Ground Resonance - Side View

[TheAdmiston]

wow!!! what is that??

[papafoxtrott]

HOLY SMOKES!!!!!

[CoDViP]

Me: Thanks for letting me borrow your helicopter.

Owner: WTH!?

Me: What? That scratch was already there.....can I borrow $20 bucks?

[chrisbaker121924]

TAKE OF THE DAMN THE HANDBRAKE!!

[nickolastd21]

can this happen in the air? or will it stop if they get clear of the ground?

[coryismyfriend]

@nickolastd21 had someone actually been inside the aircraft, they could have taken it to a hover where the blades would have stabilized.

[williambrodie]

@nickolastd21 This only really happens if you land in a certain way. If your rotor blades are going fast enough you take off, if not you try and slow the blades down as quickas possible. Although normally you are forbidden from using increased blade pictch (increased lift) to slow down the blades as you may accidentally take off, in this situation it can help. the movement odf the helicopter during ground resonance can be so violent that the pilot is knocked out.

[bigtank2185]

I talked to my friend who is a helicopter tech in the military, and he said they showed this video in ground training class, this is a demonstration to show how much vibration is in the rotors when the chinook is mounted to blocks, without the shocks and wheels, the shocks and wheels have a control system that counteract this frequency. Basically it shows what would happen if the tire pressure is off, tire pressure is most important.

[TheFr3sh1]

Was there resonance on the front rotor as well or only the rear?

[edintamayo]

 ground resonance = electromagnetic vibrational force created by aircraft

[MrJonagikster]

@edintamayo electromagnetic? I think not

[tankertel]

this is what you get ...when you spend £22 on a £0.89 light bulb?

Cost cutting in the Extreme.

[MattBlytheTheOne]

hehe back to the drawing board !

[feenixrising10]

duct tape will fix that right up

[hovito212]

WHICH ONE OF YOU FUCKIN PRIVATES FORGOT TO UNTIE THE CHINOOK, JUST FUCKIN DROP

[TheMarksmenCat]

poor helicopter its unethical what theyre doing! :'-(

[InformityAffect]

somebody get the epoxy glue

[briansmobile1]

@InformityAffect AND the duct tape... this one's serious.

[VolDep45]

The CH-47 Chinook is the only aircraft that can have a mid-air collision with itself (even on the ground).

[johnnyKillmore]

I remember seeing that in school. The story I was told, was that it was at the proving grounds and the transmission was already bad, and they wanted to run it to failure. Saw a longer and much more boring version of it in school though. The transmission with the 23mm cannon hole in it was pretty amazing.

[LLarjo]

A middle aged chopper suffers a crisis and boogies to death.

[vexviper]

They were doing a load test i think.

[TheJinxrr]

It could still fly better than a Blackhawk.

15U Ahahahah, best MOS in the service.

[robnox]

@MrWillydoit propeller, rotary wing, SAME THING.

Don't believe me? Look at the V-22 osprey.

[ebalim]

and the commander asks:"what the fuck just happened here?"

[4L60E]

NOT covered by warranty.

[hifikampy]

blades then, whatever you want to call them. Thanks for acting like a smartass!

[rottendeadite]

"Oh, cock."

-James May

[nsawilla]

wtf?!

[delfin61087]

man i wouldnt wanna be that pilot!

[galdorv]

So is this like in cars when you are idling some parts of the car shakes but when u change the rpm it stops or slows?

If so, is this just an extreme senario that it actually broke?

[hifikampy]

To me it looks like that one of the foldable propeller blades unlocked itself and shifted while decreasing the RPM. (that becomes more and more visible as slower it gets) The rear propeller got therefore a fatal imbalance which caused the damage.

I can not see any lateral twisting resonance of the airplane itself or other resonance effects.

[NexIuguolo]

This is what happens when you let women drive.

[grinch8302]

lmao!!!

[lravikiran]

@NexIuguolo ya true bro ....hahahaha

[psychanaut]

@NexIuguolo You are an idiot. have you nothing funnier to say?

[psychanaut]

@NexIuguolo if you would have said, that's what happens when you let black people drive, you'd be a racist. I guess in your world it's better to be a douche bag than a racist.

[NexIuguolo]

@psychanaut

Hey, buddy- I'm not the one who let her out of the kitchen, it's not my fault she messed up a perfectly good choppah. She shoulda been choppin me up something to eat, you know? Way to be an internet White Knight to a punchline you fuckin' tool.

Besides, you can tell she wasn't black because there wasn't any obnoxiously loud hip-hop eminating from the cockpit.

[psychanaut]

@NexIuguolo Yeah those pesky niggers really know how to ruin music, huh?

[NexIuguolo]

@psychanaut

Wow. Just for the record, I did not say that at all.

Music usually sounds better loud- except for when it's not yours.

Maybe you should just bury the hatchet that you just slammed into your own foot which currently resides in your own mouth. I wonder if you know how to delete your comments?

[psychanaut]

@NexIuguolo OH, I see, so it's not ok when it's against black people, but it is ok when it's against your mom. Got it.

[psychanaut]

@NexIuguolo Ah shucks, let's just bury the hatchet, ok? I understand that when men insult women, either for laughs or for rilz that it's about small pee pee size and under performance, I get it, or don't get it from you, as the case may be. It's cool, you don't need a big one to be a man.

[Lemur14]

@psychanaut Get back in the kitchen and make me a sandwich.

[NexIuguolo]

@psychanaut Are you saying you want to get some penis action from me? Please clarify.

[psychanaut]

@NexIuguolo Yes, that's exactly what I'm saying. I could use a good 30 second laugh.

[NexIuguolo]

@psychanaut That's cool. At least you don't cry when you orgasm, that would just be creepy.

[blueluny]

@NexIuguolo ha ha! that is excellent sir. i "lold" loudly..

[dennismlns]

@NexIuguolo Considering that there was no one actually in the chopper, there is no was it was a womans fault, and you dont DRIVE a chopper, you FLY it.

[NexIuguolo]

@dennismlns So, considering those things, then what? Lrn2Grammar, dumbfuck.

[charlesmartin82]

In this video it just looks like a cheaply made toy. Damn! That's freaky.

[shibby503]

im a helicopter pilot, i fly a eurocopter 355, and if you think about it, helicopters usually only crash on landing....get it ..like hitting the land....... its like the fall did'nt kill him it was the sudden impact at the end.

[ProphetOfBaphomet]

3 blades= 120 deg separation between each

4 blades= 90 deg separation between each.

it is a balanced system. if the gap between 2 blades decreases, the the gap from them to the ofter blades increases, putting the system out of balence, which creates a violent vibrating (harmonic) effect which will mechanically shake the craft to bits.

its all about balance within the systen

[XxXDELTAxFOXTROTXxX]

Finally! People that have knowledge!

[derekfalk99]

They made this video to show what will happen if you don't properly service the landing gear and wheels with hydraulic fluid and nitrogen. There wasn't any way to dampen the vibration on the ground. By the way, they used timed out parts that couldn't be used in an aircraft that was airworthy.

[khalilovH]

@ProphetOfBaphomet

sorry man .. but u r wrong .. what happened here was due to RESONANCE , not due to unbalanced blade gap .... do u think that they r crazy to build a chopper with unbalanced blades and watch destroying just for fun , it's not like watching a porn movie u idiot

[khalilovH]

@khalilovH

and at the beginning of this video every thing was good and it's clear that the blades are balanced , then every thing went wrong as it reaches the resonant frequency .... i am really angry that there are lots of dick heads same as u who likes ur fucking comment

[NameWasInvalid]

@khalilovH & @ProphetOfBaphomet

Sadly, this is funny because you are both right.  Ground resonance was exactly what happened. This video is old and it was done on purpose to demonstrate. Now, the rear gear box burned up due to the resonance, and seized. This caused the blades to 'break free' from the grips and put it off balance, thus ripping the rear gearbox apart and leaving the carnage you see here. So, while you guys are argueing things here, you are both right.

[staslig]

@khalilovH you are right about the resonance but they did this intentionally, not by accident

[chrisbaker121924]

@staslig Intentionally... well sort of... its a ground test so they are trying to see the limits of what the aircraft will take... and clearly... they found it.

[staslig]

@ProphetOfBaphomet

you are close, but not quite there. It can happen this way as well, but ground resonance usually happens when a shock of some sort puts the mast itself out of its center of rotation. If this happens and the aircraft is still on ground then it will shake more and more. If you take of when its starts to vibrate then it goes away just like that.

[K1w1scot]

@ProphetOfBaphomet Is that what was actually being tested there,though? It said ground resonance in the title, which is slightly different, isn't it? Usually harmonic coupling between oleos and other forces (aerodynamic, loose structure, etc).

[mikeflbiker]

Remember to unhook your helicopter from the tie-downs before trying to take off.

[dercrazyalbaner]

maybe you just got no sense of humor u imbecile!

[shibby503]

this person is an idiot this isint take off it is shut down you ... imbecile ..... reamember helicopters never crash on take off. think about it.

[kfrcandjelko]

Are you sure???

There is a video about a helo trying to take off while strong wind from side is blowing...

Check that s**t out.

[XxXDELTAxFOXTROTXxX]

Helicopters can crash during take-off. It could be occurance with weather or pilot error!

[shibby503]

air craft only crash on landing unless the aircraft stays in the air, think hits the ground = landing

[laputahayom]

you can crash a car and it is not landing

[stevenstreets3]

N0 G0

[agpilotgt]

If the comments already explained it, why waste all that money on totaling the helo?

[kkinsane]

Resonated itself to bits, that is the simplest explanation, science is too cluttered with math.

Or shook itself apart, vibrated at too high a frequency, went boom? snapped? torque would be involved as it was the rotor, basically it was a shit design.

[pratikballer57]

i dont think , vibrated at natural frequency, the amplitude increased( i.e resonance, F0=F) and it shattered.

[vietarc]

lol, aren't the chopper rotating its blades backward?

[soupisgoodfood42]

If they rotated the same way as the front blades, they'd collide.

[barkon]

Not exactly true. The blades are offset in height so they won't collide. They rotate in opposite directions to offset the torque on the airframe. On a single-rotor aircraft, the tail rotor counteractst the torque created by the main rotor. This is why the tail rotor is often called the anti-torque rotor.

[soupisgoodfood42]

Yeah, there is the torque. Not sure how I forgot about that. But it's also required to avoid collision, too. Otherwise, even though they're offset, there would still be a chance for them to hit. The video shows just how close they get.

[undertake782]

Wow, you would never expect a helicopter to rip up that bad by itself!

[JohnM3D]

Put some physics insight into the description please? I'm curious but too lazy to look it up! :D

[gtownbrian]

Ground resonance occurs when the frequency of the air being given off by the rotors is unfortunately matched with that of the air circulating below. It creates a resonance and causes a reaction similar to the Tacoma Narrows Bridge. it is an unfortunate matching of frequencies that create a vibration that literally rip things apart. Like singing to break a glass...the frequency sung matches the natural frequency the glass is vibrating at.

[JohnM3D]

Thank you!

[soupisgoodfood42]

It is to do with resonance frequencies, but it has nothing to do with the air. It involves the vibration of the rotor, the airframe, and the interference from the landing gear.

[stuntpenguin]

Good explanation, thanks :)

[markjcairns]

Wow. Shocking stuff.

[napyuu]

Top notch quality right thar...

[fusionsmarty]

animal abuser!

[Kevinite]

Made in AMERICA !

[springnet27]

That helicopter fell apart faster than a Chinese made car.

[LordKarmaUSA]

Okay, so again resonance and tuning are essential.

[nikhilkerala]

poor copter... trying to fly off... but locked to the ground.... it tries and tries till it dies........

[ravenfan205]

poor chinook..... it just wanted to dance and it exploded!

lolz (yes i know what ground resonance is im just joking!)

[DMGaina]

Poor thing :(

[ComradeLynx]

chinhook couldnt take the pressure!!

[72jamminjimmy]

Hey SQUORCH, Did they MAKE this happen deliberately? If so how? Quite an awesome thing to watch though. Thanks for posting it!

[mkarnerfors]

Yes they did. It's a "Ground Resonance" test. This is cause by an imbalance in the rotors. The helicopter resonates and thereby the imbalance adds to the jerking on each revolution of the rotors until the airframe just can't take any more and rips apart.

[morphine883]

You can see the power of the machine when the rear rotor blades disconnect. WHAP! WHAP!

I love Chinooks!!

[AspiringPhotographer]

Lol! It kind of reminds me of a little Team America model helicopter. So so funny!

[JamesCameron1]

Ground resonance is a hazardous condition during touchdown or at other times when the helicopter is running while sitting on the ground. A series of shocks to the landing gear can pass through to the rotor disk and cause an imbalance in the rotor system. Under extreme conditions, the imbalance causes violent oscillations that quickly build and result in catastrophic damage of the entire airframe. In some cases, complete destruction occurs.

[maninblack334]

wikiplagiarizer!

[ededmax]

Porque pasa este efecto?

[gbh1984]

Wow that was crazy. Ripped apart like butter

[diggerdrum]

it looks like the balance off the rear rotor blades goes out of control and the tail can't take the strain

[MetallicaRebel666]

so was it the weight of the props spinning at such low speeds the reason it started to bounce around?

[VideoJunkei]

Yea...the rear prop imbalance(1 blade is bent over) jerks the airframe around, Since this heli was chained to the ground, the energy just gets bounced back into the frame. front stayed fine, probably because it was lighter.

[luuko656]

a same sort of thing happaned to my bycicle once.... i can still feel the pain....lol

[bmc4life]

Ground Resonance is a phenomenon that can only happen in a helicopter with oleo type landing gear. As the engines power down they begin to create a vibration that gets transmitted through the oleo into the ground. The more the engines get powered down the worse it gets, the oleos arent able to keep up, and what you see in the video happens.

[JoMo91]

you cud b experiencing vortex ring!

[bigpinecone]

can this happen to a small r/c heli in the air? i'm trying to figure out why my mosquito is just falling from the air

[lastofthejuanitas]

it looks like the rear propeller turned into jelly.

[kharmachanic]

thats why they call em widow makers...

i've been on a few of those..

[squorch]

This is a phenomenon inherent in ALL fully articulated rotor systems that are chained to the deck. If a blade gets out of track and begins to resonate with the ground, the rotor disk's CG will rapidly spiral outward, resulting in the damage you see above.

The solution?

Take off.  This particular bird had experienced strange control anomalies (such as uncommanded snap roll to inverted), which is why it was struck and used for this test.

[blake350125]

@squorch How would I be able to learn more?

[vampov]

@blake350125 take physics or go into engineering. You will learn about this there. It really has come about in the last 50-60 years with research.

[jazzguitardotcom]

@squorch Uncontrolled snap roll to inverted? In a rotary wing aircraft? Bet that resulted in some dirty underwear.

[fendon]

we should give them robots that take perl scripts. i eman come on! army guys writing code to fight their wars. and the only people that die are made from metal so who cares!

although there may be too much grunting for anyone to concentrate on their "perl for dummies" book.

[properbike]

why does this happen??? and YES GET SOMETHING NEW! ffs

[Psirust]

Like what? Bicycles?

[mungo23]

See other vid for the importance of destructive testing.

We need something a whole lot better. That this airframe is over fourty years old has got to be demonstrated as completely unsafe is beyond my comprehention. I know, you will probably disagree but the time is now to find something far safer for our guys.

[airsoftsam]

You do know that this was just an experiment to show exactly what ground resonance would do, and every helicopter pilot/mechanic knew that would happen, and it would happen to every helicopter in the world with a fully articulated rotor system if they were put through that.

[closedgl]

Duh.

[singedrac]

I am a layperson so correct me if I'm wrong, but I've heard this does not happen in helis with only two blades. Is this true?

[soupisgoodfood42]

Sort of. It's far more likely to happen in helis with more than two blades because most of them use an articulated hub, which allow the blades to lead-lag (rotate forward or backward on the hinge), which causes the rotor to become imbalanced -- they're designed to do this for reasons I won't go into. Most two-blade helis don't allow the blade to lead or lag at all, so they aren't really prone to this.

[imaniguana]

I hate it when that happens.