Prop rotation in FSX

[stansdds]

So I've been messing around with Milton's excellent Howard 500, the one that was patched to make it compatible with FSX. I noticed something weird when I shut down the engines. The starboard prop rotates in the normal direction, but the port prop rotates in the opposite direction. This is visible both from the cockpit and from outside. I thought this to be rather odd. I tried the SOH A-26 and both of its props rotate correctly. I tried the stock Beech Baron and its props rotate correctly. I tried the stock DC-3 and the port prop rotates backwards like the Howard 500.

Both the DC-3 and HW-500 rotate their props in the correct direction in FS9, but in FSX the port props rotate in the opposite direction.

Things that make you go "hmmm..." Or at least make me go "hmmm...":kilroy:

[tigisfat]

I don't know if the DC-3 and Howard 500 do, but I know many aircraft have props turning in different directions. Many twins have them turning opposite of each other to make sure that there's no critical engine.

[Tako_Kichi]

Not sure what you mean by a 'critical engine' but the other reason for making a twin's props turn in opposite directions is that it cancels out engine torque meaning you can apply full power and take off in a straight line without having to do a dance with the rudder pedals to keep the nose heading down the runway. This is particularly noticeable in twin taildraggers. Having two powerful engines turning the same way makes rudder control even more difficult on take-off.

[Lionheart]

Tako is correct.

A proper Twin engine will have counter rotating props/engines. I am sure this is supposed to be like this on Miltons bird. He is a perfectionist on his work.

To check this, shut down the engine and check the blades. They should be opposite on the other side.




Bill

[tigisfat]

a proper twin? Plenty don't.

[rohan]

guys, sorry but you've all missed stansdds' point - the prop on the port engine rotates in different directions in FS9 and FSX, while the starboard prop rotates in the same direction in both sims ...
regs,
Ro
:friday:

[cheezyflier]

he's right, and besides, the props on the real dc-3 were not counter rotating.

[mustang51]

Only one that I can think of with counter rotating props is the P-38.
The Howard does not.

[stansdds]

Thanks Rohan and Cheezyflier. I know a few twins have had counter rotating props, like the U.S. versions of the P-38 (British version lacked the turbocharger and did not have counter rotating props), but I know the Howard 500 and the DC-3, both in real life and in FS9, did not, yet they do in FSX while other aircraft do not have this issue. It's weird and you would think that MS would have gotten their DC-3 correct.

[SkippyBing]

I think you have to edit the air file to alter the direction of rotation of the prop, I can't find anything in the cfg.

[stansdds]

I've tried AIRed for FS2004, any suggestions for FSX?

[Milton Shupe]

Very interesting. I do not have FSX so I cannot check it but this is how the parameter is set in the FS9 aircraft.cfg Propeller section:

rotation = 1, 1

If both the VC and exterior port engine views rotate backwards, then you might be able to correct it with this:

rotation = -1, 1

Let us know please.

[stansdds]

That was the first thing I tried. The -1 got the port prop to spin in the correct direction, but at what appear to be incredibly slow rpm's (or an incredibly fast shutter speed on a video camera). So the starboard engine has a nice prop blur, but the individual blades on the port engine are quite visible.

[Stratocruiser]

I tried this in FSX on the DC3 aircraft.cfg. While the rotation at times showed signs of straightening out, it was incomplete, jerky, and the prop animation was basically messed up. Looks like this parameter fails in FSX.

Carey


Very interesting. I do not have FSX so I cannot check it but this is how the parameter is set in the FS9 aircraft.cfg Propeller section:

rotation = 1, 1

If both the VC and exterior port engine views rotate backwards, then you might be able to correct it with this:

rotation = -1, 1

Let us know please.

[Milton Shupe]

Well, then the key is to determine the actual RPMs of that engine to see if it is an animation issue or if the engine is simply turning slow.

Using this parameter in the General section of the cfg may help, if it is animation, by using a more positive number:

prop_anim_ratio = 1

You can use Jerry Beckwith's test gauges or maybe get a digital tooltip reading from the RPM gauge as to the actual prop RPM's. The Howard has gear reduction props and I do not recall if the RPM gauge shows engine or prop speeds.

[N332DW]

prop_animation_ratio is deprecated in FSX - the rotational jerkiness is controlled by the modeldef.xml file [prop_anim] section at compile (even says it must be tuned per model) and engine params in the aircraft.cfg file - getting a smooth FS9 like, prop animation in FSX has proven challenging for me on the few Prop/rotor driven craft i have released