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RV9 best glide and ratio

ALagonia

Well Known Member
I?m using 90 mph for Vg, best glide speed and 12:1 for glide ratio in setting up the function on ForeFlight. I have an O-360 with three blade Catto prop on my 9. Does this sound right?
 
What does your POH say? Don?t have one? Go test. These are not ?type? certified airplanes.

Bevan
 
What does your POH say? Don?t have one? Go test. These are not ?type? certified airplanes.

Bevan

I would not have expected much difference in RV-9 airframes. Maybe indicated airspeed errors between airframes?

For my 9A I settled on 80kts. I am interested in what others have determined.
 
80 knots, at a less than ground acceptable idle.

I set my engine for a lower than stable ground running idle, like maybe a really rough 450rpm, and during those tests it stayed above 600rpm per my notes. 80 knots indicated was my number once the data was crunched, but the bucket was pretty flat with not much difference 75-82 knots indicated. At 85kt it starts to brick. At 10 deg of flaps 75kt is my number. I use 10-1 as my number for glide ratio, it makes the math easier once the fan is distributing.

The data was taken between 1470 lbs and 1540 lbs, me, a little baggage and mostly full fuel.
 
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Test it for your POH. My 9 had a Hartzelle constant speed and with power pulled off it went flat creating a lot of drag. Best speed was 80 mph at about 9:1. With an earlier over pitched cruise fixed pitch prop it was closer to 13:1.
 
I did some decent experimenting a few weekends ago with my 9a during my flight review with a local 7a driver. I have a 150hp IO-320-E1A and a 3 blade Catto. We ended up agreeing on 70-75kts at just shy of 800fpm loss. Way better than his 7a brick. ;)
 
Why are you using mph instead of knots?

Because my airplane came with a back up ASI in mph. It?s taking me some time to get used to mph, I?ve used knots for so many years. But I?m cheap and don?t want to spend the money or the time to change out my AS? to knots.
 
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