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  #1  
Old 07-10-2020, 03:14 PM
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N42AH N42AH is offline
 
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Default How To Prevent Flutter And Other Aeroelastic Modes

Ran across this article in Aviation Week. May require free registration/subscription to see. Very interesting on flutter.


https://aviationweek.com/business-av...oelastic-modes


Also here are two embedded videos from the article on flutter


Part 1 https://www.youtube.com/watch?v=rb3JHY_-ia4

Part 2 https://www.youtube.com/watch?v=jW8I2hX4GSs

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  #2  
Old 07-10-2020, 03:24 PM
PhatRV PhatRV is offline
 
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Interesting article and the Youtube links. There was a recent post about a F1 Rocket that lost most of the horizontal stabilizer but the pilot managed to land it safely. Scary stuff.
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  #3  
Old 07-10-2020, 05:34 PM
sailvi767 sailvi767 is offline
 
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The F1 Rocket that recently had the tail damage was above VNE however the failure appears to have been caused by a rapid G onset starting from a negative G value to above 8 G?s with a high onset rate. It does not appear to be flutter.
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  #4  
Old 07-10-2020, 06:14 PM
BillL BillL is offline
 
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I have had a prop/engine whirl mode with my 7, IO360 M1B engine w/Hartzell composite prop. The spinner moves 1/4" off center. It has occurred at low rpm after a gentle bounce on the runway. Has anyone else had this occur in an RV?
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  #5  
Old 07-10-2020, 09:28 PM
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skylor skylor is offline
 
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Default Gust Loading

Quote:
Originally Posted by sailvi767 View Post
The F1 Rocket that recently had the tail damage was above VNE however the failure appears to have been caused by a rapid G onset starting from a negative G value to above 8 G?s with a high onset rate. It does not appear to be flutter.
You probably shouldn?t rule out turbulence/gust loading as a contributor either....
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  #6  
Old 07-10-2020, 09:29 PM
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RV8JD RV8JD is offline
 
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Below is a link to a pitch I put together a few years ago. It describes different aeroelastic phenomena, including buffet, divergence, control reversal, control surface buzz, forced vibration, flutter, aeroservoelasticity; and discusses basic principles of flutter prevention.

"An Introduction to Airplane Flutter":
https://drive.google.com/file/d/18nb...ew?usp=sharing
Enjoy!
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Last edited by RV8JD : 07-10-2020 at 09:34 PM.
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  #7  
Old 07-10-2020, 11:09 PM
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Gash Gash is offline
 
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Nice briefing Carl! This thread should be a sticky just so guys can find that easier.
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  #8  
Old 07-11-2020, 04:35 AM
Northernliving Northernliving is offline
 
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Location: Boston, MA
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Quote:
Originally Posted by RV8JD View Post
Below is a link to a pitch I put together a few years ago. It describes different aeroelastic phenomena, including buffet, divergence, control reversal, control surface buzz, forced vibration, flutter, aeroservoelasticity; and discusses basic principles of flutter prevention.

"An Introduction to Airplane Flutter":
https://drive.google.com/file/d/18nb...ew?usp=sharing
Enjoy!
Excellent Carl. Thanks for creating and sharing.

Brian
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  #9  
Old 07-11-2020, 08:42 AM
Marc Bourget Marc Bourget is offline
 
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Location: Stockton, California
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Carl,

The presentation, IMHO, is beyond excellent.

I benefited from 15+ years of mentoring by John Thorp. After his passing I contacted Martin Holman (noted flutter expert) to reinforce John's position as various "modifications" were being explored by T-18 builders that my personal exposure led me to conclude they were not consistent with John's position.

The push-back to my request to "think it over" was interpreted by many as "You have to do it my way" - even if I specifically stated otherwise.

This presentation is the most "together" survey I've come across and I thank you for bringing together the concepts and teaching me what (except in limited circles) usually isn't taught!

Thanks again!
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  #10  
Old 07-11-2020, 07:07 PM
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Caveman Caveman is offline
 
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Location: Oklahoma
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Quote:
Originally Posted by BillL View Post
I have had a prop/engine whirl mode with my 7, IO360 M1B engine w/Hartzell composite prop. The spinner moves 1/4" off center. It has occurred at low rpm after a gentle bounce on the runway. Has anyone else had this occur in an RV?
That's very interesting, Bill. I have an RV7 with the aluminum 7497 blended airfoil Hartzell and have never noticed mine do that.
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