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  #1  
Old 12-30-2018, 06:20 PM
BillSchlatterer BillSchlatterer is offline
 
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Location: Arkansas
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Default Best Glide Vs Best Sink... RV7 numbers ?

Just curious what folks are using for Best Glide and Best Sink rates in the RV7A with 360/CS or similar 7 or 8? What are you putting in your POH if you have one?

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??


Thanks Bill S
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  #2  
Old 12-30-2018, 07:22 PM
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mgomez mgomez is offline
 
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Default From Roberta Hegy’s POH

...see the glide chart.

http://www.vansairforce.net/POH/n2447Apoh.doc
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  #3  
Old 12-30-2018, 07:23 PM
BillL BillL is offline
 
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Quote:
Originally Posted by BillSchlatterer View Post
Just curious what folks are using for Best Glide and Best Sink rates in the RV7A with 360/CS or similar 7 or 8? What are you putting in your POH if you have one?

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??


Thanks Bill S
Bill, not sure about best sink, but the best glide (tangent to curve) with my RV7, engine at idle (4 test points) was 103KTAS (87KIAS) for my plane at about -940 FPM. With the engine windmilling (mix pulled) I only got two points the one closest was 105 KTAS , -1000FPM as measured resulting in a 9.7 glide ratio. Tanks were near full, 160lb in cabin, empty GW is 1140lb. The test was between 9-8000 ft. While speed (103KTAS) and descent rate (-940) are taken from the graph/data points, the other info is from memory. If it is important, it can be verified. Prop pulled out fully. I have the Hartzell composite and at fine pitch, glide is much different (8% less).

Important note: This if for reference and will not likely represent any other aircraft model or serial number.
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Last edited by BillL : 01-01-2019 at 09:05 PM. Reason: Added information for clarity.
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  #4  
Old 12-30-2018, 10:37 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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Quote:
Originally Posted by BillSchlatterer View Post
I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??
Anyone who has built their plane should have real measurements derived from phase 1 testing, and every plane will be a bit different due to static/pitot/asi instrument/weight particulars. Bottom line, you really need to do this testing for your plane and, in any case, is probably beneficial anyway for a non-builder to help them get to know their plane better. It’s easy to do and good for polishing piloting skills as well.

Have fun.
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  #5  
Old 12-31-2018, 08:07 AM
SuperCubDriver SuperCubDriver is offline
 
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I did some testing with my RV-7 and came up with a best glide speed of 80 KIAS, 1,6 NM still air distance per 1000ft, gliding range almost 1:10. Most testing was done with close to max weight and between 5000 and 10000 ft with power at idle (windmilling) and prop at low pitch. Numbers are rounded as they are dependent on weight and so a little variable.
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  #6  
Old 01-01-2019, 06:31 AM
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uk_figs uk_figs is offline
 
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Default Interesting discussion

In my case (RV-7) best glide is around 110 mph, fixed pitch Catto 3 blade with heavy sabre spacer and landoll ring approximating a CS weight up front. Rate of descent around 500 ft per min (approximated prop windmilling at idle rpm).

I actually built a glide range chart (no wind) with altitude and terrain height as one of my check lists to quickly see if I could make a runway when punching "nearest" on the 796 in case of an engine failure, now superseded by the glide range ring in Foreflight.
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  #7  
Old 01-01-2019, 07:39 AM
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RV7A Flyer RV7A Flyer is offline
 
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Some recent retesting to more accurately find Vbg found ~95 KIAS, pilot + passenger, no baggage, about 3/4 tanks.

Seems in line with most others, but then I see some that are WAAAY lower, like 75 or 80 KIAS.

How can there be such wide variation in the same airframe? They're all RV7s, probably about the same weight give or take a little...75 knots all the way up to 103 knots? That's nearly 40% increase from 75 to 103...doesn't make sense to me.
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Old 01-01-2019, 08:54 AM
BillL BillL is offline
 
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Quote:
Originally Posted by RV7A Flyer View Post
Some recent retesting to more accurately find Vbg found ~95 KIAS, pilot + passenger, no baggage, about 3/4 tanks.

Seems in line with most others, but then I see some that are WAAAY lower, like 75 or 80 KIAS.

How can there be such wide variation in the same airframe? They're all RV7s, probably about the same weight give or take a little...75 knots all the way up to 103 knots? That's nearly 40% increase from 75 to 103...doesn't make sense to me.
I think we are all reporting in different conditions, altitude, temperatures, props, and weight. I reported 103 KTAS, at 9000 ft. Precisely, that is 87 KIAS for barometer and temp of that day. I am not a test pilot so did not know how to report in "standard" conditions. A recent Kitplanes article by Nigel, recommended testing a several altitudes. I only tested in one region. If you have a recommendation of a correction procedure for this testing, and a standard condition, please post, I'll do the calculations and report accordingly.
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  #9  
Old 01-01-2019, 11:32 AM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by BillL View Post
I think we are all reporting in different conditions, altitude, temperatures, props, and weight. I reported 103 KTAS, at 9000 ft. Precisely, that is 87 KIAS for barometer and temp of that day. I am not a test pilot so did not know how to report in "standard" conditions. A recent Kitplanes article by Nigel, recommended testing a several altitudes. I only tested in one region. If you have a recommendation of a correction procedure for this testing, and a standard condition, please post, I'll do the calculations and report accordingly.
Good point about the different atmospheric conditions/altitude. I don't have a procedure or analysis for computing Vbg at a specific altitude/density altitude, but someone might (given, say Vbg at another specific point). I did miss that you were reporting TAS, whereas I think most people understand all V-speeds other than Vne to be in IAS.

Still...quite a range of values for similar aircraft.
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  #10  
Old 01-03-2019, 04:39 AM
Capt Capt is offline
 
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Quote:
Originally Posted by RV7A Flyer View Post
Good point about the different atmospheric conditions/altitude. I don't have a procedure or analysis for computing Vbg at a specific altitude/density altitude, but someone might (given, say Vbg at another specific point). I did miss that you were reporting TAS, whereas I think most people understand all V-speeds other than Vne to be in IAS.

Still...quite a range of values for similar aircraft.
It's always interesting to read what pilots get out of their machines, much can be learnt from these pages I Like the last bit, VNE to be in IAS, I still hear pilots say VNE is what's on the dial at high Altitudes, now that's a worry!
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