void writeAVLMassData(FileOutputStream fos) {
        PrintStream ps = new PrintStream(fos);

        String lunit = "0.01 m";
        if(this.getLengthUnit().equals("m")) lunit = "1 m";
        else if(this.getLengthUnit().equals("in")) lunit = UnitConversor.INCHES_TO_METERS + " m";

        String munit = "0.001 kg";
        if(this.getMassUnit().equals("kg")) munit = "1 kg";
        else if(this.getMassUnit().equals("oz")) munit = UnitConversor.OUNCES_TO_KILOGRAMS + " kg";

        String tunit = "1.0 s";
        if(this.getTimeUnit().equals("h")) tunit = "3600 s";
        else if(this.getTimeUnit().equals("m")) tunit = "60 s";
        
        ps.print("Lunit = " + lunit + "\n" +
                    "Munit = " + munit + "\n" +
                    "Tunit = " + tunit + "\n" +
                    "g   = 9.81\n" +
                    "rho = " + this.getReynoldsNumber() + "\n");
        ps.print("#mass     x       y        z        Ixx      Iyy      Izz\n");

        this.getGeometry().writeAVLMassData(ps);
    }