Narrowing it down... Comanche?

wrote in message
...
Douglas Paterson wrote:

[snip great engine info]


All that said, what you say is correct from my way of thinking. Just
because
you have the horses doesn't mean you need to use them all the time. If
you run a -250
at 55% rather than a -180 at 75%, it'll definately be happier for it. You
don't even
lose a whole lot of speed and you often gain quite a few percentage points
in fuel
economy.


That's the point I was trying to make--thanks for making it better than I
did....

Tire size and the overhead crank for the elevator trim is about all I can
think of that might be common between the two. They're completely
different
airframes.


OK, parts are not in common. However, if I'm an A&P, well-versed in working
on Cherokees, would I really be out of my element on Comanches? No doubt
there are sneaky problems that a Comanche specialist might catch (one of
many arguments to get a specialist in your type, I think), but for
run-of-the-mill inspections and repairs?

: I've asked on the Comanche boards, but I'll repeat it he anyone have
: climbout figures for the Comanche (or other models for comparison) at
: 10,000' DA (a common DA in the summer here, I'm told)?

That issue right there limits your decision more than most of the other
things
you mentioned. At least the Hershey-bar PA-28s tend to blow goats at high
DA. The
taper-wings are allegedly a bet better. If you're not willing to
sacrifice
significant load or runway flexibility, the PA-24-180 is definately out,
as would be
any PA-28 less than 235 that isn't turbocharged. I seem to recall climb
rate in a
friend's PA24-250 that was mid-range loaded (40 gallons on-board,
2-people, and 50 lbs
baggage) was about 400fpm at 12k. Only one datapoint I know, but a
*takeoff* at such
DA's would burn up a helluvalotta runway loaded.

I couldn't agree more about the importance of the climb issue. No doubt, on
the hottest, most humid day of July, I *will* have to sacrifice load and/or
runway flexibility, no mater what airplane I get--that's part of my
reasoning of *not* compromising on "book" S/L numbers. A strong climber
with large loads at S/L will, in general, outclimb an airplane that is a
mediocre climber with medium loads at S/L, for any given altitude--no? My
desire is 600 sm range in 4 hours or less, with fuel on board plus
reserves--that's around 60 gallons at 75% in a Comanche, according to the
numbers I'm finding. Leave 30 gallons on the ramp, that's one more person I
can take, or keep as an additional performance benefit, as dictated by the
day's mission. I know there will always be trade-offs--that's why I want to
start with "extra" capability, so as not to lose the basics just because of
my location.

Thanks for the pointers!
--
Doug
"Where am I to go/Now that I've gone too far?" -- Golden Earring, "Twilight
Zone"
(my email is spam-proofed; read the address and make the appropriate change
to contact me)

: Considered, yes (among other tc models). Frankly, I'm scared of turbo--it
: seems like for every story of increased capability at altitude, there are
: three stories of huge maintenance bills, overhauls well short of TBO, etc.
: The Comanches have a 20K ceiling and a reputation as good climbers (though
: I'm still looking for hard numbers in the above-8K'-DA regime), and bring a
: lot of versatility to the table. Bang-for-the-buck again....

: Am I being overly (unjustifiably) cautious here?

I don't know of any *specific* examples of comparing maintenance of one turbo
system vs. another. I do know that I would never consider running an air-cooled
aircraft engine under full-time turbo. My mechanic owns a turbo-arrow with a 200hp
TSIO-360 continental 6-cyl that's known to eat jugs for breakfast.

Now, I *would* consider a turbo aircraft to circumvent the problems that
you're likely to have at high DA's. A turbo-*NORMALIZED* engine isn't inherently much
harder on the engine. You're limited to sea-level manifold pressure, but you can make
it at higher altitudes. About the only way that it's harder on the engine is
decreased cooling due to thinner airflow, and increased intake air temperature due to
the turbo. The former you're kinda stuck with, the latter can be helped with an
intercooler. Both of which become more important the higher you go, but for
relatively small increases (say, to decrease the effective DA from 12000 to 6000), it
wouldn't be hard on the engine much at all.

I like the fact that a turbo-normalizer:
- Does not have to lower the compression ratio of the engine
- Usually has a stone-cold simple control.... just another throttle to twist when you
run out of MP
- Is not required at all times to make full, rated HP (at sea-level).

I don't know what aircraft are often found with them, but I suspect they're
somewhat scarce and impractical to add yourself.

*sigh*

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Douglas Paterson wrote:
: OK, parts are not in common. However, if I'm an A&P, well-versed in working
: on Cherokees, would I really be out of my element on Comanches? No doubt
: there are sneaky problems that a Comanche specialist might catch (one of
: many arguments to get a specialist in your type, I think), but for
: run-of-the-mill inspections and repairs?

In most cases, airplanes are airplanes. P-brand vs. C-brand doesn't matter
too much, except that P-brand tends to just "bolt on" extra stuff and call it another
airplane. I've worked on both aircraft (Lots on my own Cherokee, some avionics and
engine-hanging wrenching on a Comanche). The main difference between the two is that
the Comanche has an internal sub-floor where all the control cables, plumbing, wiring,
etc go. The Cherokee has the cabin floor skin play double-duty as exterior skin as
well. All the control cables are routed through the center floor column. Kinda
disturbing to be sitting on a beer-can sometimes... Other goofy things are the
Comanche's control yokes. It's a menagerie of cables, pulleys, and bearings behind
the panel, whereas a Cherokee has a nice, simple chain/sprocket T-bar. The gear on
the Comanches (at least the older one I'm familiar with) is stone-cold simple, too.
Electro-mechanical worm gear and a "Johnson-bar" emergency gear extension. Just plain
simple. (There's a repetitive AD on landing gear bungee cord springs IIRC).


: I couldn't agree more about the importance of the climb issue. No doubt, on
: the hottest, most humid day of July, I *will* have to sacrifice load and/or
: runway flexibility, no mater what airplane I get--that's part of my
: reasoning of *not* compromising on "book" S/L numbers. A strong climber
: with large loads at S/L will, in general, outclimb an airplane that is a
: mediocre climber with medium loads at S/L, for any given altitude--no? My
: desire is 600 sm range in 4 hours or less, with fuel on board plus
: reserves--that's around 60 gallons at 75% in a Comanche, according to the
: numbers I'm finding. Leave 30 gallons on the ramp, that's one more person I
: can take, or keep as an additional performance benefit, as dictated by the
: day's mission. I know there will always be trade-offs--that's why I want to
: start with "extra" capability, so as not to lose the basics just because of
: my location.

Again... a turbo-normalizer would be good for this.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote in message
...

Now, I *would* consider a turbo aircraft to circumvent the problems that
you're likely to have at high DA's. A turbo-*NORMALIZED* engine isn't
inherently much
harder on the engine. You're limited to sea-level manifold pressure, but
you can make
it at higher altitudes. About the only way that it's harder on the engine
is
decreased cooling due to thinner airflow, and increased intake air
temperature due to
the turbo. The former you're kinda stuck with, the latter can be helped
with an
intercooler. Both of which become more important the higher you go, but
for
relatively small increases (say, to decrease the effective DA from 12000
to 6000), it
wouldn't be hard on the engine much at all.

http://www.aopa.org/pilot/bonanza/turbo_primer.html

I like the fact that a turbo-normalizer:
- Does not have to lower the compression ratio of the engine
- Usually has a stone-cold simple control.... just another throttle to
twist when you
run out of MP
- Is not required at all times to make full, rated HP (at sea-level).

I don't know what aircraft are often found with them, but I suspect
they're
somewhat scarce and impractical to add yourself.

Bonanzas primarily. One really nice thing is a TN makes lower altitudes
practical; no need to go to 12-15K feet

Beryl d'Shannon (sp) and TurboAlley are the two biggies with STC's.

I've had a TN IO-550 for just under 1700 hours now and it's been nothing
short of amazing. So far, none of the "horror stories" that Doug Paterson is
worried about. Thing is, a TN unit will run about $30K up to $45K installed.



Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

How can retractable gear *ever* be "a wash" with fixed gear? There's
just
a
lot more "stuff" in there to be maintained.

Good stuff snipped

Good points -- thanks for clarifying.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Matt Barrow wrote:
: Bonanzas primarily. One really nice thing is a TN makes lower altitudes
: practical; no need to go to 12-15K feet

: Beryl d'Shannon (sp) and TurboAlley are the two biggies with STC's.

: I've had a TN IO-550 for just under 1700 hours now and it's been nothing
: short of amazing. So far, none of the "horror stories" that Doug Paterson is
: worried about. Thing is, a TN unit will run about $30K up to $45K installed.

Like I said, impractical to add yourself. Question though... a buddy of mine
used to have a Cessna 310 Riley Rocket. In addition to the speed mods on the airframe
(bondo-buggy as he called it), it had *manual* wastegates. I would think that those
would be preferable, unless the wastegate controller on the aftermarket ones are
clever. From the looks of the ones on TurboAlley, it sounds like they are "hands-off"
turbo... Are they the same as the stock, suck-dick Piper turbo Arrow setup? In other
words, controlling the wastgate to always making maximum boost and then throttling
with the throttle plate?

Those are the kinds of "simple," yet horribly stupid design choices that lead
to premature engine/turbo wear. No point in pumping/heating 12000' air to 31" if
you're only going to run 23 squared. Anyone know?

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote in message

I don't know what aircraft are often found with them,

All turbo 182's are turbo normalized.

but I suspect
they're
somewhat scarce and impractical to add yourself.

Yes.

wrote in message
...
Matt Barrow wrote:
: Bonanzas primarily. One really nice thing is a TN makes lower altitudes
: practical; no need to go to 12-15K feet

: Beryl d'Shannon (sp) and TurboAlley are the two biggies with STC's.

: I've had a TN IO-550 for just under 1700 hours now and it's been nothing
: short of amazing. So far, none of the "horror stories" that Doug
Paterson is
: worried about. Thing is, a TN unit will run about $30K up to $45K
installed.

Like I said, impractical to add yourself. Question though... a buddy of
mine
used to have a Cessna 310 Riley Rocket. In addition to the speed mods on
the airframe
(bondo-buggy as he called it), it had *manual* wastegates.

ICK!!!!

I would think that those
would be preferable, unless the wastegate controller on the aftermarket
ones are
clever. From the looks of the ones on TurboAlley, it sounds like they are
"hands-off"
turbo...

Yup...a popoff valve will release at about 30.0-31.5" MP. Nothing to control
or worry about...just fly.
No chance to overboost.

http://www.avweb.com/news/columns/182102-1.html (Those Firebreathing
Turbo's - part 1) Read all six...really good diagrams and illustrations.

Are they the same as the stock, suck-dick Piper turbo Arrow setup? In
other
words, controlling the wastgate to always making maximum boost and then
throttling
with the throttle plate?

Those are the kinds of "simple," yet horribly stupid design choices that
lead
to premature engine/turbo wear. No point in pumping/heating 12000' air to
31" if
you're only going to run 23 squared. Anyone know?

Or if you're seldom going over 8-10000 feet.

I take it Doug is in Colorado Springs (6100-6800). He's worse than me
(5600'), but I have 14000 foot mountains to the East, and 10-12000 footers
West of me and we're down in a valley (a REALLY BIG one, but a valley
nonetheless).

It can certainly be done without a turbo, but the Springs during
June/July/August is going to be a thrill.


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

On 2006-02-20, Jay Honeck wrote:
1. Speed. The Comanche does win in speed, of course. We cruise at 140
knots, while the Comanche cruises at 157 knots. To put this in
perspective, our flight to St. Louis this weekend took us 1:18. In the
Comanche 250, it would have taken us 1:10.

To pick nits (this is USENET!) the difference is quite a bit more than 8
minutes (unless you fly the entire flight in ground effect). The
Comanche 250 climbs quite a bit quicker, and will also have a higher
speed cruise descent. The climb speed is probably a bit higher in the
Comanche too, so you'll be climbing at a higher rate and a faster
airspeed.

--
Dylan Smith, Port St Mary, Isle of Man
Flying: http://www.dylansmith.net
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de
Frontier Elite Universe: http://www.alioth.net

Matt Barrow wrote:
: (bondo-buggy as he called it), it had *manual* wastegates.

: ICK!!!!

I *like* simple. Less crap to break, and *YOU* get to choose if you want to
use the turbo or not. If you run out of MP in a climb, just crank in a bit more on
throttle #2.

: Yup...a popoff valve will release at about 30.0-31.5" MP. Nothing to control
: or worry about...just fly.
: No chance to overboost.

Exactly... likely done like the flagrantly stupid design like Piper used. The
wastgate control "controlled" the inlet to the throttle at some arbitrary pressure.
No matter what throttle setting you use, you guarantee the maximum possible inlet
air temperature, turbo temperature, and power loss due to increased backpressure on
the engine. The *correct* way would be to leave the turbo off until the throttle
plate is wide open. THEN, bring up the boost if you want more MP. It could be done
with linkages with little failure liability.

If the aftermarkets work this way, I apologize, otherwise, the "flagrantly
stupid design" comment still holds IMO.

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************