see roadmap Apache AH-64D Flight Model and further Development Status in 2024?

[metzger]

Yea.. pretty decent. Especially in yaw control :D

And Boeing designed a helicopter which with perfectly balanced loadout and no wind flies sideways and you have to look at the FPM through the side window. Or maybe this is a safety feature to confuse the enemy

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[bradmick]

10 hours ago, metzger said:

Yea.. pretty decent. Especially in yaw control

And Boeing designed a helicopter which with perfectly balanced loadout and no wind flies sideways and you have to look at the FPM through the side window. Or maybe this is a safety feature to confuse the enemy

Sent from my SM-G985F using Tapatalk
 

No, they didn’t. It’s a trait of *all* helicopters to fly crabbed even in no winds, it’s to do with the interaction of main rotor torque on the fuselage and the tail rotor anti torque. There’s also a rolling moment imparted on the helicopter as a result of tail rotor thrust as well that has to be countered with opposing cyclic. 
 

Anyway, all of this is known and has been discussed ad nauseam. Throwing zingers that are flat out wrong doesn’t help anything because Boeing designed one heck of a stable helicopter.

Edited December 9, 2024 by bradmick

[metzger]

No, they didn’t. It’s a trait of *all* helicopters to fly crabbed even in no winds, it’s to do with the interaction of main rotor torque on the fuselage and the tail rotor anti torque. There’s also a rolling moment imparted on the helicopter as a result of tail rotor thrust as well that has to be countered with opposing cyclic. 
 
Anyway, all of this is known and has been discussed ad nauseam. Throwing zingers that are flat out wrong doesn’t help anything because Boeing designed one heck of a stable helicopter.

Ok that means the rest of DCS helicopters are wrong because in no wind conditions nose/tail and aerodynamic trim in balanced level flight is matching very close in any of them.

I am very sure Boeing designed a rock solid and very responsive aircraft that doesn't crab like this.

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[Tholozor]

The tail rotor/crabbing is already a known WIP issue:

 

[LorenLuke]

6 hours ago, metzger said:

Ok that means the rest of DCS helicopters are wrong because in no wind conditions nose/tail and aerodynamic trim in balanced level flight is matching very close in any of them.

Well, let's look at the other helos for a moment. The Ka-50 is counter rotating, so nothing there. The Hind has a canted rotor, so its lift vector is tilted a few degrees sideways to offset crabbing. The Gazelle and Kiowa are so light, the output for the engines isn't the same as trying to lift a 10 ton helo, and conversely the gearboxing isn't going to turn the tailrotor into a sideways hurricane. And the Mi-8 and Huey don't have flight path markers, so could you really tell anyway? 

6 hours ago, metzger said:

I am very sure Boeing designed a rock solid and very responsive aircraft that doesn't crab like this.

The AH-64 instructor Pilot you're quoting here is also sure of this. The crabbing issues are known and have been mentioned by him and others countless times before that the Apache has about two and a half more sideways movement than it should. Doesn't mean the rest of the flight model is unstable or otherwise garbage.

[metzger]

The AH-64 instructor Pilot you're quoting here is also sure of this. The crabbing issues are known and have been mentioned by him and others countless times before that the Apache has about two and a half more sideways movement than it should. Doesn't mean the rest of the flight model is unstable or otherwise garbage.

I never said garbage nor that it isn't known.

The Apache flight model at the current state has a major issue with the tail rotor, which affects it in multiple ways, not just crabbing.



The guy before me said the flight model is decent.
But with that flaw, I personally just don't find it decent. It's annoying all the time because the crabbing alone is in your face during the whole mission, and you constantly have to fight the tail rotor.

Will it be fixed ? Probably. When ? Who knows.

It also makes lining up rocket shots more difficult than it should be.



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[admiki]

19 hours ago, bradmick said:

No, they didn’t. It’s a trait of *all* helicopters to fly crabbed even in no winds, it’s to do with the interaction of main rotor torque on the fuselage and the tail rotor anti torque. There’s also a rolling moment imparted on the helicopter as a result of tail rotor thrust as well that has to be countered with opposing cyclic. 
 

Anyway, all of this is known and has been discussed ad nauseam. Throwing zingers that are flat out wrong doesn’t help anything because Boeing designed one heck of a stable helicopter.

I'm quite sure he meant it as a dig at ED and this long  standing issue, not the Apache itself.

[mason.zh]

On 12/9/2024 at 1:45 AM, metzger said:

Yea.. pretty decent. Especially in yaw control

I can feel the pain. I think the Apache flies pretty well overall, except for the yaw control, which is caused by excessive main rotor torque. This issue has been brought up repeatedly for quite some time, but no fix has been implemented.

I'm not sure if this excessive main rotor torque issue also contributes to the erratic behavior of the yaw SAS servo at low speeds sometimes, but it's been two years since the Apache was released. It's disappointing that such a significant issue has been left unresolved for so long.

(I know this thread is about Apache, but it took ED 6 years to update the flight model and FCS in F18C, which was released in 2018... )

[ouky1991]

On 12/14/2024 at 5:17 AM, mason.zh said:

I can feel the pain. I think the Apache flies pretty well overall, except for the yaw control, which is caused by excessive main rotor torque. This issue has been brought up repeatedly for quite some time, but no fix has been implemented.

I'm not sure if this excessive main rotor torque issue also contributes to the erratic behavior of the yaw SAS servo at low speeds sometimes, but it's been two years since the Apache was released. It's disappointing that such a significant issue has been left unresolved for so long.

(I know this thread is about Apache, but it took ED 6 years to update the flight model and FCS in F18C, which was released in 2018... )

I don't think it's gonna take that long, but yea, it's not that fun to fly with the current model. It's got to be one of the hardest parts of every module to tune this. Change one value and it breaks some other thing kinda deal. Hopefully they'll fix this soon, the Apache is almost perfect otherwise.

[lee1hy]

i like  this flight model patch it is stable in many ways.
no more fight SCAS no more jumping  yaw/roll when taxing at low speeds

[Poptart]

The hold modes feel a lot better with the latest update. Didn't really notice the other changes too much.

[GrEaSeLiTeNiN]

Just a quick check - FCR TPM mode isn't implemented yet right?

[corbu1]

vor 5 Stunden schrieb GrEaSeLiTeNiN:

Just a quick check - FCR TPM mode isn't implemented yet right?

No, not implemented yet. According to DCS road map it will come after early access.

[placsea]

Things I noticed after a quick 20  min flight.

• Low speed handling in all axes improved,  much less twitchy especially yaw
• Att hold low and high speeds still borked
• Really does not like to be dived at speed now, couldnt pitch the nose down more than 15 degrees at 100kts without it going nuts
• Still crabs the same amount in trimmed flight

Overall, better than it was.

[SloppyDog]

Here are somethings I've noticed after a long test flight:

• Low speed handling is much better. No more tail whipping like crazy when inputting collective. As you slowly input collective, it will cause the normal torque reactions you would expect from a helicopter, but not crazy oscillations as before;
• Other collective/tail rotor related thing I noticed is that at high speeds, I could change altitude by "slowly" inputting collective without the tail whipping around or crazy oscillations. In more than one occasion I could input collective hands free of the cyclic.
• Att Hold: sometimes it tends to accelerate or decelerate, but I learned that I need do counter it by trimming at the desired speed and leaving it there. 
• Alt Hold, on the other hand, is not holding that much. I get a SAS saturated warning, the altitude starts changing, and then right after I get a Altitude Drift warning. Maybe it is my controls, looking at the cockpit cyclic is is trembling up and down. I know my controls are old and use potentiometers, maybe this is causing this oscillations.
• Crabbing: it does crabs, but not a lot like before. It tends to compensate for the wind where there is wind, but where there is no cross wind, it seems to be flying much more straight now.
• Position HOLD: seems to be working fine, tested it with some crosswind and stayed in position. Further tests are needed.
  • From the changelog:
  • Helicopter SCAS - known issues
  • When turning ON or OFF the Position-Hold  mode, several damped oscillations in roll and/or pitch may occur
• The oscillations do occur. It is annoying at first. What I learned to avoid them is to keep the cyclic at the position I want and not move it. Let the oscillations resolve themselves. Although, the helicopter tends to pitch up. I have to input a lot of forward cyclic to counter it, when accelerating from zero speed. Maybe it is related to my curves setting on the controls. I'm using 100% saturation and a 25 curvature. Will test later without the curvature.
• Ground taxiing: much better. Just push the cyclic forward a bit, set the collective to 30% and here you go. When unlocking the tail wheel, it still tends to snake around, doing S-turns, but it is much less noticeable now.
• Curves: cyclic curves on my controls were at 60% saturation, on the X and Y axis. Since the controls sensitivity where reduced, I cloud, actually, I needed to get them back to 100 % saturation. It shows how much the response to pilot input has been improved.
•  Overall, a much better experience, no more crazy reactions when inputting a small amount of control, be it cyclic, collective and pedals. All in all, if you behave when inputting controls, the aircraft will behave as well. This didn't happen before.
• Attached is the track from the long flight test.

 

 

Apache Flight Test- Post December 24th Patch.trk

Edited December 25, 2024 by SloppyDog

[Cyborg71]

Level flight 100kts. Entering a dive causes a hard left roll as speed increases. 

Normal behaviour or wip? I dont recall this prior to patch.

Otherwise the Apache feels more stable. Less twitchy.

[admiki]

At what speed?

Are you entering RBS?

[Floyd1212]

59 minutes ago, Cyborg71 said:

Entering a dive causes a hard left roll as speed increases.

This has been a characteristic of the FM forever. Sounds like this latest update didn’t address that issue. 

[Cyborg71]

1 hour ago, admiki said:

At what speed?

Are you entering RBS?

120 kts maybe? I will repeat a few times if exact numbers are required. 

Embarrass me now and tell me what RBS is other than something caused by too much turkey?

51 minutes ago, Floyd1212 said:

This has been a characteristic of the FM forever. Sounds like this latest update didn’t address that issue. 

I'm not surprised. I recall this being a problem way back in development. I hadn't noticed it for a while. 

[SloppyDog]

21 minutes ago, Cyborg71 said:

120 kts maybe? I will repeat a few times if exact numbers are required. 

Embarrass me now and tell me what RBS is other than something caused by too much turkey?

I'm not surprised. I recall this being a problem way back in development. I hadn't noticed it for a while. 

Too much turkey... I could think of one or two jokes about it... Too much turkey and a helo, you'd get AirWolf.

Anyway, RBS is Retreating Blade Stall.

When a helicopter starts to moving too fast, one side of the rotor disk will have more lift than the other. In the case of American helos where the rotor turns counterclowise, the right side of the rotor will have much more lift than the left side. This goes up to the point that the left side stalls and loses lift.

As the helicopter has a lot of lift on the right side, and no lift on the left side, the tendency then is to helicopter to roll to the left. 

But here is the catch: due to the gyroscopic effect, any command, controlled or not, in any part of the disk, will manifest itself with a delay of 90º. 

As the lift increases on the right side, the effect is felt 90º later , meaning it will add lift to the front of the rotor disk.

This excess lift at the front will make the helicopter pitch up. 

Combined with the loss of lift on the left side, the helicopter will pitch up and roll left.

What I believe others are experience is that in a dive, the Apache is exceeding the Never Exceed Speed (Vne) for that situation (heavy, with fuel and weapons load).Thus, when diving, the speeds increases and the retreating blade stall reaches its limit, the helicopter rolls left.

Maybe the effect is very pronounced in the DCS Apache, I will have to test it later.

Here are some videos that help understand dissimmetry of lift and retreating blade stall:

 

 

 

[Cyborg71]

11 minutes ago, SloppyDog said:

 

Thank you for the detailed reply. Very much appreciated.

I wish I could blame my inability to decipher the RBS acronym on booze.......or turkey.

Your explanation does make perfect sense of what's happening. Strange that it does not happen during a nose down "return to target" pedal turn. Accelerating downhill through 120 knts There's no discernible harsh left roll or pitch up. Accepting the fact that I demanding nose up pitch rather than pushing over. As you described the push is probably causing the roll.

Lots of complicated things occurring.

Iraqi map runway quick start. So the weights etc are constant.

Best wishes.

[SloppyDog]

25 minutes ago, Cyborg71 said:

Lots of complicated things occurring.

This single phrase defines helicopter aerodynamics perfectly.

Can you provide a track? I would like to see the kind of maneuvers you are doing.

Anyway, as ED stated, the SCAS is a WIP. Maybe for some cases it is happening, maybe not. And we must have in mind that DCS physics are not perfect and a lot of times it does not follow expected real life behavior.  

[Cyborg71]

14 minutes ago, SloppyDog said:

This single phrase defines helicopter aerodynamics perfectly.

Can you provide a track? I would like to see the kind of maneuvers you are doing.

Anyway, as ED stated, the SCAS is a WIP. Maybe for some cases it is happening, maybe not. And we must have in mind that DCS physics are not perfect and a lot of times it does not follow expected real life behavior.  

I've completed further tests. I believe your assessment is correct. Its definitely Regurgitating Bird Syndrome. (LoL)

Seriously now though, what I am seeing is the blade stall you describe, occurring as a consequence of nose down commands at speed. The rate of roll seems directly proportional to the vigour applied to nose down pitch.

Not a bug (didn't think it was) just a little shocking.

Cheers

[admiki]

Nope. If anything, nose down would unload rotor and decrease angle of attack of the blades.

I'll admit that I haven't tested it with Apache, but only helicopter that show RBS in DCS is Mi-24.

IIRC, Apache has some crazy high RBS speed.

[Floyd1212]

This is the discussion I was referring to from July 2022. I don’t think this behavior has ever been addressed.