Helicopter Questions

[Gulfstream Driver]

Ag planes have them as well.  I've heard of them being used more than once.

[Mike]

Wire cutters are not mandatory as far as the FAA is concerned in the US (right now).
BUT they have become mandatory for the forest service and we have them on almost all of our helicopters.
I am sure that sooner or later everybody will need to have them. The funny thing I thought was something I read recently. I read that there are more accidents with planes and wires than with helicopters. It seems like helo pilots are constantly trained about them and are therefore more aware when it comes to wires. Going slower than most fixed wing planes helps as well...

And yes, just like MO said, they keep you from getting your skids get hung up in the wires as well as your rotor-system. On some tradeshows they have demonstrations on how good they work and it's pretty impressive I have to say. They can cut through 1/2'' steel cable like butter!!

Most pedestrians think they are antennas!! HA HA   

[Gulfstream Driver]

The funny thing I thought was something I read recently. I read that there are more accidents with planes and wires than with helicopters. It seems like helo pilots are constantly trained about them and are therefore more aware when it comes to wires. Going slower than most fixed wing planes helps as well...

And the fact that you can go up and down in shorter distances over the ground...

[Frank N. O.]

Aha, but a cutter between the roof and the rotor? That would be extreme luck/skill if a wire came right between that and didn't hit the rotor uintil it came to the cutter right infront of the rotor-head wouldn't it? The nose-one is more understandable. Thanks for the info, one more thing though, what's a "Ag" aircraft?

Frank

[MO]

Ag Aircraft = Agricultural Aircraft (i.e. Crop Dusters)

Cheers!

[Frank N. O.]

Man, I actually did think it was that but I never heard the term before so I thought I'd just save typing-space and ask, thanks for confirming it

Frank

[Mike]

Aha, but a cutter between the roof and the rotor? That would be extreme luck/skill if a wire came right between that and didn't hit the rotor uintil it came to the cutter right infront of the rotor-head wouldn't it? The nose-one is more understandable. Thanks for the info, one more thing though, what's a "Ag" aircraft?

Frank

Well, they are there in case you hit the cable with your nose and it rides up all the way across the bubble. Then the cutter will take care of it before it goes into the swashplate. If you hit the wire with the top of the rotors it could go both ways, it will either bounce off or take a chunk off your blade...

[BoB]

I was just in a helicopter manager workshop where a bunch of Forest Service and BLM people were discussing ground resonance as we had a crash last year they are tentatively blaming it on. What are the emergency procedures they teach pilots when experiencing this? Doesn't sound like you have much time to respond....

[Mike]

I can't see how a helicopter can "crash" because of ground resonance.

In order for a helicopter to get into ground resonance you need to be in contact with the ground to transfer the shock into the rotor system and then back into the skids and then back up and so on...
So there is an easy fix if you feel ground resonance coming on while touching down. Lift the ship back up!
The centrifucal forces will straighten the blades out again.

What kind kind of aircraft are they talking about? An AStar?

I have never seen an AStar get any real problem with ground resonance. They do get into the onset of GR every now and then especially when the feather at the back of the skid doesn't make good contact or the dampers are shot but for the helo to "crash"?!?!...unlikely.
A Hughes 500 or 300 maybe. I have seen one of those come apart because one of the dampers on the rotor system was sticking but they did something stupid to begin with to even get into this situation.

  So here is the procedure:
- If you set the ship down and it starts bouncing...pick it up again, wait till everything calms down and try again!
- Or if you are starting up or slowing down the rotors already....go to flat pitch!
  (not having any pitch on the blades will make it easier for the blades to strighten out)
  That's all there is to it procedure wise....

[Gulfstream Driver]

I think there was a fatality at UND a number of years ago due to this (or something similar).  I think a kid in a Schweizer somehow started bouncing from skid to skid.  One of the rotor blades ended up coming through the cockpit and took off part of his head.

[Mike]

Woah!
How weird is that? The "real" Jason just sent me this right as we were talking about it:

Apparently a lead lag hinge broke on the rear rotor system (Chinook) and ground resonance took over from there.....
 
http://www.break.com/index/tiedheli23.html
 
In this case something on the rotor broke and since the ship was tied down (don't ask me why) the pilot couldn't lift off the ground. During ground resonance the shock "knocks" two out of three blades closer together and this shifts the center of rotation with the weight of the blades not pulling evenly on the mast anymore. If the "center of rotation" shifts and isn't directly over the center of the mast anymore, the mast now starts rotate around the new center of rotation which, as you can see in the video, makes things worse...
Does this make sense?!?!

If you look closely at the very end you can see two of the blades flying almost together on one side while the third single blade opposes it. Doesn't take a lot of math skills to figure out there is more weight pulling on one side of the mast than on the other...

[Gulfstream Driver]

Wow.  Is that something that's repairable, or does that just go for scrap?

[fireflyr]

WHOA DUDE,
That Chinook is in a world of hurt---MIKEY, repeat after me---"If the wing is going faster then the fuselage, something can go wrong-go wrong-go wrong-go wrong!!!!!!

Your stuck wing pal, Jim 

[Mike]

Wow.  Is that something that's repairable, or does that just go for scrap?

Hehe, no way!
You're talking destroying the whole running gear AND the fuselage structure.
If you roll a helo over you can sometimes rebuild it by replacing the running gear and keeping the airframe, but in this case it's better to just call the insurance and take your radios out...

To Jim:
You have a point. But I still like being able to land in a parking lot!
A Chinook by the way is a little like the V-22 we talked about, too many blades and gearboxes...

[Ted_Stryker]

Woah!
How weird is that? The "real" Jason just sent me this right as we were talking about it:

Apparently a lead lag hinge broke on the rear rotor system (Chinook) and ground resonance took over from there.....
 
http://www.break.com/index/tiedheli23.html
 
In this case something on the rotor broke and since the ship was tied down (don't ask me why) the pilot couldn't lift off the ground. During ground resonance the shock "knocks" two out of three blades closer together and this shifts the center of rotation with the weight of the blades not pulling evenly on the mast anymore. If the "center of rotation" shifts and isn't directly over the center of the mast anymore, the mast now starts rotate around the new center of rotation which, as you can see in the video, makes things worse...
Does this make sense?!?!

If you look closely at the very end you can see two of the blades flying almost together on one side while the third single blade opposes it. Doesn't take a lot of math skills to figure out there is more weight pulling on one side of the mast than on the other...

Funny... I was going to send you the same video!  It was apparently too large for the upload area here in regular WMV format.

The story I heard about this was that it was a test run up on a maintenance pad at a CH-47 USMC unit, hence why it was tied down.  Not sure if that is the correct scoop on it though.