Advanced Helicopter FDM Feedback

[quickvenge 10]

In todays dev.branch update we will add first implementation of Vortex Ring State. It is now in the code and reads new values from XML config. The first two helicopters configured now are Mohawk and Hummingbird/Pawnee/M-900.

It doesn't feel right. It's cool that it is there, but other than watching the instruments there is nothing telling you that you are in that state. It needs some vibrations, and some audio cue from the rotors. The cut line is very predictable for the Mohawk at least, will it be different for other helicopters, and dependent on load? I didn't try sling loading it.

Can you please fix the rotor torque loading, before you even consider VRS. Aggressive maneuvering, and energy management is really hard with the current behavior on the cyclic on rotor torque. Aft cyclic, and G-loading should reduce rotor torque and increase rotor RPM for a given collective setting.

Today you can basically descend with 200KMH speed, pull up, and hit a low rpm condition and crash into the ground. The behavior should have been an increase in RPM, some mushing, and then be able to translate that back into a climb without touching the collective. In actuality to prevent a rotor overspeed, I probably would have been increasing collective. Then dumped collective as I pushed the cyclic back forward.

[twisted 128]

Wow!

vortex ring state certainly dancing banana worthy.

nice surprise.

[armored_sheep 56]

Can you please fix the rotor torque loading, before you even consider VRS. Aggressive maneuvering, and energy management is really hard with the current behavior on the cyclic on rotor torque. Aft cyclic, and G-loading should reduce rotor torque and increase rotor RPM for a given collective setting.

Why do you think that stress on rotor should reduce always if you pitch up (cyclic imput) during fast descent? RPM on main rotor can rise only when collective pitch is low. IMHO same like with auto-rotation...

---------- Post added at 08:39 ---------- Previous post was at 08:37 ----------

It's cool that it is there, but other than watching the instruments there is nothing telling you that you are in that state. It needs some vibrations, and some audio cue from the rotors.

RTD does also simulate the vibrations with VRS, but this feature is not yet fully implemented / visualised in Arma.

[RuecanOnRails 10]

Last couple updates (VRS) the xH-9 seems to have no weight at all.

The slightest increase in collective and the helicopter jumps off the ground. Flying upside down is not only possible, it's easy and stable with little altitude loss. Lowering altitude for a landing and bleeding off speed is difficult due to being too "floaty" and able to climb with zero collective with low angles. Helicopter flight feels closer to fixed wing than rotorcraft with current amount of lift generated from speed. I'm not a pilot and have no real world experience, for all I know everything is behaving exactly as it should.

I will also mention that I too suffer from a lack of engine on/off control mapping option. I have controls for all other newly added functions, from wheel breaks to slight loading but nothing for engine. It's not an issue for myself, as the only need for it I have is auto-rotations, pressing space twice works well enough.

During flight, with max wind, rain/storms, the flight is still rather stable. Would it be possible to see a sort of random air temperature/density map layer generated at the start of map loading to cause random, but somewhat persistent pockets of turbulence? Something to make long cross map trips require more than trim and forget. Using some sort of data layer would allow a seamless multiplayer experience where flying in formation has the same effect on all players, not semi random wind gusts seen only by individuals. If there is already something like this in place, perhaps make its effect on helicopter flight much more prominent?

[CaptainAzimuth 714]

Last couple updates (VRS) the xH-9 seems to have no weight at all.

The slightest increase in collective and the helicopter jumps off the ground. Flying upside down is not only possible, it's easy and stable with little altitude loss. Lowering altitude for a landing and bleeding off speed is difficult due to being too "floaty" and able to climb with zero collective with low angles. Helicopter flight feels closer to fixed wing than rotorcraft with current amount of lift generated from speed. I'm not a pilot and have no real world experience, for all I know everything is behaving exactly as it should.

I will also mention that I too suffer from a lack of engine on/off control mapping option. I have controls for all other newly added functions, from wheel breaks to slight loading but nothing for engine. It's not an issue for myself, as the only need for it I have is auto-rotations, pressing space twice works well enough.

During flight, with max wind, rain/storms, the flight is still rather stable. Would it be possible to see a sort of random air temperature/density map layer generated at the start of map loading to cause random, but somewhat persistent pockets of turbulence? Something to make long cross map trips require more than trim and forget. Using some sort of data layer would allow a seamless multiplayer experience where flying in formation has the same effect on all players, not semi random wind gusts seen only by individuals. If there is already something like this in place, perhaps make its effect on helicopter flight much more prominent?

Well, the only time I experienced jumping off the ground, is when I put the Cyclic straight up after the engine was fully ready. Besides that, never tried flying upside down...

[armored_sheep 56]

Last couple updates (VRS) the xH-9 seems to have no weight at all.

Right. The new RTD libraries / code with VRS changed all helicopters performance. Most noticeable is the vertical speed performance (helicopters inserted flying now do climb instead of steady hover). We are still evaluating the code and it is not sure if VRS will be in the DLC release at the start. It may be postponed to some later patch.

[quickvenge 10]

Why do you think that stress on rotor should reduce always if you pitch up (cyclic imput) during fast descent? RPM on main rotor can rise only when collective pitch is low. IMHO same like with auto-rotation...

It has to do with rotor coning.

Taken from the FAA document: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch02.pdf. Page 2-15.

"The rotor blade rotating about the rotor hub possesses angular momentum. As the rotor begins to cone due to G-loading maneuvers, the diameter or the rotor disk shrinks. Due to conservation of angular momentum, the blades continue to travel the same speed even though the blade tips have a shorter distance to travel due to reduced disk diameter. The action results in an increase in rotor rpm which causes a slight increase in lift. Most pilots arrest this increase of rpm with an increase in collective pitch. This increase in blade rpm lift is somewhat negated by the slightly smaller disk area as the blades cone upward."

The first page of basic flight manuvers of helicopters from the FAA also mention inputs and their effect on torque loading. Read page 9-2.

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch09.pdf

"• Left turns, torque increases (more antitorque). This applies to most helicopters, but not all.

• Right turns, torque decreases (less antitorque). This applies to most helicopters, but not all.

• Application of aft cyclic, torque decreases and rotor speed increases.

• Application of forward cyclic (especially when immediately following aft cyclic application), torque increases and rotor speed decreases."

This applies to counter clockwise helicopters for left right cyclic movement.

Edited October 17, 2014 by quickvenge
Added snippet of cyclic input.

[aggressorblue 2]

Right. The new RTD libraries / code with VRS changed all helicopters performance. Most noticeable is the vertical speed performance (helicopters inserted flying now do climb instead of steady hover). We are still evaluating the code and it is not sure if VRS will be in the DLC release at the start. It may be postponed to some later patch.

This sounds like a very fair proposition. Would it be possible to make the VRS enabled flight models available (if they're also stripped from the dev branch) to users who want to continue experimenting with this post launch?

[Brisse 78]

I'm sure it would be easier for everyone if they just reenabled it on devbranch the day after stable release, if it were to be removed at some point. Argh, whatever... I'm sure the devs know what to do!

[gatordev 219]

Why do you think that stress on rotor should reduce always if you pitch up (cyclic imput) during fast descent? RPM on main rotor can rise only when collective pitch is low. IMHO same like with auto-rotation...

I have a feeling we've stumbled upon why many of us are giving feedback with limited results... As quickvenge has quoted from a publication, what you have described in the above quote is not correct. This is why myself, b00ce, quickvenge, et al keep harping on this. And I don't say this as an internet nerd, but as someone who has done this in real life for a career.

Collective pitch isn't the only factor for Nr when you factor in induced velocity (blades in an autorotative state...either because of autorotation, quick stop, or pitch up maneuver). The result may be more dramatic in certain conditions compared to others, but regardless of collective setting or helicopter, when you pitch up, Nr is going to increase. Maybe not a lot at times, sometimes A LOT, but it's still happening. The engines can't govern high Nr, only low Nr.

[tinter 186]

Is the implementation for retreating blade stall final(RBS)?

I'm asking this a bit cautiously as I'm not sure this is right.

At the moment, RBS seems like a rare encounter, I can only recall it happening when diving at high speeds but I haven't tested it recently and I might even be wrong on that.

From my understanding the speed limit of helicopters should not be how much the engine can push it, but rather in the area of velocity never exceeded, where going faster would result in RBS.

I can fly the ghosthawk at a speed of 360kph and sustain forward flight just fine. Pulling a turn didn't do anything either.

Is RBS perhaps not even implemented? It was in TKOH.

http://helicopters.takeonthegame.com/technology-checklist/

I'd be glad to hear other people's thoughts on this or info on RBS.

[b00ce 160]

The BIS devs need to read chapter 1 of FM 3-04.203 before doing anything else with the RTD.

[quickvenge 10]

It's hard to simulate a helicopter. As gatordev pointed it's simply not conning that causes RPM to increase as well. As you pitchup the rotors do enter an auto-rotation state also. So its a combination of both coning, and TAF that causes the RPM to increase. DCS does a good job, but you had an entire development team tuning one helicopter module that you pay for. BIS has RTD which they pay for and are trying to model a bunch of helicopters. So it probably will never get to the fidelity of DCS, and X-plane helicopters.

Looking from where they stated BIS devs have done a descent job for a good chunk of the flight envelope particularly for the xH-9 family. Are there issue? sure, ETL still not strong enough in my opinion, left and right cyclic inputs don't actually behave properly on torque, but I really don't care at this point. They can improve those if they choose in the long run. Where I do care is when the correct control input results in catastrophic failure or causing me to crash. That is why I have been harping on behavior of aft and forward cyclic input. The behavior is wrong, and it is getting me killed in game. It's fine if I never do aggressive maneuvering, but this is also military sim. I'm getting shot at, and it's really hard to trade altitude for energy given the current behavior.

I like flying in arma because of the really fine detail in the terrain. No other sim gives you that, and in a helicopter you can hug the earth and fly slow to enjoy that detail. Something DCS, and x-plane can't match today. I love following a road at high speed, below treetop level trying not to hit power lines and trees.

[b00ce 160]

^ Agreed ^

The thing with RTD is that the physics are engine level and each vehicle has only the performance properties like torque, RPM, blade properties, stabilizers etc. If they get the physics right in the engine, the helicopters should fall in line (In theory, provided they are config'd properly).

On a semi-related note; I'm curious how the blade, fuselage and wing/stabilizer lift and drag coefficients are supposed to work and be calculated...

[vicx 10]

The thing with RTD is that the physics are engine level and each vehicle has only the performance properties like torque, RPM, blade properties, stabilizers etc. If they get the physics right in the engine, the helicopters should fall in line (In theory, provided they are config'd properly).

Dynamic systems are never simple. You build a model via trial and error OR lots of math and then trial and error. Anyway they make games so they are probably used to this sort of thing.

So I just tested the latest dev branch FDM out after a two week break and I found it improved and I like the new sound effects.

Testing Version 1.35.127815 (Last version I tested was 1.31.127352)

Helicopter Flight Model: Advanced

Show Gauges: Enabled

Rough Landing: Enabled

Wind Effects: Enabled

Auto-Trim: Disabled

Stress Damage: Enabled

Inputs

Saitek X55 HOTAS Throttle and Stick

Razer Lachesis Mouse

Razer Keyboard

The HOTAS seems a more enjoyable way to control the helis compared to last time. Maybe they have done something here. Controlling the collective using a throttle feels good. I was able to make the controller customisation curve more flat. The cyclic control using the stick felt more direct without being too twitchy.

Now to the individual choppers.

• It's hard not to like the Blackfoot. It is the most predictable and safe of all the choppers and it is armed to the teeth. There are no downsides; it is like an automatic that beats all the stick shifts. I would prefer that the Blackfoot was not such a safe experience.
  
• The chopper that should have the nimble and safe characteristics is probably the ORCA but as it is the ORCA feels the more performance oriented and edgy of the two. Some players will try and fly the Orca aggressively and they will die because it is easy to fly the ORCA like a genius, until you fly straight into the ground. I like the Orca but I crash in it a lot.
  
• The Ghosthawk feels really good to fly but it was also pretty fussy when it came to landing. Sometimes it wanted to roll over after I'd touched down more less perfectly. It tips over in slow motion, drives a blade into the ground and then explodes into the air.If Bohemia could make another way to wreck a chopper that might be cool I'd love to see a blade strike create a cloud of smoke, dust and debris. Then when the smoke cleared the injured chopper crew could be lying prone next to the wreck and inventory from the chopper (medkits) could be scattered nearby. That would be cool.
  
• The xH-9 choppers are fun to fly. Although sometimes you do a hard turn and end up flopping across the sky; it doesn't kill you but looks quite silly. You can land the xH-9 choppers harder than any other (a feature). People will like them. I like them.
  
• The Mohawk feels like a big ass chopper and you can make good landings only if you are patient. I just don't think people who fly the Mohawk now are going to like the new Mohawk. If the other big chopper is really good, who will want to use the Mohawk?
  
• Hellcat feels more raw compared to other helis - like it has a bit of Huey in it. Just like the xH-9s you can land it hard. I like it, but I should fly it some more.
  
• The Kajman is good but I think it needs to be damned good. I like the yaw and the way it side slips but it feels underpowered for a heli with two rotors.
  

---

Now some comments on the HUDS that are in the Blackfoot and Hellcat.

• These HUDS are awesome for flying, not just for combat
  
• The green line velocity vector is really useful. I want that on every HUD.
  
• I think all the choppers should have a HUD available because the HUD can be made superior to using on-screen dials or looking down at the instrument panel.
  
• As good as the HUD is now it can also be better.
  
• the Green line could span across more of the screen.
  
• the HUD design could be made easier to read at a glance and offer slightly more information. Here I will reference the a modified Ka-50 HUD that a someone posted on DCS forum that improves nicely the original KA-50 HUD.https://www.digitalcombatsimulator.com/upload/iblock/a69/Screen_140722_130931.jpg Bank angles, pitch angles, and two sets of climb rates are shown (low scale on left, larger scale on right) That low scale is crucial for avoiding stall. I also prefer the larger digit size which is more readable.
  
• A nav mode could be built into the HUD. Waypoints.
  Some suggestions for the Opofor HUDS
  
• Give them the Green Line feature
  
• Replace the reticule shape with something more simple. The best shape would be one that resembles the nose of the chopper you are in. It is a handy mimetic.
  
• Put the pitch indicator digits down the sides instead of in the middle where it is hard to read.
  What should be in a 21st century helmet hud?
  

[armored_sheep 56]

Quote Originally Posted by RuecanOnRails View Post

Last couple updates (VRS) the xH-9 seems to have no weight at all.

After some investigation we found the issue - added weight of the helicopter is realy not calculated, so you are flying always with just empty weight. It will be hopefully fixed soon.

[armored_sheep 56]

In today's update you should have all helicopters with VRS set (just except Huron). The weight simulation is repaired. You also get camera shake inside cockpit on VRS entry.

[jcae2798 132]

Was hoping the DLC issue would be fixed but sounds like its steam related.....Oh well...

[tinter 186]

I don't know if it's okay to ask this here, as it is a question generally related to helicopters, but no the flight model specifically.

I'm wondering if it'd be possible to allow the co-pilot to have more control over stuff like gear and gear brakes. It would make the co-pilot more useful for organized players.

[blackpixxel 53]

I don't know if it's okay to ask this here, as it is a question generally related to helicopters, but no the flight model specifically.

I'm wondering if it'd be possible to allow the co-pilot to have more control over stuff like gear and gear brakes. It would make the co-pilot more useful for organized players.

The idea itself is awesome, but there aren't that many organized Arma-players. I think it will become a trolling feature in multiplayer (copilots turn engines of, waste all flares etc.)

But it would be cool to have a mod doing this, because it could enhance the gameplay, especially in critical situations where the pilot has to concentrate on flying (tail rotor loss, under fire, ect.)

[St. Jimmy 272]

I don't know if it's okay to ask this here, as it is a question generally related to helicopters, but no the flight model specifically.

I'm wondering if it'd be possible to allow the co-pilot to have more control over stuff like gear and gear brakes. It would make the co-pilot more useful for organized players.

Would be cool thing to happen. I wouldn't dump that idea because of some trollers. There are already many way to troll other players.

[tinter 186]

A thing actually relating to helicopter flight models. I've noticed getting into VRS a lot and trying to recover, normally increasing collective feeds the vortex and in real life when you want to recover you actually lower it. Ingame this "feeding the vortex" behaviour is missing. So if you're in VRS you do not want to lower collective unless it is somehow at max.

[the_demongod 31]

Would be cool thing to happen. I wouldn't dump that idea because of some trollers. There are already many way to troll other players.

"Trolling" really isn't even a valid excuse for this game. You can troll somebody by simply shooting them, so allowing things like this certainly should've cause problems.

[roshnak 41]

This does not seem like a useful addition to me, or at least not something worth spending development resources on. There aren't currently any actions in the game that can't be managed by the pilot during even the most hectic situations. If there was some sort of sensor package for the copilot to operate, that would makes sense.

Allow the copilot to take command of the aircraft in case of an emergency? Sure. Let the copilot fiddle with buttons while the pilot is flying? Seems pretty pointless.

[b00ce 160]

The idea itself is awesome, but there aren't that many organized Arma-players. I think it will become a trolling feature in multiplayer (copilots turn engines of, waste all flares etc.)

But it would be cool to have a mod doing this, because it could enhance the gameplay, especially in critical situations where the pilot has to concentrate on flying (tail rotor loss, under fire, ect.)

None of that should be an issue, you should be able to recognize and react to a griefer turning your engines off with no issue. Co-pilot pops all your flares cause he's a tard then don't fly over the AO with a known missile threat, use masking and terrain flight to get you from A to B. Granted, landing gear being retracted at the last second would be a tough pill to swallow; but at the end of the day, ArmA is just a game. I think BIS should allow the Co-pilot to have more control over things and/or allow the Pilot to deny the Co-pilot's "button privileges". 1. Its realistic and 2. it allows for more cooperative play.

Don't disallow things because people may abuse them, people will abuse everything. If not retracting your landing gear on approach, it'll be shooting your engines out from the ground.