Helicopter Crash in Goshen, Indiana Due to Ground Resonance

[Fox6]

Skids on the other hand have nothing to absorb the vibrations and undulations. That is the biggest reason why you will never see a fully artuculated head on an aircraft with skids. If anyone knows of one, please let me know.[/QUOTE]

The OH-6/MD 500 has a fully articulated (lead,lag,flap,feather) rotor head and skids. Of course the skids are attached to oleo dampners. Not sure if that is what you meant or not.

 

[flyifrvfr]

Here is a good video of a Chinook getting ground resonance. http://www.chinook-helicopter.com/video/Ground_Resonance_Rear_View.mpg

http://www.chinook-helicopter.com/video/Ground_Resonance_Side_View.mpg

 

[hawg2hawk]

Not to be confused with collective bounce.

 

[RJPilott]

I never flown a helo aside from being a pax, but i would think anything that spins is subject to the described action.. regardless of what it is mounted on, number of blades, or completely solid disk (as described in Fracs spinning top example). Of course some configurations may be more prone than others, but i would expect it to happen with any spinning object if the right conditions exist.


I say this because i've felt it on a motorcycle.. and the only way to stop it is to slow down now or a hard lean and accelerate.. and pray of course....


By the way, what is a fully articulate rotor?

 

[helimech]

You're talking about a spinning mass being unbalanced. This isn't quite the same, although similar. Ground resonance primarily happens when the moving mass, primarily one blade or sometimes more, does not return to the proper path or plane after being "bumped" out of it's plane usually by a rough landing, sticking a skid or wheel, or one of the lead-lag hinges sticking and oscillates the aircraft so bad that it causes damage, which is usually the case, unless the pilot corrects for it immediately.
A fully articulated rotor system allows each blade freedom to flap, feather and lead-lag. This eliminates dissymmetry of lift which is when the advancing side of the rotor blades has greater lift than the retreating side which if not corrected would roll the aircraft to the left side in conventional helicopters or the right side in Aerospatiale or some Mil helicopters.

 

[Phrogboy]

Yeah, what he said.......

 

[ShyFlyGuy]

Thanks for the info, fellas. Makes sense, and the videos really helped visualize what happened. Kinda spookey. Is it a freak occurance, or does it happen quite regularly? I was thinking about adding rotorcraft to my blue card...


Shy

 

[pilotmiketx]

You helo guys are always blabbering about how helicopters can do all kinds of things that airplanes can't, but nobody ever mentions ground resonance, settling with power or that other trick you do when you just flip over on your side for no apparent reason.

 

[skiddriver]

Have you ever heard of an airplane doing any of those things?

 

[GravityHater]

How did Ground Resonance get its name??
I think I understand the mechanics of it but can't relate the name to the action.