Trouble w/DC-3 Air Dynamics Mod

[beaky]

DLd an interesting cfg file for the FS9 DC-3 (by M. Beaumont and D. Bitzer- called "DC BB3") recently, and installed it just as specified.
 The mod is supposed to make the DC3  perform closer to 1939 book specs, and although on my first test flight I noticed it seemed a little more sprightly (among other claimed changes), there is a serious problem: She wants to roll left, a lot, at any airspeed or attitude.
I checked the aileron trim- even tried levelling the wings with it. That got old fast, all that rolling back and forth.
It wasn't a need for rudder correction, either, - it doesn't yaw first, it just starts rolling over. And rudder does nothing to help, even with the sensitivity turned way up. Besides, with both engines going at the same settings, a big twin like that isn't going to roll over like that because of torque or p-factor, even if both props are going in the same direction. It's extreme, and renders the plane unmanageable.
The yoke doesn't move in VC when this happens, and the ailerons do not appear to move in Spot view. It's as if one wing is heavy...
It also has nothing, apparently,  to do with fuel quantity in the wing tanks, and I compared the altered cfg line-for line with the original (to some extent) and didn't see anything that would explain it.
Obviously I have to dig deeper, but I'm wondering if anyone else has tried this mod, and if they had similar problems.
Meanwhile, I've reinstalled the original file, and she handles fine, just as before.

[Graycat8524]

Heya Rottydaddy,

I see what you mean.  I downloaded this same update awhile back, however, I didn't see really any difference in handling (aside from the fact that the aircraft's tailwheel wouldn't steer on the ground and the left banking issue).

I'm like you, I went back to the original Aircraft.cfg file which works just fine.  It may not be 1% approved, but it's OK to me.

I downloaded, unzipped, and installed the DC3_bb3 file.
I noticed the same handling problems that you did with the DC-3 with the Mark Beaumont Aircraft.cfg.  
I knew that when an aircraft is banking either left or right it's a problem with the center of gravity balance.

With the aircraft sitting on the ground (engines off) I went into Aircraft --> Fuel and Payload.  The "Center of Gravity" (Circle and Bullseye) appeared to be in the correct position along the X-Axis of the aircraft (1/4 down from the mean root wing chord), however, the CoG was a little off centerline to the left of the Y-axis.  There's the problem!

Looking at the Mark Beaumont Aircraft.cfg (DC3_bb3 file) I noticed that the [Weight and Balance] section looked good, however, the [Fuel] section had the Center Fuel tank positioned -6.7 in the Y-Axis.  This means that the DC-3's Left Fuel Tank and Center Fuel Tanks were both placed in the same location!

To cure this issue, you have to locate the [Fuel] section in the Aircraft.cfg and make the following changes:

[fuel]
//LeftMain =  -22.55,  -6.7, -3.0, 202.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
//RightMain=  -22.55,   6.7, -3.0, 202.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
//Center1  =  -22.55,   0.0, -2.7, 200.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
LeftMain=  -23.0,  -6.7, -3.0, 202.0,  5.0  // was changed below. See above  //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
RightMain= -23.0,   6.7, -3.0, 202.0,  5.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
Center1=   -20.0,  -6.7, -3.0, 200.0,  5.0    // Left Aux Tank
fuel_type = 1                                //Fuel type: 1 = Avgas, 2 = JetA
number_of_tank_selectors = 2                    
electric_pump=1

Delete the lines that I have highlighted in blue.  Next, remove only the // (two slash marks) in front of the lines that I have highlighted in red.  Save the Aircraft.cfg.  You're done!

When complete your Mark Beaumont DC3_bb3 Aircraft.cfg should look like this:

[fuel]
LeftMain =  -22.55,  -6.7, -3.0, 202.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
RightMain=  -22.55,   6.7, -3.0, 202.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
Center1  =  -22.55,   0.0, -2.7, 200.0,  0.0    //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
fuel_type = 1                                //Fuel type: 1 = Avgas, 2 = JetA
number_of_tank_selectors = 2                    
electric_pump=1  

This will resolve the left bank issue.  

As far as the tailwheel not being able to steer this is because the steering angle in the [Contact_Points] section is set to 180 degrees.  If you correct this number to about 36 degrees it works fine (the turn radius will be a little wide, however, from what I've read the DC-3 could not turn "on a dime" on the ground).

To correct the tailwheel issue first locate the section titled

[Contact_Points]
point.0=1,  -56.00,  0.0,   -2.3, 1200.0, 0, 0.60,180.0, 0.200, 2.5, 0.695,  0.0,  0.0, 0.0,   0.0,   0.0

Change the number that I have highlighted in blue above to around 36 then Save.

This should resolve these two issues.

See 'Ya up there in the air!

[ashaman]

I begin this answer admitting I know nothing about the config files you installed, still the DC3 is one of those airplanes I like to fly when I'm in retro mood.

Since people at M$ are not famous for their flight dynamics I went around some time ago and found new and improved dynamics in the all-DC3 site at: http://www.douglasdc3.com/

Having never flew on a real DC3 I can't really say how much real-like they are, but the author is a pilot of DC3 so they must be pretty good.

AND I never had the problems you list.

[Graycat8524]

Heya Ashaman--

Thanks a lot for the link -- I'll check it out over the weekend!

See 'Ya up there in the air!

[beaky]

Thanks guys- as I said, I only took a brief look in that section and missed those errors.

[SilverFox441]

You should be able to correct the bank issue by changing the following:

[fuel]
//LeftMain =

[beaky]

Graycat:
Doesn't the real DC3 have a non-steerable (castering) tailwheel? That was my understanding; I've always steered it with brakes, and used the tailwheel lock on takeoff.

[Graycat8524]

Heya Rottydaddy,

True, the original DC-3 had a caster type tailwheel.