Try next time write following line into whine box: .ord 0 0
that should clear drop tanks..
(.ord <group> <ordnance> )
group 0 is the right side stuff in the hangar
group 1 is main weapons, stuff in the center
group 2 is stuffs on the left side of plane in hangar.
Usually ordnance 0 is 'nothing', this excludes main weapons stuff (.ord 1 0 is usually default main weapons)
Ie. when having Fw190, you type .ord 1 0 into whine box, you'll get 4x20mm guns, then you type .ord 2 1, you'll get drop tanks, then you type also .fuel 3, to get 100% internal fuels.
Thats the way I do arm my plane, if its not set up correctly.