What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

glidescope

HansLab

Well Known Member
Anyone tried engine-off thermaling yet with their 12?
Restarting by diving speed is one exercise I still have on my list, and I'm curious what the glide scope of this beauty is? Engine off, so little drag from the prop.
 
Are you talking about glideslope?
A glidescope is what we guys use to intubate a patient. :)
 
Anyone tried engine-off thermaling yet with their 12?
Restarting by diving speed is one exercise I still have on my list, and I'm curious what the glide scope of this beauty is? Engine off, so little drag from the prop.

I believe van's states 13 to 1
Alan
N603NH
 
Rotax

I don't think you will be able to restart the Rotax without using the starter. Not enough RPMs.
 
I doubt you can restart Rotax 912 by reverse-driving the prop in a dive. Engine has 2.41 gear reduction and high-compression. I wouldn't attempt it....
 
I doubt you can restart Rotax 912 by reverse-driving the prop in a dive. Engine has 2.41 gear reduction and high-compression. I wouldn't attempt it....

Not that it matters in this discussion but I am pretty sure all the 912ULS 100hp engines were 2.43:1.

This is a video of the Remos GX doing an air restart. They don't say but the 912ULS is the standard engine on that plane.
https://www.youtube.com/watch?v=VwPAiuu1dxw
 
Is there a slipper clutch? If so, is it designed for intentional, non-feathering propeller use?
Glide ratio is how far you can go, no wind.

Minimum sink speed best exploits weaker thermals/lift sources.

Airliners have decent glide ratios, but high L/D speeds, high min sink speeds, and high sink rates- so it would take decent mountain wave or one heck of a thermal source to climb.

I can always find just enough to make me work at being stable on short final/s;)

ETA- In the above Remos video the prop stopped at 65 knots at 11000+ feet MSL and restarted the engine with the key in both around 115 knots. No idea how the prop pitch and diameter compares to a RV-12.
 
Last edited:
Make sure you have a good story made up for the NTSB if there’s an issue!😝

If I'm not mistaken, in Hans's case that would instead be the RvTV. :rolleyes:

If it were in the US I'd be recommending doing this over some place like the Black Rock or Alvord desert. Actually pretty fun and good practice to do real prop-stopped dead stick landings. I can't speak to the whole Rotax restarting bit however.
 
Y'all were right: the Rotax did not start in dive. Tried it out today. Fairly good glide scope though, I feel confident when the thing stops. Hope I have the guts to slow down a bit to stop the prop (when heigh enough), for that makes a big difference.
 
The ENGINE AIR RESTART emergency procedure in the POH says the prop will not windmill below 80 KTS. It doesn’t say whether it would start to windmill again by going above 80 KTS if it stops.
 
11 : 1 compression ratio for the engine and the reduction gearbox is a lot of resistance to overcome to get the prop spinning again.

Maybe someone will try it this summer when the air density is low, and then again this winter on a cold day, when the air density is high.
 
What was the glide ratio?

Y'all were right: the Rotax did not start in dive. Tried it out today. Fairly good glide scope though, I feel confident when the thing stops. Hope I have the guts to slow down a bit to stop the prop (when heigh enough), for that makes a big difference.

So what glide ratio did you have (I'll assume you were at best glide speed) with the prop windmilling and engine shut down?
 
Best glide speed is 63 kts... well below 80kts to stop the prop from windmilling. It should be in your POH.


Y'all were right: the Rotax did not start in dive. Tried it out today. Fairly good glide scope though, I feel confident when the thing stops. Hope I have the guts to slow down a bit to stop the prop (when heigh enough), for that makes a big difference.

I read the OP's post to mean that he had not yet achieved prop stoppage, but he hoped to once he "had the guts". Maybe I just misinterpreted what he was trying to say, the post was a little confusing for me, might just be my mistake! I'm well aware of best glide speed and where to find it, but thanks anyway!

I've seen Larry's video on his dead stick demo in a -12 and he had to slow to 65 knots to stop the prop- there goes the 80 knot thing! I've heard of "someone" that had to get to about 58 knots to stop it:D
 
Last edited:
Seems a moot point wondering at what airspeed the prop stops. If your engine fails you should pitch for best glide and try a restart with the starter. If that doesn’t work you probably won’t get it restarted with airflow. I had an engine stop once due to a carburetor that wasn’t seated in the socket properly. Fortunately it restarted with the starter.
 
Back
Top