Not sure if this is the intent for the OP question, but one of the potential reasons it would be good to know is due to Foreflight's latest update that uses the glide ratio along with best glide speed to display the glide range in the form of a ring around your location on the moving map display for your airplane. It graphically displays the glide range at all times should the need arise. It is a nice new feature but it requires knowing those two performance components of your airplane in order to configure it.No sure it matter that much which RV.......
but I use 1 mile per 1000 foot AGL.
Just a rule of thumb.
FYI...if you are trying to squeak out every last foot, you might consider looking into a AOA.
Does anyone have a good engine out glide ratio for a RV8?
The GRT EFIS units look at your real, current rate of descent and your actual ground speed (so wind is taken care of) and show how far you can go in your current direction. Tells you right away if you can make an airport or other landing site, or not.
. . . Also try to get your numbers with the aircraft as close to gross as you can. This will give you a little extra bonus distance if you have to glide at a lower weight. . . . Yours, R.E.A. III 80888
When sailplanes race, they often carry water so that they go down their glide slope faster. They can jettison the water if the lift gets weak or cool off the crowd at the finish line.
If you calculate your glide speed with the engine running, even at idle, you will get a false glide ratio and sink rate. A windmilling prop causes significant drag that a prop at idle power will not simulate. So if you get 11:1 glide ratio at idle, you are likely to get no better than 8 or 9:1 in a true engine out windmilling situation.
The GRT EFIS units look at your real, current rate of descent and your actual ground speed (so wind is taken care of) and show how far you can go in your current direction. Tells you right away if you can make an airport or other landing site, or not.
What function is that? Where do you turn it on and off?
Hi Bob, I was curious about this a found this:
"Variations in aircraft weight do not affect the glide angle provided that the correct airspeed is flown. Since it is the lift over drag (L/D) ratio that determines the gliding range, weight will not affect it. The glide ratio is based only on the relationship of the aerodynamic forces acting on the aircraft. The only effect weight has is to vary the time the aircraft will glide for. The heavier the aircraft is, the higher the airspeed must be to obtain the same glide ratio. If two aircraft have the same L/D ratio but different weights and start a glide from the same altitude, the heavier aircraft gliding at a higher airspeed will arrive at the same touchdown point in a shorter time. Both aircraft will cover the same distance but the lighter one will take a longer time to do so."
Reference: http://www.skybrary.aero/index.php/Glide_Performance
As a practical matter, it would appear either AoA or known glide speeds vs weight should be documented for ones serial number - right?
Yes. Pick a calm morning day and a remote area away from mountains so you won't have updrafts and downdrafts. What I did was begin my descents at 5,500', stabilize at the test airspeed, and start the timer when passing 5,000'. You can double up and determine your best rate of climb speed on the way back up.Does that sound like a solid plan?
IIRC it is just there - I don't think you can turn it off. Put your plane into a descent and look at the Hx's map page. Out in front of you you should see a green arc. That's where you'll hit the ground, if you continue at the same horizontal and vertical speed.
In most EFIS systems, this arc shows when you will intercept the altitude bug, not hit the ground.
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The only way to know what your glide ratio really is, is to turn off the fan. In a real engine out situation the prop will probably continue to turn unless the engine seizes up or you slow enough to stop the prop. Your glide ratio will be less with it turning and higher glide ratio with it stopped. So you really need two glide ratios. And don't forget the effects of wind.
Alternatively, choose a lower than real number for planning purposes. Remember that unless you are as cool as John Glenn, you really won't have a lot of time to be calculating whether you can make it to that airport at 10 to 1 from your present altitude.