RV-7 "Best Glide" numbers

I just installed software 9.0 in my G3X screens. My bird is a rather low drag unit, with Hartzell Trailblazer CS prop, winglets, butt rib fillets, and fairings over anything that sticks down. (Airspeed is in MPH to appease my car driver pilot friends)
The other day I tested glide rates at 1800# gross weight and between 7500' to 3500' and determined the following: (slight wind, flying 90 degrees to a 3 mph wind)
Minimum sink airspeed: 86 mph (feet per minute) ((Prop selected coarse pitch))
Maximum glide airspeed: 111 mph (Feet per mile)
This is almost exactly as previous aircraft research data shows, that in a no wind condition, the aircraft will cover the most distance at 1.3 x minimum sink airspeed. (Wind will effect the distance greatly).
Sooooo, what do we enter into the G3X "smart glide" window? I'm going for distance, so I enter the 111 mph airspeed, which is slightly higher sink rate (710 fpm) than minimum sink, but it gets me more range. If I really need more time, I can always select 640 on the vertical speed and have a bit more time to sort out the problem. These speeds will be different than the published or flight tested VX and VY, as there is no propeller thrust vector to enter into the equation.

DAR Gary

I suggest that you look up Jack Norris's experiments with zero drag in a C-150 that had no prop and his Luscombe on which he rigged a zero thrust indicator. If the prop is stopped you have negative thrust (drag) If the prop is turning you may have zero thrust at very low RPM or you may have positive thrust.

Those articles should be in the EAA archives. Let me know if you want them and cannot find them.

However, when the fan stops turning all you really want to know is your correct speeds in that condition.

As for airspeed, it's OK in a pinch but AOA is better. With the prop stopped only one AOA will be best sink or best glide but airspeeds can vary with load and density altitude.

On my website is a spreadsheet that integrates a lot of the variables for the zero thrust condition and I have numbers for my 7A if you are interested.

Yes I am familiar. Most engine failures are not mechanical, most fuel related, and the majority still have oil pressure to the propeller at failure.
I teach single and multi engine 135 pilots for aerial wildfire work, and the single engine guys are over nasty terrain most of the day. P
We demonstrate pulling the prop, will reduce most Cessna 182 and 206 sink rate at best glide by almost 200 ft/min. Cessna publishes minimum sink airspeeds in their old pilot handbooks, and got wise and now publishes maximum glide airspeeds in the POH. Of course, that is density altitude dependent, but just being close is a lot better than way off target. The performance of the Aero Commander Shrikes we fly demonstrated at windmilling vs feather will usually impress on the pilots the necessity to "Identify, Fix or Feather" to have any performance when heavily loaded.
Thanks for the input!
Gary

hevansrv7a said:

I suggest that you look up Jack Norris's experiments with zero drag in a C-150 that had no prop and his Luscombe on which he rigged a zero thrust indicator. If the prop is stopped you have negative thrust (drag) If the prop is turning you may have zero thrust at very low RPM or you may have positive thrust.

Those articles should be in the EAA archives. Let me know if you want them and cannot find them.

However, when the fan stops turning all you really want to know is your correct speeds in that condition.

As for airspeed, it's OK in a pinch but AOA is better. With the prop stopped only one AOA will be best sink or best glide but airspeeds can vary with load and density altitude.

On my website is a spreadsheet that integrates a lot of the variables for the zero thrust condition and I have numbers for my 7A if you are interested.

Click to expand...

Evan, I went over to your website, following the link in your footer, and arriving there, it seemed like the link to the spreadsheet on drag would not load. Any tips? Thanks in advance,

Ed