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#31
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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
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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
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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
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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
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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
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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
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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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