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  #1  
Old 06-22-2017, 11:09 PM
BruceP BruceP is offline
 
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Default Glide Ratio?

What is everyone using as a glide ratio for their 9A's? Searching the threads I've sort of landed on 8:1 for the time being. I'm using the new Foreflight glide feature which is really great but I want to make sure I'm using the right number.
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  #2  
Old 06-22-2017, 11:15 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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8:1 sounds very low for the -9. That's closer to what the short-wing RV's get.

The Cafe Foundation report is probably the best place to start...

http://cafe.foundation/v2/pdf_cafe_apr/rv-9a.pdf

They measure it at about 12:1.
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  #3  
Old 06-23-2017, 07:22 AM
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Zuldarin Zuldarin is offline
 
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I use 12:1 in foreflight and it seems to be pretty accurate.
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  #4  
Old 06-23-2017, 08:21 AM
ssturges ssturges is offline
 
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The number I want to know is what is it going to be with a CS prop on an engine out? I don't want to every find that out the hard way.
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  #5  
Old 06-23-2017, 12:33 PM
Bevan Bevan is offline
 
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There are so many airframe/engine/prop combinations. Further, in amateur built, no two are the same as in type-certificated aircraft. Therefore, the only way to know for sure for YOUR airplane is to go and test it. Then enter the data into your POH.

Bevan
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  #6  
Old 06-23-2017, 06:57 PM
BruceP BruceP is offline
 
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Quote:
Originally Posted by alpinelakespilot2000 View Post
8:1 sounds very low for the -9. That's closer to what the short-wing RV's get.

The Cafe Foundation report is probably the best place to start...

http://cafe.foundation/v2/pdf_cafe_apr/rv-9a.pdf

They measure it at about 12:1.
Thank you. The link would not work, said I didn't have permission.
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  #7  
Old 06-23-2017, 06:58 PM
BruceP BruceP is offline
 
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Quote:
Originally Posted by Bevan View Post
There are so many airframe/engine/prop combinations. Further, in amateur built, no two are the same as in type-certificated aircraft. Therefore, the only way to know for sure for YOUR airplane is to go and test it. Then enter the data into your POH.

Bevan
Everything about my 9A is nominally built to the plans. The only deviation is I have a Catto 3-blade fixed pitch prop.
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  #8  
Old 06-23-2017, 07:35 PM
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mikehoover mikehoover is offline
 
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Quote:
Originally Posted by BruceP View Post
Thank you. The link would not work, said I didn't have permission.
Go to http://cafe.foundation/v2/main_home.php then click the "RESEARCH" tab, then on the right side menu click "CAFE APRs" and choose an aircraft.
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  #9  
Old 06-23-2017, 08:15 PM
BruceP BruceP is offline
 
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Quote:
Originally Posted by mikehoover View Post
Go to http://cafe.foundation/v2/main_home.php then click the "RESEARCH" tab, then on the right side menu click "CAFE APRs" and choose an aircraft.
Great article with lots of good information. I did note that there was a range of glide ratios depending on airspeed from 9.5 to 12, and was 11 around the glide speed I have been using in my POH based on my own tests. I guess I should go out and repeat some of my testing to see if the results are similar. Anyway, thanks for the link.
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  #10  
Old 06-23-2017, 09:28 PM
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Steve Melton Steve Melton is offline
 
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I use 10:1. Makes the calculation easy and gives a little margin.

1000 ft above x 10 = 10,000 ft or roughly 2 miles glide

2000 ft above x 10 = 20,000 ft or roughly 4 miles glide

or simply use the the number of thousand feet AGL x 2 = miles glide (does not consider wind, wind will affect the number)

any RV9 will be able to make this glide range
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Last edited by Steve Melton : 06-24-2017 at 08:58 AM.
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