38 minutes ago, jcomm said:

Took that excellent Alouette III for a ride and really liked it, but most helis in xplane behave in what I believe to be a rather strange way... Even with near zero winds they start flying in a sideslip precisely when I center the ball int their turn coordinators... 

Could it be because compensating for the side force of the tail rotor, the main rotor/fuselage must be banked the other way ("left skid low")? In this case the ball would be on the left for an helicopter flying straight and with a CCW main rotor.

Although, I don't know if in RL this effect is actually there, during cruise. Or it could be possibly canceled by other effects maybe?

2 minutes ago, Murmur said:

during cruise

spot on.

during cruise the tail rotor will be (mostly) neutral with rotor torque countered by the airflow over the vertical stabiliser. in a hover with a lot of pedal input need to counter the sideways thrust from the tail rotor.

1 hour ago, mSparks said:

spot on.

during cruise the tail rotor will be (mostly) neutral with rotor torque countered by the airflow over the vertical stabiliser. in a hover with a lot of pedal input need to counter the sideways thrust from the tail rotor.

As I suspected. So, it could be possible that in X-Plane helicopters, this aerodynamic effect is underestimated. I always had a "feeling" that XP helicopters required too much pedal during cruise, so this seems to confirm that.

What could be the cause? Maybe the vertical stabiliser in XP helicopters is not effective enough? Or maybe most XP helicopter designers do not fine-tune the geometry of the stabiliser so that the ball is centered during cruise? Who knows.

In a short holiday trip so unable to test, but I think you got it, and it's either lack of precise design or an underestimated tail effect.

Although I do recall from my test with the Alouette III that indeed as it gains speed the vertical strap appears to get more effective and with the ball centred the it flies less in a sideslip.

But along a long range of IAS I do get that weird effect of flying sideways IF I use the "rudder" to center the ball in the turn coordinator while flying a straight path...

Edited June 24, 20241 yr by jcomm

7 hours ago, Murmur said:

this aerodynamic effect is underestimated

it was, at least in the R44s, because the R44 vertical stabiliser is an airfoil and there isnt/wasnt support for a vertical airfoil creating sideways "lift".

really noticeable irl as you come to a stop, it loses effectiveness, and you have to dump left pedal quickly to keep her straight.

There is at least some of this behaviour simulated now tho, I exchanged a few emails with Austin about it a while back and it seemed to improve a couple versions later - as with all things Austin tho, no documentation of note of what exactly he did.

Edited June 24, 20241 yr by mSparks

50 minutes ago, mSparks said:

it was, at least in the R44s, because the R44 vertical stabiliser is an airfoil and there isnt/wasnt support for a vertical airfoil creating sideways "lift"

I believe it's possible and was used for instance by MLDAG to model the tail of the Bf109, just like the real thing, but was then overdone...

59 minutes ago, jcomm said:

I believe it's possible and was used for instance by MLDAG to model the tail of the Bf109, just like the real thing, but was then overdone...

email exchange was nov 2021

not sure the bf is comparable, the vertical (not horizontal) stabiliser on the 44 is a "proper" wing airfoil that generates torque while you fly then loses it when airspeed drops to the point it stalls (around 40kts)

not looked at planemaker helis for a long time now (mine all good) but there wasnt a way to configure that. but the effects themselves are well done - at least in the VSL44

Looks like VSL does it by giving a NACA 9 symmetrical airfoil on the vert stab a 7' incidence. - or maybe I have it the wrong way round - is the vertical stabiliser the one that is horizontal.... meh. its pushing 40 degrees again, my head isn't fit for this rn.

Edited June 24, 20241 yr by mSparks

In the BF 109 it was the vertical stab that was modeled with an asymmetrical airfoil and zero incidence, both IRL and by MLDAG.

Yes some developers add incidence to the vertical stab too, but... Sparks, when you're flying the real thing on a day with wind not being a factor, and flying straight with the ball centred on the turn coord, will it be possible for the helicopter to be flying in sideslip? 

Probably if we add a string to the heli in XP we can see it cants while the ball is centred, and then it's probably a bug in the model of the turn coord?

It's very noticeable in the Alouette III.

Edited June 24, 20241 yr by jcomm

36 minutes ago, jcomm said:

the ball centred on the turn coord

erm, there was bugs in the ball in default helis - especially at low speeds. always difficult to track down the source of any weirdness because everything affects everything else

flying cruise zero wind with the pedals not in neutral will make it side slip, its perfectly possible to then get the heli level with the cyclic.

I was doing that around 1 min into

 

BTW, returned from short holidays, I picked the Alouette III again and took it for a short ride last night and.... after all, it does have a string!

Also enabled the new HUD mode and used it to compare the sideslip indications between what's displayed in the aircraft turn coordinator, the string ( a bit difficult to read ) and the HUD sideslip cue.

VSKYLABS is working on a MD 902: https://forums.x-plane.org/index.php?/forums/topic/310009-vskylabs-test-pilot-902x-notar-wip/&

Hi all

I am just starting out in the world of helicopters in XP12, what would be for you the current top 5 helicopters in XP12 in terms of quality and realism?

Rotosim E135

Philip Ubben SA315 B Lama

These are my Favorits.

On 8/3/2024 at 6:20 PM, Aglos77 said:

I am just starting out in the world of helicopters in XP12, what would be for you the current top 5 helicopters in XP12 in terms of quality and realism?

If you're just starting out, don't spend money right away until you've decided that you want to fly helicopters more often.

To that end, try freeware first. Maybe even with a bit of a complexity ladder:

VTOL beginner:

• XP12 default ALIA 250: This is absolutely not a joke as it's great training for VTOL ops without having to worry about torque and all other helicopter oddities.

Training, single engine piston:

• Default XP12 R22 - great for learning to cope with handling and helicopter frustration; you'll throw it away sooner or later, but if you can fly that one, you can fly almost anything with a virtual rotor.
• Bell 47 - looks outdated, but handles slightly mmore forgiving than the R22 and the developer is a rotorhead, so it's realistic: https://forums.x-plane.org/index.php?/files/file/84421-bell-47g-2/

Intermediate, single engine turbine:

• HSF Alouette III - the design is not Aérosptiale's high water mark, but the virtual thing is complex and made by rotorhead devs, so you just know it's good: https://forums.x-plane.org/index.php?/files/file/88663-hsf-alouette-iii-xp12/
• OH-58D - if you want to add munitions deployment to your heli flying portfolio, made by a retired Army helicopter pilot, which vouches for accuracy: https://forums.x-plane.org/index.php?/files/file/74696-oh-58d-kiowa-warrior/

High performance twin engine turbine:

• EC135 - you'll probably end up here as this project has been refined over a long, long time and the head developer is extremely dedicated: https://www.rotorsim.de
• AS365 - it does not have an FMOD soundset (yet), but the rest is very well done; good if you want to train retractable gear operations: https://forums.x-plane.org/index.php?/files/file/84086-as365-n2-dauphin/