Tu-144

**Blackwood550** · 04-10-2008, 07:08 PM

I'm attempting to fix up the cg system in the tupolev TU-144 SST

My problem:

When flying the CG moves forward as i use fuel...

What i want her to do:

As i accelerate to the supersonic speeds i'd like the CG to move back. As it should in real life...I've noticed that the sim doesn't pump from the main tanks...as it should...how can i fix that?

Ive attatched a txt which has my fuel and cg set up.

could a forum mod move this thread to the Aircraft Design section please...thanks

**sirbruchie** · 04-11-2008, 09:05 AM

I don't have any experience with the Tu-144 but the concord actually had pumps that continually where pumping the fuel into the aft tanks to keep the CG where it needs to be. As a solution to your problem I can think of two suggestions: 1. Get a panel that allows you to select what tanks you burn fuel from so you can burn fuel in order to adjust the CG or a panel that allows you to transfer fuel from tank to tank. Option 2 would be to determine what tanks the plane starts burning fuel from first. You mentioned it does not take fuel from the mains as it should. I am assuming therefore it take from some other tanks first such as the aux. Try moving the position of the tanks. I noticed from the CFG file that there are a number of tanks including trim tanks. Try moving the tanks that fuel is burned from first forward and moving tanks fuel is burned from last back. This approach may take some experimenting and you may need to flight plan carefully to load the tanks accordingly before takeoff. Such as if the flight is a shorter range make sure you put the right amount of fuel is each tank so as to keep the CG where you want it. I would recommend making a copy of the CFG file before you modify it just to be safe. I am also assuming you know what numbers to change. The first number after the tank name is the Longitudinal position (front to back) 0 being the center of the plane. The larger the negative number the further back the tank is posistioned. This is just a though. Obviously finding a panel that would allow you to do all of this would be the better solution. I hope you get it all figured out, but then again that is half the fun of this hobby.

**Blackwood550** · 04-11-2008, 04:27 PM

the higher the negative # the further back yes...this might work...

(Prepares his brain for a burnout.

**sirbruchie** · 04-11-2008, 06:06 PM

Let me know how it works. You might want to move the ones that are burned from first forward too.

**Blackwood550** · 04-11-2008, 07:21 PM

i defaulted to the 4 tank config she came with...which threw the cg all the way forward, but still on the chart. I then started playin with the pumps. I discovered that burning from the L and R tanks brought it forward. So i shut them off and moved to the center two tanks.

Draining from tank 1 (front) moved fuel to tank 2 (back). However i noticed that tank 2 was full

. The programmer gave tank 2 a max capacity of 5617 gallons. Which was less than tank 1, which was 6k something. I did some math using SSTSIM calc and decided to double the capacity of tank 2 to about 11234 gallons.

This moved the cg way to the back...but only 2-3 % from the aft bug. It also pitched the plane back about 45%. So i reloaded the bird with 100% in L, R, And C1 tanks, and 64.8% in tank 2. The bird went back to normal and the cg hasn't slipped...yet

ok maybe a little but she's doing really badass. Not like concorde but she's ok.