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-   -   How To Prevent Flutter And Other Aeroelastic Modes (https://vansairforce.net/community/showthread.php?t=184513)

N42AH 07-10-2020 03:14 PM

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


PhatRV 07-10-2020 03:24 PM

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.

sailvi767 07-10-2020 05:34 PM

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.

BillL 07-10-2020 06:14 PM

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?

skylor 07-10-2020 09:28 PM

Gust Loading
 
Quote:

Originally Posted by sailvi767 (Post 1445346)
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....

RV8JD 07-10-2020 09:29 PM

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!

Gash 07-10-2020 11:09 PM

Nice briefing Carl! This thread should be a sticky just so guys can find that easier.

Northernliving 07-11-2020 04:35 AM

Quote:

Originally Posted by RV8JD (Post 1445379)
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

Marc Bourget 07-11-2020 08:42 AM

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!

Caveman 07-11-2020 07:07 PM

Quote:

Originally Posted by BillL (Post 1445356)
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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