Why do helicopters "chop"?

shoppintractors · Mar 16, 2004

Re: Why do helicopters \"chop\"?

That That
was was
an an
amazing amazing
demonstration demonstration
of of
a a
Huey Huey
Helicopter Helicopter
/forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

Don Don

RockyMnt1 · Mar 16, 2004

Re: Why do helicopters \"chop\"?

Standard rate of turn is 3 degrees/second (Thus the 2 minute turn to do a 360). Bank angle for a standard rate turn will vary based on ground speed, among other things. The faster an aircraft goes the greater the bank angle needed to achieve the standard rate. Some aircraft would need geater than 30 degrees of bank to attain the standard rate. So generally, pilots either use a standard rate or a max of 30 degrees of bank when manuevering for landing.

This is all needed so that controllers know when to turn pilots and pilots know how fast to turn.

Probably more than you ever wanted to know.

jdmar · Mar 17, 2004

Re: Why do helicopters \"chop\"?

Great post! The doppler effect and nearing speed of sound is correct...it is amazing these things work so well. I have been lucky enough to either fly or fly in several of our countries great aircraft (F18, F14, F5, S-3, A6, EA6B, H3, SeaHawk/BlackHawk, and a few others). I loved flying the fastmovers but a helo at low altitude (aka feet above ground/water/trees) is probably the greatest illusion of speed I have ever had. I have exceeded the speed of sound but it did not have the "feel" of the helo. The next closest illusion of speed is actually on a windsurfer...no kidding! **** I guess I have been lucky (an am really honoured) to have been given some of these opportunities...I love this country!

Peter

riptides · Mar 17, 2004

Re: Why do helicopters \"chop\"?

The sound of the air ambulance chop was the sweetest sound I have ever heard in my life.

AirCare 1 in Northern Virginia. I got the tee-shirt.

-Mike Z. /forums/images/graemlins/smile.gif

RobS · Mar 17, 2004

Re: Why do helicopters \"chop\"?

I'm sitting here listening to the sound of the Huey wondering this:

If you are in the aircraft and there is no other helicopter around you, do you still experience the "chop" sound?

Inquiring mind wants to know /forums/images/graemlins/smile.gif

EastTexFrank · Mar 17, 2004

Re: Why do helicopters \"chop\"?

"do you still experience the "chop" sound?"

I love this board. I've flown hundreds and hundreds of hours as a passenger in French, British, American and Russian helicopters and you know what? ... that question never occured to me. I'm trying to remember but it seems that the sound inside, if you CAN hear it, is a lot less noticable than outside. Personally, I find the sound reassuring. It means everything is still together and working. I would also add that I prefer helicopters to small planes anyday. Those things just scare me to death.

DAP · Mar 17, 2004

Re: Why do helicopters \"chop\"?

Ordinarily, we tend to think of sound as being a stationary phenom. Sound travels to be sure. And if you're in a helicopter, you can bet your bunyons that any sound made by the rotor blades is moving away from your ears at an extremely high rate of speed.

/forums/images/graemlins/shocked.gif

Jimbrown · Mar 17, 2004

Re: Why do helicopters \"chop\"?

Having spent several 100's of hours in a UH-1 I assure you that you do. You can actually feel the chop as it flies and you can hear it on the radio and the intercom. It is much worse if one of the blades is out of track with the other. In my expeierence the later UH-1's D and H models and cobras with the wider blades produce the loudest and most noticable chop.

RobS · Mar 17, 2004

Re: Why do helicopters \"chop\"?

Well now isn't this interesting /forums/images/graemlins/confused.gif There was some science behind my question. I would assume most of the "chop" was from the doppler shift in blades moving toward/away from a distant observer. In the vehicle, the blades aren't moving towards/away but rather around which is more steady state. If the chop is still present in the vehicle there must be another element going on? Something to do with the variation in pitch as the rotor revolves? Someone else mentioned effects over the tail versus over open air elsewhere?

Idle curiosity is killing me here /forums/images/graemlins/smile.gif