Larry Brons
Member
I need some info...I don't remember there being an RPM limit on the metal Sensenich prop for an O-320. I noticed in the prop logbook that came with it, a placard to place in view of the pilot, "2600 RPM Limitation". Huh?
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rpm limit on Sensenich prop for O-320?
- Thread starter Larry Brons
- Start date
Larry Brons
Member
How much of an issue is it to stay below the limit?
terrykohler
Well Known Member
I have the same combo on my 9A. You shouldn't be able to exceed the limit at WOT at cruise. Pay attention to RPM limit while descending.
Terry
Terry
Keeping below the 2600 rpm limit is not an issue on my plane. The prop pitch is selected so that it maxes out right about at the limit.
In normal flight it becomes something you are aware of, but not something that interferes with the flying. In normal cruise operations it is a non-factor. It becomes 2nd nature that when the nose goes down the throttle backs off a little.
It can become an issue in some situations, such as where you want to quickly descend while increasing or maintaining speed (such as when joining up in formation). You can find yourself running out of RPM pretty quickly.
Similarly, the prop will overspeed if you put the nose down. As Sensenich says, if you perform aerobatics you will overspeed the prop. Of course, with this airplane you'd probably overspeed the engine anyway even without the placard.
I read once that the harmonic problem is at or around 2700 RPM, therefore the limit is set at 2600 to provide a buffer. (Now, when someone on the internet says "I read once" you can flip a coin as to whether it's true or not. Since this is a pretty critical issue you will want to check with the factory yourself.)
Since the engine redlines at 2700 and it's a fixed pitch, I believe this means that static RPM is also decreased. In other words it seems intuitive to me that a prop that gives you diminished horsepower at the top end also gives it to you at all the speed ranges below it. I am no expert in props, but the static RPM of 2150 seems pretty low to me.
For my type of flying, which is cross country cruising, I find it to be an excellent propeller.
John Allen
RV-6A
In normal flight it becomes something you are aware of, but not something that interferes with the flying. In normal cruise operations it is a non-factor. It becomes 2nd nature that when the nose goes down the throttle backs off a little.
It can become an issue in some situations, such as where you want to quickly descend while increasing or maintaining speed (such as when joining up in formation). You can find yourself running out of RPM pretty quickly.
Similarly, the prop will overspeed if you put the nose down. As Sensenich says, if you perform aerobatics you will overspeed the prop. Of course, with this airplane you'd probably overspeed the engine anyway even without the placard.
I read once that the harmonic problem is at or around 2700 RPM, therefore the limit is set at 2600 to provide a buffer. (Now, when someone on the internet says "I read once" you can flip a coin as to whether it's true or not. Since this is a pretty critical issue you will want to check with the factory yourself.)
Since the engine redlines at 2700 and it's a fixed pitch, I believe this means that static RPM is also decreased. In other words it seems intuitive to me that a prop that gives you diminished horsepower at the top end also gives it to you at all the speed ranges below it. I am no expert in props, but the static RPM of 2150 seems pretty low to me.
For my type of flying, which is cross country cruising, I find it to be an excellent propeller.
John Allen
RV-6A
Larry Brons
Member
Thanks for all of your input. I'm confident it will perform fine.
I have the same limit on my RV-7 with the H2AD engine it has not been a problem even with a low take off rpm about 2150 it still takes off great even with full load untill now
I flew the plane for about 100 hours before paint and when i painted it (tail art section Plane crazy) i installed a sam james plenum yes i had to do alot of work to make it fit the H2AD motor but now at cruise i'm at 2650 and more with any pitch down i have to throttl back and watch carefully the RPM's
I would like to change my prop the only one taht comes to mind and is affordable is the catto but with many emails to him with no replys i dont know what to do
again the limits only became a concern once i reduced some drag
ken flying in maine
I flew the plane for about 100 hours before paint and when i painted it (tail art section Plane crazy) i installed a sam james plenum yes i had to do alot of work to make it fit the H2AD motor but now at cruise i'm at 2650 and more with any pitch down i have to throttl back and watch carefully the RPM's
I would like to change my prop the only one taht comes to mind and is affordable is the catto but with many emails to him with no replys i dont know what to do
again the limits only became a concern once i reduced some drag
ken flying in maine
vlittle
Well Known Member
az_gila said:Actually, it's 157 HP at 2600 rpm per the Lycoming O-320 Operator's Manual... (98.1%)
gil in Tucson ... who likes real numbers...
Actually, Lycoming has different numbers for different O-320 models. The -B amd -D series show about 159.5 HP at 2600 RPM, sea level power. I think Superior's data is similar.
Lycoming's D2J model shows 155 HP at 2600 RPM.
Finally, the reality of the typical RV installation, is that you'll a bit of MAP boost due to ram air affects on the intake. My calibration data shows that this gives about 3-4 HP.
Bottom line? You may actually be seeing more than rated HP.
az_gila
Well Known Member
Versions - curves?
OK Vern.... now I'm confused....
My O-320 Lycoming Operators Manual has two applicable figures for 160 HP versions.
Both are titled Sea Level Power....
Fig 3-5 "Sea Level Power Curve - O-320-B and -D series"
and
Fig 3-14 "Sea Level Power - O-320-D1D"
The first one is t 157 HP I quoted, the second one shows about 155 HP @ 2600 rpm, and is a version with a horizontal HA-6 carb.
The pages have a revision date of Jan, 1977.
Am I looking at the curves wrong? are these the correct curves? or do I have old data?
The two curves quoted above have 160 HP at 2700 rpm as a marked point (makes sense... ...)
gil in Tucson - more inconsistent Lycoming data?
vlittle said:
OK Vern.... now I'm confused....
My O-320 Lycoming Operators Manual has two applicable figures for 160 HP versions.
Both are titled Sea Level Power....
Fig 3-5 "Sea Level Power Curve - O-320-B and -D series"
and
Fig 3-14 "Sea Level Power - O-320-D1D"
The first one is t 157 HP I quoted, the second one shows about 155 HP @ 2600 rpm, and is a version with a horizontal HA-6 carb.
The pages have a revision date of Jan, 1977.
Am I looking at the curves wrong? are these the correct curves? or do I have old data?
The two curves quoted above have 160 HP at 2700 rpm as a marked point (makes sense...
...)gil in Tucson - more inconsistent Lycoming data?
Sam Buchanan
been here awhile
The only source of a valid answer to your question is Sensenich. This is a far too critical issue to trust your life to internet fodder.
you got that right internet "experts" are to be avoided. The forces on propellers are absolutely incredible.
YEP, I believe it was Abraham Lincoln who first said, "Never believe anything you read on the internet!"
Are you sure??? Were you there.....
No, but I read it o my computer!
