Low / Zero Speed AR leads to Vortex

[dahui]

When Reducing the Airpseed to 0 in the AR, with Throttle Closed, the Helo "falls" into a Vortex and the NR is getting unnormally high, it needs 1/2 to 3/4 Collective to keep it down.

[Furia]

I am not sure if I do understand your statement correctly. So you are in an autorrotation at 0 Kts airspeed with throttle closed... I am not sure how do you expect the helicopter to react but an autorrotation at 0 Knots airspeed any helicopter "reacts badly". If you have no pitch in your blades you are droping like hell but that is not vortex since for a vortex ring state  to develop you need pitch and power. No vortex ring during an autorotation with no pitch or power.

I am not sure what would be your expectations of how the helicopter "should" behave in a vertical autorrotation but in any case unless you get some airspeed before your flare, you will crash.

If you could clarify a bit better your question. Maybe I have not understood your point. What do you think it is wrong with the module it will help to understand the "issue"

[dahui]

Hello

the decent rate in a 407 with 0 knots airspeed, throttle at idle and NR kept at 100% is about 2k feet. When applying collective to NR 95% its a bit less. It is possible to land with 0knots but the window when to stop the the decsent with the collective is very small.

the issue here is that it needs more than 50% collective to keep the NR within limits and when doing that the kiowa falls into vrs. Thats not a normal behaviour

i will try to post a trackfile on the weekend

[Ramsay]

14 hours ago, dahui said:

the decent rate in a 407 with 0 knots airspeed, throttle at idle and NR kept at 100% is about 2k feet.

That sounds unlikely, like the Kiowa, the 407 has a best Auto descent rate at 55 KIAS and best Auto Glide (distance) at 80 KIAS.

Kiowa Autorotation

Bell 407 Autorotation

14 hours ago, dahui said:

It is possible to land with 0 knots but the window when to stop the the descent with the collective is very small.

AFAIK the RL Kiowa landing technique is to land with a little bit of forward momentum/speed.

DCS Autorotation Tutorial by Harpoon.

AFAIK Polychop hope to refine rotor behaviour a bit further in subsequent patches.

Edited August 21, 2024 by Ramsay
Add link to Autorotation Tutorial

[dahui]

13 hours ago, Ramsay said:

That sounds unlikely, like the Kiowa, the 407 has a best Auto descent rate at 55 KIAS and best Auto Glide (distance) at 80 KIAS.

Kiowa Autorotation

Bell 407 Autorotation

AFAIK the RL Kiowa landing technique is to land with a little bit of forward momentum/speed.

DCS Autorotation Tutorial by Harpoon.

AFAIK Polychop hope to refine rotor behaviour a bit further in subsequent patches.

 

Its not about the forward AR. Its about the unrealistic behaviour with 0 speed. Regardless what the graphs say. A helicopter does not behave like that. Otherwise i would be dead already…

its also not about the touchdown. 

[LorenLuke]

1 hour ago, dahui said:

Regardless what the graphs say.

I mean, the graphs say how the helicopter behaves. That's literally all they do.

It may be different for the helicopter you've flown, but I bet that has different graphs.

[Tiger-II]

People need to learn to think a bit more.

A vertical autorotation may not be the best thing, but it can be done. It says nothing of the crash, only the result while falling!

In autorotation VRS is not a thing because the motion of the air drives the blades.

VRS only happens under power with pitch, because the net thrust is higher, forcing a cusion of air out in front of the rotor system with a negative velocity.

Like a ship encountering bubbles in water, this downwards accelerated air increases sink rate.

Autorotation can't do this. Helicopters reach a point of equilibrium, and settle in a stable sink rate during autorotation, regardless of forward speed.

Edited August 28, 2024 by Tiger-II