Simviation Forum - 757-200 Center of gravity

Oct 13^th, 2009 at 5:40pm

Frozen1 Offline
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For some reason my 757 C/G is all the way in the nose. The plane is flying nose down. Is this a panel issue?

Thanks

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Reply #1 - Oct 13^th, 2009 at 10:40pm

garymbuska Offline
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Frozen1 wrote on Oct 13^th, 2009 at 5:40pm:

For some reason my 757 C/G is all the way in the nose. The plane is flying nose down. Is this a panel issue?

Thanks

Now I ask you how in gods green earth would the panel cause this kind of problem.
Your problem could be one of two places. If the model was made that way there is not a whole lot you can do to fix it. But usually adjusting the weight and balance in the aircraft cfg file will solve this problem.
Just make sure you make gradual changes as you could get tail heavy in a hurry. Cool

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Reply #2 - Oct 14^th, 2009 at 2:20pm

Capt.Propwash Offline
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you will need a pair of Tin Snips, Wire Strippers / cutters, a Sawz-all, and a few screw drivers, a 3lb sledgehammer, and a 20lb sledgehammer.

first off, use the sawz-all to neatly cut the panel on both ends (right and left) then the top near the windshield and once more underneath.

once you have done this, use the screwdrivers to unbolt any wires that you can get to, and the wire cutters or Tin snips to cut the wires that you can not unbolt.

using the sledgehammers, beat the ever living crap out of the panel until it pops loose. Remove it from the cabin and throw it out of the plane.

--- buy a new panel and install it per manufacturer's specifications.

** put your passengers/luggage in the BACK of the plane. not the cockpit!!!!

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Reply #3 - Oct 14^th, 2009 at 9:48pm

757200ba Offline
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Are you sure is a CG problem?Or it could be a trim thing?
Shocked

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Reply #4 - Oct 14^th, 2009 at 9:49pm

Jersey Flyer Offline
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How much does your Co-Pilot weigh?

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Reply #5 - Oct 14^th, 2009 at 9:57pm

N. Chapman Offline
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Generally the weight and balance is all in the Aircraft.cfg not a panel issue.

Click for Computer info overload!

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Reply #6 - Oct 15^th, 2009 at 7:07am

gypsymoth Offline
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Frozen1. Some aircraft have a cog that is misplaced & this happens because the maker hasn't been careful enough to get it right.
When FS is running go into Fuel & Payload & you'll see a plan of the aircraft with a cog high-lighted. You can change its position by altering the amout of fuel. The other way is by looking at your aircraft's cfg. Before changing anything, make a copy! Go to the section [airplane geometry] & then 'wing_pos_apex_lon' & opposite the = there will be a number.
This is from my ATR72-500 - 3.500 & it places the cog where I can see it in the Fuel/Payload plan. Increasing this number moves the cog back, & decreasing it forward, or is it the other way round? It's been ages since I changed a cog!! I usually place // before the number so it will be unread, & then go to the = type the number & change it to move the cog back or forwards. For big moves change the first number & use those after the . for minor changes. Go to Fuel/Payload & change your aircraft, reload the one you're editing so FS can pick up your edit. Remember, if you don't like what you see you still have to original number after the //
I've done this to quite a few nose-heavy aircraft. I got this change tip from a forum topic a couple of years ago. Roll Eyes

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Reply #7 - Oct 15^th, 2009 at 12:27pm

microlight Offline
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Location of CofG in the nose like this is a flight dynamics design issue. Just as gypsymoth says, increasing the positive number will move the CofG backwards. Usually it doesn't have an effect on nose-down, which can be addressed by adjusting the cruise_lift_scalar parameter in [flight_tuning] (lowering the number, often below 1 to 0.9 or lower, will raise the nose as the winglift is incrementally decreased).

A CofG that's too far forward will have the effect of making the plane fly like a shuttlecock; pitching, rolling and yawing around a point that's artificially too far forward. Likewise for the tail if it's too far back. It can be noticeable on rotation or landing where the main wheels can partially disappear into the tarmac as the plane pitches around the nose rather than normal CofG which is around a 0.3 wing chord, waterline, centreline.

Wink

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Reply #8 - Oct 17^th, 2009 at 11:03am

Frozen1 Offline
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Thanks for the help but...It seems all of my Add-on A/C have the same problem. I downloaded them from Posky and have been using them for years. I never mess with the A/C cfg, I just add a panel and go. Don't know what happened.

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Reply #9 - Oct 18^th, 2009 at 4:31am

gypsymoth Offline
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"all of my Add-on A/C have the same problem" sounds a trifle
odd. All mine are different.....seems to me it's a payload/fuel, trim, or CoG problem. Why not copy a file & play with it. You'll have the copy if your editing doesn't work. As long as you have the copy you cannot do any harm Cool

When the c**p hits the fan, get a tent.
It's never too late for a happy childhood....

1) Intel I7 980X Extreme CPU Professionally overclocked to 4.2Ghz
Gigabyte X58 UD7 Motherboard (USB 2 & 3)
12GB Corsair Vengeance (3 x 4Gb) Tri Channel DDR 3 1600Mhz
OCZ Bigfoot 2E 120 Gb SSD HDD (OS and applications)
2 x 1.5TB HDD’s Samsung Spin point F1 (RAID 1) Drives (Data inc maps, photos music etc.)
LG Blu-Ray RW Drive
Samsung DVDRW Drive
Asus GTX 590 Graphics Card, Dual GPU
Antec 1200 Twelve Hundred Tower Case
Corsair 1000w Modular True Power, Power Supply
Corsair H70 Water-cooled sealed CPU Cooler
Windows 7 Professional 64 Bit & I use a 24" Dell U2412M monitor.
2) AWD-IT GPC36 E8600 Overclocked Intel E8600 Core 2 Duo @ 4.0Ghz 6MB Cache 1333FSB CPU / Asus P5Q Pro Intel P45 Crossfire DDR2 Motherboard / ATI 4870 512Mb / OCZ 4GB DDR2 PC8500 1066Mhz Memory / 500Gb SATA Hard Drive / 22x DVD-RW/Vista 64bi & 20" Dell widescreen.

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