I posted a mail asking how to make a twin have contra rotating props

Kiwi,The Baron is one of my favorite aircraft!Thanks for providing this XML challenge, as I needed the samefix on one of my projects :)I have revised the Baron RPM and Sync gauges, put them in theirown sub-folder, revised the panel CFG, reversed one of my props,and the gauges seem to work normally this way...If you would contact me by email, I will send it to you:)JR

There are several ways to solve this. One general way that makes the rpm display completely independent from the rotation sense, is to use the "abs" operator to make rpm's always positive. For example the "Left RPM Indicator.xml" can look like this:<Gauge Name="Left RPM Indicator" Version="1.0"> <Image Name="RPM_Background.bmp" ImageSizes="52,52,82,82"/> <Element> <Position X="26" Y="26"/> <Image Name="Engine_Gauges_Needle.bmp" PointsTo="East" ImageSizes="13,5,20,8"> <Axis X="-9" Y="2"/> </Image> <Rotate><!-- <Value Minimum="0" Maximum="35">(A:Prop1 RPM,RPM) 100 /</Value>--> <Value Minimum="0" Maximum="35">(A:Prop1 RPM,RPM) abs 100 /</Value> <Failures> <SYSTEM_ENGINE Action="0"/> </Failures> <Nonlinearity> <Item Value="0" X="5" Y="19"/> <Item Value="20" X="46" Y="17"/> <Item Value="35" X="27" Y="48"/> </Nonlinearity> <Delay DegreesPerSecond="15"/> </Rotate> </Element> <Mouse> <Tooltip ID="TOOLTIPTEXT_ENG1_PROP_RPM"/> </Mouse></Gauge>The right rpm can be changed the same way. The prop spinner can look like this: <Gauge Name="Prop Sync Spinner" Version="1.0"> <Image Name="Prop_Sync_Bezel.bmp" ImageSizes="20,20,31,30"/> <Element> <Position X="10" Y="10"/> <Image Name="Prop_Sync_Blades.bmp" PointsTo="East" ImageSizes="16,16,26,25"> <Axis X="8" Y="8"/> </Image> <Rotate><!-- <Value Minimum="0" Maximum="210">(A:Prop2 RPM,RPM) (A:Prop1 RPM,RPM) - (*get difference between props*) 0.01 * (*100 rpm -> 1 rpm*) 18 / (*18 frames per sec*) 360 * dgrd (*convert rpm to radian/sec*) (G:var1) + (*add to accumulator*) rnor (*normilze*) d (>G:var1) (*update accumulator*)</Value>--> <Value Minimum="0" Maximum="210">(A:Prop2 RPM,RPM) abs (A:Prop1 RPM,RPM) abs - (*get difference between props*) 0.01 * (*100 rpm -> 1 rpm*) 18 / (*18 frames per sec*) 360 * dgrd (*convert rpm to radian/sec*) (G:var1) + (*add to accumulator*) rnor (*normilze*) d (>G:var1) (*update accumulator*)</Value> <Failures> <SYSTEM_ELECTRICAL_PANELS Action="Freeze"/> </Failures> </Rotate> </Element> </Gauge>Arne BartelsP.S. the Baron prop does rotate also visually counterclockwise with "rotation=-1,1"

Ah I forgot to change the tooltip for the RPM gauges, use something like this at least for English versions: <Mouse><!-- <Tooltip ID="TOOLTIPTEXT_ENG1_PROP_RPM"/>--> <Tooltip>%Propeller 1 RPM (%((A:Prop1 RPM,RPM) abs)%!.0f! RPM)%</Tooltip> </Mouse>The right gauge needs the same with "1" replaced by "2".Arne Bartels

Yo Guys

Does this fix actually cancel-out all left-turning tendencies such as P-Factor, Gyro effect, prop wash,etc as in real life ???And just another remark: counter-rotating props doesn't necessarily mean that the engines still turn both the same way. The Seneca V has counter-rotating engines & props ! The left engine is a Continental LTSIO-360 while the right one is a TSIO-360. In this case, there is no gearboxing to reverse one of the props rotation, they already counter-rotate ! BTW, a reduction gearbox is not primarly intended to reverse the rotation, it's meant to reduce the prop shaft speed compared to the engine speed, which turns faster. Of course, you can still make it reverse the rotation...just a detail !Cheers !

If you put the commandRotation=1,-1in the Prop section of the aircraft.cfg file the right engine will reverse in both rotation and torque.The bad news here is that unless you've made the aircraft yourself the aircraft's visual appearance does not change. By that I mean the prop blades will be set the wrong way for the reversed rotation - they will be going backwards. :-)The other disadvatage is, as mentioned above, the gauges may not work.

I haven't checked the external visual effects of this upgrade... It isn't important to me....What interested my was:A. the handling of the aircraftB. the fact that the real aircraft I'm trying to emulate has contra rotating props.....Yes it does even out the adverse torque effects of having 2 such powerful engines going the same way.Yes I know you can have 2 configurations for contra rotating props.The one engine running in reverse, and the gearbox reversing the prop.The aircraft I'm modelling has the same engines.. The reverse is in the gearbox.The problem with the right RPM gauge not working is solved by the syntax that Arne Bertels supplied above....Cheers//Tonni

Cool ! Way to go !Good luck on modeling that plane !