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."
The obligatory 'shakey-cam' video of the prop strike incident can be seen here
(you can hear the scrape at 1:02):
Pictures from the flight
and the subsequent blade damage are below.
