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-   -   Glide Ratio? (http://www.vansairforce.com/community/showthread.php?t=150712)

BruceP 06-22-2017 11:09 PM

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.

alpinelakespilot2000 06-22-2017 11:15 PM

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.

Zuldarin 06-23-2017 07:22 AM

I use 12:1 in foreflight and it seems to be pretty accurate.

ssturges 06-23-2017 08:21 AM

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.

Bevan 06-23-2017 12:33 PM

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

BruceP 06-23-2017 06:57 PM

Quote:

Originally Posted by alpinelakespilot2000 (Post 1182438)
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.

BruceP 06-23-2017 06:58 PM

Quote:

Originally Posted by Bevan (Post 1182575)
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.

mikehoover 06-23-2017 07:35 PM

Quote:

Originally Posted by BruceP (Post 1182657)
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.

BruceP 06-23-2017 08:15 PM

Quote:

Originally Posted by mikehoover (Post 1182670)
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.

Steve Melton 06-23-2017 09:28 PM

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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