What is the CHOP button for?

[FalcoGer]

When the chop button is pressed, engine power is set to idle until pressed again. Is this per crew station or can both pilot and cpg activate/deactivate independently?

What is this button used for? It seems like a good way to die unnecessarily. Why is it on the collective? Is it important enough to warrant the space on the HOTAS (HOCAC?)?

The only real reason I can think of is that if there is some sort of malfunction with both engines you could press it and take maybe a few seconds to figure out which one while on idle power to close the throttle. But then again you could just pull the throttle back. The immediate fire actions include closing the throttle, not pressing chop.

It's just confusing to me.

[Raptor9]

11 minutes ago, FalcoGer said:

Is this per crew station or can both pilot and cpg activate/deactivate independently?

What is this button used for? It seems like a good way to die unnecessarily. Why is it on the collective?

It's in each crew station and when either is pressed it idles the engines as stated.

And yes, it is a good way to die, which is why the button is covered with a guard, with the guard lock-wired down to ensure the button is only activated when someone is stupid enough to deliberately break the lock-wire and press the button.

The idea was that if I have some sort of tail rotor malfunction, and during the course of whatever emergency actions I am taking to land, I can (without taking my hand off the collective while flying) instantly bring the engines to idle to prevent the resulting torque increase during my landing "flare" from inducing a spin. Having said that, there are some peculiarities with that button I don't want to get into; but needless to say most 64 pilots wish it wasn't there.

FYI, that function isn't present on all AH-64's, but certainly all in the US Army. Interestingly, in AH-64A's it wasn't a chop button, there was a chop collar. I know of at least one AH-64A crew that crashed (and survived thankfully) because they inadvertently used the chop collar when trying to rotate the friction collar on the collective grip.

[FalcoGer]

What i meant was if the pilot presses chop, can the cpl press his chop button to undo it or is it like the fire switches where the crew that pressed them has to press them again to undo it?

[Raptor9]

If one crewmember presses it on, the other can press it off.

[Hiob]

It's for the chop-chop-chop sound of the helicopter - you need to press it accordingly....

[FalcoGer]

6 minutes ago, Hiob said:

It's for the chop-chop-chop sound of the helicopter - you need to press it accordingly....

 

I leave that experiment up to you. I'll stay away from that thing.

[kgillers3]

Typically we do

Edited October 15, 2021 by kgillers3

[Remco]

I for one will be using the button in DCS to check if my backseater is paying attention, very useful.

[fargo007]

Might come in handy for autorotation practice.... 

[kgillers3]

3 hours ago, fargo007 said:

Might come in handy for autorotation practice.... 

yeah… practice

Edited October 15, 2021 by kgillers3

[PHMAC]

On 10/15/2021 at 8:41 AM, FalcoGer said:

The immediate fire actions include closing the throttle, not pressing chop.

@FalcoGer I just read this comment that you made some time ago.
Do I understand correctly that you need to pull your throttle levers back when taking fire?…Can you tell me more about this procedure?

Thanks!

[FalcoGer]

15 hours ago, PHMAC said:

@FalcoGer I just read this comment that you made some time ago.
Do I understand correctly that you need to pull your throttle levers back when taking fire?…Can you tell me more about this procedure?

Thanks!

I wasn't talking about taking fire, but having an engine fire.

1. Identify affected engine
2. Throttle affected engine: off
3. Affected engine fire button: push
4. Fire extinguisher primary: push
5. consider dropping external stores
6. if engine fire persists, discharge secondary fire bottle
7. land as soon as possible

[PHMAC]

9 minutes ago, FalcoGer said:

I wasn't talking about taking fire, but having an engine fire.

Doh!...that makes much more sense ofcourse...

Thanks for coming back to me on this.

[aaronwhite]

On 10/15/2021 at 2:03 AM, Raptor9 said:

It's in each crew station and when either is pressed it idles the engines as stated.

And yes, it is a good way to die, which is why the button is covered with a guard, with the guard lock-wired down to ensure the button is only activated when someone is stupid enough to deliberately break the lock-wire and press the button.

The idea was that if I have some sort of tail rotor malfunction, and during the course of whatever emergency actions I am taking to land, I can (without taking my hand off the collective while flying) instantly bring the engines to idle to prevent the resulting torque increase during my landing "flare" from inducing a spin. Having said that, there are some peculiarities with that button I don't want to get into; but needless to say most 64 pilots wish it wasn't there.

FYI, that function isn't present on all AH-64's, but certainly all in the US Army. Interestingly, in AH-64A's it wasn't a chop button, there was a chop collar. I know of at least one AH-64A crew that crashed (and survived thankfully) because they inadvertently used the chop collar when trying to rotate the friction collar on the collective grip.

That's what was always confusing to me. I guess is it just slightly quicker than just shoving the collective down in the same scenario? Or is that the engines idling means there's less of that power going to the tail rotor, which the collective drop itself wouldn't cover? I'd love to know what happened during testing or with older helicopters for the McDonnell Douglas team to have included the button.

[bradmick]

The tail rotor also slows down with the main rotor. The transmission is the central connection for both. The purpose of the chop button is to electronically idle the engines and near instantaneously remove the majority of rotor torque from the airframe  it he event of a loss of tail rotor thrust (i.e. a severance or breakage of the tail rotor drive shaft, or in the event the tail rotor decides to separate from the helicopter). I’ve always briefed that if we’re in a violent enough spin that neither crewmember can get to the power levers, the chop button is to be used to reduce the spin, with the proviso that the collective needs to be rapidly going down and then the power levers brought to idle by the non flying pilot. 

[aaronwhite]

3 hours ago, bradmick said:

The tail rotor also slows down with the main rotor. The transmission is the central connection for both. The purpose of the chop button is to electronically idle the engines and near instantaneously remove the majority of rotor torque from the airframe  it he event of a loss of tail rotor thrust (i.e. a severance or breakage of the tail rotor drive shaft, or in the event the tail rotor decides to separate from the helicopter). I’ve always briefed that if we’re in a violent enough spin that neither crewmember can get to the power levers, the chop button is to be used to reduce the spin, with the proviso that the collective needs to be rapidly going down and then the power levers brought to idle by the non flying pilot. 

Appreciate it! I love having a forum where we've got actual experts on the stuff around. It's definitely a lot better than people like me trying to Google my way to something that makes sense! 

[FalcoGer]

On 2/6/2024 at 12:26 PM, bradmick said:

I’ve always briefed that if we’re in a violent enough spin that neither crewmember can get to the power levers,

If neither pilot can get to the power levers, why would they be able to get to the chop button, which is much smaller and also guarded? Wouldn't that be even harder to action?

[AlphaOneSix]

Because their hand is already on the collective, which is where the CHOP button is.

[bradmick]

AlphaOneSix wins.

[Dangerzone]

I thought it's called the CHOP button because if a student presses it, they risk having some important part of their anatomy chopped off by their instructor. 

Edited February 22, 2024 by Dangerzone