1) Without prop any vibration will be from engine and PSRU and can inspect engine (leaks, etc.) with no fear of prop. 2) With prop less chance of over rev and some cooling air through rads and oil cooler. What do you think? Finn -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html