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HighBypass

Levitating undercarriage - iFDG MD-11 - contact point help

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I wonder if anyone might help with adjustment of the contact points for the above aeroplane.

 

As it stands (pun intended!) the trijet sits nicely on the left & right main gears. The nose tyres are slightly below ground level, but the wheel rims are showing. It's the centre gear which is the main culprit! It's a few inches off the tarmac.

 

I've investigated the contact points and understand the theory:-  x, y and z values are +ve when forward of, above and to the right of the reference datum (default 0, 0, 0 in this config file). I successfully made the nosewheel sit on the tarmac, but cannot sort out the mains. If I increase the negative value for the centre main the plane leans to one side.. Here's the messy contact points of the original cfg file:-

 

 

[contact_points]

static_pitch = 0
static_cg_height = 18.2
max_number_of_points = 16
 
point.0 = 1, 73.0771, 1, -17.2, 1181.1, 0, 1.6, 70, 1, 0.8, 0.7235, 7, 7, 0, 0, 0
point.1 = 1, 73.0771, -1, -17.2, 1181.1, 0, 1.6, 70, 1, 0.8, 0.7235, 7, 7, 0, 0, 0
point.2 = 1, -11.75, -20.2719, -18.3, 1574.8, 1, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 2, 0, 0
point.3 = 1, -11.75, -15, -18.3, 1574.8, 1, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 2, 0, 0
point.4 = 1, -6, -20.2719, -18.3, 1574.8, 1, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 2, 0, 0
point.5 = 1, -6, -15, -18.3, 1574.8, 1, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 2, 0, 0
point.6 = 1, -6, 20.2719, -18.3, 1574.8, 2, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 3, 0, 0
point.7 = 1, -6, 15, -18.3, 1574.8, 2, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 3, 0, 0
point.8 = 1, -11.75, 20.2719, -18.3, 1574.8, 2, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 3, 0, 0
point.9 = 1, -9.4062, 1.7218, -18.2999, 1574.8, 2, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 3, 0, 0
point.10 = 1, -9.4062, -1.7218, -18.2999, 1574.8, 1, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 2, 0, 0
point.11 = 1, -11.75, 15, -18.3, 1574.8, 2, 2.3, 0, 1.91, 0.9, 0.747, 7, 7, 3, 0, 0
point.12 = 2, -41.798, -84.3089, 0, 787.4, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0
point.13 = 2, -41.7975, 83.8839, 0, 787.4, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0
point.14 = 2, -83.6619, 0, 0.5259, 787.4, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.15 = 2, 100.5887, 0, -0.6915, 787.4, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0
gear_system_type=0

 

Points 9 & 10 should be for the centre gear. The  -9.4062 is in between the -6 and -11.75 longitudinal values for the left & right mains which would be as it should be.

 

Does it matter that the points list is not in a proper order? The centre gear splits the points for one of the main gears. I know that points 12-15 are scrape points (2 for the first number).

 

I have since found a different iFDG MD11 config where the contact points are thus:-

 

 

[contact_points]

static_pitch = 0.25
static_cg_height = 17
max_number_of_points = 13
//ns
point.0  = 1,  73 ,  1 , -17.76  , 1181 , 0 , 2.1 , 70 ,  1.1 , 1.0 , 0.4 , 7 , 7 , 0, 230, 250
point.1  = 1,  73 , -1 , -17.76  , 1181 , 0 , 2.1 , 70 ,  1.1 , 1.0 , 0.4 , 7 , 7 , 0, 230, 250
//lmg
point.2  = 1, -12  , -20, -17.76 , 1578 , 1 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 2, 230, 250
point.3  = 1, -12  , -15, -17.76 , 1578 , 1 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 2, 230, 250
point.4  = 1, -12  , -20, -17.76 , 1578 , 1 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 2, 230, 250
point.5  = 1, -12  , -15, -17.76 , 1578 , 1 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 2, 230, 250
//blg
point.6  = 1, -12  , -1 , -17.76 , 1578 , 1 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 2, 230, 250
point.7  = 1, -12  ,  1 , -17.76 , 1578 , 2 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 3, 230, 250
//rmg
point.8  = 1, -12  , 20 , -17.76 , 1578 , 2 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 3, 230, 250
point.9  = 1, -12  , 15 , -17.76 , 1578 , 2 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 3, 230, 250
point.10 = 1, -12  , 20 , -17.76 , 1578 , 2 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 3, 230, 250
point.11 = 1, -12  , 15 , -17.76 , 1578 , 2 , 2.3 , 0  ,  5.3 , 0.2 , 0.3 , 7 , 7 , 3, 230, 250
 
gear_system_type=1
 

 

The points seem to be on top of one another but all the mains sit on the tarmac.

 

You're going to say well, just use that set of points then! However, why did someone appear to create a set of quite precise points having different positions for each wheel? Do they tie in to the real MD-11 wheel positions (centre gear excepted)?

 

I'm going to have another go, double checking the values, but another set of eyes is always helpful! :)  Thanks.

 

Mark.

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I just tried a free version of the IFDG MD-11 for FS2004.  I also have a Simmersky freeware version.  Now the

 

IFDG model sits nicely on the 2 outer main mounts showing a slight flatness to the bottom of the tires,

 

indicating the weight of the aircraft. The middle main gear is just touching the ground.  The

 

Simmersky model has the middle gear about 2 inches off the ground.

 

I would have to check out some real world shots of the MD-11 to see if all 3 gears share the weight equally.

 

Looking at a real world picture of a KLM MD-11 just as it is rotating on takeoff, shows more weight on

 

the 2 outer main mounts and the middle gear just touching the runway.  I suspect that the outer main

 

gears are supporting much more aircraft+ fuel weight.

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Thanks charlie - could you post up the contact points for that iFDG MD-11 please? Are they the same as the "tidy" ones I posted above?

 

EDIT: I've found a Boeing document:-

http://www.boeing.com/assets/pdf/commercial/airports/acaps/md11.pdf

 

It lists the typical weight on the main gears as 245400 lbs so that's 122700 each, whereas the centre gear supports 106300 so yes, you're right that the L&R mains support more weight

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BAH! I've given up trying to tinker with the "messy, exact looking" numbers and used the "tidy" set instead, just to go flying! :dance:  I am annoyed that I can't seem to alter the set in logical ways. I'm not a "rivet-counter" but, like many other flight simmers I'm sure, we like things to look right even though some compromises have to be made  :smile:

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I have since deleted the IFDG MD-11 for FS2004.  To tell you the truth, I never noticed the middle gear on the

 

Simmersky MD-11 until you made your post! :wink:  Now I noticed that the DC-10 has a middle gear.

 

  Yeah, go fly!

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