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misho_TerraBuilder

Helicopter Flight Model tweaking

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I was wondering if anyone knew if there was a variable in *.air or aircraft.cfg that would control the amount of lift if the helicopter was pitched up/down while in flight?Thanks in advance,

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First, you have to realize that there are two helicopter flight models.The B206 based flight model is a highly modified Cessna flight model.The R22 (newer) flight model has additional entries you can make in the aircraft.cfg, which are documented in the SDK.In each, there are variables that are used to determine lift, but there is not any one that works alone. .air file editing is a black art.Good luck.

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Hi Patrick (and all),I went through SDK but I couldn't get any more info than I already had (I actually did go through that document a long time ago when I started working on this). Below is what I posted in hovercontrol.com, but no answers yet. As far as flight model tweaking, I'm fairly adept at editing both CFG and AIR files and I managed to edit quite a bit to get the flight model just right for my needs - except for this one thing that is still persisting.I am trying to figure out if there is a variable that governs a specific helicopter flight behaviour, namely:If I fly level and pitch up, the helicopter rises and slows down. This is a normal behaviour, but, I'd like to diminish or completely remove the lift caused by pitching up (and sink caused by pitching down). I would like to have the main propeller thrust vector only (pointing to whatever the cyclyc is), without residual aerodynamic effects that are caused by forward speed. I'd like to point out that the behaviour I'm after is observed in hover: if you push cyclyc forward, you lose a bit of lift and drop slightly. However, during cruise, the aerdynamics are different (namely, there is airspeed), and you get a bit of lift. It's that lift that I'm trying to remove.Any pointers, suggestions or help would be greatly appreciated!

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Hy.what you are dealing with in terms of forward flight in hover position is caused mainly by ground effect.As you gain altitude and speed,your blade angle changes.If you raise the nose at cruise speed you would get a terrible amount of blade slap if you do it to abruputly.In real life most the time you would increase collective to gain altitude and keep the helicopter at an angle of flight so as not to loose foward speed and viceversa.In an approach,you would lower collective has you raise the nose so as to slow down and NOT gain altitude.Tell me what you have in mind exactly and for witch helicopter and what version of it.Hyfly.

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BTW, I forgot to say that the "hang" angle in hover is based on the position of the model when exported.

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>I am trying to figure out if there is a variable that governs>a specific helicopter flight behaviour, namely:>>If I fly level and pitch up, the helicopter rises and slows>down. This is a normal behaviour, but, I'd like to diminish or>completely remove the lift caused by pitching up (and sink>caused by pitching down). I would like to have the main>propeller thrust vector only (pointing to whatever the cyclyc>is), without residual aerodynamic effects that are caused by>forward speed. I'd like to point out that the behaviour I'm>after is observed in hover: if you push cyclyc forward, you>lose a bit of lift and drop slightly. However, during cruise,>the aerdynamics are different (namely, there is airspeed), and>you get a bit of lift. It's that lift that I'm trying to>remove.Well, not sure why you want to "remove" this, b/c it is the way a helicopter performs.There is what is called transitional lift caused by the rotor disk moving through space. If you pitch up without reducing collective, you will climb.In the hover, you see the behavior you do b/c you are "dumping" the air off the top of the rotor disk and also vectoring some of the thrust from the vertical to the lateral.The way to remove this is by proper pilot input to the controls.

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Hi there,Thanks for the input. I actually got ahead a bit, and managed to get more or less what I want by:1) Dramatically decreasing the rotor size.2) Dramatically increasing the inflow_vel_reference value.However, and this is really strange - my instruments are now showing odd values - climb rate still goes up, and the readouts on the top of the screen (SHIFT-Z options) clearly show I am falling. Is there any reason that vspeed values that heli gauges use would show such erroneous readings???Aside from that, this model is now doing more or less what I wanted. I might have to tweak the numbers a bit...

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Hi Patrick,"Well, not sure why you want to "remove" this, b/c it is the way a helicopter performs."Actually, if you check my website, I am about to release my TerraBuilder:Moon package and I wanted to get as close as possible to the true rocket flight model. I got pretty close and this one thing was still a bit unrealistic. Check out my other post from today - I managed to actually get close to what I want by drastically reducing rotor size and increasing the air flow through the rotor - basically, a true vectored flight model...The only odd thing is the vspeed (climb rate) readout, which for some reason shows the climb when I am clearly falling (as shown with the "red", SHIFT-Z readouts on the top of the screen)... any idea on that??

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really? I thought MDL file geometry has absolutely nothing to do with the flight model... I think all the flight model parameters are exclusively in the CFG and AIR files...

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Oh yeah, I remember looking at that awhile back. You have done some great work, and yeap reduce the rotor size would be a good start. You might want to play with the moments too. There is a great post about that somewhere, and I have a white paper somewhere on the equations you can use to calculate them, but for your purposes, you propbably can just play with them.

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For helicopters (don't know about planes) you should place the CG at 0,0,0, and the attitude should be what it is in a hover. For your space craft, not sure what would be best, but probably the same.

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