IO 360 Power down (danger, long, rambling post!)

Kevin Horton wrote in message ...

Please detail how you determined the cruise speed and climb rate. If you
used the IAS and converted to TAS there are a lot of ways that errors can
be introduced. For example, I've seen reports of ASIs with over 10 mph of
instrument error, and I've communicated with builders who found that flush
static ports causing the airspeed to read over 10 mph too low. A local
RV-8 builder had that problem recently. And some of the methods that
people quote for using GPS to get TAS aren't mathematically sound,
although the error here would only be a few mph, unless you've done
something really creative.

Lots of info on how to figure out TAS from GPS data, how to calibrate ASIs
and how to measure static source position error at my web site:

http://go.phpwebhosting.com/~khorton...ex.php?&PID=48
http://go.phpwebhosting.com/~khorton...ex.php?&PID=49

If you used the VSI to determine climb rate, be aware that VSIs can have
very large errors. You really need to use an altimeter and a stop watch.
And you need to understand that the rate of climb that Van quotes is
almost certain an extrapolation down to sea level at standard temperature.
You are almost certainly at a higher altitude when you do your testing,
and the temperature may very well be warmer than standard, so your rate of
climb would be a bit less than 2500 even if everything else is sorted out.

First to Jerry: Yep, am a member of the RV-8 list. Got a couple of
great ideas from them.

Now to Kevin: Yer right. I am currently using TAS from a Blue Mountain
Efis compared to GPS ground speed. The two seem to match up pretty
well. I am fully cognizant that the the GPS ground speed is affected
by wind, but over a hundred hours or so I am recognizing that the two
track quite well. This ain't science, yet. :-)

Climb rate is absolutely based on VSI and again, agree that there is
substantial error present...possibly.

What started this quest was more of a global sense that we were way
off from the standards...followed by a flight with an acquaintence's
RV-8 with ostensibly the same set-up as mine (well, different prop,
and no nose wheel)...and he made me look like I pretty much have been
making everyone ELSE look.

As I said, we went through everything on Tuesday and are replacing the
gas filter for one that is less restrictive and tuning the prop
governor for FULL take-off power. I am quite a lot more confident that
there are no subtle engine problems, and it is likely going to be a
fix each aerodynamic detail at a time to get it to where I want it to
be.

We have also fixed the fuel-flow indicator, and between that and the
BMA EFIS's ability to record flights, I am going to be able to
actually generate some data. My first two projects will be actual
time-to-climb vs fuel usage and the leaning exercise needful to work
with the GAMI folks so I can further tune my fuel system.

I will be (after I have some better data (as opposed to
impressions...hey, impressions are good enough for newsgroups, I need
data to dicker with manufacturers)) talking with the aerocomposites
folks to make sure I have the right prop. They are advertising an RV 8
with fairly spectacular performance with one of their props (but a 74
inch prop, mine is considerably shorter, but with (I think) a
considerably wider chord). We'll compare and contrast and see if we
can gain from the prop losses that I suspect are occuring.

Then on to the nickle-and-dimers...off with the tie-down rings, better
seals at the various interfaces, maybe have a look at a different
cowl/induction system.

I have an outstanding airplane. It is fast, climbs very well, and is
more airplane than I have ever flown. And a great deal of fun. Now I
just want more! :-)

Jim