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Prop question

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dkallen

Well-Known Member
Joined
Apr 21, 2010
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I have my plane in for it's annual. I had decided that since I have done everything else to the plane over the last 2 years and the prop is showing a little sign of wear, I am going to send it in for overhaul. It has about 900 hours since new and was replaced in 2000. The question I have is about whether to repitch it or not. My plane is a PA28-180 with all speed mods on it. I have the standard Sensenich 76EM8S5 with a 60 inch pitch. When I transition from climb to cruise I have to be really careful to not overspeed and have to pull the throttle back quite a bit when transitioning. When I do a static RPM check, it is around 2325 RPM and the min by the TDC is 2275. While my goal is not necessarily speed, it would be a good byproduct. I currently cruise at 135-138 kts TAS at 7-8000 Ft. The prop shops I have talked to don't seem to have the information I would think they would have. I would think they would have charts from the manufacturers showing % performance change with X" pitch change. In talking performace, what I would be interested in is to quantify the %change in climb and cruise performance as well as % change in static RPM for a given pitch change. My primary goal is to be not as sensitive to overspeeding the prop without losing too much in climb performance. By my rough uneducted calculation, a 2" pitch change could increase my speed by approx 4 knots assuming an approximate 85% blade efficiency and I would expect the % climb performance change to be rather small to insignificant and I have a hard time grasping what that would actually do in terms of helping with the RPM issue when transitioning to cruise. With this said, at what pitch change would be a significant change in climb peformance. Right now, lightly loaded, I usually climb at nearly 1000 fpm to about 5000 ft most of the year and at gross during the summer, my initial climb is about 500 fpm (>100F ambient temp). OR, just leave it alone and leave the pitch as is. :?: :?:

Any educated guess on this one is better that I have.
 

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