During my 40 hour test flying on the Mustang I got bored to tears and decided to test the windmilling or not theory. I was surprised to find that on that plane I had a better glide ratio with the prop windmilling than with it stopped. With my particular prop and engine combination the prop would windmill until I slowed to about 90. It would not start spinning again until I speed up to about 140 so I had a pretty good range where I could choose a windmilling or stopped prop. I actually did something like 5-10% better glide with it still windmilling.
Keep in mind that this was one particular airplane, prop, and engine combination and I don't doubt that many, if not most, other combinations will glide further with the prop stopped. With a lower pitch prop and a higher compression engine you also might not be able to keep it windmilling at anywhere near your best glide speed. It all boils down to if you want to know try it yourself in your plane. Now that I have cut two inches off the prop and had it pitched 4" lower I will try again and see if I still get the same results. Oh, and don't try this experiment if you don't have a mixture control. Shut your engine with the mag switch and then turn it back on with the prop windmilling and you are going to get the backfire from hell. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Mark Langford Sent: Saturday, March 11, 2006 9:15 AM To: KRnet Subject: KR> windmiling props Bobby wrote: >When the engine quit for real, it amazed me how fast it > came down with a prop stopped. That's interesting, because conventional wisdom is that planes glide better with the prop stopped than with it idling or windmilling, so I've always used my idling glide rates as "worst case". See http://selair.selkirk.bc.ca/aerodynamics1/Multi/Page2.html#Windmilling for more on drag produced by windmilling props, or idling props. The small diameter props and high compression engines that we use on KRs won't windmill anyway, so engine-off glide should be better than idling glide. I haven't proven that yet, but once it gets warmer and shock cooling isn't as bad, I plan to test that one too. Anybody want to give me a speech on shock cooling? Mark Langford, Harvest, AL see homebuilt airplane at http://www.N56ML.com email to N56ML "at" hiwaay.net _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
