Ed,
On my c-130 model I used the prop rotation expressions shown on other threads plus an action file like yours (I made a 24 frame animation though)
I then made them I alos made a prop rotation disk, a disk that is decaled to look like a prop already rotating, then I made them transparent to a % , as The prop starts slowly rotation up using the actions and/or expressions I slowly switch from props to rotation disk using traansparency, props solid at begining and disks 100% transp. then reverse the transparency as the prop rotates faster,
Cool looking aircraft so far....
Michael