Why does airspeed change when I adjust the prop?

He is, of course, right. Pilots often do act on "voodoo" when it
comes to engines, and other flight details. Or at least on the tales
their CFIs told them... some correct, some not. How many times have we
had someone here say "I was told this", and half the replies are "but
no, it's really that!" It's often hard to sort the wheat from the
chaff, not least because there can be so much difference between
airplanes.

No, he is not right at all. There are a few "rules of thumb" that work for
basic training aircraft--which are specifically manufactured to be tolerant
of those practices. However, flying most modern trainers, you can improve
both performance and economy if you operate them "by the book."

The more sophisticated the engine, the more important important it is to
operate "by the book." Geared engines and controllable props are excellent
examples.

In short, you are attempting to defend the idefensible.

It's only fairly recently that researchers outside of the engine
manufacturers really began looking into how the motors work in
practice. And we needed those outside people because for a long time
the manufacturers had conflicting advice, or no advice at all. If it
seems strange at times to pilots, it must be doubly strange to a
non-pilot. Anyway, we all know about GAMIjectors as one example of
research. Here's an interesting read:

That's not true. Most of this was known and documented during (and a lot of
it prior to) World War II, and much of it is documented in old NACA reports.

GAMIjectors are not an example of new research, but of the evolution of
market forces. The relative costs of fuel, certification, and precision
manufacturing reached a balance at which some investors saw an opportunity.
I have no idea whether others saw the same opportunity at an earlier date
and failed in their marketing, or simply ran out of money--but the
underlying knowledge had already been in the public domain for decades.

Peter

He is, of course, right.


It's a gad damn stupid question to begin with. Does changing prop pitch
affect speed? If it didn't we'd be well on our way to a perpetual
motion machine.

BDS writes:

Then again, "virtually unrecoverable" isn't the same as "unrecoverable"
either, so apparently it is recoverable.

It more likely means that no recovery has been found. The fact that
none has been found doesn't mean that none exists, but it's enough to
say "virtually unrecoverable." Now all that's needed is for someone
to step forward and prove a recovery technique.

--
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Thomas Borchert writes:

In that context, if there's any litigation to fear, it's because of
slander.

Only if he said it out loud.

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Peter Dohm writes:

Well, gosh, golly, aren't you the dedicated (not) little investigator!

I'll leave that determination to the reader.

I don't like being wrong, and I've been given incorrect information
far too often in my life. I therefore press for supporting reasoning
and facts whenever anyone makes an isolated assertion about anything.
Trust no one.

There is little need for hard facts to circulate.

Perhaps. As I've said, the reality seems to be that these adjustments
generally aren't that important; one can fly safely with or without
them. That might also explain why so much mythology and urban legend
persist on these topics--since they are not safety-of-life issues, the
truth tends to remain buried among endless rumors.

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Kev writes:

Oh mx definitely can sound that way. But in this case, if anyone else
had said it, there'd be virtually zero argument. With little or no
information in the old POHs, and pilots using techniques ranging from
LOP to ROP, then his observation is right... it seems like you can use
almost any adjustment incantation and the engine doesn't blow up :-)

That's pretty much the logical conclusion.

If certain procedures were dangerous, they would rapidly be sifted out
by natural selection. Word would get around quickly, NTSB reports
would accumulate, and that procedure would rapidly be abandoned. The
fact that this is not happening in the domain under discussion very
strongly implies that just about any procedure is safe.

How many accidents have been caused by shock cooling? How many have
been caused by any particular LOP or ROP setting? How many have been
caused by small adjustments in props?

Heck, just look at how much discussion is generated here about the
"right way" to adjust the engine. Not to mention that students are
rarely taught much about leaning / EGT / etc, partly because it's hard
to find definitive information. (Even though it's not hard to find
articles on the topic.). In the end, that's why we usually rely on
word-of-mouth from other pilots of the same aircraft type.

And in the final analysis, it apparently doesn't make any difference,
so it gives pilots something to argue about forever.

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Thomas Borchert writes:

Regarding MP and RPM combination, there's a ton of information even in
the oldest POH.

Then why is there no consensus?

They have all been explained to him, in detail, with the factual
background and further reference. No voodoo about it.

No, all I've seen is argument and widely varying points of view.

Nobody really has the answers, although many would like to give the
impression that they do.

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Morgans wrote:

"Jim Logajan" wrote in message
.. .
Jose wrote:
Not according to the test pilots:

"Once in a spin the SR20 and SR22 are virtually impossible to recover,
according to the test pilots."

First I've heard of that. Where'd you find it?

A Google search indicates the quote came from this article:

http://philip.greenspun.com/flying/cirrus-sr20

Hardly seems definitive, to me. Company pilots, reciting the company
position.

As I read the article there's a phrase there that worries me.
About if the parachute is deployed in a spin 'the cords may not take
the strain of the high speed'
In a spin ???????????????????????

As I've said, the reality seems to be that these adjustments
generally aren't that important; one can fly safely with or without
them.

Did I just hear Mx say "one can fly safely..."?

Take a demo flight. Safely.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

As I've said, the reality seems to be that these adjustments
generally aren't that important; one can fly safely with or without
them.

Did I just hear Mx say "one can fly safely..."?

Take a demo flight. Safely.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

The really amazing part is that he openly admitted that he is trolling.

Peter