depends on what they mean by maximum. A ratio of 6:1 for max cruise over
stall would be pretty magical. 4:1 is more like it for a good homebuilt
and few spam cans attain 3:1. However, if they are talking about Vne,
then 6:1 might not be so unreasonable.


Matt