Why does airspeed change when I adjust the prop?

Peter Dohm writes:

Actually, I am impressed that MSFS simulates this part of an airplane's
opereation. I would have though that it was beyond the scope of typical
training useage in a PC based simulator. I have no idea how accurate it
might be, but I do give them credit for including it.

Note that I'm using an add-on aircraft (Dreamfleet's Baron 58
simulation), which is vastly more authentic than the default
simulation. I don't know how much of the engine behavior is simulated
by MSFS, and how much is simulated specifically by this add-on. The
latter is renowned for its meticulous dedication to accuracy, though.

--
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"Jose" wrote

Some limits and procedures are designed by lawyers. Consider the
Cirrus' spin recovery technique: pull the chute. I've never spun the
beast, but I bet it would recover conventionally if it didn't get too
far into the spin.

Not according to the test pilots:

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

So, us pilots are left to figure it out as best we can. Look at the
actual instruction booklet that came with the Piper J-3 cub, and see how
little it says.

You don't have to go back anywhere near that far - check out the POH for
something like a 1963 Mooney M20C.

BDS

Your actual airspeed drops from zero to zero!

On Jan 16, 3:14 am, Mxsmanic wrote:
When I change the prop setting on my (simulated) Baron 58, lowering
the prop RPM, my airspeed drops. I thought that for a given throttle
setting, the actual thrust produced by the powerplant was supposed to
remain the same for a wide range of prop settings, because of
automatic pitch changes made when I change the prop RPM. However,
that doesn't seem to be the case. A lowering of the prop RPM also
lowers airspeed, which implies a change in thrust. The fuel flow also
diminishes, which implies a change in power (?).

So, exactly what do I gain or lose by adjusting prop RPM when I'm
cruising along? Why would I want to change it? Some sources I've
read say that the prop makes less noise, which is surely true, but it
seems that I can't lower the RPM without losing airspeed (and thus I
must be losing power, right?).

--
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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?

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

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

Peter Dohm wrote:
As to the issue of Mxsmanic, I am amazed that the thread went as far as it
did before he saw most of the common proceedures as "voodoo or tea leaves."
Perhaps we all just provided sufficient dialog until all of the views were
known.

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.

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:

http://www.avweb.com/news/reviews/182558-1.html

Cheers, Kev

"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.

Kinda' like a "he said she said" type of deal.

I'm pretty sure I have read that some owners have successfully spun and
recovered it.
--
Jim in NC

Morgans writes:

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

Kinda' like a "he said she said" type of deal.

I'm pretty sure I have read that some owners have successfully spun and
recovered it.

Why don't you demonstrate, and then you can write an article about how
to do it?

--
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Mxsmanic,

But it doesn't go into much detail on the fine adjustments of
mixture, throttle, and prop, and their interactions.

Of course it does. Read it. There are several pages of tables detailing
the settings.

This would also explain why so many pilots can
depend on voodoo or tea leaves to determine how they make the
adjustments, and yet they never have any problems.

And you really wonder why people think you're a first-class asshole and
regret answering to your question EVERY TIME? It's because you are.

--
Thomas Borchert (EDDH)

Bds,

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


Just by putting it in quotation marks, you don't make it a quote (which
in itself is quoting someone else - really funny). So which test pilot
said this when to whom?

--
Thomas Borchert (EDDH)