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Autorotation


MrNelz

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I'm really struggling to get this thing to autorotate, seems I keep loosing hydraulics and therefore controllability.

Test conditions

Alt: 1500-1800 ft agl

IAS: 70-80 Kts 

Pull power levers to idle, lower collective and raise nose to maintain 103-105% NR

Even at this nominal NR I seem to lose control response almost as if the hyd pumps are connected to the engines rather than the front of the MGB.

Any of the SMEs want to chime in here and give some tips?

@kgillers3@Raptor9

 

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1 hour ago, MrNelz said:

I'm really struggling to get this thing to autorotate, seems I keep loosing hydraulics and therefore controllability.

Test conditions

Alt: 1500-1800 ft agl

IAS: 70-80 Kts 

Pull power levers to idle, lower collective and raise nose to maintain 103-105% NR

Even at this nominal NR I seem to lose control response almost as if the hyd pumps are connected to the engines rather than the front of the MGB.

Any of the SMEs want to chime in here and give some tips?

@kgillers3@Raptor9

 

I don’t believe you’re losing hydraulics if you’re maintaining your rotor, which honestly is better than what I can at that percent and the apaches flight profile is wip.  So I’ll post a couple tracks in a minute but I need to test something before, it’s rough to auto rn but it’s doable. 

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@MrNelz So first off I apologize I didn't turn on the control indicator until I was halfway started.  So it seems it's better now than it used to be.  In this clip I want you to see how much nose authority I have with full down collective.  At the decel > initial look at how the nose jumps up when I pull collective.  While in autorotative state in dcs 64 your directional control is greatly reduced especially with the collective full down

The second track is the same thing, same starting scenario roughly maybe a little different entry, but the main difference is the lack of weapons and fuel.  Almost all the way through the auto I was full aft cyclic and the aircraft would not nose up any more, When  I tried to flare at the bottom I wasn't able to flare enough to trade airspeed for rotor because the rotor was already decayed so low.  I also tried with man stab in the full up position and it was a barely noticeable change. 

If you're light it's pretty much impossible to maintain rotor at a descent level, just due to NR decay being high already (which has already been reported).  However it seems a lot better since the update but that might be a placebo too idk. If you're loaded you'll fall faster but you'll have an easier time maintaining rotor.  If I recall the first version of the apache you had to have a little collective input regardless of what your rotor % is to maintain directional control, and I thought the UH-1 was the same, but I just tried it and it worked. So maybe I'm miss remembering. 

I find if I make a cyclic input in game and the aircraft doesn't do what I want to do I decide if I have enough rotor to lead with a little collective for that movement.  

Long and short is you may have to trade a little rotor by pulling a little collective to get your nose authority back, in game there's a very quick point of no return. I'm sure it'll continue to improve. I think the loss of control is how they simulated the aerodynamics which is heavy WIP and not hydraulic related. But that is a very large guess.  

I hope you find this helpful. 

Noseauthoritywithnocollective.trk Noseauthoritywithnocollective(empty).trk


Edited by kgillers3
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13 minutes ago, kgillers3 said:

@MrNelz So first off I apologize I didn't turn on the control indicator until I was halfway started.  So it seems it's better now than it used to be. ......... (empty).trk 430.54 kB · 0 downloads

 

@kgillers3That's awesome thanks for popping in the time to have a look at this. So at the moment at minimum pitch this is exactly what happens to me I just run out out of cyclic pitch authority first and roll gets really sloppy even though NR is maintained above 100%, eventually this decays into an approx 90 degree nose down unrecoverable attitude. The aircraft remains stable in roll but with no control authority in that axis at all. I'll try again with a bit of pitch added to see if I can maintain some control authority. At present I'd be snagging the MF700 as "rogue aircraft in autoration phase" 😆

The reason I thought hyds was the decay in control authority with more inputs felt like when you're using up the accumulator pressure in a total loss of hyds, each control movement resulting in less authority until accumulator pressure is too low to power the MRAs.

Good to hear that this is WIP and NR decay is being worked on, obviously I don't want to keep the NR too high as strap packs are a pain to replace! 

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During steady state AR : Rate of descend -- 3300ft/min @77kts -- is way too high. Rpm droop @77kts with collective full down should not happen.

Cyclic and Yaw controls are insufficient during AR.

Straight-ins are possible, but very rough.

180s or 360s (especially to the right) are impossible.

And this is only in regard of autorotations... This is the worst early access flight model ED has ever delivered. They shouldn't have made the Apache available in this very early state of its FM. A lot more time in the oven is necessary. I guess the pressure to put it into early access was too high.

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To practice it - Start at 1,000 ft, “Emergency occurs”, lower collective and pitch down 10 degrees. Counteract the weird roll with right pedal and back/right cyclic. Lower power levers to idle. Now adjust cyclic as necessary to maintain a pitch angle to achieve 100kns. When you hit 250ft, pitch up and add a tiny bit of collective. Then add some more collective as necessary to continue arresting descent, maintain slight pitch up. Tail strikes first, then roll and brake.

 

I’m sure this can be done lower than 1,000 ft. The rotor expends a lot of energy very quickly when adding collective back in. Biggest thing is to pitch down when you lower collective 

https://youtu.be/fOsnba4-Hv8

1 hour ago, iFoxRomeo said:

During steady state AR : Rate of descend -- 3300ft/min @77kts -- is way too high. Rpm droop @77kts with collective full down should not happen.

Cyclic and Yaw controls are insufficient during AR.

Straight-ins are possible, but very rough.

180s or 360s (especially to the right) are impossible.

And this is only in regard of autorotations... This is the worst early access flight model ED has ever delivered. They shouldn't have made the Apache available in this very early state of its FM. A lot more time in the oven is necessary. I guess the pressure to put it into early access was too high.

They shouldn’t have made it available?Yeah what a massive evil they’ve committed letting me have fun. 
 

i was straight up bored of the other helos. I’m glad they released Apache when they did and I’m sure they’ll improve it.

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Its almost like they haven't modelled the clutches that would allow the rotor to autorotate faster than the engine. Notice how a power on autorotation is also impossible, with the rotor dragging the engines up to 105% or so. It also exhibits with how immediately on power down the rotor will spin down  regardless of collective setting, affecting both autorotation and also making the shutdown a lot quicker.

Perhaps its some odd bug where the clutch doesn't disengage until the engine is at idle, so any RPM above idle will drag the rotor down with it.

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The power-on rotation in the simulation is indeed possible. I dont know if it’s accurate or not but yeah it’s possible. Eagle 7 demonstrates it in the video I posted above. Power on, collective down, terminates to a hover at about 15ft.

Again I can’t say how accurate it is but there you go 

 

 

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58 minutes ago, S. Low said:

The power-on rotation in the simulation is indeed possible. I dont know if it’s accurate or not but yeah it’s possible. Eagle 7 demonstrates it in the video I posted above. Power on, collective down, terminates to a hover at about 15ft.

Again I can’t say how accurate it is but there you go 

Indeed, by 'impossible' I meant that you cant enter an autorotative state, not that you cant descend in a controlled manner whilst attempting it. The act of doing so will 'pull' the engine RPM up as the rotor RPM increases. Indicating the clutches arent working.

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On 5/9/2022 at 1:46 PM, S. Low said:

They shouldn’t have made it available?

I said: not in its current state

On 5/9/2022 at 1:46 PM, S. Low said:

Yeah what a massive evil they’ve committed letting me have fun.

For me, fun in a flight simulator is very closely connected to a "plausible" flight model (e.g. that's why Gazelle is zero fun for me). But everyone has one's own preferences. It will be interesting how the Apache's FM will evolve in the future. 

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Actual gaz pilots say it’s not bad lol. I understand what you’re getting at though but it’s a subjectivity thing. We’re all here for flight simulation and not arcade flying, but it’s never going to be exactly right so we all have to have a tolerance level for inaccuracies. 

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On 5/13/2022 at 7:44 PM, S. Low said:

Actual gaz pilots say it’s not bad lol.

Afaik, one person from PC said, that actual Gazelle pilots would have said this about the FM.... Actual pilots (active in this forum) said otherwise... but the discussion is old and leads to nothing, regarding the DCS Gazelle.

On 5/13/2022 at 7:44 PM, S. Low said:

I understand what you’re getting at though but it’s a subjectivity thing. We’re all here for flight simulation and not arcade flying, but it’s never going to be exactly right so we all have to have a tolerance level for inaccuracies. 

That's why I said "plausible"

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2 hours ago, Swift. said:

It must be, considering how all the SMEs are saying the rotor doesnt have enough inertia

The AH-64D rotor system is a low inertia rotor system, but the variables that affect rotor RPM in an autorotative descent are numerous, ranging from density altitude to cyclic movement, direction and magnitude.

I haven't had time to look at the tracks posted by the OP, nor am I interested in making black and white statements on realism at this stage in Early Access. So you can can count me out of the "all the SMEs" generalization, since I don't know where the "all" is coming from.

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I think Swift perhaps means "all the SMEs who have publicly commented so far".

At the moment if you follow the procedure per the (real) manual the rotor RPM decays to the point where you have zero control authority and the generators drop offline. The rotor inertia may or may not be correct, but the current auto behaviour can't possibly be overall correct because the airspeeds listed as ideal in the real procedure result in guaranteed total aircraft loss. The minimum airspeed to keep control and the generators going right now is in the region of 100KTAS. I haven't exhaustively tested mainly because the actual AH-64 pilot in our online group immediately said it wasn't properly modelled so we kind of skipped past it as a technique on the assumption that we would get something better later in EA.  Two ED SMEs I'm aware of have both also said it's work in progress and not to try to hard to learn it right now because the behaviour is grossly incorrect.,

The other thing, that may or may not be 100% related, is that currently the engine RPM is driven by the rotor RPM during autorotation, and engine RPM never falls below rotor RPM. Our best guess therefore is that the sprag clutches are either not yet modelled or for whatever reason don't disengage. That could explain (if the turbines have mechanical drag/friction modelled) why the rotor RPM decays so low in the recommended airspeed window.

 

EDIT: P.S. Can someone move this to the Bugs sub-forum?


Edited by Scaley
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10 hours ago, Raptor9 said:

The AH-64D rotor system is a low inertia rotor system, but the variables that affect rotor RPM in an autorotative descent are numerous, ranging from density altitude to cyclic movement, direction and magnitude.

I haven't had time to look at the tracks posted by the OP, nor am I interested in making black and white statements on realism at this stage in Early Access. So you can can count me out of the "all the SMEs" generalization, since I don't know where the "all" is coming from.

Here is a Mission file where you can choose a helicopter and perform a nice autorotation.

Straight in, 180 to the left and right, 360, high hover.

No wind. 

Try the straight in and both 180s. Good luck. 

Btw, as I posted before. At 77kts you will have 3300ft/min rod. I'm sure you know where to look for the correct value that the Apache should have.

Fox

 

AR Training_zeroWind.miz

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On 5/13/2022 at 5:58 AM, iFoxRomeo said:

I said: not in its current state

For me, fun in a flight simulator is very closely connected to a "plausible" flight model (e.g. that's why Gazelle is zero fun for me). But everyone has one's own preferences. It will be interesting how the Apache's FM will evolve in the future. 

Then why are you buying EA aircraft?

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On 5/16/2022 at 1:01 AM, Raptor9 said:

I haven't had time to look at the tracks posted by the OP, nor am I interested in making black and white statements on realism at this stage in Early Access. So you can can count me out of the "all the SMEs" generalization, since I don't know where the "all" is coming from.

I fully understand not wanting to be part of generalizations but your "at this stage in Early Access" part of the comment doesn't really apply when the issue has been tagged as "correct as is" imho.

So I hope you can find the time to look into this because given that tag I'd assume this is how ED wants it to be and how it is going to be in the final release.

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The team will be taking a closer look at it in the future, for now I have marked it w.i.p

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