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Centre of Gravity Location

P

PeteHam

Charter Member
A query about the C of G location when looking at the Aircraft Fuel & Payload window in the sim.

The aircraft in question is the TDS Boeing 737 series ( but it applies to other aircraft as well ) the C of G is too far forward , on the nose , rather than at about 25 - 30 % of the chord.

This was also an issue with a lot of the old Posky models , but some updates fixed it on certain models.

In my view it makes the aircraft too nose heavy which requires a lot of trim to suit and take off rotation is slow unless heaps of nose up trim is set.

Is there an easy way adjust the aircraft cfg to bring the C of G back further where it should be?

Thanks for any help.

Pete.
 
I don't have that model, but the first place to look is the aircraft.cfg. There should be a listing for station loads as well as placements for the fuel load. There is also the empty weight C of G position. Some people though do use the manufacturers design method of placement at station zero as opposed to the FS convention of 25 % chord. You might have to be careful though as a change of C of G can affect the contact points reactions & it might sit on its tail! Try emptying the aircraft of all removable things & see where it indicates the C of G.
HTH
Keith
 
Hi Keith,

Thanks for you reply. I emptied all fuel & pax/cargo and the C of G is still on the nose.

When I get home from work I'll try fiddling with the empty C of G location in the aircraft cfg.

Pete.
 
Hmmmmm......looks as if the base model .mdl has been placed at zero, rather than according to the SDK position of 25% chord, which might throw the FS drop down C of G calculation & hence seem a problem. A further clue - thinking about it on the hoof......If all of the variables for weight (fuel pax etc, & the contact points for the wheels have a negative value - going aft - ( as opposed to some positive) then that is what has happened.
In which case cannot do anything about it sensibly, just experiment with the Empty weight position, fuel & pax & see what happens - dont forget to keep a copy of the original aircraft.cfg first though!!! It might seriously affect other aspects of flight too, not just the take off.
Not a lot of help I'm afraid.
Keith
 
I suggest getting the free utility AFSD from Herve Sors. This allows you to read a multitude of airctaft parameters, including the CG. Hard to say where they placed the CL, the planes tend to fly better if the CG and CL are placed within the chord of the wing. This stuff is in the cfg file. I did the flight dynamics for the Milviz 737, which like the real Boeing had the zero point at the bulkhead that the radome is attached to. it is true that for many FS applications, placing the zero point of the model at about 25% MAC make life for most of us easier. For that plane the CG might be something like 42-45 ft behind the nose. If the CG is moved to the correct location there may be further adjustments necessary in the .Air file to get it to fly in trim.

Good luck! Tom
 
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