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Flight dynamics (important issues)


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nightsta1ker
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#1

Posted 30 October 2011 - 07:25

These are the real issues plauging the flight model IMO. I am stealing the first part of this from my other post.

My impression so far is as follows:

Light and medium helos. In expert mode, with everything mapped except throttle, I feel like the helicopter wants to float. Full down collective and the helicopter settles at a very very reduced rate from the real thing. Lowering the collective in a real helo gives you a descent rate of 1500-2000 FPM. I am getting maybe 500 FPM in TOH. Also, the stability dynamics seem backwards. By this I mean that, a helicopter fuselage dangles from the rotor system, which is supporting it as it is the part that is actually flying. So imagine holding a pendulum from your hand. As you move your hand, the pendulum responds, this is the kind of motion that should be depicted in a hover. It seems opposite to me, more like trying to balance a pencil on your hand. It wants to fall over, whereas a pendulum wants to dangle directly below you and is trying to find its equilibrium. When you tilt the rotor disk in a helicopter in a hover, you slide in that direction, not roll over, because the airframe wants to stay DOWN. In order to roll the helicopter over, you need a pivot point, like a skid touching the ground, or a rock or a grass patch. It needs to GRAB something in order to give it that rolling moment. You cant just roll the heli over by applying lateral cyclic in the hover, you will just take off in whatever direction you pointed the cyclic until you correct it, or hit something. Not to say it WOULDN'T roll over if you completely rediculously overcontrolled the thing. But it doesn't inherrently WANT to do that.

How to fix it: Increase the descent rate to 2000 FPM with full down collective. Reduce the "ground effect" present in the game. It's totally overdone. The medium helo feels better about this than the light helo. I would recommend you make the light helo feel a little bit heavier. Reduce the rolling moment with cyclic input. Cyclic input should give the helicopter a directional movement over the surface without wanting to flip it over. Basically, stabilize the body of the helicopter a bit. The rotorsystem is tilting, not the airframe (at least, not as much, there is still some banking, etc, but it's way overdone here).

Regarding the throttle.... I have a full helicopter control set with a twist grip throttle on the collective. Is there any way you could assign an analogue setting for those of us that have the hardware to simulate a roll on/off throttle? This also may be helpful to people who have a HOTAS joystick. Being able to control the throttle is key to starting, shutting down, simulating power failures and dealing with things like governor failures (manually controlling the throttle setting for a given pitch setting). This would definitely make the pilot types happy.

Dyssemetry of lift: Modeled on the wrong side of the helicopter. The helicopter seems to have a tendency to roll right, and when I deliberately got over VNE to test retreating blade stall, the helicopter did what it was supposed to, except in the wrong direction.

How to fix it: Get rid of the rolling tendency in forward flight. Real helicopter rotor systems have the ability to flap which nulls the rolling moment. Basically, the dyssimetry is there, but the pilot can't tell because the rotor system is doing the fixing on it's own. Retreating blade stall happens when the dyssimetry of lift becomes too great for the flapping hinge to overcome, THEN you get the rolling/pitch up tendency, but it will roll to the LEFT on counter-clockwise turning rotor systems. So get rid of the rolling tendency below VNE, and then, when VNE is exceeded, have the helicopter roll to the LEFT.

Torque effect: Not present? Very limited? I can't tell because the slip ball does not seem to work. In any case, I get almost no feeling of torque in a hover on Expert settings. No left pedal required.

How to fix it: As torque is applied to the rotor system, the helicopter wants to yaw in the opposite direction of the blades rotation. In counter clockwise turning rotor systems, it wants to yaw right, so the pilot needs to add left pedal. I am not seeing this in game, although I saw it in the Community Preview. Keep in mind that as forward airspeed increases, less left pedal is required due to a combination of increased tail rotor efficiency as well as the vertical stabilizer becoming effective.

That's all I currently noticed.

Edited by nightsta1ker, 30 October 2011 - 07:27.


MD500Enthusiast
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#2

Posted 30 October 2011 - 08:23

agreed to OP, but you forgot the stupidly annoying overly exaggerated ground effect. the ground effect ballooning of the helicopter is still there but it's not as bad as before, i don't think they understand when we tell them it's a cushion of air when we're IGE and that it requires LESS collective/blade pitch to hold a steady hover. i do agree that there is a ballooning effect in helicopter flight during hovering but it's not caused by ground effect. this is the only reason that i have encountered the ballooning effect. say if we do a left pedal turn and do not add more collective which means more power is transferred to the tail rotor to rotate the helicopter and there's less power available for the main rotor so we slowly descend, and when we see that descend we add more power but add too much and now we're gaining altitude and we just keep chasing the collective up and down. same thing for right pedal turns and not decreasing collective because we're using less power on the tail rotor so the main rotor has more power so we raise up a little bit and forget to lower collective, then we lower the collective when we realize we're ascending and we lower too much and we drop down again etc. however none of that is a big springing effect that bounces the helicopter back up 20ft when we're coming to IGE while descending down to the ground. how it should look like is we're descending and maybe 25ft above ground and we slowly increase collective to arrest the descend, as we're coming near the ground but still descending we stop adding collective at around 10ft or so and let the helicopter settling itself into IGE and that extra cushion of air will arrest our descend and we come into a hover. what it does NOT do is bounce us back up into the air unless we've added too much collective in the descending process which would result in us flying straight and level instead. it's not so bad when we're landing into solid ground but when you're trying to land on top of a building it gets ridiculous and totally throws you off your approach. i've landing on top of a building before in real life and there's no bouncing up when you get close to the top of the roof.

Edited by MD500Enthusiast, 30 October 2011 - 08:35.


Speed_NYC
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#3

Posted 30 October 2011 - 08:32

Totally agree. I hope BI listens to OP.

hon0
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#4

Posted 30 October 2011 - 11:05

It's really cool to read real Life pilot feedback. Keep giving us your impressions guys :bounce3:

gonk
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#5

Posted 30 October 2011 - 11:42

I guess we need some Flight Data to compare this Sim against... That is usually very exe.... Run a few FAA/EASA test.;)
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AS350
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#6

Posted 30 October 2011 - 12:08

also totally agree +1
thanks for these very very great feedbacks:bounce3::jump_clap:
it should be help BIS or some modders to improve the FM a lot :)

4 IN 1
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#7

Posted 30 October 2011 - 12:47

Yeah, the ludricously over exaggerated Ground effect is by far the most annoying thing.

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Bothersome
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#8

Posted 30 October 2011 - 15:49

Things that I know from flying real RC helicopters...

1. Ground cushion goes at least as high as 1 rotor diameter.
2. 2 Degree down pitch (full down collective)is not much when you are wanting to loose altitude. 2 degrees is best for keeping the head speed up for auto rotation landings.
3. There is no rolling right or left when increasing or decreasing collective.
4. In an auto rotation landing (no power and thus no torque from then engine) when you apply up collective to flair, you don't get torque from the engine that needs countering.
5. Retreating blade stall can cause a boom strike.
6. The Chaos and Piro-Flip are the hardest stunts to do. Uhh, maybe that doesn't apply here. :)

scarp
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#9

Posted 30 October 2011 - 15:57

Yes, you really have to fight/work your way through the GE for sure, as OP said, should be more of a cushoning effect, not ballooning effect that is currently the case.

4 IN 1
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#10

Posted 30 October 2011 - 15:58

6. The Chaos and Piro-Flip are the hardest stunts to do. Uhh, maybe that doesn't apply here. :)


Well given enough AGL you can do it in the game as well:p(if the main rotor or the tail did not break off:o)

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nightsta1ker
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#11

Posted 30 October 2011 - 16:31

agreed to OP, but you forgot the stupidly annoying overly exaggerated ground effect. the ground effect ballooning of the helicopter is still there but it's not as bad as before, i don't think they understand when we tell them it's a cushion of air when we're IGE and that it requires LESS collective/blade pitch to hold a steady hover. i do agree that there is a ballooning effect in helicopter flight during hovering but it's not caused by ground effect. this is the only reason that i have encountered the ballooning effect. say if we do a left pedal turn and do not add more collective which means more power is transferred to the tail rotor to rotate the helicopter and there's less power available for the main rotor so we slowly descend, and when we see that descend we add more power but add too much and now we're gaining altitude and we just keep chasing the collective up and down. same thing for right pedal turns and not decreasing collective because we're using less power on the tail rotor so the main rotor has more power so we raise up a little bit and forget to lower collective, then we lower the collective when we realize we're ascending and we lower too much and we drop down again etc. however none of that is a big springing effect that bounces the helicopter back up 20ft when we're coming to IGE while descending down to the ground. how it should look like is we're descending and maybe 25ft above ground and we slowly increase collective to arrest the descend, as we're coming near the ground but still descending we stop adding collective at around 10ft or so and let the helicopter settling itself into IGE and that extra cushion of air will arrest our descend and we come into a hover. what it does NOT do is bounce us back up into the air unless we've added too much collective in the descending process which would result in us flying straight and level instead. it's not so bad when we're landing into solid ground but when you're trying to land on top of a building it gets ridiculous and totally throws you off your approach. i've landing on top of a building before in real life and there's no bouncing up when you get close to the top of the roof.


Actually, I DID mention the ground effect, I just did not go into as much detail as you did. The reason being, you had already covered it in another forum thread :D. Read my second paragraph again.

Regarding the torque effects on the tail rotor and the tail rotor on available power, I agree with you that this is not modeled properly, however, I this is a very difficult thing to model (not even Flight Simulator can model it properly, although somehow the Dodo team managed it with some external plug ins) and I don't expect to see that working fully in this game (it is after all, a game, not a simulator), though it WOULD be nice to see. I am trying to focus mainly on the blatantly OBVIOUS things that are annoyingly wrong. Things that contradict their claim of "realistic" flight dynamics.

Yes, it's a game, we know that. But if you claim "realistic" flight dynamics, the program needs to live up to that. I don't expect perfection here, but some of this stuff is very very backwards.

There are many great flying videos on Youtube, including some that I have done. Here's my channel: http://www.youtube.c...r1?feature=mhee Watch control movements and how the helicopter responds in some of these and compare it to the game. You can see the obvious differences.

Bothersome
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#12

Posted 30 October 2011 - 17:37

Dyssemetry of lift: Modeled on the wrong side of the helicopter. The helicopter seems to have a tendency to roll right, and when I deliberately got over VNE to test retreating blade stall, the helicopter did what it was supposed to, except in the wrong direction.

How to fix it: Get rid of the rolling tendency in forward flight. Real helicopter rotor systems have the ability to flap which nulls the rolling moment. Basically, the dyssimetry is there, but the pilot can't tell because the rotor system is doing the fixing on it's own. Retreating blade stall happens when the dyssimetry of lift becomes too great for the flapping hinge to overcome, THEN you get the rolling/pitch up tendency, but it will roll to the LEFT on counter-clockwise turning rotor systems. So get rid of the rolling tendency below VNE, and then, when VNE is exceeded, have the helicopter roll to the LEFT.

One thing to note here. Real helicopter pilots aren't likely to get in the air and try to test this on a real helicopter. It is a very dangerous thing to test. But when you lose lift because of blade stall on the left side of the rotor disk, the disk doesn't fall on the left. It will fall on the back (90 degree precession thing). Then as the rotor blades come around on the right they are starting to flop back up and have greater attack on the air on the right side. This causes an excess lift on the right but the effect is a rise on the rotor disk in the front. Thus making the situation even worse. The roll to the left comes in when then body of the helicopter is resisting the pitch up effect of the rotor disk. This downward strain on the blades at front cause the disk to rotate down on the left and up stress on the back causes the disk to rotate up on the right. This is left roll you feel. So basically, you get a drastic up and left roll effect and usually serious damage to your rotors blades.

This would be a very UGLY situation to be in.

Edited by Bothersome, 30 October 2011 - 17:41.


nightsta1ker
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#13

Posted 30 October 2011 - 19:01

One thing to note here. Real helicopter pilots aren't likely to get in the air and try to test this on a real helicopter. It is a very dangerous thing to test. But when you lose lift because of blade stall on the left side of the rotor disk, the disk doesn't fall on the left. It will fall on the back (90 degree precession thing). Then as the rotor blades come around on the right they are starting to flop back up and have greater attack on the air on the right side. This causes an excess lift on the right but the effect is a rise on the rotor disk in the front. Thus making the situation even worse. The roll to the left comes in when then body of the helicopter is resisting the pitch up effect of the rotor disk. This downward strain on the blades at front cause the disk to rotate down on the left and up stress on the back causes the disk to rotate up on the right. This is left roll you feel. So basically, you get a drastic up and left roll effect and usually serious damage to your rotors blades.

This would be a very UGLY situation to be in.


It's not that bad... and on some helicopters it's really difficult to get into. Where it becomes dangerous in situations where you are low to the ground, high density altitude, etc where it's hard to recover. The thing about retreating blade stall is, it's self correcting, when the nose pitches up, the helicopter slows down and it recovers itself. There have not been many incedences where this has caused a crash that I am aware of. One such incident happened to a Finnish military MD 500 Defender that was doing high speed NOE training and had the blades stall in a left bank. They rolled right into the ground. Often times, the helicopter does not even have enough power to get going that fast in the first place. You would see it at high density altitudes, where the rotors are less efficient and the blade stall happens at lower airspeeds, like mountain flying, and in descents with high forward airspeed. Also, there is usually a warning first, the helicopter sill start to oscillate on the edge. You really have to be accellerating THROUGH that barrier at a rapid rate to get into full blown RBS.

nightsta1ker
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#14

Posted 31 October 2011 - 01:28

More issues: With a new graphics card that runs everything well so poor hardware performance is no longer an excuse.

First off, everything mentioned before this still applies. I just wanted to tack on some other things I find really irritating and unrealistic.

Pedal turns... What the hell is up with the pedals? They don't want to work! Even with null zone gone and full sensitivity I kick the pedal all the way over and the helicopter slowly, lacadazically turns in whatever direction... Pedals on helicopers are sensitive. You kick that pedal (or fail to kick it in some cases) and you are going to be watching the world spin around you in a blur. The pedals need to be more sensitive. Alot more.

Man they REALLY want to roll over. That stability thing I talked about needs to get fixed pronto.

Control lag. Yes, there is still a control lag. Perhaps those of you not accustomed to flying helos, or even simulators for that matter, don't notice this, but there is a half second lag between my control inputs and the response. This would be a little more realistic in the heavy helicopter, but not the light or even much in the medium.

There is also a weird relationship between the pedal and the cyclic. I cannot quite put my finger on what is going on because it is unpredictable, but when I move the pedals, the helicopter wants to roll and pitch around a bit. Very strange and not lifelike at all. Also, there seems to be a need for left pedal at higher airspeeds... this is backwards from reality. More pedal is needed in a hover, less is needed as the aircraft accelerates.

Also, thought I should note, the jump between trainee and expert is pointless. The helicopter is exponentially harder to fly, but not because it is "more realistic" It's just harder. Nothing that changes from trainee to expert is something that you would see or feel in a real helicopter. I am sure with some time, I could get used to the quirks and learn to fly it, but it's not comparable to a real helo. Too many behaviors are not present, backwards, or otherwise modeled incorrectly. I can see some of this behavior and can recognize what BIS was trying to do, but they misunderstood something critical and got it wrong.

I know this is going to sound rude, and for that I apologize, but in my opinion it's the truth. BIS needs to fix these behavioral issues or they need to take this out of their advertisement of the game: "Authentic Flight Model - Incredibly realistic piloting experience." You failed to deliver.

Now with that said, if there is anything I or any of us real pilots can do to HELP you deliver, please please feel free to pick our brains. We WANT this game to be successful.

Edited by nightsta1ker, 31 October 2011 - 01:46.


Daimaju
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#15

Posted 31 October 2011 - 02:13

nightsta1ker really seem to know about this stuff, I just hope BIS will listen and fix the issues...

Edited by Daimaju, 31 October 2011 - 02:16.

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Panther353
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#16

Posted 31 October 2011 - 02:25

Yes, he does. However I know at least on other real pilot that is not seeing what he is so we need to figure out what is different.

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#17

Posted 31 October 2011 - 02:28

I find the medium to be the worst flyier of the 3. The damn right roll is crazy when you add collective.

roy86
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#18

Posted 31 October 2011 - 02:38

nightsta1ker really seem to know about this stuff, I just hope BIS will listen and fix the issues...


Agreed, there is a lot of greatly detailed feedback here which would improve the game above any competition.

I'd recommend that these issues should be logged here TOH Community Issue Tracker

That way these are trackable.

nightsta1ker
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#19

Posted 31 October 2011 - 05:47

Yes, he does. However I know at least on other real pilot that is not seeing what he is so we need to figure out what is different.


Chris, it could be something as simple as where we downloaded the game from? Are you using Steam or Sprocket?

Also, what settings do you have? Perhaps I missed something in the setup. I have all my controls configured, with no null zones and medium sensitivity (full sensitivity makes it uncontrollable due to the control lag I am experiencing) with my difficulty on Expert. Are there any other settings that affect the realism?

I'm sorry but I am just absolutely not getting a realistic sensation of helicopter flight from this game. Some of what I am experiencing is just plain WRONG. Backwards, or incorrect, or just plain weird. I would really like to get to the bottom of it. It seems some people are really happy with the game overall, but all of the pilots I have heard from so far are very displeased with the flight characteristics... except you and your friend of course.

Another thing it could be is my controls... they are extremely sensitive. My cyclic alone has 400 increments across its x and y axis (twice to three times what you see on a normal joystick). This makes it great for simming, but maybe not so great for TOH? I will try flying around with my Logitech next time and see if it changes anything for me, but I doubt it will. Controls are controls.... they work just fine in X-plane and FSX. Why wouldn't they work in TOH? I will try it anyway just to see.

Edited by nightsta1ker, 31 October 2011 - 05:52.


MD500Enthusiast
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#20

Posted 31 October 2011 - 05:52

actually i disagree about medium helicopter to be the worse, i think it's the easiest one to fly. it actually descends some what near what a real helicopter would descend like if the throttle was full down. you can see over torquing on the helicopter and it starts to shake and rattle constatly until the point where it stops flying all together if you're not easy on the controls and just throw the helo around i.e using lots of rudder to assist in high speed turns adds a lot of stress on your tail rotor and transmission or raising the collective from idle to full power really fast.