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marcus11

X-Plane 11 Propeller Modeling / X-Plane Developer Blog

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New blog post by Austin:

 

http://developer.x-plane.com/2017/01/x-plane-11-propeller-modeling/#more-7343

 

Excerpt:

 

So, in X-Plane, we of course break the prop down into tiny little pieces and add up the effects from all of them to get a weighted average of the spiraling-slipstream speed for the entire prop, and scale that rotational speed from zero right at the axis of the prop hub to maximum out at the prop tip, and bang, we got a spiral slipstream with math that I believe proves that we are making a very good approximation. (And, doing the math in this new way results in propeller spiral slipstream that runs about 45% higher than the previous model… a positive indication since the spiral slip-stream was previously under-represented!)

So, now we have better propeller spiraling slip-stream, with the needed rudder effects, and it feels GREAT to fly.

 

___

 

 

I'm now really looking forward to beta 4.

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Curious, when he changes stuff like this, does it affect existing aircraft or only new aircraft?

 

Wondering what (if anything) changes like this do to my existing 3rd party fleet of awesome Simcoder REP planes.

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Quite an interesting read. Might take them a bit to get that one dialed in correctly, I'm thinking. 

 

However, it's great to know that they're constantly working on refining the flight model.


Curious, when he changes stuff like this, does it affect existing aircraft or only new aircraft?

Wondering what (if anything) changes like this do to my existing 3rd party fleet of awesome Simcoder REP planes.

 

I'm thinking that there's been quite a bit added under the hood in XP11 - I'm speculating that the changes in the electrical systems alone likely mean that the REP programs are going to need (or could benefit from) some adjustment and rework for XP11.

 

Any changes to the internal flight model are also liable to throw off the REP stuff as well.

 

End of the day though, since the REP devs are trying to get everything as close to real life as possible, these under-the-hood changes should make their lives easier in the long run.

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Curious, when he changes stuff like this, does it affect existing aircraft or only new aircraft?

 

Wondering what (if anything) changes like this do to my existing 3rd party fleet of awesome Simcoder REP planes.

 

With changes to the basic flight model like this, the answer has usually been that it doesn't affect current models, but you get the changes by loading the model into Planemaker and saving out a new version. I suspect that's the case here.

 

For a model with plugin-enhanced flight model changes like the REP series, I'd wait to see what the developer says about it. 

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Best news ever ! This has been one of my biggest gripe with XPX. Do I finally get to use the rudder to counter act the the left turning tendencies when in the air !?

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Best news ever ! This has been one of my biggest gripe with XPX. Do I finally get to use the rudder to counter act the the left turning tendencies when in the air !?

 

I second that, can't wait for the next beta...

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Curious, when he changes stuff like this, does it affect existing aircraft or only new aircraft?

Wondering what (if anything) changes like this do to my existing 3rd party fleet of awesome Simcoder REP planes.

I think that's why Laminar was encouraging developers not release any native XPX-11ADDONS till 11 goes final.

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Does it mean that the left vanning tendency is going to get more worse during crosswind takeoff? Sorry I don't understand the aerospace stuff..

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Does it mean that the left vanning tendency is going to get more worse during crosswind takeoff? Sorry I don't understand the aerospace stuff..

If the cross wind is from the left then probably. If it's from the right then left turning tendency should counter act the weather vanning a bit. Austin has been hard at work on the flight model lately so I'm sure the weather vanning will get some attention ! Google 'left turning tendencies'.

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If the cross wind is from the left then probably. If it's from the right then left turning tendency should counter act the weather vanning a bit. Austin has been hard at work on the flight model lately so I'm sure the weather vanning will get some attention ! Google 'left turning tendencies'.

 

 

Left turning tendencies can be due clockwise rotating propeller without any weathervaning

fig1-18.jpg

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Left turning tendencies can be due clockwise rotating propeller without any weathervaning

fig1-18.jpg

Huh ? I am pilot, I familiar with the left turning tendencies ! The spiraling slipstream might exasperate the weathervaning bug is all I am saying.

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Huh ? I am pilot, I familiar with the left turning tendencies ! The spiraling slipstream might exasperate the weathervaning bug is all I am saying.

 

Sorry I misread you sentence 

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sorry but i used to fly REAL cessnas and the left pull isnt as exptreme as the model in xp11. there is some but not nearly as much as what is modelled in this program, turn it down!!

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sorry but i used to fly REAL cessnas and the left pull isnt as exptreme as the model in xp11. there is some but not nearly as much as what is modelled in this program, turn it down!!

 

What left pull ? Are you talking about the engine torque? That makes the plane roll to the left in the longitudinal axis. The spiraling slip stream model has been broken forever. Are you sure you use to fly Cessnas ? The left turning tendencies should make the plane yaw to the left, as in real life. That doesn't happen with current model. When was the last time you flew a real Cessna ? Left turning tendencies is the basics we lean about in ground school.

 

Maybe you need to take a look at your joystick calibration!

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sorry but i used to fly REAL cessnas and the left pull isnt as exptreme as the model in xp11. there is some but not nearly as much as what is modelled in this program, turn it down!!

 

It's kind of  depending on how you look at this. The problem may comes from your PC control input which has different sensitivity (or rudder authority feedback) comparing with real aircraft. A lot of us get to use to hold the right rudder to the point that we don't register that action.

 

I get to fly with primary students a lot and if I don't touch the rudders and let them handle, it often we quickly ended up on left side of the runway. This effect significantly increases with take off roll speed grows. If I don't take over on time I always fear we may skid and ground loop.

 

Now, comparable with other aircraft 172 indeed requires less rudder authority to keep on the centerline during take off roll

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152 and 172 dont need as much rt rudder in real life on taxi and take off roll as in the sim. Ive checked my controls and they seem to be ok. 

 

It's kind of  depending on how you look at this. The problem may comes from your PC control input which has different sensitivity (or rudder authority feedback) comparing with real aircraft. A lot of us get to use to hold the right rudder to the point that we don't register that action.

 

I get to fly with primary students a lot and if I don't touch the rudders and let them handle, it often we quickly ended up on left side of the runway. This effect significantly increases with take off roll speed grows. If I don't take over on time I always fear we may skid and ground loop.

 

Now, comparable with other aircraft 172 indeed requires less rudder authority to keep on the centerline during take off roll


What left pull ? Are you talking about the engine torque? That makes the plane roll to the left in the longitudinal axis. The spiraling slip stream model has been broken forever. Are you sure you use to fly Cessnas ? The left turning tendencies should make the plane yaw to the left, as in real life. That doesn't happen with current model. When was the last time you flew a real Cessna ? Left turning tendencies is the basics we lean about in ground school.

Maybe you need to take a look at your joystick calibration!

yea mr professor, engine torque. Just made a comment that this sim pulls on taxi and takeoff more than i have experienced in real life. no need to get hostile sir and question if I have flown or not. dont you want me to post my logbook for ya?? 

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152 and 172 dont need as much rt rudder in real life on taxi and take off roll as in the sim. Ive checked my controls and they seem to be ok. 

 

Yes not much, but have many of us tried to take off without rudder at all?  I'm using CH rudder I had to scale down sensitivity to somewhat match real aircraft. 

Another thing to consider is that when we compare something with real counterpart. Same model of the aircraft in real life can big rigged differently. For example, I had to re-rig control cables in my 172 (with A&P of course) because they were to stiff and people were complaining about it. In fact, I had to do it twice because over the time they stiffen a lot for some reason  

 

There is also little fixed rudder trim tab om the bottom of vertical fin. That can be adjusted as well to reduce left turning tendency completely for example in climb, but then trade off will be a cruise flight with a lot of rudder input

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152 and 172 dont need as much rt rudder in real life on taxi and take off roll as in the sim. Ive checked my controls and they seem to be ok. 

 

yea mr professor, engine torque. Just made a comment that this sim pulls on taxi and takeoff more than i have experienced in real life. no need to get hostile sir and question if I have flown or not. dont you want me to post my logbook for ya?? 

 

I am not getting hostile ! Your log book please ! lol... The developer finally fixes the broken spiraling slip stream model and you were saying "turn it way down". So your original comment made no sense. But now that you clarified it, ok. The torque feels about right in flight to me. I'm not sure if the torque plays into the plane pulling to left on the ground roll or not. That is beyond my pay grade. The plane pulling extremely to left or right on the ground roll is a weather vanning bug when there is a cross wind. There is whole separate post on that subject in this forum. If you adjust your rudder pedals Control Sensitivity that helps.   

 

 

 

sorry but i used to fly REAL cessnas and the left pull isnt as exptreme as the model in xp11. there is some but not nearly as much as what is modelled in this program, turn it down!!

Yes not much, but have many of us tried to take off without rudder at all?  I'm using CH rudder I had to scale down sensitivity to somewhat match real aircraft. 

Another thing to consider is that when we compare something with real counterpart. Same model of the aircraft in real life can big rigged differently. For example, I had to re-rig control cables in my 172 (with A&P of course) because they were to stiff and people were complaining about it. In fact, I had to do it twice because over the time they stiffen a lot for some reason  

 

There is also little fixed rudder trim tab om the bottom of vertical fin. That can be adjusted as well to reduce left turning tendency completely for example in climb, but then trade off will be a cruise flight with a lot of rudder input

 

The 172 that I currently rent has a adjustable rudder trim in the cockpit. The strange thing about that plane is that it used to require a lot of rudder peddle on climb, but now it does not. Nor does it require any rudder trim in cruise, go figure. I will have to ask the owner about that. 

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The 172 that I currently rent has a adjustable rudder trim in the cockpit. The strange thing about that plane is that it used to require a lot of rudder peddle on climb, but now it does not. Nor does it require any rudder trim in cruise, go figure. I will have to ask the owner about that. 

 

I believe 172 N has cockpit wheel for a rudder trim, and max 40 degrees flaps. Next model up which is "P" lost both in cockpit rudder trim control and 10 extra degrees of flaps. I bet Cessna got couple lawsuits that forced them to do those changes.

 

When I fly N I usually adjust rudder trim few notches to the left unless I want to torture my student of course  :Devil:

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I believe 172 N has cockpit wheel for a rudder trim, and max 40 degrees flaps. Next model up which is "P" lost both in cockpit rudder trim control and 10 extra degrees of flaps. I bet Cessna got couple lawsuits that forced them to do those changes.

 

When I fly N I usually adjust rudder trim few notches to the left unless I want to torture my student of course  :Devil:

 

Yes that would be the N model !

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