full scale chopper
 

If you are going to fly a helicopter please make sure it is not still secured (tie down) lmao [link]http://www.break.com/index/tiedheli23.html[/link]

RE: full scale chopper
 

That doesn't look real to me for some reason. :eek:

FBD.

RE: full scale chopper
 

Its real...its a effect called ground resonance. It occurs in helicopters that have more than two bladed heads. One blade moves out of its alignment and starts leading or lagging. This causes a gyroscopic wobble that starts to resonate due to the solid contact with the ground, eventually resulting in destruction of the helicopter. You actually dont even have to have it tied down. On some helis, even a rough landing can cause this. The only option is to takeoff immediatly, and allow it to regain stability, then set it down more gently.

RE: full scale chopper
 

Thats Crazy ! I wonder if that video is acually a test , since they had the chopper tied down, or if it were a true accident. Man how do you tell the Commander that you just cost the Army about 2 million dollars.

[X(]

RE: full scale chopper
 

ouch! That was a bad crash that did not even get of the ground.:D

RE: full scale chopper
 

Looks more like a test rather an accident.

RE: full scale chopper
 

Wow, you can even see the one blade on the rear rotor that gets into the lead/lag resonating thingy, and as the rotor slows down, it gets worse and worse. It's also striking how wide those rotor blades are.

DKjens

RE: full scale chopper
 

This has to have been a test, If you look at the center of the tail rotor near the top of the engines there is a yellow strip that has to be a post. If you watch this spot it does not move until the tail rotor seperates and falls on it, if you look closley you can follow the stake to the ground.

Egor

RE: full scale chopper
 

This was indeed a test. The airframe performed a barrel roll uncommanded [X(] and was subsequently relegated to testing in Aberdeen, Maryland.

Here's a link to a side view of the same test.

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

RE: full scale chopper
 

its a test ... i have it on tape from challenge of flight

RE: full scale chopper
 

Exactly....The test that everyone is viewing was set up for a ballistics test and turned into ground resonance because it was chained down too tightly. The aircraft has oleo struts to dampen vibrations, but the chains did not allow these to occur. The breaking you see in the aft rotor is a result of the droop stops not engaging and acutally launches one off!

RE: full scale chopper
 

I wish, I would have tax-payers money to play with full scale RC toys:eek:

RE: full scale chopper
 

This test footage is shown in helicopter ground school as a sample of ground resonance. I saw this footage a while back and forwarded it to a coworker going through helicopter flight training and they had seen it in class. Full scale helicopters have so many things that will bite you in the rear if you don't follow the rules....

RE: full scale chopper
 

It's nice :) I'm thankful every day I fly!!

RE: full scale chopper
 

You could get into the same sort of destructive situation with the OH-58 A and C models. I did see a flight test video of that happening in the air during autorotation. That mainly has to do with dynamic resonances and the transmission pylon mounts bouncing.

bdavison- I think you are talking about articulated rotor systems which have dampers for the blades to lead and lag. You can get into ground resonance with those if you hit one oleo strut hard, and then let the other struts start a bouncing (tap dancing) sequence. This in turn starts the blades to slamming against the damper stops, which transfers more energy to the oleo struts. It is a cycle that can't be stopped most of the time unless you take off to a hover. At least that is what they taught us in flight school for helicopters with skids. That site mentions tire pressure being important.

FBD- It's a real test. They do all kinds of things like that before any aircraft is released into the inventory. That's how they make the performance limitations, charts, dead man curves, etc. I've seen videos of aircraft being crashed to determine correct autorotation profiles. I have a video somewhere of an overgrossed Huey doing a steep autorotation. The tail boom broke off and the fuselage spun on the runway. You can see the test pilots white helmets slam forward as they went forward against the straps.

You can see the pilot apply full collective pitch once that rear pylon started breaking apart. This helped save more damage from the blades, especially the front rotor system.