Conducted 07/07/2012 –
After feeling the oil temps were under control well enough to continue flight testing, we reviewed the next few flight test protocols. The next in sequence (protocol #5) was climb testing, followed by airspeed indicator calibration in protocol #6. This was clearly a bit of a flaw in our sequencing as really we needed to calibrate the ASI first so that we had accurate airspeed information when determining climb rates and speeds. So we decided to flop the order and conduct the ASI calibration next.
Unfortunately, things didn’t go well. John’s flight report to the Cozy Builders list is below:
“Well, Saturday I was chomping at the bit to get back up in the air. My agenda for the day was to do airspeed calibration runs for the first flight, and then take some time to go biking with a friend before returning to the airport to do climb testing.
I had picked some road intersections as my fixed points for the ASI calibration test the night before, and drove to them to mark them in my portable GPS. The plane was fueled and ready to go, and the next morning all I needed to do was preflight and strap in.
Things started off just fine, and the tower asked me to report established at 5k, and although I wasn’t really thinking much about my climb rate (I climbed out at 110Kts), I had hit 5K just near the end of the downwind. I reported established, and the surprised controller responded “Wow, you JUST LEFT!” I chuckled and said “yeah, she likes to fly.”
I navigated to my first waypoint, getting the plane set up for 120Kts at 5k, but en route to the second waypoint the RPM started climbing. I checked the prop control hadn’t moved, and it was exactly where I set it. It was acting just like it did when the oil temps were high, but this time the oil temp was 192F. I throttle back to keep the RPM down and started back towards the first waypoint. En route the RPM started decreasing, and I started to worry that I was losing power, but my altitude was holding and my airspeed was picking up. It dawned on me that prop was regaining it’s composure.
I restarted my test, and made it all the way to the second waypoint but in the turn to the third, it did it again. I played with the prop control a bit trying to see if it was just air in the system, but it still didn’t seem to have much bite to it when I pulled back on the control. Then all of sudden, just like before it regained it’s pitch authority. I decided to abort the airspeed calibration runs and get myself back over the top of the airport.
I circled the airport at 5K and decided to try speeding the plane up a bit to see how the oil temps and CHTs reacted to more power and faster airspeeds. I slowly crept up on 21”/2100RPM and was showing 174KIAS. CHTs were 311 on the coldest and 348 on the warmest. Oil Temp was holding nicely at 194. I was pretty happy with it. But alas, the fun would not last. The prop began acting up again, and this time I had to reduce throttle more quickly to prevent overspeed. I decided I had better just land and call Whirlwind to figure out what was going on, as I didn’t think it could be an air bubble in the oil any more.
I dropped down to pattern altitude and joined the downwind for 31. Dropped the nose gear, flattened the prop, and got my clearance to land. About 1/8 mile out on final, the rpm surged a bit again, and I slowed slightly. I re established my airspeed and hoped that the prop was done playing games with me. Not so lucky, another little surge just before the threshold and again a slight drop in airspeed. I tried keeping my airspeed at 80Kts, but the ground seemed to be coming up faster than I was used to. I didn’t want to slam it on, and tried to arrest the descent rate with pitch….bad call…(you can probably guess where this is going now). I should have just aborted and gone around. Instead I brought the canard up above the horizon and yup, you guessed it, kissed the prop on the runway. Some how, I decided to go around at that point, not really knowing what I had hit on the ground. I went around, and came back in for a normal landing. Got back to the hangar and confirmed it was the prop.
I ended up grinding about 3/16-1/4” off the tips. The prop is on it’s way back to Whirlwind now. They’re pretty sure they know how to fix the surging problem. They also told me that it may be possible to salvage the blades, but they won’t know until they get them stripped down to inspect the carbon fiber.”
