Kawa rough landing?

On Saturday, August 31, 2019 at 3:31:32 PM UTC-4, Jonathan St. Cloud wrote:
Not sure how accurate FB translate is, but it appear as if Mr. Kawa had some sort of incident with an electric motor not working and a rough uphill landing. Gas, electric or jet be careful guys!

Re prop drag;
At the end of towing in the Citabria, I would cut the engine and then stall
it to stop the wind-milling. This reduced the for a reasonable L/D.
However, a wind-milling prop running free probably has much less drag than
stationary prop.
Who will perform a test?

John F

john firth wrote on 9/23/2019 1:48 PM:
On Saturday, August 31, 2019 at 3:31:32 PM UTC-4, Jonathan St. Cloud wrote:
Not sure how accurate FB translate is, but it appear as if Mr. Kawa had some sort of incident with an electric motor not working and a rough uphill landing. Gas, electric or jet be careful guys!

Re prop drag;
At the end of towing in the Citabria, I would cut the engine and then stall
it to stop the wind-milling. This reduced the for a reasonable L/D.
However, a wind-milling prop running free probably has much less drag than
stationary prop.
Who will perform a test?

http://www.peter2000.co.uk/aviation/misc/prop.pdf

The article concludes "it depends"; briefly, high pitch - let it rotate, low
pitch, stop it. Other sources pointed out helicopters autorotate to slow their
descent with the engine disconnected, and clearly that's slower than stopping the
blades!

I'm guessing a 26E with a broken belt has more drag from the spinning prop than a
stopped prop, but do not plan any testing; however, I will be happy to do a
comparison glide with another 26E that has the belt removed. That could be done on
the ground, and then glider towed to height required for the test glide.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Interesting rotating verses stationary, I always was taught in power that a rotating prop was more drag than a stopped one as the rotating one acted more like a "disc" than just 2 blades stopped. But know real evidence of that.

CH

We should get an aero engineer to comment but in simple terms the AOA of the prop can become negative with a windmilling prop(depending on pitch design and rotational speed). If that happens you get negative thrust.

On Monday, September 23, 2019 at 5:24:13 PM UTC-7, wrote:
We should get an aero engineer to comment but in simple terms the AOA of the prop can become negative with a windmilling prop(depending on pitch design and rotational speed). If that happens you get negative thrust.

Here is a study of the subject:
http://www.peter2000.co.uk/aviation/misc/prop.pdf
Conclusion: it depends.

In this paper the same conclusion is reached (note the date):
http://naca.central.cranfield.ac.uk/...report-464.pdf

Tom