Helicopters in AA

[Gimpster 0]

To clear up some misinformation that seem to be growing legs:

To describe helicopter physics correctly you need to think of it as a weight suspended under a lift disk and not a weight riding embedded in some inverted thrust cone.

Helicopters fly because of the lift generated at the surface of their rotor blades. Downwash is a side effect of helicopter lift, not the cause of it.

Hillslam,

You are correct in that the lift is generated by the rotor plane not the downwash.  I was mearly using that description to help people visulise a concept.  In reality it is a weight suspended below a spinning disk.  That spinning disk is not flat though.  Rotor blades are a little flexable and will under load develop a slight upward curve towards the ends and the resulting lifting plane becomes slightly bowl shaped.  This combined with the suspeneded weight makes the helicopter a fairly stable platform when ballanced and in stable air.  But a helicopter is never perfectly ballanced or in stable air so constant small corrections are needed to maintain a stationary position.

Franze,

While a 5lb RC model helo may seem vastly removed from a full scale military helo, they both use the same mechanics and conform to the same laws of physics.  Flying the model is more diffacult as you do not have the benifit of your inner-ear's ability to tell you what the model helo is doing.  Models are also more affected by wind and because of the much larger power-weight ratio, they have exagerated rotor torque effects.  Which make a RC helo more manuerable and allows it to perform well beyond a full scale helos envelope.

3dom,

You took off turned 90 degrees to the right and took out a stationary BMP after flying less then 100 meters and used half your rockets.  I woud llike to see you engage a moving convoy of 5 trucks at least 1km away from where you took off, which are traveling down a not so straight road.  Then give then an hostile armed guard, perhaps a BMP or two and do it again.  Then I will be impressed.

[4 IN 1 0]

To clear up some

Franze,

While a 5lb RC model helo may seem vastly removed from a full scale military helo, they both use the same mechanics and conform to the same laws of physics.  Flying the model is more diffacult as you do not have the benifit of your inner-ear's ability to tell you what the model helo is doing.  Models are also more affected by wind and because of the much larger power-weight ratio, they have exagerated rotor torque effects.  Which make a RC helo more manuerable and allows it to perform well beyond a full scale helos envelope.

thats what i always want to tell ppl how differently between both, whenever someone talk how realistic it is for the BF chopper, and i dont want arma to become the same

[killaalf 0]

I agree OFP heli flight model was not perfect as you say no side slipping, no increased collective when pulling back etc., but it was a fairly good compromise between real and gameplay and there was a noticeable feel of mass and inertia when turning especially the heavy ones like the MI-17.

Increased collective is simulated quite well in OFP, I'd say, maybe you should dust it off and give it a spin :P I agree with the rest of your statement, though. It was the right mix.

Have any of you doubters seen Dslyecxi's track-ir video? Here's the thread, I think it shows some very nice flying, makes you wonder if it's really all bad, no?

[3dom 0]

3dom,

You took off turned 90 degrees to the right and took out a stationary BMP

shhh ppl wont buy the game because the choppers need tweaking lol.

[Gimpster 0]

BF2 did the best they could given the limitations of the physics engine they had to work with but the end result was somthing short of user friendly or realistic. The add-on makers for OFP such as BAS have proved that the basic pieces needed to make a moderatly realistic helicopter are there in the engine.

Armed Assault's basic physics for helocopters was not changed that much if what we have been told is correct, they say its been improved to some degree. I can only surmise that the current helo's handeling wierdness is a result of small errors bugs in their stats or design rather then a flaw or limitation in the physics engine.

[Journeyman 0]

Increased collective is simulated quite well in OFP, I'd say, maybe you should dust it off and give it a spin :P I agree with the rest of your statement, though. It was the right mix.

Yeah, I haven’t played OFP in a while but I can't remember choppers pulling up sharply when flying forwards at speed and then pulling back on the cyclic stick! This is what should happen IRL and is modelled quite well in FS 2004 & FSX! Also speed induced roll was not modelled in OFP where as you gain speed the rotors offer more lift on one side and less lift on the other forcing a correction on the cyclic stick. This effect also limits forward speed, as rotor stall would be the eventuality. In OFP choppers had a slightly ridiculous forward speed in general with no ill effect on the rotors. Modelling this sort of thing though is not what I would expect of a general military sim such as ArmA, but limiting forward speed would be a move forwards as I've already heard someone say that they can fly choppers at 300mph in ArmA already! Please BIS kill this sort of behaviour if nothing else!  

[Barely-injured 0]

It seems to me that alot of people are basing their judjment of the helicopters in ArmA on the fact that it is difficult to control and different from the way it was in OFP.

I cant see how those things are BAD, First of all Helicopters in real life ARE HARD TO CONTROL, as they are very Unstable and even a simple task such as hovring requires constant input from the pilot to counteract external effects on the chopper. As for the OFP controls well they were very simplified for example in real life there is no such a button that you press that make the chopper go up or down (( the way the Q and Z work in OFP )) you can only increase power to the engine which will cause the chopper to go up or decrease it to go down and at the desired engine level you pitch the chopper slightly down to go forward and again use engine controls to change speed. Moreover the flight models in OFP were almost the same for all chopperes (( so that a dual rotor KA-50 is no different from an Ah-1 )) the only chopperes that were nicely done were the Mi-17 and the KIOWA both were very enjoiable to fly.

I guess the point that I am trying to make here that has nothing to do with what I was talking about above is that I wish that someone who have ArmA AND have played some Serious Helicopter sims can give us his input as the rest of us cant really judge from the videos

[Gimpster 0]

I have been trying to do just that. From what I have experanced in ArmA the helicopters feel wrong, very different from the ones in EEAH/EECH, different from Longbow 2, different from the last version of OFP, and vastly different from the closest thing I have to a true simulator Realflight 2 & 3 (Profesional RC Sim used for Training).

In the current version of ArmA the reactions to cyclic input are very quickly translated to pitch and roll of the airframe as if it has no weight. It also does not attempt to right itslelf when the stick is re-centered. Now once the helo is tilted it kind of hangs there, slowly starting to move in the direction of the tilt. So the reaction to cyclic is too fast and its effect on movment is too slow.

It is also very easy to get the helos moving too fast for them to respond to normal input for manuvering, which is part of the issue. When moving about at 50-75 mph they fly very well if you have an extreamly light touch or the ability to reduce the controlers axis sensitivity which I do not. The problems start when the vehicle starts to react too quickly to input and you find yourself traveling at far too great of a speed.

I am also having alot of trouble effectivly controling the throttle/colevtive to a fine degree. The AH-6 for example will not leave the ground until I have advanced the trottle to 50% at which point it climbs to about 50ft-75ft. The reactions to throttle modulation seem very muddy and slow.

It is quite posible that my old joystick is just about at the end of its life and in need of replacement as some of the video I have seen shows that these helos can be flown with more control then my stick is able to. So until I rule the input device out i will have to take a back seat in this debate.

[frederf 0]

Does ArmA model ground effect for helos?

Does ArmA take into consideration that all helocopter blades bend (the rotor plane is actually a 'dish'? This is important for generating stability in hovered flight.

[GaX 0]

i just took this vid of the cobra ah-1z,the controls just take getting used to  , the choppers are still amazing but turning at high speed needs to be tweaked.

it's still easy to take out bmp's with ffars, like in this vid..

AH-1Z Video (13Mb rar)

p.s dont watch it full screen cos i reduced the resolution to cut down on file size..and have the sound turned on

OMG 3dom are you serious?

There is 1 bmp just in front of your take off and you shooted at that bmp something like 10 FFAR to take it out....and when you tried to turn and go back, you almost lost the control (at first turn)...lol

I think it's almost impossible to make SMOOTH fly especially to take out enemy during fly...

PLEASE ANYONE (WHO THINK TO BE A GOOD PILOT) UPLOAD SOME VIDEOS WITH CHOPPER USING ONLY FFAR AND MANUAL FIRE (AH1 SINGLE PLAYER MISSION)

I bet NOBODY here can end that mission with manual fire and a smooth flying...

WAITING FOR YOUR VIDEOS........

[franze 196]

@Red Kite

That's actually one of the major things that bugs me about FP's flight modeling. Flying an Mi-26 does feel sluggish, I'll give it that, but the little things start to annoy the heck out of me - when I start yawing around and having the whole damn thing tip forward and start gaining speed.

I will concede that it's fair for light helicopters and some medium helicopters.

@Gimpster

I'm sorry, but even though the principle remains the same from a lightweight RC sport heli to a 7 ton Apache Longbow, the practice is quite a bit different. The wind is the least of your worries in a real aircraft.

As for ArmA, that doesn't sound good, but again... FP wasn't perfect either.

I'm pessimistic about things getting done in regards to ArmA's flight model - it's not the center of attention, and I fear we'll be lacking some important avionic systems that were desperately needed.

[Gimpster 0]

They are quite different but the same principles apply to either despite the size differences. But we don't need to argue that point.

The AH64-D you produced for OFP was a dream to fly and was a great overal-all package. Do you have any plans to release the same birds for ArmA in the near future? At least then I would have a direct compairison between the two engines.

[Mr_Tea 0]

Maybe people should start to realise, that you can`t control a chopper with the digital inputs from an keyboard, ore with the mouse.

That is what analogue flight control systems are made for.

[franze 196]

The AH64-D you produced for OFP was a dream to fly and was a great overal-all package. Do you have any plans to release the same birds for ArmA in the near future? At least then I would have a direct compairison between the two engines.

We do plan to port it over to ArmA, but that hinges on when the right tools are available and how lengthy the conversion process is.

I don't expect we'll have any luck prior to spring '07.

[GaX 0]

Maybe people should start to realise, that you can`t control a chopper with the digital inputs from an keyboard, ore with the mouse.

That is what anlogue flight control systems are made for.

I tried with joystick/joypad too and i assure you that chopper isn't drivable smoothly to take out tanks manually...

Maybe u can show us how to fly properly MrTea.....

Oh....and give a look to this video....

It's a AH1 attack video....really funny....

At the end of the video, pilot clearly try to turn to take out 1 bmp (at least) but it fail cause chopper doesn't turn at that speed....

lol

[Guest RKSL-Rock]

Since alot of people are comparing OFP's lack of realism to the "improved" ArmA flight model I thought i drop in a quick explanation of how it worked.

The thing with OFP flight model and helicopters was that very few people understood how it actually worked.  So you got alot of addons that did unrealistic things, eg: helos doing 500kph etc.

Just like planes in OFP, helicopter handling is defined by mass and distribution.  Make the helo nose heavy and it will nose down just like a plane.  To make a nimble and fast helo you need to distribute the mass in the centre of the model under the main rotor with the CofG high up.  This gives:

- A high 'roll' rate

- High Yaw rate.

To make a heavy handling monster.  distribute the mass more evenly around the model.  Drop the CofG lower and it will be more stable in normal flight but it will "flick" around in dives and high angles of attack.  But you will have:

- Low roll rate

- Slower yaw rate.

Now for speed!  Unlike planes, where in OFP, a high mass means slower/longer take of runs and a slower acceleration.  In helo's more mass mean more speed! eg:

Take a BIS Mi-17. (These are example figures and not accurate)  By default the mass is 2000kg and goes 260kph max.

To make the helicopter faster you need to beef up the mass - give it 5000kg and it will go 500kph.

Slower make it 1000kg and it will only go 120kph.

Unlike the planes that seem to have a negative inertia.  Helicopters have a positive inertia.  So the rule is:

The more weight the higher the speed.

Now returning to ArmA, and assuming that it uses a similar system to OFP it shouldn’t be too hard to tweak the handling of the helos to “correct†the handling to “our own†requirements.  

Lets face it guys this really is a very early release.  Its just like OFP:CWC its going to have its problems.  Just like OFP there will be improvement over time.  We’ll have to live with it until BIS can either patch it or someone comes up with a tutorial for aircraft handling!

[Mr_Tea 0]

@GaX

Try the MS Flightsimulator 2004 with 100% realism settings, than you`ll se how a chopper react on engine torque, wind and weather. It`s out there for a few € or buck`s.

When i fly, i take my Saitek X52 to contol the aircraft or heli i`m flying.

How to fly properly must be learned.

In about one week i`ll get Arma. When all goes well i can record a flight with my "good old" VHS system. I don`t want fraps to slow down my system, when i record a video.

[Scrub 0]

Any dual-corer know if fraps is on the opposite core of ArmA (affinity), does it still slow the system down?

[max power 21]

A few things regarding aerodynamics..

At its most basic level a helicopter is a weight suspended from a rotating disk that is the source of a diverging cone of air. The spreading of the downwash acts to stabilize the rotor in level flight and hover and the fuselage acts as a counter weight to resist input to the rotors and acts as a damper against the inputs. This is why the heaver the helo the slower and smoother its motions are.

I think that that's more a property of mass ie. Inertia.

In a helicopter you fly the rotors not the fuselage. Applying left stick causes the cyclic to increase the pitch of the right side of the rotor path and lower the pitch of the left side of the rotor path. This increases the lift on the right and decreases the lift on the left causing the helo to fall to the left as the divergent cone of lift shifts to the right and off center of the center of gravity.

No, I don't think so. Due to gyroscopic precession, control inputs on the swashplate have to be made at 90 degrees from the desired control input. ie. Inducing forward pitch requires an increase in lift on the port side of the helicopter.

At this point if you center the stick and restore the cone of lift under the center of mass relative axis of lift, the helo will stop increasing the angle banking and slowly start to right itself as the weight of the fuselage seeks to find its balance point under the center of the source of lift, so long as you have banked so far as to move the center of mass outside the divergent cone of lift.

I think you'll find that with any wing, including rotating ones, the amount of lift is only relevent when it is countering the forces of gravity. As the helicopter banks, it begins to lift on an angle, and the amount of lift available to keep the helicopter aloft decreases with the square of the angle of the amount of bank. This also goes for pitch. A stabilizing effect might be found in the dihedral produced by the angle of some rotor blades.

Regarding this 'cone of lift' idea you seem to have... Lift is generated by a differential between the pressure on either side of the rotor. The movement of air is a biproduct of the lift effect. Lift is actually done by generating a low pressure area above wings or rotors. Lift is a sucking action, not a blowing action. Downwash may serve to stabilize a helicopter, but since the angel of lift is always perpendicular to the angle of the rotor disk, I think this is highly unlikely.

In short, helicopters may be more stable than many people believe, but I'm not sure it's for the reasons you're citing here.

Quote[/b] ]

Hovering 10 ft above the ocean and 10 ft above a 3000' mountain top should require about the same power setting.

I'm not sure that's true. There is a lot of difference between the engine and rotor performance at sealevel and the performance of the same at altitude. For instance, the maximum hover-in-ground-effect altitude for an Ah-64 apache is 4845 m. The maximum hover-out-of-ground-effect altitude is 3866 m. The ground effect only subtracts 1000m in altitude related loss of air density for that particular aircraft.

[Gimpster 0]

plaintiff1,

You are right on all those points and at the time I just could not find the right teminoligy to describe the concepts I wanted to convey. It was not my intention to mislead or misrepresent the concepts.

Now I took the oppertunity to reaquaint myself with flying RC helo's in my training sim. The new version has improved physics and I now understand some on my previous assumptions are indead wrong.

I now see only a few small issues:

1) Helo's in ArmA can accelerate like a bat out of hell but take a long time to slow down. Acceleration and deceleration shoud be the same in any direction because the exact same mechinism is used in doing so.

2) Translational lift does not appear to be modeled which might be the cause of the odd accell/decell traits.

3) Throttle/Collective inputs have little effect on altitude or speed and there seems to be some sort of auto throttle modulation designed to maintain speed. I noticed this in the ground vehicles and the two fixed wing aircraft as well. This leads me to believe the throttle is just a relitive speed or in the case of the helos, relitive altitude selector.

4) There are two different sets of contols for rotating the tail. One is called Pedel and only workes as very slow speeds and will never induce roll. The other is Turning which will cause yaw below 50 and will cause roll over 100.

My crapy joystick was also adding somewhat to the twitchy contol I was experancing prior to this.

So basicly the lack of tranlational lift, not having direct control of the throttle/colective and a inconsistant or confused tail rotor control solution combined with severly hampered ability at speed combine to really throw off the helo flight model. It should really be its own model and have its own contol config seperate from fixed wing.

[Journeyman 0]

@Gimpster can you not test your joystick function in the game controllers dialogue box? Click properties and you will see if it is malfunctioning or not by the movement of the cursor.

As for needing a joystick to fly helis in a game this is cobblers MrTea! It is possible to use a keyboard and it is certainly very easy with a mouse esp. a trackball mouse like I have got! I can fly helis (in max realism) in FS 2004/FSX with any input device! It is just easier and more intuitive with a joystick! I used to fly helis in OFP with my trackball mouse all the time; it saved my grabbing my joystick each time I jumped into a chopper!

Thanks for the inside info on how chopper flight dynamics are modelled in OFP RockofSL! This kinda makes sense now that I know this, as there was some peculiar heli flight behaviour occasionally in OFP!  

[feersum.endjinn 6]

My pet peeve with OFP flight model has always been that collective doesn't seem to have much effect at all. Real helicopters can slow down a lot faster from full speed with pulling stick all the way up and pushing collective forward, only way to do that in OFP is to yank nose all the way up and spin around copter on a spot to kill speed. It's almost impossible to do fast spec ops type landings (watch Black Hawk Down to see what I mean ) in narrow spaces since killing off speed requires a lot of space in OFP.

Transitional lift would be one of those nice things to have but tail rotor effectiveness variations during transition from hover to full speed are better left out since most people don't have pedals installed (I always left it disabled in EECH, the rudder on Saitek X45 sucks).

[T J 0]

well well well..........

During part of the dev process on the BAS helo's, blackhawks and lilbirds, I spent many many hours flying them, and could get them to perform admirably and under full control. (yeh ok, the models were great and a credit to Wayne and DM, beautifully balanced etc)

Maybe, just maybe its those hours of conditioning to old OFP that have affected me, but I hate hate HATE the new flight model. I fly with keyboard and mouse btw. But to me it seems that the helo's are flying along a rail, like an underslung rollercoaster. And the worse part is that the rail seems determined to lead down to the ground after any attempt at a fast turn.

Last night we played MP "CTI", and time after time the hawk ended up slewing into the ground. It seems almost impossible to correct the loss of lift once it sets in, and down she goes.

Obviously there has to be a lot of compromise in an arcade simulation like arma, but surely, and hopefully, those compromises would enable the game to run on the easier side, rather than make it more difficult?

Perhaps we could do with one of those vote polls setting up about the new flight models?

TJ - UK

[GaX 0]

Maybe, just maybe its those hours of conditioning to old OFP that have affected me, but I hate hate HATE the new flight model. I fly with keyboard and mouse btw. But to me it seems that the helo's are flying along a rail, like an underslung rollercoaster. And the worse part is that the rail seems determined to lead down to the ground after any attempt at a fast turn.

Last night we played MP "CTI", and time after time the hawk ended up slewing into the ground. It seems almost impossible to correct the loss of lift once it sets in, and down she goes.

Obviously there has to be a lot of compromise in an arcade simulation like arma, but surely, and hopefully, those compromises would enable the game to run on the easier side, rather than make it more difficult?

Perhaps we could do with one of those vote polls setting up about the new flight models?

TJ - UK

I totally agree...

Anyway i think the flying model is bugged...

It's impossible that an heli can't turn on his vertical axis when flying over 50-60 MPH

[Pierrot 0]

Maybe people should start to realise, that you can`t control a chopper with the digital inputs from an keyboard, ore with the mouse.

That is what analogue flight control systems are made for.

Agreed. So it would be wonderful if there were veteran mode in which people need joystics to control chopper properly in ArmA.

*Still we need caded mode because none of all us have joystics.