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  #1  
Old 07-31-2018, 05:28 PM
AeroDog AeroDog is offline
 
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Default Vy versus best glide speed

Looking at the latest POH, Vy is given as 75 kts and speed for best glide distance is given as 63 kts. I've never seen a spread this large between the two speeds in other aircraft I've flown. Does this square with what people with flying airplanes are seeing?

Jerre
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  #2  
Old 08-06-2018, 12:51 PM
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flytoboat flytoboat is offline
 
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I have read that best glide speed is typically about half way between Vx and Vy.
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  #3  
Old 08-06-2018, 02:29 PM
Scott Hersha Scott Hersha is offline
 
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On my RVís, Vy and best glide was very nearly the same: 80-85 KIAS, depending on GW & air density. This should be approximately your best lift/drag speed which of course varies with density altitude. If you have an AOA, you can program this, but a target indicated airspeed is usually close enough.
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  #4  
Old 08-06-2018, 04:05 PM
BobTurner BobTurner is online now
 
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In an ideal case they should be the same. Real world, most of the difference comes from prop efficiency - typically prop efficiency is a strongly increasing function of airspeed, in this speed range. Especially for fixed pitched props.
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  #5  
Old 08-06-2018, 07:35 PM
49clipper 49clipper is offline
 
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Default 49clipper

In my flight testing of my RV-6, Vy came out about 95mph. Best glide was sort of hard to nail down, but I use Vy that also. Seems to work out well.
Jim
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  #6  
Old 08-07-2018, 09:36 PM
Marc Bourget Marc Bourget is offline
 
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Those speeds are also dependent on weight. It might be worthwhile to investigate the effect weight makes in your initial test period(s)
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  #7  
Old 08-08-2018, 08:46 AM
49clipper 49clipper is offline
 
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Default 49clipper

Quote:
Originally Posted by Marc Bourget View Post
Those speeds are also dependent on weight. It might be worthwhile to investigate the effect weight makes in your initial test period(s)
I did test at the weight that I fly at 90% of the time. If at gross, I will add a knot or two.
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