Prop balancing and assorted observations - long

I've had a kind of unnerving vibration in my RV-4 since first
flight. I looked into harmonic dampers, but they're pretty
expensive, so I decided to give dynamic balancing a shot first.
$200 and 1 hour later, my engine runs *much* smoother. It
measured 0.3+ ips on the first run, so the guy weighed and
added an AN-4 bolt, nut, and a few washers to the flywheel.
Next run it was down to 0.05 ips and felt markedly different,
much smoother and quieter. I ran out of time and weather at
the same time, so I haven't flown it yet, but I don't see how
it can't help but be smoother. It remains to be seen whether
or not I'll have the pronounced shake at some power settings
and speeds, but I've also cut back the baffles where metal
rubbed on fiberglass and tightened things under the cowl a bit.
We'll see.

A little disturbing when the A&P noticed that a screw had backed
out of the left harness-to-mag mount. As I was tightening
it I noticed that another was missing altogether - a single
screw was holding the left harness to the mag. I've replaced
and tightened everything and sealed the threads, and done
a thorough check of every other fastener under the cowl.
I *hope* it was vibration-related and that we've fixed the problem,
but you can bet I'll keep a pretty close eye on it from now on.
I also had to replace the oil temp sender which failed inside
the sender, again presumably (hopefully?) due to vibration.
Sandy at Grand Rapids came through for me and got a new
one out in what must be record time. They're very pleasant to
deal with.

Also took the opportunity to do a compression test (first one)
while the cowl was off. Three strong cyls, #3 (the continuing
problem child) was a little low, but the A&P said it *should*
come up as the engine breaks in. No valve leakage that he could
tell, it seemed like it was getting past the rings. Oil shows
a little blow-by too. Chrome cylinders with 20 hr, so my
assignment is to "run the [snot] out of it" and see if it
improves in 10 or so hours.

Things I love about this airplane (in addition to the usual stuff
you hear about RVs):

Grand Rapids Engine Monitor
4-cyl temps have really helped troubleshooting, and adjustable
alarms are a comfort.

AnywhereMap GPS
Awesome. Freakin' awesome.

160 KIAS in the overhead pattern and a 4g break to downwind.
Hehe. John Ousterhout once told me "I hope you don't start
doing those 'break' entries like the rest of the RV guys."
It's the only way I can slow it down. Ob.safety note: Only
at home when it's not busy and the wind favors a direct entry
to upwind.

Taildraggers for the brain-dead.
I've only got a little taildragger time, but (like the rest
of my experience) spread thin over a bunch of different types.
The RV-4 is by far the easiest-landing taildragger I've ever flown,
and that includes other RV's. Increased confidence and proficiency
probably have a lot to do with it, but that's the way it seems,
anyway.
Of course I still nearly had it off the runway once in a stiff
crosswind.

Electric Trim and Flaps.
I work the heck out of the trim, as you might expect in an airplane
with such a wide speed range. Lateral trim (electric or manual) is
an absolute necessity in flight test as far as I'm concerned.
Electric flaps are less of a struggle than manual at a fairly
high-workload part of the flight (see 'break entry' above ,
although manual (in a -6, anyway) aren't that big of a deal to use
either.


Things I'm still working on (that I'd do differently next time):

The panel:
The engine monitor is on a sub-panel, where it's out of my
primary scan. Given that I'm trying to keep a close eye on
temps, it's in a less-than-ideal spot. I wish I had room
for it on the panel.

Single radio, no VOR:
While I love the AnywhereMap stuff, I don't trust the iPaq
it's installed on. The batteries are ^(*)&. It's wired into
the airplane electrical system, but still needs to charge
in between flights. If it dies enroute or on an overnight
I'm committed to dead reckoning. As such I plan to stick
close to highways and well-defined landmarks for trips
over unfamiliar territory. A second comm, while certainly
not required, would be nice as well. I've got a handheld,
but haven't patched it into the comm system yet.

External power:
Dead battery. No external power jack. Do the panel crawl.

^*&%%*&( Switches:
I harp and harp and harp about human factors, and then I
use identical switches throughout the switch panel (in
my defense I *did* try and space them so that the differences
would be obvious). I've turned the electrical system off
at least once thinking I was turning off the fuel pump.
Now I look. I think I'm going to rotate the FP switch
so that it's side-to-side throw or put a different bat
on the master switch. At least it wasn't the mags.

Vacuum gyros:
A dead AH and probably dying VG. What with all the
solid-state (or nearly so) attitude systems out there
I don't see any reason to mess with these again.
Interestingly enough, the Falcon (electric) turn
coordinator is holding up better than the vacuum gyros,
in spite of its reputation.


Done for now.

Dave 'brain dump' Hyde

RV-4 in flight test, EAA Tech Counselor