Now, THIS is a worthwhile, constructive thread!

 

I feel the R22 does indeed appear more controllable with this mods hinted by @Bjoern, but it's been so long since I last used PM that I have to recall again most of it's sections and parameters...

I am having some difficulty understanding why I can't make the orange sphere that supposedly corresponds to the "rotor engine", which should actually be the exact same engine, when I change the arms in the second column.

On 10/20/2025 at 9:41 AM, Bjoern said:

Sounds like the default R22, which is nigh unflyable out of the box.

 

On 10/20/2025 at 7:20 PM, Litjan said:

Come back when you can land on the moving frigate 😁

 

On 10/21/2025 at 3:46 AM, FPVSteve said:

All bets are off with the Robinson though, it's incredibly twitchy 😅

 

So I realized I have never flown the R22 itself anywhere, let alone onto a constrained landing pad that’s also running away at 30kts…

(to be clear, I love shipboard evolutions - I’ve just always used payware helos here or in DCSW)

I started out from a seaside airfield, but I could only get about 70kts out of it, and the frigate was >10nm out AND steaming directly away at 30kts! And who’s got time for THAT 😂

so I used the Frigate Approach special start and that gave me half a chance to catch it 😉

After holding off due to an oil tanker doing its level best to run down the frigate (it missed just aft of the fantail, but literally by just a few feet!), I proceeded in. 

And found it really quite difficult to get cleanly onto the deck! 😮

now, I’m admittedly rusty, but the R22 made me seem positively ham fisted…

so I proceeded to run the Frigate Approach with a few of my other helos:

the JRX B407, Nimbus UH-1, Ubben SA315, and even the R22’s big brother, the VSL R66…

and was able to plop them all on the deck with varying degrees of aplomb. 😎

I cranked up DCSW and practiced a few reps onto a Destroyer there, and had a similar experience  

Now I’ve never flown any helo IRL (quite a few rides as pax) so I can’t judge which addons are most accurate. 

and while I’m confident I could get the R22 responding better with more practice in it, it does seem to be one of the most difficult helos to fly smoothly of the many helo addons I own

which seems a bit strange as training aircraft are usually purpose designed with benign handling characteristics. And I personally enjoy trainers and “back to basics” flying, so I do it frequently

In sum, probably not going to mess with the R22 any further since it’s definitely a relatively unpleasant outlier in terms of handling (and it’s definitely THE slowest by a huge margin 😂)

but I may make a copy and try bjoerns PlaneMaker hacks and see if that proves helpful 🤙

Edited October 24, 2025Oct 24 by UrgentSiesta

11 hours ago, jcomm said:

I am having some difficulty understanding why I can't make the orange sphere that supposedly corresponds to the "rotor engine", which should actually be the exact same engine, when I change the arms in the second column.

Because you proably moved it along the lateral axis, which you will not see when you're in side view...

But stay away from the tail rotor anyway.

 

5 minutes ago, Bjoern said:

Because you proably moved it along the lateral axis, which you will not see when you're in side view...

But stay away from the tail rotor anyway.

 

It was alread displaced to starboard in the standard ACF. I didn't touch the lateral arm, just the longitudinal and vertical, but saw no effects, as if the "two orange spheres" were actually interconnected(?)

9 minutes ago, jcomm said:

It was alread displaced to starboard in the standard ACF. I didn't touch the lateral arm, just the longitudinal and vertical, but saw no effects, as if the "two orange spheres" were actually interconnected(?)

You're right, they are kind of interconnected because the R22 only has a single actual engine, so "long/lat/vert arm" already moves the tail rotor itself. "Thrust-point long/vert offset" also moves the tail rotor.

It isn't like this on two or three engined helicopters, where you can place all engines where they are on the real helicopter, but then have to define a thrust-point for the main rotor relative to the first engine's location and a thrust-point for the tail rotor relative to the second engine's location.

Welcome to Plane Maker...

Edited October 24, 2025Oct 24 by Bjoern

11 hours ago, Bjoern said:

You're right, they are kind of interconnected because the R22 only has a single actual engine, so "long/lat/vert arm" already moves the tail rotor itself. "Thrust-point long/vert offset" also moves the tail rotor.

I thought so, and it even makes sense. Only thing that could be adjustable is the relative position between the two references / spheres in such cases. The gearbox for the tail rotor shaft is certainly displaced from the one of the main rotor, but probably not as much as Xp12 represents it in PM (?)

Anyway, I do feel the R22 behaves a bit more "realistically" with your suggested mods!

5 hours ago, jcomm said:

Anyway, I do feel the R22 behaves a bit more "realistically" with your suggested mods!

That's great to hear!

On 10/22/2025 at 4:09 PM, Bjoern said:

Yes, RoG calculation is dynamic and a change in engine position does have an effect on the values in a FM cycle dump.

Because Body 22 is linked to the engine. And has a Cd value. And a weird shape.

And the rotor airfoil Cl has a nasty stall characteristic that doesn't appear in the printouts available on the interweb of the numerical prediction of the same. Hmmm

Edited October 27, 2025Oct 27 by blingthinger

16 hours ago, blingthinger said:

Because Body 22 is linked to the engine. And has a Cd value. And a weird shape.

The only function this can have is to simulate the drag of the rotor hub and shouldn't affect mass distribution as bodies (AFAIK) do not have any (usually being part of the airframe and thus governed by the empty mass set elsewhere).

 

16 hours ago, blingthinger said:

And the rotor airfoil Cl has a nasty stall characteristic that doesn't appear in the printouts available on the interweb of the numerical prediction of the same. Hmmm

Note that Airfoil Maker only supports symmetrical stall characteristics for pos and neg alpha. I figure Austin's reasoning is that you're mostly only seeing positive alpha stalls anyway. In order to have asymmetrical ones, as usual on real airfoils, you'll need to generate new polars in an external utility and put those directly into the airfoil file without touching Airfoil Maker whatsoever.

Edited October 27, 2025Oct 27 by Bjoern

The sim uses the overall body distribution to predict the gyration radii. And even if that drag element was the only thing odd going on up there, it certainly wasn't helping stability having that moment arm flopping around above the fuselage.

I wasn't referring to asymmetry. I was talking about the vertical cliff of Cl at stall, which is not only drastically steeper than the numerical predictions online, but is happening a few degrees early. I wonder if this is contributing to the seeming instability at high airspeed.

For me, the model is significantly more stable overall with the thrust offsets applied but still a bit wild on the edges. I'm super curious what the next round of flight model improvements will bring to the helis.

Also noticed that the landing skids are too far inboard relative to the Blender model. Pushing them out a bit helps just a bit at takeoff/landing.

With flight models at 2 per frame, does the R22 bounce or move on its own for you on (slightly) inclined surfaces? I don't have an example ready, but there should be plenty of unflattened ground level helipads in the default scenery to test this on*. This only happens with the engine location tweak for me and I just can not figure out why.

P.S: You're very welcome to post the numbers for the changes in the skids' locations.

 

- Edit: *Happens to me at LOWS, runway 15 with the default "Broken" weather preset. FPS is 35 there on my laptop, so not really a low FPS scenario. 10 flight model iterations per frame only slows the rate of the bouncing and sliding to be hardly noticable, and does not eliminate it.

Edited October 27, 2025Oct 27 by Bjoern

I've been running 5 FM/frame for a very long time because it's not a perf hit for me. It doesn't bounce around (even at 2) but it does move. Even on flat ground I can kick the rudder and it will spin on the skids. Sometimes it will spin on its own even with no rudder input (realistic? dunno. The Google did say the tail rotor airfoil is actually asymmetric to combat torque). It does slide down the incline surfaces.

When I go to 10 FM/frame...Wow! All that goes away. Zero sliding or slipping even with rudder input. And it becomes much more stable in air. Actually usable! I see no difference vs. the stock R22 as far as skid-ground interaction goes.

I ended up leaving the engine position at:

Main: long=0.1, lat=0, vert=-0.7,   longoff=-5.89, vertoff=0

Tail: long=14.6, lat=0, vert=-0.7,   longoff=0.6, vertoff=3.0

 

Now that I can spend time in it without flipping a bird to the screen, I notice the stall horn going off regularly. That's annoying. The airfoil-stall drefs are flipping around. I imagine rotor wash on the various wing surfaces is triggering that.

Skids symmetrically went to 1.8ft. I tried correcting the vertical too but I think the blender zero point is throwing that off. Sinks into the ground when in sim.

Edited October 28, 2025Oct 28 by blingthinger

The longitudinal cant of the Robinson R22's main rotor axis is approximately 1.5 degrees forward.

This slight forward tilt is a deliberate design feature to enhance flight stability and control. Here's how it works and why it matters.

I believe it isn't modeled that way in the default xp12 model.

I believe the upcoming changes / updates to the xp12 FM will deal with that counter-torque bug due to some feature related to slipstream effects over the wings and tail that Austin has fixed early this year but hasn't yet made it's way into any of the releases so far.

19 hours ago, blingthinger said:

I've been running 5 FM/frame for a very long time because it's not a perf hit for me. It doesn't bounce around (even at 2) but it does move. Even on flat ground I can kick the rudder and it will spin on the skids. Sometimes it will spin on its own even with no rudder input (realistic? dunno. The Google did say the tail rotor airfoil is actually asymmetric to combat torque). It does slide down the incline surfaces.

When I go to 10 FM/frame...Wow! All that goes away. Zero sliding or slipping even with rudder input. And it becomes much more stable in air. Actually usable! I see no difference vs. the stock R22 as far as skid-ground interaction goes.

I ended up leaving the engine position at:

Main: long=0.1, lat=0, vert=-0.7,   longoff=-5.89, vertoff=0

Tail: long=14.6, lat=0, vert=-0.7,   longoff=0.6, vertoff=3.0

 

Now that I can spend time in it without flipping a bird to the screen, I notice the stall horn going off regularly. That's annoying. The airfoil-stall drefs are flipping around. I imagine rotor wash on the various wing surfaces is triggering that.

Skids symmetrically went to 1.8ft. I tried correcting the vertical too but I think the blender zero point is throwing that off. Sinks into the ground when in sim.

Not a fan of increasing FM per frame. If it needs more than the default value, something is wrong on some end, aircraft or engine. On moving decks, increasing FM per frame actually tends to make things worse.

I've played with the skids to see if I can stop the sliding in some way, but every change only made matters worse and worse. WTH is wrong with this aircraft...

 

P.S: For an anger control exercise, I recommend trying to fly the default R22 (unmodified) with a gamepad.

 

@jcomm The forward tilt of the rotor is controlled by the "vert cant" parameter in Plane Maker.

Edited October 28, 2025Oct 28 by Bjoern