Chinook ground resonance - side

[crispycritterz]

Gone wrong? I'd say it went as expected. I wish that they had done this to 10 46/47's with full instrument and monitoring packages so we could see the data.

[yueqianxiong2]

expensive!!

[thatguyoverthere45]

lol what happened?

[jaydabee]

later they checked underneath *MADE IN CHINA* = epic fail

[Znitso]

What is that caused by? I am stunned.

[gkwas]

forced vibrations has the same frequency as self vibrations. so machine absorbs the power of forced vibrations instead of dissipating them

[Znitso]

@gkwas Oh ok, thanks for the info.

[HurpDurr]

Holy crap that's violent. So what forces cause something like that?>

[jingling30]

with this idea, according to tesla, you can take down a bridge with a hammer if you know the exact frequency of energy.

[napoleonpp]

What amazes me is how the aft blades never contacted the forward or hendered them in any way.

[Testacojones]

I meant to say semi rigid, lol, I just noted that I said fully articulated instead. Fully articulated are in danger if blades not balanced or a hard touch down.

[12alboch]

FAIL

[Testacojones]

If ground resonance happens after a hard landing to compensate for it one has to take the helicopter to a hover right away, this doesn't happen to fully articulated rotor systems if I remember right, I got my rating back in '96.

[glifburg454]

ground resonance only happens with fully articulated rotors, because they can independently move from one another.

[uh60ch47chief]

Ground Resonance does not occur in rigid or semi-rigid rotor systems(such as the Huey), because there is no drag hinge on the rotor head, It is the drag hinge that allows any given pair of blades to either get closer to or farther away from each other. When the pair of blades get too close or too far away, the balance of the entire rotor disk is compromised. Not to mention the vibe freq this movement produces, causing sympathetic resonance. generally 3+ bladed helis are full articulating

[DocVuDu]

Now, OK, I'm not angry or anything. I'm sure there's a perfectly reasonable explanation for why you did that to that nice Chinook. So I'm staying calm, right? We're all staying calm. And we're all going to stay staying calm. Of course. I promise. All I want to do, if it's not too much of interruption of what you guys call "party-ime", is just ask one simple question...

WHY THE #&%@! DID YOU &#%!@-ING DO *THAT* FOR???

[jdisom]

This was a successful test...it found out something that needed to be addressed...hence a successful test!

[DaveStarr4]

was amazed at the power of the rotor blade good thing it was not in use in the air that would be very tragic

[mystic988]

"Ground" implies the airframe must be in contact with the ground.

"Resonance" refers to the natural vibration frequency of the airframe resulting from the design and manufacturing process.

Each part of the airframe, including the rotor system, vibrates at a certain frequency.Instability can occur when the lead-lag frequency of the rotor couples with one of the natural frequencies of the fuselage, usually due to a shock to the airframe

[shaych47]

holy crap, the dam title says its a test, arent some of you people smart enough to look in the top right corner. holy crap. and some of you people just dont need to open your mouths, because most of the people that post on here are jackasses, that really just talk shit and post, something such as no no its this or it is doing this or it should be this way, and then followed by i think. if you dont have enough knowledge of this aircraft or any other then dont give your input. no one cares.

[nbgwho]

This only happens, I believe, when the blades are out of sync, and any good pilot should be able to correct it.

The video, I might point out to the miffed helicopter builder, doesn't say that this is a test, so stop whining about what other people say! Jeez, if you're smart enough to build a 'copter, you should have the intelligence to figure out that unless people are told it's a test, what else are they going to think? Doh.

[indyschmidt]

I'm guessing you didn't read the video description?

[Pearlharbor350]

it looks like it was chained down??

[indyschmidt]

Wow. It is astonishing how many blubbering fools think this is some demonstration of how poorly made the aircraft is. I work in the factory that builds it, so it's hard to not take it personally that you people have zero clue and zero respect for what amounts to a fantastic helicopter. When they bring an officer of the Army in to tell us how much they love our product and how they would not be able to survive without it, it means something special. Don't knock it unless you've flown it/in it.

[SnKGoat1]

That aircraft is going to be active for many years to come. My company makes many noise/vibration dampeners for the Chinook; the biggest, is the rubberized mounts that isolate the synch shaft, which keeps the 2 rotor heads synched so they do not strike each other, since they cross paths over top of each other.

[samarigil66]

this is testing the rotor strenght on the chinook

[Icepacalapse]

That's not ground resonance.

You can clearly see a blade becomes unlatched and swings out of index toward another blade causing the imbalance.

[DaveStarr4]

yeah and the rear rotor actually sheered off the rear shroud completely it's kinda hard to believe that the blades could have that much power and that could really happen on a real Chinook WOW!

[ViciouslyEpic]

This wasn't a test gone wrong; they did it on purpose to find out the weak stress points of a chopper. Tests like these save lives.

[skywalk762]

pop some new spark plugs in there she'll run fine

[highps3]

I dont know exactly what this is but I can tell you it can be fixed with duct tape.

[evol911]

and bailing wire

[DrGreenThumbs1]

Right on...you'll need some blue tac too

[piye40]

well thats the end of that chopper

[tharrington11]

the rotors werent even spinning that fast... unless the framerate was all screwed up.

[kandem360]

doesn't matter...this was a test for GR:

Ground resonance, in fully articulated multi-bladed helicopters, 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.

[Stevieb83]

nice to hear some one whom knows what they are talking about for a change.thank you for the informative comment sir

[kandem360]

thanks, I am an aircraft technitian in the CF, and i actually took a course on the Basics of rotary flight which is where i got my information. This course was a part of a 15 month long course, all on becoming an AVN TECH.

[cb6926]

This is more to do with a feedback loop that eminates from the rotor itself. Ground resonance like this occurs when the driving frequency from the individual cyclic movement of the blades in the lead/lag plane coincides with the natural frequency of the undercarriage shock absorbers. They have tethered the chinook to the ground, thus changing the natural frequency to within the range of the lead/lag frequency and resonance occurs. positive feedback results in the catastrophic failure.

[kandem360]

i forgot about lead/lag....you are right.

[stealhty1]

@kandem360 thats true also an imbalance rotor amplifies this theory 

[fuzzywzhe]

Don't worry folks, the Chinese will continue to lend money by purchasing all the treasury bills that Fed makes. The US will never go bankrupt.

[mke15]

LOL

[mke15]

how does that happen.

ive never known anything about that xD.

does it lose balance from the torque of the blades or sumthing when it slows down :s.

i have absolutely no idea. but i wanna :D.

[craigdoolan1]

i like it when the back rotor came off

[valeyk]

Its not a pass fail test. Its an investigation type of test, experimental almost ...except its more putting theory to practise... some things you have to test to destruction for mechanics of solids type things ( I do engineering!) Sometimes they do this with materials with torsion and tensile tests! Sometimes structures such as pipes are subject to pressure too. AND we also do stuff to test how many cycles to failure. and this is kinda like that.. and to find modes of failure. :) helpful i hope!

[Stevieb83]

this is why volkswagen locate big solid resonance blocks of solid steel on there car chassis in the golf or jetta for instance

[kuyakev]

why do they do these test for?..

[scarybaldguy]

So they can determine the aircraft's failure modes, and train the crews accordingly (namely, DON'T LET THIS HAPPEN).

[gjkrej]

that was a test to see how the helicopter will endure without a gearbox....

[DannyMcGurkMonifieth]

No that test didnt go wrong, they have to go to the maximum.

[geeselouise]

I'd like to book a flight for my wife on that helo...

[stucollett]

its testing come on. if you were required to fly in this chopper then you would want them to test it, just like they did. if they didnt they couldn't tell the crew how to opperate safely.

[britarthc]

"dont worry billy joe i got some duct tape and paper clip she will be runnin in no time"

[Spitzrock]

"ummm, that one's yours steve"

[gavsky23]

"Er, we better put that down as a fail then, guys" ;-)

[rocktruggy03]

All helicopters will do this buddy. It's a test being run to define the vibrational limits of the airframe.

[Idahohelopilot]

actually only multi-blade rotor helicopters which lead and lag can do this... a two bladed rotor will remain balanced in all flight conditions

[ziegenhirte]

WOW,

American Engineers are the greatest in the World.

HAHA

[aflacduky]

its a test they were trying to test the limits

we are the only country "USA" that has enough money to trash things to help save lives lol

[jippyjester]

yeah - with a multi trillion dollar debt to the east!!! hehe - u know nothing about anything do you...

[aflacduky]

your from belgium do you know how much money we have sent to your country LMAO i would check my own before laughing at the size of someone elses dick and you have to buy all your weapons from other countrys because you cant make your own and you have french tanks because you cant buy the best American LOL

[folkertvankuijk]

do u know how much money the european bank is pumping in the american economy since the crash? u don't even WANNA know coz u'd probabley kill urself. btw im dutch, we drive german tanks coz they really ARE the best> look up greatest tanks discovery channel

[MgpMontville]

Oh the discovery channel makes you a friggin expert LMFAO! I DO hope you dont believe everything the media tells you as well????!?

[Arnechk]

It doesn make us an expert, but i'd rather have something german than Abrams.

[mrmookie]

Why would you doubt someone named idahohelopilot discussing helocopters?

Ground resonance happens in helos with lead-lag hinges. It occurs only on the ground. It starts when the blades "bunch up" on one side of the rotor disc where they generate an unbalanced centrifugal force that gets in phase with the natural frequency of the aircraft rocking on it's landing gear. The emergency action is to lift the helo to a hover..

[skier210is]

not centrifugal...centripetal

[brendonnz1964]

Which bank is doing the funding.

[Humbag]

this guy is probably the typical eurofag

[petbedding01]

alrite enough of the slaggin of europeans

[Mikitsubizunizu]

lol look at soviet engineers, oh wait, their helos cost to much for the new government to pay for flight time.

[1291918]

WOW! i've read about and trained to avoid ground resonance, to see it in action is just amazing i don't know about you guys but this blows my mind!

[turbotraker]

WHY?

[dalzilla]

wow. what is "groud Resonence?"

[Fish880]

It is basically a hard landing that starts a shockwave going from the ground to the rotor and back to the ground, increasing in intensity until the helicopter lifts off the ground again. In this case it cannot lift off again, so it tears itself apart.

[dalzilla]

Thanks.

[ZUES65]

lol wat the hell was that model made out of? a helicopters blades and engines dnt just fall off lmao. im guessing its model?

[Corktip14]

No it's not model. It's just the structure of the helicopter that's entering into a resonance phenomenon. And that can break anything apart if it's not stopped ASAP.

[banyani]

choriolis effect

[dimebox23]

When a helicopter with a fully articulated rotor system strikes the ground hard or unevenly it sends a shock up through the heli to the rotor head and back down to the ground. if the helicopter isn't lifted away from the ground or the blades aren't immediately flattened and stopped, this shock will continue to travel from the ground to the rotor head.

[dimebox23]

The blade accelerates and momentarily goes out of phase with the other blades. This is corrected by a set of hydraulic or flexible rubber dampeners. Anyway back to the point.

[dimebox23]

When a blade flaps up to compensate for dissymmetry of lift, the rotor blades center of mass moves in towards the axis of rotation or rotor hub. this has the same effect as an ice skater pulling in their arms in a spin to speed up.

[dimebox23]

don't worry paul, bushman doesn't know what he's talking about either."It is a feature of all helicopters.." wrong. Fully articulated rotor systems are subject to ground resonance. These systems lead and lag on a hinge to compensate for the law of conservation of angular momentum or coriolis effect.

[ei2232]

If it was a ground resonance test it doesn't look like it went wrong. I do believe though that it was a LFT&E test that went wrong.

[KeuhHuy]

it has a seizure?

[ElAdchi]

Uhhhh that hurts....

[DukeImperator]

thats the chinook in a nutshell

[yektiyek]

bizim orda buna hoşaf oldu diyorlar

[chadsexinton]

is that canadian made?

[paul2808]

This is what happens when the blades are not balanced or tracking correctly

[bushman14]

Shhh....it's okay, everybody likes you. You don't have to make up an explanation that is total bull.

[paul2808]

So what is your explanation of what caused the aircraft too distroy itself????

[bushman14]

Ground resonance is the result of the frequecy produced as the blades pass through the air, finding the natural resonant frequency of the aircraft structure. It is a feature of all helicopters. The solution for this is to have the landing gear "soft" to soak up this motion (the resonance can only manifest when in contact with a solid object, I.E. earth). You will notice the landing gear deflated and strapped down to the ground. This lets the aircraft vibrate unchecked.

[SenorSpode]

You had to pick a name like 'Bush', didn't ya? "Bummer of a birthmark, Hal"...

[rakh1]

No no - this is totally for real using a real chinook. Of course - it is unmanned and controlled remotely.

[BerggreenDK]

is this for real or just a model test bench?