Sorry for double post , I just want to thank you all for your help. I made it , there's not a problem anymore.
Here's another screenshot.
Screenshot
// Weapon Stations ---------------------------------------------------------
[LeftOuterWingStation]
SystemType=WEAPON_STATION
StationID=1
StationGroupID=1
StationType=EXTERNAL
AttachmentPosition=-2.68,-1.49,-0.42
AttachmentAngles=0.0,0.0,0.0
LoadLimit=500.0
LengthLimit=3.5
AllowedWeaponClass=BOMB,RCKT,RP,IRM,FT,EOGR,ARM,LGB -> I just added "LGB" to AllowedWeaponClass line and now it works!
AttachmentType=WP,NATO,USAF,USN,ISRAEL,FRANCE
ModelNodeName=WingPylon_Outer_L
PylonMass=60
PylonDragArea=0.02
LaunchRailNodeName=MissileRail_Outer_L
LaunchRailHeight=0.10
LaunchRailMass=25
FuelTankName=Tank490_MiG21
[RightOuterWingStation]
SystemType=WEAPON_STATION
StationID=2
StationGroupID=1
StationType=EXTERNAL
AttachmentPosition=2.68,-1.49,-0.42
AttachmentAngles=0.0,0.0,0.0
LoadLimit=500.0
LengthLimit=3.5
AllowedWeaponClass=BOMB,RCKT,RP,IRM,FT,EOGR,ARM,LGB
AttachmentType=WP,NATO,USAF,USN,ISRAEL,FRANCE
ModelNodeName=WingPylon_Outer_R
PylonMass=60
PylonDragArea=0.02
LaunchRailNodeName=MissileRail_Outer_R
LaunchRailHeight=0.10
LaunchRailMass=25
FuelTankName=Tank490_MiG21