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Constant speed prop question



 
 
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  #31  
Old July 22nd 08, 01:18 AM posted to rec.aviation.piloting
Mortimer Schnerd, RN[_2_]
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Posts: 597
Default Constant speed prop question

Morgans wrote:
"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote

Now you have nice new buildings, with the compliments of the Eighth Air
Force. Quit yer bitching.


Actually, for once (this time) I didn't take Thomas's remarks it as
bitching.

He was observing that the Eighth Air Force did indeed have a good grip on
running over square.

Read it again, and agree, or not.




I was just having some fun with him. I don't disagree at all.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com


  #32  
Old July 22nd 08, 05:00 AM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
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Posts: 2,969
Default Constant speed prop question

"Morgans" wrote in
:


"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote

Now you have nice new buildings, with the compliments of the Eighth
Air Force. Quit yer bitching.


Actually, for once (this time) I didn't take Thomas's remarks it as
bitching.

He was observing that the Eighth Air Force did indeed have a good grip
on running over square.

Read it again, and agree, or not.



They didn't run "oversquare"


Bertie

  #33  
Old July 22nd 08, 05:17 AM posted to rec.aviation.piloting
Morgans[_2_]
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Posts: 3,924
Default Constant speed prop question


"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote

I was just having some fun with him. I don't disagree at all.


Okey - doekey.

I missed it. My sarcasm detector is in the shop, being fixed, at the
moment. g
--
Jim in NC


  #34  
Old July 23rd 08, 06:08 AM posted to rec.aviation.piloting
Frank Olson
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Posts: 90
Default Constant speed prop question

Bertie the Bunyip wrote:
Terence Wilson wrote in
:

In the course of trying to understand how a constant speed prop works
I came across the following passage in one of the Jeppesen books:

"If the throttle is advanced without decreasing the pitch of the prop
blades to increase ___ rpm, the manifold pressure increases as the
prop mechanism attempts to keep ___ rpm constant by increasing the
blade angle. The combination of high manifold pressure and low ___ rpm
can cause damage due to high internal manifold pressures."

I found this paragraph to be confusing


I'm not surprised. It's a **** poor explanation and actually misleading,
not to say wildly inaccurate in some places. "High internal manifold
pressures" WTF is that? The author has no understanding whatsoever ofwhat
he's talking about.


Bertie



I've yet to see a normally aspirated horizontally opposed engine "blow
up" due to "high manifold pressure". I've seen governors fail (which
caused an engine overspeed), but all things being "normal", there is no
way you're going to damage your engine running with the throttle wide
open and your prop on "fine"... One of my engine checks (pre-flight) is
to cycle the prop. Is the idiot that wrote this article saying that I'm
damaging the engine when I do that???
  #35  
Old July 23rd 08, 01:42 PM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
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Posts: 2,969
Default Constant speed prop question

Frank Olson wrote in
news:F1zhk.23979$nD.19490@pd7urf1no:

Bertie the Bunyip wrote:
Terence Wilson wrote in
:

In the course of trying to understand how a constant speed prop
works I came across the following passage in one of the Jeppesen
books:

"If the throttle is advanced without decreasing the pitch of the
prop blades to increase ___ rpm, the manifold pressure increases as
the prop mechanism attempts to keep ___ rpm constant by increasing
the blade angle. The combination of high manifold pressure and low
___ rpm can cause damage due to high internal manifold pressures."

I found this paragraph to be confusing


I'm not surprised. It's a **** poor explanation and actually
misleading, not to say wildly inaccurate in some places. "High
internal manifold pressures" WTF is that? The author has no
understanding whatsoever ofwhat he's talking about.


Bertie



I've yet to see a normally aspirated horizontally opposed engine "blow
up" due to "high manifold pressure". I've seen governors fail (which
caused an engine overspeed), but all things being "normal", there is
no way you're going to damage your engine running with the throttle
wide open and your prop on "fine"... One of my engine checks
(pre-flight) is to cycle the prop. Is the idiot that wrote this
article saying that I'm damaging the engine when I do that???



Well, you will do damage with a low rpm and high enough MP to raise the
BMEP to the point where knocking occurs. Knocking will apply loads that
will exceed the ability of the oil to keep the metal parts seperated and
wear the engine or even overstress parts to the point of breaking.
Observing manufacturer's limitations should ensure that knocking doesn't
occur and while there is obviously a margin included in those to account
for conditions instrument error and so forth, I know i would take care
if it were my engine!

Bertie

  #36  
Old July 23rd 08, 02:23 PM posted to rec.aviation.piloting
[email protected]
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Posts: 181
Default Constant speed prop question

On Jul 23, 1:08*am, Frank Olson
wrote:
Bertie the Bunyip wrote:
Terence Wilson wrote in
:


In the course of trying to understand how a constant speed prop works
I came across the following passage in one of the Jeppesen books:


"If the throttle is advanced without decreasing the pitch of the prop
blades to increase ___ rpm, the manifold pressure increases as the
prop mechanism attempts to keep ___ rpm constant by increasing the
blade angle. The combination of high manifold pressure and low ___ rpm
can cause damage due to high internal manifold pressures."


I found this paragraph to be confusing


I'm not surprised. It's a **** poor explanation and actually misleading,
not to say wildly inaccurate in some places. "High internal manifold
pressures" WTF is that? The author has no understanding whatsoever ofwhat
he's talking about.


Bertie


I've yet to see a normally aspirated horizontally opposed engine "blow
up" due to "high manifold pressure". *I've seen governors fail (which
caused an engine overspeed), but all things being "normal", there is no
way you're going to damage your engine running with the throttle wide
open and your prop on "fine"... *One of my engine checks (pre-flight) is
to cycle the prop. *Is the idiot that wrote this article saying that I'm
damaging the engine when I do that???


Unless there's a good reason to do otherwise, it would be good
practice to stay within the limits of the POH. Ours lists many
manifold pressures, (measured in inches of Hg) greater than RPM. Most
times in cruise at 5000 to 12000 feet we have rpms cranked pretty far
down with the throttle at max. 1950 rpm with our IO 360 is pretty
common.
  #37  
Old July 23rd 08, 09:01 PM posted to rec.aviation.piloting
Robert M. Gary
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Posts: 2,767
Default Constant speed prop question

On Jul 20, 6:24*am, Terence Wilson wrote:
In the course of trying to understand how a constant speed prop works
I came across the following passage in one of the Jeppesen books:

"If the throttle is advanced without decreasing the pitch of the prop
blades to increase ___ rpm, the manifold pressure increases as the
prop mechanism attempts to keep ___ rpm constant by increasing the
blade angle. The combination of high manifold pressure and low ___ rpm
can cause damage due to high internal manifold pressures."


Go to you tube. There are a couple of videos out there taken from "How
its made" that shows a prop being made. They don't show the gov but
they do a great job of showing you the inside of the hub.

-Robert

 




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