"Simple' math

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
I think the blades on my prop move six and one quarter feet forward over the ground in still air, each time they make a complete revolution, during cruise.
I set the rpm at 2400 and get on ave; 150kts. I don't think any other information is required.
So, each bang of a cylinder propels me about 2 feet. (io520)

Since you are wondering, I also figured the fuel:
If I run LOP I can get about 12gph in many cases. So I think it comes out to one-twentieth of an ml of 100LL for each of those three cylinders that propelled me that 6.25feet. Doesn't sound like much.
 
What you need, Dave, is more spare time.
 
Let'sgoflying! said:
I think the blades on my prop move six and one quarter feet forward over the ground in still air, each time they make a complete revolution, during cruise.
I set the rpm at 2400 and get on ave; 150kts. I don't think any other information is required.
So, each bang of a cylinder propels me about 2 feet. (io520)

Since you are wondering, I also figured the fuel:
If I run LOP I can get about 12gph in many cases. So I think it comes out to one-twentieth of an ml of 100LL for each of those three cylinders that propelled me that 6.25feet. Doesn't sound like much.
Click to expand...

Now, what is your exact fuel consumption, startup to shut down, from your hangar to the ramp at Kitty Hawk...to the nearest cylinder firing?
 
Unless you have a FP prop, you don't know what the pitch is at any given point. With a CS prop, you can get the same airspeed at different RPM's by varying MP (which indirectly drives pitch up and down). Also, the pitch on an FP prop is a nominal value measured at a particular station on the blade, and the pitch changes from hub to tip, so it's at best an approximation.
 
Interesting Dave.
Lets see, my fixed pitch gets me 2650 at 8000' and about 9.5 gph up there. Looks like I use 0.00191 fl oz per cylinder per revolution at 8000 and cruise while turning 5.2 feet per revolution.
 
Also, props flex under load, changing their effective pitch, FP or CS. Wood props particularly.

Ron Levy said:
Unless you have a FP prop, you don't know what the pitch is at any given point. With a CS prop, you can get the same airspeed at different RPM's by varying MP (which indirectly drives pitch up and down). Also, the pitch on an FP prop is a nominal value measured at a particular station on the blade, and the pitch changes from hub to tip, so it's at best an approximation.
Click to expand...
 
I think pitch is a way of measuring how far the prop would go through a solid substance, but in air there is some "slippage" (for lack of a better term.) So a prop pitched at six feet will travel less through air for one revolution.

Maybe I'm just misunderstanding this, and I'm a fool.
 
I misunderstood, I thought that you had used a basic pitch number for your prop assumption, I now realize that you derivied it from your speed.


150*1.15*5280/(60*2400)=6.325

(1.15 is to convert 150 KTS into MPH)

Cool post.
 
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