Why does apache roll so much?

[skypickle]

Put yourself on a steady heading and then raise collective quickly. I would expect a yaw to the right as the helicopter reacts to the increasing angular momentum of the rotor. Instead i see a roll to the right. And of course a roll to the left with a quick drop of the collective.

[BIGNEWY]

please include a short track replay example so we can see what is happening, you can save a track replay when you exit the mission.

ensure you have game flight and game avionics unticked in DCS settings 

[skypickle]

In the attached track, I start off  at Batumi and by the time I reach the sea I am trimmed out. Then look at the controls indicator and you will see ONLY the collective gets advanced but the Apache rolls to the right. I repeat this once. I also drop collective from a trimmed out path and the Apache rolls to the left.

ApacheRoll.trk

[skypickle]

If anything the apache should roll left when applying collective. Why? Because pulling collective the apache wants to yaw rightwards. If you give it left boot to counter this tendency, pressure from the tail rotor (which is below the main rotor) should force the lower half of the aircraft rightwards-giving a left roll.

 

correction: i got the above backwards 

Edited September 19, 2022 by skypickle

[Rogue Trooper]

The Apache tail rotor sits high on its tail fin.

The tail fin is connected to the tail boom, the tail boom sits low on the helicopter's centre of gravity because it has a tail wheel.

You will find no other chopper in the world (except the blackhawk) that has such a high tail rotor compared to its low tail boom configuration..... no one else does it like this. Only the Apache and Blackhawk and both have a massive tall tail fin in between the tail rotor and the tail boom.

This incredibly tall fin acts as a force times distance multiplier between the top of the tail (rotor) and the base of the tail fin (coupling to tail boom and helicopter total mass).  This is a rotational force acting in the roll and yaw axis. 

Just look at any profile of any chopper ever produced, and you will never see such a low installed tail boom with such a high tail and tail rotor.

I would expect a lot of roll in this girl when changing lift.

Edited September 17, 2022 by Rogue Trooper

[skypickle]

@BIGNEWYany news?

[skypickle]

On 9/16/2022 at 8:47 PM, Rogue Trooper said:

The Apache tail rotor sits high on its tail fin.

The tail fin is connected to the tail boom, the tail boom sits low on the helicopter's centre of gravity because it has a tail wheel.

You will find no other chopper in the world (except the blackhawk) that has such a high tail rotor compared to its low tail boom configuration..... no one else does it like this. Only the Apache and Blackhawk and both have a massive tall tail fin in between the tail rotor and the tail boom.

This incredibly tall fin acts as a force times distance multiplier between the top of the tail (rotor) and the base of the tail fin (coupling to tail boom and helicopter total mass).  This is a rotational force acting in the roll and yaw axis. 

Just look at any profile of any chopper ever produced, and you will never see such a low installed tail boom with such a high tail and tail rotor.

I would expect a lot of roll in this girl when changing lift.

 

Yes but only if you apply left boot to correct yaw when you pull collective. I understand that left boot pushes tail rotor to the right and the moment arm you are describing would give right roll. In my track i am ONLY pulling collective

[BIGNEWY]

1 hour ago, skypickle said:

@BIGNEWYany news?

Not yet, as soon as the team have made changes we will let you all know. 

thanks

[bradmick]

When you increase the collective, the heading hold attempts to maintain heading and will “apply pedal” as necessary to make this happen. I suspect this is what’s happening, the heading hold is putting in pedal to counteract the main rotor torque (which is what it’s supposed to do) and you’re getting the roll.

[Sacarino111]

Hi.

Couldn't it be the advancing blade "biting more air" and thus creating more lifting than the retreating blade ( if forward speed is hight, this phenomenon is important)?

Just a thought on it .

Saludos.

Saca111

[skypickle]

@Sacarino111The advancing blade is starboard so that would make it roll left.

@bradmickHeading hold is not activated in the track. If you mean the SCAS, that I dont know.

[bradmick]

Heading hold is always active when the the helicopter is off the weight on wheels switch.

[skypickle]

@bradmick now I'm a little confused. When I hear 'heading hold' I think 'autopilot'. Is this the SCAS? If heading hold is always active, do mean the flight computer making adjustments to my junk without my consent? I forget what it's called - an EDCU (https://militaryembedded.com/avionics/computers/us-army-helicopter-flight-computer-contract-won-by-triumph)

[Swift.]

10 minutes ago, skypickle said:

@bradmick now I'm a little confused. When I hear 'heading hold' I think 'autopilot'. Is this the SCAS? If heading hold is always active, do mean the flight computer making adjustments to my junk without my consent? I forget what it's called - an EDCU (https://militaryembedded.com/avionics/computers/us-army-helicopter-flight-computer-contract-won-by-triumph)

The 'heading hold' should disengage if the pedal displacement exceeds 3% from the trimmed position, so in effect it should be more of a 'dampens out torque changes and turbulence' than 'stops you from using the pedals'. But in DCS this disengagement number seems closer to 15-20% from trimmed. Which adds to this 'sticky yaw' feel that people experience.

[skypickle]

@Swift. Thank you much. clears up a lot of 'quirks' that I noticed while flying. Any chance I could fly w you as a number 2 in another bird as your trail?? You seem to have the knowledge and I think I could up my tactical game just watching you.

[Swift.]

13 minutes ago, skypickle said:

@Swift. Thank you much. clears up a lot of 'quirks' that I noticed while flying. Any chance I could fly w you as a number 2 in another bird as your trail?? You seem to have the knowledge and I think I could up my tactical game just watching you.

I'm just reading the ED manual

I'd love to fly with you, but I really just fly on our squadron servers nowadays. Maybe I'll see you applying one day

 

[bradmick]

So it’s not an autopilot in the traditional sense, but it works to maintain the heading of the aircraft that was set when the force trim was last interrupted. Additionally there are breakout values that allow you to initiate a pedal turn without interrupting the force trim. Within the 10% authority of the SAS, the heading will be maintained +/- 2 or so degrees when the collective is adjusted. I can pull all the away up to 100% from my hover torque and see an initial about 2 degree right shift and then the heading will return to the reference. It will also hold the heading during lateral hovers equally as well. Bottom line, this is all without direct pilot input on the pedals.

[Swift.]

20 minutes ago, bradmick said:

So it’s not an autopilot in the traditional sense, but it works to maintain the heading of the aircraft that was set when the force trim was last interrupted. Additionally there are breakout values that allow you to initiate a pedal turn without interrupting the force trim. Within the 10% authority of the SAS, the heading will be maintained +/- 2 or so degrees when the collective is adjusted. I can pull all the away up to 100% from my hover torque and see an initial about 2 degree right shift and then the heading will return to the reference. It will also hold the heading during lateral hovers equally as well. Bottom line, this is all without direct pilot input on the pedals.

Is the idea that the hold will prevent unintentional yaw (ie, changing collective, sliding left/right), but should in theory not impede pilot input noticeably? 

[Lurker]

13 hours ago, Swift. said:

But in DCS this disengagement number seems closer to 15-20% from trimmed. Which adds to this 'sticky yaw' feel that people experience.

I assume you are talking about pedal displacement. If this DCSism is true than that is a HUGE problem. I've experienced this in the Hind and have had to stop flying the helicopter with YAW AP on. Why is it like this?

Edited September 20, 2022 by Lurker

[bradmick]

14 hours ago, Swift. said:

Is the idea that the hold will prevent unintentional yaw (ie, changing collective, sliding left/right), but should in theory not impede pilot input noticeably? 

The entire SAS system is to provide a rock solidly stable firing platform. Since the aircraft was designed to operate in the hover to deploy its weapons, it makes sense to me that the heading hold would be designed specifically to hold a heading for you.

[Swift.]

8 hours ago, Lurker said:

I assume you are talking about pedal displacement. If this DCSism is true than that is a HUGE problem. I've experienced this in the Hind and have had to stop flying the helicopter with YAW AP on. Why is it like this?

 

It's fortunately only 'sticky' with the stock FM values. If you tweak them yourself you can get a experience much closer to that described in the manual. Which is to say, rock solid, responsive, a pleasure to fly.

[Swift.]

8 hours ago, bradmick said:

The entire SAS system is to provide a rock solidly stable firing platform. Since the aircraft was designed to operate in the hover to deploy its weapons, it makes sense to me that the heading hold would be designed specifically to hold a heading for you.

I agree, I'm just wondering whether the logic is to remove the pilots direct inputs ie to prevent the a foot spasm from jogging the yaw, or whether the logic is to dampen secondary inputs (ie bobbing up causing the nose to drift).

Both of those logics would 'provide a rock solidly stable firing platform' however one of them would fly like DCS: Sticky and sluggish. And the other would fly like DCS used to: responsive and nimble.

Edited September 20, 2022 by Swift.

[bradmick]

Well, the real aircraft never fights me when I apply pedal past the breakout. It responds my pedal input and recaptures the new heading just fine, the breakout values on the pedals expand as the airspeed increases to prevent over controlling I think is how it’s written. So it’s definitely responsive, my feet rest lightly on the pedals when not actively pushing them.  

[skypickle]

Todays update resolved this issue.!   Now applying collective only yaws to the right as expected 

[corbu1]

Installed today‘s OB patch and did a first flight.

I noticed some changes, too. 
Especially pedal behaviour changed was my impression. I think hold mode doesn‘t fight against pedal input as strong as bevor this new Patch. At least in hover with hold modes I noticed it.

Heading hold is more stable I think.

Hovering without hold mode I thought is easier and more stable as  less pedal input needed.

when rolling on the ground straight forward I had to apply right pedal. In previous versions I always had to apply some left pedal for rolling straight forward and tailwheel unlocked.

just a few first impressions. Will do some more testing the next days.

Edited September 21, 2022 by corbu1