Are You Flying a "Beater?"

In article , Jay Masino wrote:
Exactly. I also think the rotating assembly (crank, rods, pistons) are
not balanced well enough to operate for any extended time at or above
redline, especially when you consider the large tolerances of an air
cooled engine.

I'd agree with above redline, but *at* redline? The majority of aircraft
engines are certified (and I would dare say designed) to be run
continuously at max rated power, which is usually achieved at redline
RPM and sea level pressure. There are one or two exceptions you'll find
in lower horsepower aircraft (such as the turbocharged Rotax engines,
which incidentally sound very odd to fly behind if you're used to a
lumbering old O-320 - the 912S is geared and you're cruising with the
engine running at something like 5400 RPM)

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

I don't normally "top-post", but it seems appropriate here.

I am NOT a pilot, but a lurker ... however, I think I can smooth some
feathers here. The issue appears to be one of definitions.

We've a misunderstanding of "redline" as classically used. That was,
in the old auto days, the speed at which an engine self-destricts,
valves hitting pistons. The line on a tach in an airplane where the
manufacturer has defined as the maximum continuous power for that
plane is also, by FAA regs I think, red.

Think about this for a minute; a friend owns a Cessna 182, and flies a
206 occasionally, neither turbonormalized. He tells me the engine is
the same, but is rated differently. From Cessna's website,
182; IO-540-AB1A5 230 BHP at 2,400 RPM
206; IO-540-AC1A5 300 BHP at 2,700 RPM
on both tachs, the "rated" speed is a red line. Neither 2400 nor 2700
is the speed at (nor PROBALBY near) which the engine floats valves.

In machine design, we routinely assume that frictional wear is a
function of somewhere between the square and cube of "speed"
proportion, iow that the 2700 would have between 70 and 80% the life
of the 2400. BUT, the manufacturer designed and ok's operating them
there. (maybe the C vs B in the model # means better materials?g)

On Sun, 13 Jun 2004 07:43:01 -0000, Dylan Smith
wrote:

In article ptGyc.32742$HG.16217@attbi_s53, Jay Honeck wrote:
Somehow you've determined that operating an aircraft -- specifically a
Piper/Cessna/Beech/Cirrus spam can -- at full power is potentially
dangerous. I'd be interested to hear your evidence behind this assertion.

I flew my C140 half way across the United States at full throttle
and 2550 RPM (redline) because that's the only way a C85 will make
enough power to get you over the high ground. The engine was built to be
able to run at maximum rated power - continuously.

About operating near red line engine speeds. Even thought the handbook gives
data for engine speeds near redline, the only time my Mooney sees anything like
that RPM is at takeoff. I've found the engine does better, fuel lasts longer,
and lots of good things happen when RPM gets down as soon as possible. The
handbook lists some "oversquare" settings as acceptable, you're much more apt
to see my panel show 2100 RPM 22 inches than 2500 RPM, 22 inches.

An earlier poster pointed out machine designers think of wear as a function of
speed squared or speed cubed, and I'd agree. But even if it's a linear
function, a bearing or rotating seal has only so many revolutions until end of
life. You get to that limit faster at 2550 rpm than you do at 2100 rpm. If it's
your personal dollars that are going to pay for the overhaul, if it can be put
off 10% longer or 15% longer, the answer to me is obvious.

My engine logs a tach hour for about every 2500 rpm * 60 minute revs. When that
number gets to 2000 hours or so, someone is going to pay a big bill.

That's my $20,000 worth.

You aircraft is supposed to be able to reach red-line RPM at full
throttle.
If it's not, your prop is misadjusted, or something is up with your
engine.

I've never heard that. Where did you get that info?

My A&P.

One caveat: This is with a constant-speed prop. Fixed pitch props may be
different.

With our CS prop, there is an adjustment screw can be turned one way or
'tother to adjust the maximum/minimum prop pitch. This is adjusted until
the tach is just touching red-line at full throttle.

Anything less than that, and you are not taking best advantage of the
prop/engine combination.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

About operating near red line engine speeds. Even thought the handbook
gives
data for engine speeds near redline, the only time my Mooney sees anything
like
that RPM is at takeoff.

Same here, but that's not the point. The question is not whether it's
economical to operate at redline for extended periods, but whether it's
*safe* to do so.

The answer to that question is "yes". You'll just turn more money into
noise than normal.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

data for engine speeds near redline, the only time my Mooney sees anything
like
that RPM is at takeoff.

Same here, but that's not the point. The question is not whether it's
economical to operate at redline for extended periods, but whether it's
*safe* to do so.

The answer to that question is "yes". You'll just turn more money into
noise than normal.
--
Jay, I concur with your statement. Will you agree with this one? "Other
considerations aside, it's safer to not operate near red line."

That was the point I was trying to make, although I can accept I didn't make it
very well.

AJW

Jay Honeck wrote:

My Maule will redline about 10 seconds after I level off in cruise,
whatever the
altitude. I *will* have to reduce throttle at that point to prevent it
from
overspeeding.

Is that normal?

Yes.

Does your Maule have a constant speed prop?

No.

George Patterson
None of us is as dumb as all of us.

In article IJYyc.22622$2i5.11813@attbi_s52, "Jay Honeck"
wrote:

You aircraft is supposed to be able to reach red-line RPM at full
throttle.
If it's not, your prop is misadjusted, or something is up with your
engine.

I've never heard that. Where did you get that info?

My A&P.

One caveat: This is with a constant-speed prop. Fixed pitch props may be
different.

ah. That probably contributes to our different views on running
at redline. Remember, my 140 has a fixed-pitch prop. And the
redline, iirc, is partially limited by keeping proptip speed
within reason.

--
Bob Noel

In article uMYyc.82659$3x.16996@attbi_s54, "Jay Honeck"
wrote:

About operating near red line engine speeds. Even thought the handbook
gives
data for engine speeds near redline, the only time my Mooney sees
anything
like
that RPM is at takeoff.

Same here, but that's not the point. The question is not whether it's
economical to operate at redline for extended periods, but whether it's
*safe* to do so.

The answer to that question is "yes".

Wouldn't it depend on the airplane?

For my airplane, I have a five-minute limit on
operations at and above 2650 rpm. I think the limit
was put on the STC for noise reasons but I don't know.

--
Bob Noel

The quantity of one gallon is a constant, but testers constantly find
gasoline pumps that indicate one gallon pumped yet there's only 9/10 gallon
in the bucket.

True, the speed of light is a constant, but if you don't properly translate
time into distance the accuracy of the constant is irrelevant.


"Morgans" wrote in message
...

"Bill Denton" wrote in message
...
And you are perfectly making my point...

The only way we could be assured of the laser's accuracy would be to
first
measure it with some sort of ruler, then compare the laser with the
ruler
measurement. This has not yet been done.


Not much into science, are you? Unless the speed of light has changed,
the
laser is still accurate, to a very high degree. The speed of light is one
of the most studied constants, known to scientists, to very many
significant
figures.
--
Jim in NC


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