Fuel flow will be one of the key data points, too.
It doesn't matter if I post that I've seen 183-4kts
with my RV10, because the times that I've seen
over 180kts I was burning 19+gph. It would be
insane to try to run the engine like that to go
on a trip. So really, to make any data valuable,
you'd want RPM, MP, Fuel Flow, Altitude, OAT, Loaded
weight (and distribution) and things like that so you
can get realistic comparisons. It's like saying "My
car gets 85mpg", but not stating that when it does
this, you're rolling down an mountain.
Almost all of my experience is with flying in a mode
that provides best economy. I have very little time
spent flying for max performance. I enjoy being
able to flight plan 160-165kts, and do it with
fuel flows generally being 10gph or less. Various
loadings produce vastly different cruise speeds,
so sometimes I cruise 157-160kts, and sometimes
I cruise 173-175kts, but I rarely cruise over 13.5gph,
and there is usually a few more kts available if
I'm willing to bump up the fuel flow.
Speaking of loadings being important, last year at
OSH while flying people around, I found that I was
easily 2 or 3kts slower than Scott. We weren't
loaded identically, but I remember being slower.
This year, on the way to OSH, I was easily outclimbing
and then out-cruising him...even though we were
both loaded up. But, I don't think his loading
was as light as mine. It was interesting to see
how a little added passenger load or distribution
of CG caused really different performance numbers.
Again, most of my experience and numbers I know,
are loaded up with the wife, kids, my portly
self, and maybe 10-125lbs of baggage. How it
performs with just one or two people in the
plane is much more foreign to me. We all remember
what we know best...for me, I know that if I
want to burn 8-10gph, I can count on 157-165kts
depending on altitude and loading, and if I
want to burn 12.5-14gph, I can plan to fly 164-175kts
...loaded with the family.
I would say that Rob's estimate of being 7kts slower
is probably in the ballpark. I would have guessed 8-12,
but, without fuel flow data included, it's hard to
tell how directly it compares. 2600 RPM is a speed
that almost nobody will ever cruise at. When the
numbers were first posted at 2450RPM, my first
question in my head was "hmmm, wonder what the fuel
flow was...", because 2450 is a little more aggressive
of a cruise RPM, and almost certainly is burning
more fuel than what people are used to hear reported
by the MT and Hartzell 2-blade folks. If it was
171kts at 13.5gph and 2450RPM at 8500', then
that's not really too bad at all. If it's 171kts at
18gph, then I'd say that kinda stinks. Most
people I've talked to find something between 2200
and 2360 that they cruise at. Most of my cruising
is at 2360, as I haven't found that I can keep the
speeds up when I go down towards 2200. I've just
found 2360 to be a sweet spot for smoothness and
economical performance. To me, it's all about
economy....it stands out in my head that on ONE trip
to Oregon alone, just cruising LOP saved me over
$200 in fuel. On this weekend's trip, with 2
hours to go to destination, I had to choose between
10-20 minutes of time savings, or 6 gallons of
fuel...I chose to save the fuel. So fuel flow
numbers are important parts of the data set.
Tim Olson - RV-10 N104CD - Flying
do not archive
Lenny Iszak wrote:
>
> It would be pretty useful to make a surface chart using Rob's engine data.
> rpm vs airspeed vs fuel flow...
>
> --------
> Regards,
> Lenny
> #40803
> Fuel System...
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p 2327#202327
>
