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Cobra RPM doing whatever the hell it likes.

Lemonater47

Grizzled Veteran
Sep 25, 2014
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P1doUNv.jpg




Like Why is it doing that??? The RPM just drops significantly for no reason. Making flight impossible. No damage shown at all and Barely a shot fired at us from the ground.

If you bump into the ground the RPM improves for some reason as well.

Either way makes the helicopter unflyable.
 
I've also encountered this issue as well, I did a rocket run in on Hill 937 and on our banking turn the helo just started dropping (no lift to speak of). I was able to keep her level, we hit the ground and then the lift came back. It almost happened every single time I did a pass on that hill.
 
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This issue still happens a lot in the latest wave (6). There are spots outside of the edges of the map that make the altitude meter shoot up to 800+ meters for a second, causing your helicopter to lose thrust and crash.

Another issue is the one pointed out above, where after doing a maneuver/turn the helicopter loses thrust. If you manage to touch the ground and not crash on impact, the helicopter behaves normally again.
This doesn't happen as much when flying more carefully, so it probably has something to do with doing hard turns.
 
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There are 3 reasons you might lose rotor RPM and therefore lift.

1) You've flown off the edge of the map/there's no terrain collision under you - Some locations around the outskirts of maps appear to have terrain, but actually have no collision, so the helicopter thinks it's at unlimited altitude and tries to cap your lift to bring you back to a normal level, which makes you plummet rapidly until you move over something that does have collision. If you find these spots, please point them out to us for fixing.

2) If you've taken damage to your engine, your max rotor RPM will decrease and make it harder to stay airborne (similarly you will lose lift from hits to the rotor assembly which will also make it harder to keep in the air, but this is harder to visibly identify)

The main cause though, and the one that appears to be your issue in that screenshot (based on what I see on the screen and HUD):

3) You've raised the collective all the way and then rolled into a hard bank. What this does is first increase the rotor drag to maximum, which starts to slow the rotor straight away, then blasted the underside of the rotor with a heap of air. Initially it tries to speed the rotor up, but the sudden excess of lift causes you to bleed off speed rapidly, while the rotor drag stays high, so the rotor can't stay up to speed and the drag then causes it to slow rapidly. So now you've lost a chunk of rotor RPM, meaning your lift is already down. You've got the helo rolled onto one side, so the lift component is angled and only a small percentage is actually able to fight gravity. And lastly, you've just bled off all your speed, so you're no longer getting much (if any) Effective Translational Lift (ETL). i.e. You've rapidly gone from a high energy, high lift state, to a low energy, low lift state, and you sink like a stone.

At this point you probably try to fight it by holding the collective at max and pulling the nose up to try and point rotor straight up and maximise your lift vector, but that's the worst thing you can do once you've entered this state. Now you're making it as hard for your rotor as possible to build back up to speed and you're taking active steps to prevent any chance of getting translational lift back, and so you accelerate downwards, or at the very least you decelerate very slowly, nowhere near enough to avoid an impact.

The last mentioned point there is the way the RPM suddenly comes back when you hit the ground. That's because in an instant you've snuffed out all airflow up into the rotor, the drag has dropped by a huge margin and the rotor is able to rapidly regain RPM. In fact, if you're bounced, now there's air moving the other way through the rotor, further reducing drag and speeding up the rotor even more.

But enough of what people do wrong - here's how to avoid it:

When you bank, you should avoid using full collective as much as possible unless you're trying to prevent an imminent collision with something like a cliff, a tree or another helicopter, or you intentionally want to cause a rapid fall (i.e. because you're being lit up by a SAM). You want to maintain as much kinetic energy as possible and that means gentle, gliding turns, and careful collective control.

If you do stuff it up and find yourself in the above situation, the way to recover is actually quite counter-intuitive; Lower the collective to 50% or thereabouts (even less can work too) and tip the nose into the direction of travel to build up speed. As you increase speed, you'll start getting ETL back, which will slow your descent, and the lower collective will let your rotor pick up speed more rapidly. Once the RPM has come up a bit it will already have started to boost your lift back again, and then you can lift the nose and start to reapply collective, at which point you'll find you are able to pull up quite easily.

It's the same principle as performing an auto-rotation on engine failure.


As a last aside, you only get away with being able to pull these moves because I deliberately omitted two real-world effects that would kill you long before these things because a problem, on account of them being too unexpected and difficult for most gamers to deal with (as conditioned as we all are to video game physics). In reality, if you tried to pull either of the above manoeuvres, you'd be dead real quick, but we made some concessions to the fact that this is a game and not a full sim. :)

The first is rotor overspeed - if you try a hard bank at full collective in a real helicopter, you'll likely do some critical damage to the rotor assembly, if not rip it off entirely. That'd be 99% of our in-game pilots dead on their first attempt at turning, which isn't much fun.

The second is that if you yank on the collective while doing a rapid vertical descent, you would realistically enter a vortex ring state, where the RPM will climb back up but your descent will accelerate rapidly, as you descend through your own downwash and kill the effective angle of attack of the rotors by changing the direction of airflow.

But as I said, these were omitted as a concession to the fact that this is a game. The effects that are included are to make the realism level of the helicopters roughly equivalent to the realism level of the infantry, i.e. Somewhat realistic but not a full sim. :)

And on a vaguely related note, here's a pro-tip for everyone: When you're waiting for the helo engine to wind up at the helipad, leave the collective at 0% until the rotor RPM reaches the green bar on the dial. Any collective you apply will add drag and that will slow down the acceleration of the rotor during startup (you can see that if you apply full collective, the rotor needle starts to fall behind the engine needle on the gauge), so leaving the collective all the way down will get you airborne faster than impatiently holding the "Up" key. ;)
 
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PsYcH0_Ch!cKeN
Holy fu**. I never realized that the helicopters in RS2 are that complicated. Mainly because I don't expected it because other things you do as infantry are way more simplyfied. It seems a bit inconsistent. It's a bit like having simulator-like health mechanics in a Sims game while everything else is simple and easy to understand. Or do I overestimate the situation because of the huge wall of text? How do you guys want to deliver this to the players when the rest of the game is quite simple? With this level of detail things like shaking hands because you aimed the weapon too long totally should be a thing for example.
 
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Sorry I should have updated this.

We tested this and determined that it is engine damage. But it's not showing up on the HUD. 2 m1911 rounds to the engine will make the RPM go that low. The engine will also visibly spurt flames every now and again although not be completely on fire.

But it yeah something with the HUD is bugged. It fails to show the correct damage.


No manoeuvre I performed could get the RPM that low. The lowest I managed to get the rotor RPM was just below 3000 RPM. Which included things such as drops from 200m into a full collective recovery. But in that image its at 2600 rpm.
Then there's the engine RPM which I barely moved at all. Pretty much always sat on that red line. But in that image it's below the yellow. Below 6000 RPM. The engine RPM doesn't go that low unless the engine is damaged.


With an engine RPM of 5800 we found that it's almost impossible to get lift without a great deal of forward momentum. Your rotor RPM will never get high enough. You will hit the ground. If you survive the impact along with the helicopter surviving the maximum vertical takeoff speed you can get is about 0.5 metres per second. And that starts to decrease over 10m in altitude. Pitch forward to move somewhere and you can say goodbye to your altitude.


But yeah the main issue is the HUD not displaying damage all the time.
 
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nilsmoody;n2292388 said:
PsYcH0_Ch!cKeNother things you do as infantry are way more simplyfied. It seems a bit inconsistent.
Not at all. It fits right in with the level of simplification of the infantry. Our infantry combat sits somewhere in between Battlefield and ArmA on the realism scale - so our helicopters do too. More realistic than BF, less than ArmA. While there are a bunch of fancy effects modelled in, they are simple approximations rather than realistic simulations and as I mentioned in my earlier post, we opted not to include some of the more complicated and scary ones. And even with the ones we do have, for the majority of players (who will be using the Simplified Flight Model) these are reduced even further, or not calculated at all in some cases.

Basically, for most players, if you don't know this stuff then you can get by just fine without it - many testers have done over the last few months. But if you do understand the systems involved, you can push the limits of the helicopters a lot further and be a better pilot as a result.


Lemonater, you could be right about the damage stuff. I'll look into it.
 
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Ok, an update: The RPM problem is a bug caused by an accidental inversion of the damage vs RPM scaling. The RPM loss you're experiencing is meant to be when the engine is critically damaged and about to pack it in entirely, but instead it's applying at 1 damage, and then as you take more damage, the RPM improves again.

An easy fix once I realised what was happening. :)
 
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