Dave,
Short field takeoff performance? Here are some data points to consider: I learned to fly at a grass field listed as 2400' long but which only had 1800' useable - but, with no obstructions. I bought my Coupe there. Sometime early that first summer I did a runup on grass that had hidden loose gravel underneath. The prop wash picked up some gravel and made a pinging sound. Not knowing what was going on, I did a full power runup to diagnose it and got a lot more pinging. The resulting prop dings required that the prop be sent to a prop shop for reconditioning. They called and I was asked what the pitch was supposed to be. Going from hazy memory, I told them 7146. By the wisdom of the time, on a C-85 the pitches were: 7152 cruise 7150 "normal" 7148 climb Last year, in a discussion on the forum many of us decided to redefine the numbers to be: 7150 cruise 7148 "normal" 7146 climb Coupes just don't have that much climb - especially when loaded. If you stay below 1260 pounds, you might be able to go by the old labels. At 1320 pounds, not so much. C-85 and 7146 prop With my C-85 and 7146 prop, I'd usually be off the grass by the mid point of our 1800' of useable runway. Then, I'd let it pick up speed in ground effect and climb out. I only went past mid point a few times on hot days at 1400 pounds gross or when the mud was retarding the takeoff roll significantly. I later moved to a 2400' asphalt field with a bit of slope and trees at one end. The power lines at the other end were buried for one segment but that segment looked narrow and I always wanted to pass above the level of the lines and poles. Again, I felt adequately comfortable on obstacle clearance. (There was still pucker factor in taking off over the woodlot.) Going to rural fly-ins in Iowa, I was comfortable on 1800' grass fields with no obstacles and would even accept a 1500' field with no obstacles (at least none taller than corn). My most nervous takeoff was when taking a friend for a flight. We stopped at a little used field by a small town. The grass was pretty tall, the temp was about 90 and there was NO wind at all but the only obstacle was a 4' farm fence. I thought about it carefully and decided on my go/no-go point. We did a rolling turn at the far end to gain 10-15 mph and were at adequate speed at my go/no-go point. I got off, stayed in very low ground effect at a yard or two high, got speed up then climbed out. On my one trip out west, I was flying solo which, counting my weight and gear put the plane in the 1320-1350 pound ballpark. I was always off the ground by the 1/3rd mark of every high altitude air field (all paved - 6813' at Rawlins, WY, the highest). And, while my climb wasn't much starting from high field elevations, I did have some climb and could make it up to 12,500 to clear the peaks and ridge lines when I wanted. On that trip I flew from cool and smooth dawn till the thermals made me crazy. Twice I took off just before 10:30 a.m. and the thermals made me want to get on the ground by the next airport. (Next trip over the desert Southwest, I land at 10:30-11:00 and go play tourist.) The only time I ever couldn't make it to 12,500 was on that trip. One time, in west Nevada, I waited out the thermals and took off at 5:00 p.m. for one last leg to my destination. The thermals were still going - what I'd call medium turbulence in a light weight Coupe. Between the heat and turbulence, I couldn't get past 11,500 msl. That was 14,500 density altitude. I'm a believer in climb props and am willing to give up some cruise speed for the short field and climb ability. If your field has trees or power line obstacles, I'd take them very seriously. The Ryznar Aviation report you sent me on the one plane said the prop had been repitched from 50 to 48. If you wanted, from what I understand, it could be repitched again to 46 as the change is going the same direction. As I said earlier, at 2400 rpm, C-85 and 7146, I got a very accurately measured 100 mph (within a couple of tenths) airspeed. And, many people spin the engine up to redline when cruising with a little Continental and a climb prop as the engine is not heavily loaded. (Redline on the C-85, 2575, is well below redline on the very similar O-200, 2750. http://edburkhead.com/Ercoupe/continental_engines.htm ) Me, I'm a chicken pilot. I don't like it when I don't have BIG safety margins. Ed
